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1
Weiss, Austin M. "REMOVING VEHICLE SPEED FROM APPARENT WIND VELOCITY." UKnowledge, 2019. https://uknowledge.uky.edu/bae_etds/67.
Full textAbstract:
Variable-rate technologies for sprayer applications stand to increase efficacy by ensuring the right amount of chemical is applied at the right location. However, external environmental factors such as droplet drift caused by variable ambient condition, are not yet integrated into modern sprayer systems. Real-time wind velocity measurements can be used to control droplet spectra for reducing spray drift by actuating a variable-orifice nozzle. This work aimed to develop data processing methods needed to filter noise and remove vehicle speed from wind velocity measurements collected with an ultrasonic anemometer aboard a moving platform. Using a global navigation satellite system (GNSS), vehicle speed was calculated in the field and subtracted from apparent wind velocity for comparison to static measurements. Experiments under stationary and dynamic sensor deployments were used to develop an algorithm to provide instantaneous local wind velocity and to better understand the local spatiotemporal variability of wind under field conditions.
2
Schönfeldt, Hans-Jürgen. "Systematische Überschätzung der Windgeschwindigkeit und der Schubspannungsgeschwindigkeit durch Schalensternanemometer infolge der Turbulenz." Universitätsbibliothek Leipzig, 2017. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-217478.
Full textAbstract:
Die mittlere Windgeschwindigkeit kann aus den Komponenten der Geschwindigkeit (Vektorwind) und aus dem Windweg eines Schalensternanemometers (Skalarwind) berechnet werden. Diese beiden Geschwindigkeiten werden verglichen, indem große Datensätze von Windmeßreihen hoher Auflösung, die mittels Ultraschallanemometer gewonnen wurden, benutzt werden. Der Skalarwind ist verursacht durch die Turbulenz immer größer als der Vektorwind, die Abweichungen betrugen bis zu 4%. Durch Benutzen von Normalverteilungen für die Komponenten des Windes wird eine analytische Lösung für diesen systematischen Fehler angegeben. Windmessungen mit einem Schalensternanemometer zeigen einen zweiten systematischen Fehler, das sogenannte Overspeeding. Dieses Verhalten wird durch ein einfaches Modell beschriebenMean wind velocity can be calculated from the components of velocity (vector wind) and the wind way of a cup anemometer (scalar wind). The wind velocities resulting from different definitions of mean wind velocities are compared by using large dataset of fast-response wind measurements with an ultrasonic anemometer. It is found that the scalar wind is always greater then the vector wind up to 4% owing to the turbulence. Using Gaussian normal distribution for the components of wind velocity, an analytical solution is given for this systematic error. Wind velocity measured with cup anemometer shows second systematic error called overspeeding which is described by a simple mathematical model
3
Gordon, Robert. "Advanced 2-D and 3-D particle velocimetry techniques for quantitative fluid flow visualisation in real-time." Thesis, University of Aberdeen, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.262919.
Full textAbstract:
The aim of this study was to develop and implement a low cost, high speed, flow visualisation tool for 3-D velocity measurement throughout time dependent particle seeded fluid flow volumes. To achieve this, a new high performance wind / water tunnel was designed and constructed using CFD as a design aid. The tunnel provided the necessary platform for obtaining consistent high quality images of fluid flow. Images were grabbed using low cost CCD cameras and downloaded via a PC mounted image capture board, to system RAM. The conventional high cost laser sheet illumination method was replaced with a low cost, portable floodlight system, which enabled both 2-D and 3-D flow volumes to be illuminated. For the 3-D image capture, stereo photogrammetric techniques were employed. Advanced calibration algorithms were developed which automatically detected camera positioning. This reduced the inherent human error associated with setting-up a complex imaging system. 2-D pattern matching and particle tracking algorithms were developed, optimised and tested using real and synthetically generated flow data, to establish practical limits for particle seeding density, particle image size, flow velocity and flow complexity. These results demonstrated that particle tracking was more suited to real-time 3-D applications. The developed algorithms formed the base of a Windows 95/Windows NT package for general purpose analysis of 2-D and 3-D single exposure image streams of particle seeded fluid flow.
4
Tourn, Cremona Silvana Cecilia. "Characterization of a New Open Jet Wind Tunnel to Optimize and Test Vertical Axis Wind Turbines." Doctoral thesis, Universitat Rovira i Virgili, 2017. http://hdl.handle.net/10803/461079.
Full textAbstract:
Basat en el creixent interès en les tecnologies ambientals urbanes, l'estudi de turinas d'eix vertical de petita escala mostra desafiaments motivadors. En aquesta tesi, es presenten els criteris de disseny, les característiques i potencialitats d'un nou túnel de vent de secció de prova oberta. Té un àrea de sortida i la broquet del túnel de 1,5 x 1,5 m2, i es pot operar amb velocitats de sortida de 3 m / s a 17 m / s. La caracterització del flux s'ha dut a terme amb tubs pitot calibrats, anemòmetres de cassoletes i anemòmetres de fil calent. Es consideren dues configuracions diferents de l'àrea de prova, amb i sense sostre. Els mesuraments en el rang de velocitats de sortida disponibles mostren que la secció transversal, on les intensitats de velocitat i turbulència mostren un nivell acceptable d'uniformitat, té una àrea de 0,8 x 0,8 m2 i una dimensió de 2 m des de la sortida del broquet del túnel. En aquesta secció de treball, la intensitat màxima de la turbulència és del 4%. La caracterització detallada del flux realitzat indica que el túnel de vent es pot utilitzar per provar models a d'aerogeneradors de petita escala.Basado en el creciente interés en las tecnologías ambientales urbanas, el estudio de turinas de eje vertical de pequeña escala muestra desafíos motivadores. En esta tesis, se presentan los criterios de diseño, las características y potencialidades de un nuevo túnel de viento de seccion de prueba abierta. Tiene un área de salida e la boquilla del túnel de 1,5 x 1,5 m2, y se puede operar con velocidades de salida de 3 m/s a 17 m/s. La caracterización del flujo se ha llevado a cabo con tubos pitot calibrados, anemómetros de cazoletas y anemómetros de hilo caliente. Se consideran dos configuraciones diferentes del área de prueba, con y sin techo. Las mediciones en el rango de velocidades de salida disponibles muestran que la sección transversal, donde las intensidades de velocidad y turbulencia muestran un nivel aceptable de uniformidad, tiene un área de 0,8 x 0,8 m2 y una dimensión de 2 m desde la salida de la boquilla del túnel. En esta sección de trabajo, la intensidad máxima de la turbulencia es del 4%. La caracterización detallada del flujo realizado indica que el túnel de viento se puede utilizar para probar modelos a de aerogeneradores de pequeña escala.
Based on the increasing interest in urban environmental technologies, the study of small scale vertical axis wind turbines shows motivating challenges. In this thesis, we present the design criteria, characteristics and potentials of a new open jet wind tunnel. It has a nozzle exit area of 1.5 x1.5 m2, and it can be operated with exit velocities from 3 m/s to 17 m/s. The characterization of the flow has been carried out with calibrated pitot tubes, cup anemometers, and hot wire anemometers. Two different configurations of the test area, with and without a ceiling, are considered. Measurements in the range of available exit velocities show that the cross section, where the velocity and turbulence intensities show an acceptable level of uniformity, has an area of 0.8 x 0.8 m2 and a streamwise dimension of 2 m from the nozzle exit of the tunnel. In this working section, the maximum turbulence intensity is 4%. The detailed characterization of the flow carried out indicates that the wind tunnel can be used to test small scale models of wind turbines.
5
Jacobi, Christoph, Rudolf Schminder, and Dierk Kürschner. "D1 LF wind measurements in autumn and early winter 1994 at Collm, Germany." Universitätsbibliothek Leipzig, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-213054.
Full textAbstract:
Results of total reflection mesopause wind measurements, carried out at the Collm Observatory of the University of Leipzig in 1994 are presented with special regard to the CRISTA period in November 1994. Height-time cross-sections of the prevailing wind and the semidiumal tidal amplitude and phase show the variation of these parameters during the course of the year. In autumn and early winter oscillations of the prevailing wind with a period of about 2 - 3 weeks are found. They are partly due to an overshooting of the parameters while the circulation adjusts to its winter conditions. A comparison of the zonal prevailing wind in 1994 with the values measured since 1982 shows a solar cycle dependenceErgebnisse von Windmessungen in der Mesopausenregion mit Hilfe der Reflexion von Funkwellen, die am Observatorium Collm der Universität Leipzig durchgeführt wurden, werden vorgestellt, wobei besonderes Gewicht auf die Zeit der CRISTA-Satellitenmission im November 1994 gelegt wird. Höhen-Zeit-Schnitte des Grundwindes und der Amplitude des halbtägigen Gezeitenwindes zeigen die Änderung dieser Parameter im Lauf des Jahres. Im Herbst und frühen Winter werden Oszillationen mit Perioden von 2 - 3 Wochen festgestellt. Diese sind zu Teil durch ein Überschießen bedingt, daß mit der Anpassung an die Winterbedingungen zusammenhängt. Ein Vergleich des zonalen Grundwindes 1994 mit des Werten aus anderen Jahren gibt Hinweise auf eine Abhängigkeit von der solaren Aktivität
6
Jacobi, Christoph. "Solar cycle dependence of winds and planetary waves as seen from midlatitude mesopause region wind measurements at Collm." Universitätsbibliothek Leipzig, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-213432.
Full textAbstract:
Windmessungen im Mesopausenbereich über Mitteleuropa (Collm, 52°N, I5°E) werden im Hinblick auf Langzeittrends und eine eventuelle Abhängigkeit vom 11-jährigen Sonnenfleckenzyklus hin untersucht. Der Einfluß der solaren Variabilität ist jahreszeitenabhängig; nur in Frühjahr und Sommer wird eine signifikante Korrelation gefunden. Im Sommer ist diese Abhängigkeit mit stärkeren vertikalen Gradienten des mittleren zonalen Grundwindes im solaren Maximum verbunden. Dies weist auf einen Ursprung dieser Abhängigkeit in der Stratosphäre/Mesosphäre sowie auf Koppelungsmechanismen zwischen Stratosphäre, Mesosphäre und unteren Thermosphäre hin. Da die 2-Tage-Welle vom Gradienten abhängt, führt dies zu einer positiven Korrelation zwischen der Amplitude der 2-Tage-Welle und der SonnenfleckenrelativzahlMesopause winds over Central Europe (Collm, 52°N, I5°E) are analysed with respect to longterm trends and 11-year solar cycle dependencies. The response of the prevailing wind to the solar cycle differs throughout the year. While in winter no significant correlation between the zonal prevailing wind and the solar activity is found, in spring and summer a negative correlation between solar activity and zonal prevailing wind can be seen from the measurements. This is connected with strenger vertical gradients of the zonal prevailing wind during solar maximum than during solar minimum. This hints to a forcing of the mesopause region dynamical reaction on solar activity from the stratosphere/mesosphere and to coupling processes in the stratosphere-mesosphere-lower thermosphere system. Since the amplitude of the quasi twoday wave is dependent on the zonal mean wind gradient, this is connected with a positive correlation between solar activity and quasi two-day wave activity
7
Mesrobian, Chris Eden. "Concept Study of a High-Speed, Vertical Take-Off and Landing Aircraft." Thesis, Virginia Tech, 2009. http://hdl.handle.net/10919/35574.
Full textAbstract:
The purpose of the study was to evaluate the merits of the DiscRotor concept that combine the features of a retractable rotor system for vertical take-off and landing (VTOL) with an integral, circular wing for high-speed flight. Tests were conducted to generate basic aerodynamic characteristics of the DiscRotor in hover and in fixed-wing flight. To assess the DiscRotor during hover, small scale tests were conducted on a 3ft diameter rotor without the presence of a fuselage. A â hover rigâ was constructed capable of rotating the model rotor at speeds up to 3,500 RPM to reach tip speeds of 500fps. Thrust and torque generated by the rotating model were measured via a two-component load cell, and time averaged values were obtained for various speeds and pitch angles. It has been shown that the DiscRotor will perform well in hover. Ground Effects in hover were examined by simulating the ground with a movable, solid wall. The thrust was found to increase by 50% compared to the ground-independent case. Pressure distributions were measured on the ground and disc surfaces. Velocity measurements examined the flow field downstream of the rotor by traversing a seven hole velocity probe. A wake behind the rotor was shown to contract due to a low pressure region that develops downstream of the disc.
Wind tunnel experimentation was also performed to examine the fixed wing flight of the DiscRotor. These experiments were performed in the VA Tech 6â X6â Stability Tunnel. A model of the fuselage and a circular wing was fabricated based upon an initial sizing study completed by our partners at Boeing. Forces were directly measured via a six degree of freedom load cell, or balance, for free stream velocities up to 200fps. Reynolds numbers of 2 and 0.5 million have been investigated for multiple angles of attack. Low lift-to-drag ratios were found placing high power requirements for the DiscRotor during fixed-wing flight. By traversing a seven-hole velocity probe, velocities in a 2-D grid perpendicular to the flow were measured on the model. The strengths of shed vortices from the model were calculated. A method to improve fixed-wing performance was considered where two blades were extended from the disc. An increase of 0.17 in the CL was measured due to the interaction between the disc and blades.
This research utilized a wide range of experiments, with the aim of generating basic aerodynamic characteristics of the DiscRotor. A substantial amount of quantitative data was collected that could not be included in this document. Results aided in the initial designs of this aircraft for the purpose of evaluating the merit of the DiscRotor concept.
Master of Science
8
Schönfeldt, Hans-Jürgen. "Systematische Überschätzung der Windgeschwindigkeit und der Schubspannungsgeschwindigkeit durch Schalensternanemometer infolge der Turbulenz." Universität Leipzig, 2003. https://ul.qucosa.de/id/qucosa%3A15238.
Full textAbstract:
Die mittlere Windgeschwindigkeit kann aus den Komponenten der Geschwindigkeit (Vektorwind) und aus dem Windweg eines Schalensternanemometers (Skalarwind) berechnet werden. Diese beiden Geschwindigkeiten werden verglichen, indem große Datensätze von Windmeßreihen hoher Auflösung, die mittels Ultraschallanemometer gewonnen wurden, benutzt werden. Der Skalarwind ist verursacht durch die Turbulenz immer größer als der Vektorwind, die Abweichungen betrugen bis zu 4%. Durch Benutzen von Normalverteilungen für die Komponenten des Windes wird eine analytische Lösung für diesen systematischen Fehler angegeben. Windmessungen mit einem Schalensternanemometer zeigen einen zweiten systematischen Fehler, das sogenannte Overspeeding. Dieses Verhalten wird durch ein einfaches Modell beschrieben.Mean wind velocity can be calculated from the components of velocity (vector wind) and the wind way of a cup anemometer (scalar wind). The wind velocities resulting from different definitions of mean wind velocities are compared by using large dataset of fast-response wind measurements with an ultrasonic anemometer. It is found that the scalar wind is always greater then the vector wind up to 4% owing to the turbulence. Using Gaussian normal distribution for the components of wind velocity, an analytical solution is given for this systematic error. Wind velocity measured with cup anemometer shows second systematic error called overspeeding which is described by a simple mathematical model.
9
Jacobi, Christoph, Rudolf Schminder, and Dierk Kürschner. "D1 LF wind measurements in autumn and early winter 1994 at Collm, Germany." Wissenschaftliche Mitteilungen des Leipziger Instituts für Meteorologie ; 4 = Meteorologische Arbeiten aus Leipzig ; 2 (1996), S. 144-150, 1996. https://ul.qucosa.de/id/qucosa%3A15061.
Full textAbstract:
Results of total reflection mesopause wind measurements, carried out at the Collm Observatory of the University of Leipzig in 1994 are presented with special regard to the CRISTA period in November 1994. Height-time cross-sections of the prevailing wind and the semidiumal
tidal amplitude and phase show the variation of these parameters during the course of the year. In autumn and early winter oscillations of the prevailing wind with a period of about 2 - 3 weeks are found. They are partly due to an overshooting of the parameters while the circulation adjusts to its winter conditions. A comparison of the zonal prevailing wind in 1994 with the values measured since 1982 shows a solar cycle dependence.Ergebnisse von Windmessungen in der Mesopausenregion mit Hilfe der Reflexion von Funkwellen, die am Observatorium Collm der Universität Leipzig durchgeführt wurden, werden vorgestellt, wobei besonderes Gewicht auf die Zeit der CRISTA-Satellitenmission im November 1994 gelegt wird. Höhen-Zeit-Schnitte des Grundwindes und der Amplitude des halbtägigen Gezeitenwindes zeigen die Änderung dieser Parameter im Lauf des Jahres. Im Herbst und frühen Winter werden Oszillationen mit Perioden von 2 - 3 Wochen festgestellt. Diese sind zu Teil durch ein Überschießen bedingt, daß mit der Anpassung an die Winterbedingungen zusammenhängt. Ein Vergleich des zonalen Grundwindes 1994 mit des Werten aus anderen Jahren gibt Hinweise auf eine Abhängigkeit von der solaren Aktivität.
10
Arnold, Klaus, Astrid Ziemann, and Armin Raabe. "Acoustic tomography in comparision to in-situ temperature and wind measurements." Universitätsbibliothek Leipzig, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-216523.
Full textAbstract:
Acoustic travel time tomography is presented as an experimental technique for remote monitoring of areally averaged meteorological quantities as the air temperature and the horizontal wind speed. This ground based remote sensing technique uses the nearly horizontal propagation of sound waves in the atmospheric surface layer. Here the acoustic travel time tomography was applied by measuring the travel time at defined propagation paths between several sound sources and receivers. The resulting sound speed were used to obtain estimates of the meteorological parameters. A measuring campaign was carried out at the test site in Lindenberg (DWD) to compare the acoustically derived data with conventional systems. These observations demonstrated that on one side the accuracy of the acoustic system is comparable with in-situ measurements and on the other side the temperature was particularly significant overestimated by the standard sensors, e.g. due to the radiation influenceDie Akustische Laufzeittomographie wird als ein experimentelles Verfahren zur Sondierung meteorologischer Parameter, wie z.B. der Lufttemperatur und der horizontalen Windgeschwindigkeit, vorgestellt. Dieses bodengebundene Fernerkundungsverfahren nutzt die horizontale Ausbreitung von Schallwellen in der atmosphärischen Grenzschicht. Hier wird das Verfahren der Laufzeittomographie angewendet, d.h. bei bekannter Weglänge wird die Ausbreitungszeit von ausgesendeten Schallsignalen zwischen mehreren Schallquellen und Empfängern gemessen. Die resultierenden Schallgeschwindigkeitsinformationen werden genutzt, um daraus die entsprechenden meteorologischen Parameter abzuleiten. Auf dem Gelände des Meteorologischen Observatoriums Lindenberg (DWD) wurde eine Messkampagne durchgeführt, um die akustischen Sondierungen mit konventionellen Systemen zu vergleichen. Die Auswertungen zeigen, dass einerseits die Genauigkeit der Akustischen Tomographie vergleichbar mit den konventionellen in-situ Messungen ist und andererseits, dass die Lufttemperatur aufgrund des Strahlungseinflusses bei Messungen mit den üblichen Sensoren zum Teil erheblich überschätzt wird
11
Bartl, Jan. "Wake Measurements Behind An Array Of Two Model Wind Turbines." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for energi- og prosessteknikk, 2011. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-14715.
Full textAbstract:
During the last decades the exploitation of energy from the wind has become one of the most promising renewable energy technologies. The main strive in today’s development of wind turbines is to increase the efficiency of the turbine and to build bigger rotors that are able to extract more power out of the wind.When it comes to the planning and designing of a wind park, also the aerodynamic interactions between the single turbines must be taken into account. The flow in the wake of the first row turbines is characterized by a significant deficit in wind velocity and by increased levels of turbulence. Consequently, the downstream turbines in a wind farm cannot extract as much power from the wind anymore. Furthermore, the additional turbulence in the wake could be a reason for increased material fatigue through flow-induced vibrations at the downstream rotor.The main focus of this experimental study is to investigate the local velocity deficit and the turbulence intensities in the wake behind an array of two model wind turbines. For two different turbine separation distances, the wake is scanned at several different downstream positions behind the second model turbine. Thus, it is possible to map the axial development of mean velocity and turbulence intensity and to evaluate the influence of turbine separation distance. Furthermore, the effect of varying tip speed ratios of the first and second turbine onto the wake flow field is investigated.The experiments are performed at the wind tunnel (1.9m x 2.7m cross section) at NTNU Trondheim using two model wind turbines with a rotor diameter of 0.9m. A hot wire probe is used to scan the wake behind the model turbines in defined positions.The velocity deficit and the turbulence intensity behind an array of two turbines are found to be significantly higher than behind one unobstructed turbine. Moving axially downstream, a gentle broadening of the wake can be observed. The wake profiles measured in close distances behind the rotor are characterized by evident asymmetries. Further downstream in the wake, the flow field becomes more symmetrical. The flow conditions in the inner part of the wake behind the two turbines are observed to be mainly dominated by the operational characteristics of the second turbine rotor. Although the first turbine has hardly any influence on the inner part of the wake, the outer dimensions of the wake can be tracked back to the influence of the first turbine.
12
King, Matthew A. "Measurement of Threshold Friction Velocities at Potential Dust Sources in Semi-arid Regions." Thesis, The University of Arizona, 2015. http://hdl.handle.net/10150/596087.
Full textAbstract:
The threshold friction velocities of potential dust sources in the US Southwest were measured in the field using a Portable Wind Tunnel, which is based on the Desert Research Institute's Portable In-Situ Wind Erosion Laboratory (PI-SWERL). A mix of both disturbed and undisturbed surfaces were included in this study. It was found that disturbed surfaces, such as those at the Iron King Mine tailings site, which is part of the EPA's Superfund program and contains surface concentrations of arsenic and lead reaching as high as 0.5% (w/w), had lower threshold friction velocities (0.32 m s⁻¹ to 0.40 m s⁻¹) in comparison to those of undisturbed surfaces (0.48 to 0.61 m s⁻¹). Surface characteristics, such as particle size distribution, had effects on the threshold friction velocity (smaller grain sized distributions resulted in lower threshold friction velocities). Overall, the threshold friction velocities of disturbed surfaces were within the range of natural wind conditions, indicating that surfaces disturbed by human activity are more prone to causing windblown dust.
13
Jacobi, Christoph. "Solar cycle dependence of winds and planetary waves as seen from midlatitude mesopause region wind measurements at Collm: evidence for forcing from below." Wissenschaftliche Mitteilungen des Leipziger Instituts für Meteorologie ; 9 = Meteorologische Arbeiten aus Leipzig ; 3 (1998), S. 106-116, 1998. https://ul.qucosa.de/id/qucosa%3A15083.
Full textAbstract:
Windmessungen im Mesopausenbereich über Mitteleuropa (Collm, 52°N, I5°E) werden im Hinblick auf Langzeittrends und eine eventuelle Abhängigkeit vom 11-jährigen Sonnenfleckenzyklus hin untersucht. Der Einfluß der solaren Variabilität ist jahreszeitenabhängig; nur in Frühjahr und Sommer wird eine signifikante Korrelation gefunden. Im Sommer ist diese Abhängigkeit mit stärkeren vertikalen Gradienten des mittleren zonalen Grundwindes im solaren Maximum verbunden. Dies weist auf einen Ursprung dieser Abhängigkeit in der Stratosphäre/Mesosphäre sowie auf Koppelungsmechanismen zwischen Stratosphäre, Mesosphäre und unteren Thermosphäre hin. Da die 2-Tage-Welle vom Gradienten abhängt, führt dies zu einer positiven Korrelation zwischen der Amplitude der 2-Tage-Welle und der Sonnenfleckenrelativzahl.Mesopause winds over Central Europe (Collm, 52°N, I5°E) are analysed with respect to longterm trends and 11-year solar cycle dependencies. The response of the prevailing wind to the solar cycle differs throughout the year. While in winter no significant correlation between the zonal prevailing wind and the solar activity is found, in spring and summer a negative correlation between solar activity and zonal prevailing wind can be seen from the measurements. This is connected with strenger vertical gradients of the zonal prevailing wind during solar maximum than during solar minimum. This hints to a forcing of the mesopause region dynamical reaction on solar activity from the stratosphere/mesosphere and to coupling processes in the stratosphere-mesosphere-lower thermosphere system. Since the amplitude of the quasi twoday wave is dependent on the zonal mean wind gradient, this is connected with a positive correlation between solar activity and quasi two-day wave activity.
14
Arnold, Klaus, Astrid Ziemann, and Armin Raabe. "Acoustic tomography in comparision to in-situ temperature and wind measurements." Wissenschaftliche Mitteilungen des Leipziger Instituts für Meteorologie ; 22 = Meteorologische Arbeiten aus Leipzig ; 6 (2001), S. 60-68, 2001. https://ul.qucosa.de/id/qucosa%3A15201.
Full textAbstract:
Acoustic travel time tomography is presented as an experimental technique for remote monitoring of areally averaged meteorological quantities as the air temperature and the horizontal wind speed. This ground based remote sensing technique uses the nearly horizontal propagation of sound waves in the atmospheric surface layer. Here the acoustic travel time tomography was applied by measuring the travel time at defined propagation paths between several sound sources and
receivers. The resulting sound speed were used to obtain estimates of the meteorological parameters. A measuring campaign was carried out at the test site in Lindenberg (DWD) to compare the acoustically derived data with conventional systems. These observations demonstrated that on one side the accuracy of the acoustic system is comparable with in-situ measurements and on the other side the temperature was particularly significant overestimated by the standard sensors, e.g. due to the radiation influence.Die Akustische Laufzeittomographie wird als ein experimentelles Verfahren zur Sondierung meteorologischer Parameter, wie z.B. der Lufttemperatur und der horizontalen Windgeschwindigkeit, vorgestellt. Dieses bodengebundene Fernerkundungsverfahren nutzt die horizontale Ausbreitung von Schallwellen in der atmosphärischen Grenzschicht. Hier wird das Verfahren der Laufzeittomographie angewendet, d.h. bei bekannter Weglänge wird die Ausbreitungszeit von ausgesendeten Schallsignalen zwischen mehreren Schallquellen und Empfängern gemessen. Die resultierenden Schallgeschwindigkeitsinformationen werden genutzt, um daraus die entsprechenden meteorologischen Parameter abzuleiten. Auf dem Gelände des Meteorologischen Observatoriums Lindenberg (DWD) wurde eine Messkampagne durchgeführt, um die akustischen Sondierungen mit konventionellen Systemen zu vergleichen. Die Auswertungen zeigen, dass einerseits die Genauigkeit der Akustischen Tomographie vergleichbar mit den konventionellen in-situ Messungen ist und andererseits, dass die Lufttemperatur aufgrund des Strahlungseinflusses bei Messungen mit den üblichen Sensoren zum Teil erheblich überschätzt wird.
15
Schouten, Shane Michael. "Complete CFD analysis of a Velocity XL-5 RG with flight-test verification." Texas A&M University, 2008. http://hdl.handle.net/1969.1/85894.
Full textAbstract:
The Texas A&M Flight Research Laboratory (FRL) recently received delivery of its
newest aircraft, the Velocity XL-5 RG. The Velocity can fly faster than the other aircraft
owned by the FRL and does not have a propeller in the front of the aircraft to disrupt the
air flow. These are definite advantages that make the Velocity an attractive addition to
the FRL inventory to be used in boundary-layer stability and transition control. Possible
mounting locations built into the aircraft for future projects include hard points in the
wings and roof of the fuselage. One of the drawbacks of the aircraft is that it has a
canard ahead of the main wing that could disrupt the incoming flow for a wing glove or
research requiring test pieces mounted to the hard point in the wing. Therefore, it is
necessary to understand the influence the canard and the impact of its wake on the wing
of the aircraft before any in-depth aerodynamic research could be completed on the
aircraft.
A combination of in-flight measurements of the canard wake and Computational
Fluid Dynamics (CFD) were used to provide a clear picture of the flowfield around the
aircraft. The first step of the project consisted of making a 3-D CAD model of the
aircraft. This model was then used for the CFD simulations in Fluent. 2-D, 3-D, inviscid,
and viscous simulations were preformed on the aircraft. A pressure rake was designed to
house a 5-hole probe and 18 Pitot probes that extended forward of the main wing to
measure the location and strength of the canard wake at various flight conditions. There
were five primary test points that were recorded at multiple times over the course of three flights. Once all of the data were collected from the flights, the freestream
conditions became the inputs into the final, 3-D CFD simulations on the aircraft.
The good agreement between the CFD results and the in-flight measurements
provided the necessary verification of the CFD model of the aircraft. These results can
be used in the future planning and execution of experiments involving the Velocity XL-5
RG.
16
Berkesten, Hägglund Patrik. "An Experimental Study on Global TurbineArray Eects in Large Wind Turbine Clusters." Thesis, KTH, Mekanik, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-202630.
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It is well known that the layout of a large wind turbine cluster aects the energyoutput of the wind farm. The individual placement and distances betweenturbines will in uence the wake spreading and the wind velocity decit. Manyanalytical models and simulations have been made trying to calculate this, butstill there is a lack of experimental data to conrm the models. This thesis isdescribing the preparations and the execution of an experiment that has beenconducted using about 250 small rotating turbine models in a wind tunnel. Theturbine models were developed before the experiment and the characteristicswere investigated. The main focus was laid on special eects occurring in largewind turbine clusters, which were named Global Turbine Array Eects.It was shown that the upstream wind was little aected by a large windfarm downstream, even though there existed a small dierence in wind speedbetween the undisturbed free stream and the wind that arrived to the rstturbines in the wind farm. The dierence in wind speed was shown to beunder 1% of the undisturbed free stream. It was also shown that the densityof the wind farm was related to the reduced wind velocity, with a more densefarm the reduction could get up to 2.5% of the undisturbed free stream at theupstream center turbine. Less velocity decit was observed at the upstreamcorner turbines in the wind farm.When using small rotating turbine models some scaling requirements hadto be considered to make the experiment adaptable to reality. It was concludedthat the thrust coecient of the turbine models was the most important parameterwhen analysing the eects. One problem discussed was the low Reynoldsnumber, an eect always present in wind tunnel studies on small wind turbinemodels.A preliminary investigation of a photo measuring technique was also performed,but the technique was not fully developed. The idea was to take oneor a few photos instantaneously and then calculate the individual rotationalspeed of all the turbine models. It was dicult to apply the technique becauseof uctuations in rotational speed during the experiment, therefore thecalculated values could not represent the mean value over a longer time period.
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Duhaut, Thomas H. A. "Wind-driven circulation : impact of a surface velocity dependent wind stress." Thesis, McGill University, 2006. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=101117.
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The use of an ocean surface velocity dependent wind stress is examined in the context of a 3-layer double-gyre quasigeostrophic wind-driven ocean circulation model. The new wind stress formulation results in a large reduction of the power input by the wind into the oceanic circulation. This wind stress is proportional to a quadratic function of Ua--u o, where Ua is the wind at 10m above the ocean surface and uo is the ocean surface current. Because the winds are typically faster than the ocean currents, the impact of the ocean surface velocity on the wind stress itself is relatively small. However, the power input is found to be greatly reduced with the new formulation. This is shown by simple scaling argument and numerical simulations in a square basin. Our results suggest that the wind power input may be as much as 35% smaller than is typically assumed.The ocean current signature is clearly visible in the scatterometer-derived wind stress fields. We argue that because the actual ocean velocity differs from the modeled ocean velocities, care must be taken in directly applying scatterometer-derived wind stress products to the ocean circulation models. This is not to say that the scatterometer-derived wind stress is not useful. Clearly the great spatial and temporal coverage make these data sets invaluable. Our point is that it is better to separate the atmospheric and oceanic contribution to the stresses.
Finally, the new wind stress decreases the sensitivity of the solution to the (poorly known) bottom friction coefficient. The dependence of the circulation strength on different values of bottom friction is examined under the standard and the new wind stress forcing for two topographic configurations. A flat bottom and a meridional ridge case are studied. In the flat bottom case, the new wind stress leads to a significant reduction of the sensitivity to the bottom friction parameter, implying that inertial runaway occurs for smaller values of bottom friction coefficient. The ridge case also gives similar results. In the case of the ridge and the new wind stress formulation, no real inertial runaway regime has been found over the range of parameters explored.
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Simley, Eric J. "Wind Speed Preview Measurement and Estimation for Feedforward Control of Wind Turbines." Thesis, University of Colorado at Boulder, 2015. http://pqdtopen.proquest.com/#viewpdf?dispub=3721887.
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Wind turbines typically rely on feedback controllers to maximize power capture in below-rated conditions and regulate rotor speed during above-rated operation. However, measurements of the approaching wind provided by Light Detection and Ranging (lidar) can be used as part of a preview-based, or feedforward, control system in order to improve rotor speed regulation and reduce structural loads. But the effectiveness of preview-based control depends on how accurately lidar can measure the wind that will interact with the turbine.
In this thesis, lidar measurement error is determined using a statistical frequency-domain wind field model including wind evolution, or the change in turbulent wind speeds between the time they are measured and when they reach the turbine. Parameters of the National Renewable Energy Laboratory (NREL) 5-MW reference turbine model are used to determine measurement error for a hub-mounted circularly-scanning lidar scenario, based on commercially-available technology, designed to estimate rotor effective uniform and shear wind speed components. By combining the wind field model, lidar model, and turbine parameters, the optimal lidar scan radius and preview distance that yield the minimum mean square measurement error, as well as the resulting minimum achievable error, are found for a variety of wind conditions. With optimized scan scenarios, it is found that relatively low measurement error can be achieved, but the attainable measurement error largely depends on the wind conditions. In addition, the impact of the induction zone, the region upstream of the turbine where the approaching wind speeds are reduced, as well as turbine yaw error on measurement quality is analyzed.
In order to minimize the mean square measurement error, an optimal measurement prefilter is employed, which depends on statistics of the correlation between the preview measurements and the wind that interacts with the turbine. However, because the wind speeds encountered by the turbine are unknown, a Kalman filter-based wind speed estimator is developed that relies on turbine sensor outputs. Using simulated lidar measurements in conjunction with wind speed estimator outputs based on aeroelastic simulations of the NREL 5-MW turbine model, it is shown how the optimal prefilter can adapt to varying degrees of measurement quality.
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Wang, Jialin. "Building integrated wind energy." Thesis, University of Manchester, 2013. https://www.research.manchester.ac.uk/portal/en/theses/building-integrated-wind-energy(81978798-e68a-4189-87b0-4159b280b6e9).html.
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In considering methods of reducing the emission of carbon dioxide; there is a growing interest for use of wind power at domestic building in U.K. But the technology of wind turbines development in building environment is more complicated than in open areas. Small wind turbines in suburban areas have been reported as having unsatisfactory energy output, but it is not clear whether this is due to insufficient wind resource or low turbine efficiency. The aim of this research is to discover whether the wind resource in suburban areas is large enough for small wind turbines to produce a useful energy output.Historical wind data and manufacturers' turbine characteristics were used to estimate the hourly wind speed and energy output for different U.K. cities, terrain zones and turbines. It was found that for turbines at 10 m height in suburban areas and depending on city, the annual wind energy conversion efficiency ranged from about 20 to 40%, while the number of turbines required to produce the annual average electricity consumption of a UK dwelling ranged from about 6 for the smallest turbine (5.3 m² rotor area) to about 1 for the largest (35.26 m² rotor area).This analysis was based on average conditions, but the wind speed near buildings can vary considerably from one point to another. In order to predict the performance of wind turbines more accurately, the atmospheric boundary layer (ABL) of suburban areas was simulated in both CFD and wind tunnel models, and models of groups of semi-detached and terraced houses were set in this ABL. It was found that at 10 m height in the area of the houses, the turbulence intensity was too high for satisfactory operation of wind turbines (19 to 35%) while the mean velocity at different points ranged from 86 to 108% of the 10m reference velocity. At 30m height the turbulence intensity was satisfactory (less than 19 %), while the mean velocity ranged from 92 to 103 % of the 30 m reference velocity. It is concluded that for wind turbines in suburban areas, at 10 m height the wind speed is too low and the turbulence is too high for satisfactory performance, while at 30 m height the wind speed is much higher and the turbulence is low enough.
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Styles, Julie M. "A wind tunnel study of the velocity field above a model plant canopy." [Canberra] : CSIRO Land and Water, 1997. http://nla.gov.au/nla.arc-13482.
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Thesis (B.Sc. (Honours)) - Australian National University, 1997.Title from title screen (viewed on May 20, 2002). "A thesis submitted in partial fulfilment of the requirements for the Degree of Bachelor of Science (Honours)"--Title screen. Bibliography: p. 64-66. Available full text via the internet.
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Straw, Matthew Peter. "Computation and measurement of wind induced ventilation." Thesis, University of Nottingham, 2000. http://eprints.nottingham.ac.uk/10110/.
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This thesis aims to predict wind induced ventilation of a structure through the application of current analytical techniques, computational fluid dynamics simulations and novel techniques for ventilation flows induced by turbulent mechanisms. Validation of the predictions was carried out through full-scale measurements undertaken on a purpose built test structure. The structure was of cubic design with an external dimension of 6m. The construction of this full-scale research structure at Silsoe Research Institute, Bedfordshire, England, provided a unique opportunity for undertaking full-scale experimentation on a fundamental wind engineering test case which, prior to this thesis, had only been investigated using scale models in wind tunnels and computational simulations.
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Schlink, Uwe, and Gerd Tetzlaff. "Kürzestfristvorhersage der Windgeschwindigkeit in einem Wirbelschleppenwarnsystem für Flughäfen." Universitätsbibliothek Leipzig, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-213315.
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Die lange Lebensdauer und die hohe Intensität der Wirbelschleppen landender Großraumflugzeuge kann zu einer Gefährdung des nachfolgenden Verkehrs führen. Zur Vorhersage einer gefährdungsfreien Nutzungszeit der Landebahn, nach der die Staffelungsabstände der landenden Flugzeuge bestimmt werden, dient ein Wirbelschleppenwarnsystem. Ein wesentlicher Teil dieses Warnsystems ist die Vorhersage des quer zur Landebahn wehenden Windes. Dafür wird bisher ein auf Persistenz beruhendes Verfahren eingesetzt. Die vorliegende Arbeit zeigt, daß durch Verwendung eines autoregressiven Modells die Querwindprognose verbessert werden kann. Dazu werden die Meßdaten analysiert und die Modellparameter geschätzt. Der Einsatz der AR Prognose im Wirbelschleppenwarnsystem führt im Vergleich zur bisherigen Methode zu längeren Nutzungszeiten und vermeidet das Auftreten von Diskontinuitäten (Sprüngen) in der Vorhersage. Besonders durch letzteres wird die Akzeptanz des Warnsystems bei den Fluglotsen verbessert.
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Viertel, René, and Gerd Tetzlaff. "Vorhersageverbesserung des Windes im Küstenbereich." Universitätsbibliothek Leipzig, 2017. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-222001.
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Nachdem der weitere Ausbau der Stromerzeugung aus Windenergie an Land an seine Grenzen stösst, rücken die küstennahen Bereiche der Seegebiete in den Mittelpunkt der Planungen. Aufgrund seiner Komplexität sind die Vorhersagen der relevanten Größen im Zeitbereich bis 48 Stunden in diesen Gebieten oftmals ungenau. Mittels systematischer Vergleiche von Prognosen und Messreihen meteorologischer Größen wurde untersucht, ob sich charakteristische Muster der Abweichung der Windprognose von der Messung in Abhängigkeit meteorologischer Größen und Prognosezeit finden und sich die Abweichungen verringern lassenAfter the further development of the generation of current by wind energy on land areas is pushed to the borders the near-shore areas of the see regions moves into the center of plannings. Because of the complex behavior of such areas the prediction of the required meteorological values often becomes uncertain within the forecast range of 48 hours. Measurements of meteorological values and forecasts were compared systematically. By means of this comparisons it was examined, whether characteristical pattern of the deviation between measurements and forcasts, dependent on other meteorological values and forecast time, can be found. The possibility to reduce this deviations was verified
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Weithäuser, Ina, Gunter Stober, Kristina Fröhlich, and Christoph Jacobi. "Untersuchung der Quasi - 2 - Tage Welle im Sommer 2005." Universitätsbibliothek Leipzig, 2017. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-223188.
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Das seit Juli 2004 kontinuierlich arbeitende Meteorradar am Observatorium Collm (53,3°N, 13°E) der Universität Leipzig dient der Messung des horizontalen Windfeldes sowie der Temperatur in der Mesopausenregion. Neben der Betrachtung des jahreszeitlichen Verhaltens von Grund- und Gezeitenwind ist es möglich, die Aktivität planetarer Wellen zu untersuchen. Spezielles Interesse gilt dabei der Quasi-2-Tage Welle im Sommer 2005, da zu dieser Zeit sowohl eine Verschiebung der maximalen Amplituden hin zu kürzeren als auch zu längeren Perioden beobachtbar war. Als mögliche Ursache dafür werden nichtlineare Wechselwirkungen zwischen der Quasi-2-Tage Welle und planetaren Wellen mit größeren Perioden gesehen. Die Untersuchung derartiger Wechselwirkungen erfolgt mit Hilfe der BispektralanalyseSince July 2004 the meteor radar operates continuously at the Observatory (53,3°N, 13°E) of the University of Leipzig. It provides data of the horizontal wind field as well as the temperature of the mesopause region. In addition to the consideration of the seasonal behaviour of prevailing and tidal winds it is possible to examine the activity of planetary waves. Because of the shift of maximum amplitudes of the quasi-2-day wave in summer 2005 to shorter as well as longer periods the event has to be considered more in detail. Possible reasons for the displacements are nonlinear couplings between the quasi-2-day wave and planetary waves with longer periods. The examination of those couplings is performed using bispectral analyses
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Jacobi, Christoph, Peter Hoffmann, and Dierk Kürschner. "Trends and climatic shifts in mesosphere / lower thermosphere planetary waves Collm (52°N, 15°E)." Universitätsbibliothek Leipzig, 2017. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-223160.
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Long-period oscillations in the period range between 2-30 days, interpreted as planetary wave (PW) signatures, have been analysed using daily upper mesosphere/lower thermosphere wind measurements near 90 km over Collm (52°N, 15°E) in the time interval 1980-2005. Strong interannual and interdecadal variability of PW are found. Since the 1990s, a tendency for larger zonal amplitudes compared to meridional ones, has been observed, thus long-term trends are visible, which are positive in the zonal component, but negative in the meridional component. The change appears in a stepwise manner, so that a sudden change of the mean is visible rather than a linear trend. The behaviour of the upper middle atmosphere winds is similar to analysed wave changes in the stratosphere, indicating a coupling of the atmospheric layers through planetary wavesMit Hilfe von täglichen Windmessungen im Mesopausenbereich bei 90 km werden langperiodische Schwankungen im Zeitbereich von 2-30 Tagen untersucht, die als das Signal planetarer Wellen gelten. Im Zeitraum 1980-2005 werden deutliche Schwankungen von Jahr zu Jahr als auch langfristige Trends gefunden. Einer Zunahme der zonalen Komponente der Schwankungen seit 1990 steht eine Abnahme der meridionalen Komponente gegenüber. Diese Änderung erfolgt in rascher Form, so dass sich die Änderung der Zirkulation im Mesopausenbereich als klimatische Verschiebung, und weniger als Trend darstellt. Das Verhalten der Dynamik im Mesopausenbereich korrespondiert mit möglichen Änderungen klimatischer Parameter in anderen Schichten der Atmosphäre und weist auf eine Kopplung atmosphärischer Schichten untereinander hin
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Jacobi, Christoph, and Dierk Kürschner. "Interannual variability of the quasi two-day wave over Central Europe (52°N, 15°E)." Universitätsbibliothek Leipzig, 2017. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-223179.
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Using the spaced receiver method in the low-frequency (LF) range, lower E-region ionospheric drifts are measured at Collm Observatory, Germany since several decades. These drifts are interpreted as upper mesospheric winds at the reflection height of the used amplitude modulated LF radio waves, the latter being measured since 1983 using travel time differences between the ground wave and the ionospherically reflected sky wave within a small sideband range near 1.8 kHz above and below the carrier frequency. One regular feature of midlatitude upper mesosphere winds is the quasi twoday wave (QTDW), known as a wavenumber 3 or 4 wave in the middle atmosphere, usually occurring as one or more bursts during the summer season at midlatitudes. The OTDW bursts, as measured in LF winds, shows substantial decadal and interannual variability. Comparison with the background winds show that the onset of QDTW bursts is found near maximum values of the vertical wind shear, and maximum QTDW amplitudes are measured, on average, about one week after the maximum wind shear. This supports the theory that the QTDW is forced by instability of the summer mesospheric wind jetAm Observatorium Collm werden seit mehreren Jahrzehnten Langwellenwindmessungen in der unteren ionosphärischen E-Schicht durchgeführt. Die zugehörige Reflexionshöhe wird, auf der Basis von Laufzeitdifferenzmessungen zwischen der Raum- und Bodenwelle, seit 1983 ebenfalls registriert. Eines der regelmäßig beobachteten Phänomene ist die quasi 2-Tage-Welle, die als eine planetare Welle der Wellenzahl 3 oder 4 bekannt ist. Diese Welle erscheint in mittleren Breiten in einem oder mehreren Schüben im Sommer. Nach den Messungen am Collm besitzt die Welle eine deutliche Variabilität von Jahr zu Jahr. Vergleiche mit dem zonalen Grundwind zeigen, dass das Auftreten von Maxima der 2-Tage-Welle in vielen Fällen mit erhöhter vertikaler Windscherung in Verbindung steht, so dass im langzeitlichen Mittel maximale Wellenamplituden einige Tage nach dem Auftreten maximaler Windscherung zu finden sind. Dies unterstützt die These, dass die quasi 2-Tage-Welle durch barokline Instabilität des sommerlichen Mesosphärenjets angeregt wird
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Nan, Li. "Methods of drag force measurement in wind tunnels." Thesis, Högskolan i Gävle, Akademin för teknik och miljö, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:hig:diva-13873.
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Wilson, Colin Frank. "Measurement of wind on the surface of Mars." Thesis, University of Oxford, 2003. http://ora.ox.ac.uk/objects/uuid:08343673-77de-4e46-a2fd-5c7c6e3be0e8.
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The Martian atmosphere is of great scientific interest, both because of its similarity to Earth’s atmosphere, and because of its relevance to exploration of Mars. Although satellite instruments have provided a wealth of atmospheric data, they have provided little information about the atmospheric boundary layer. Conditions in the lowest few metres of the Martian atmosphere are perhaps the most directly interesting to humans, as this is the portion of our own atmosphere with which we have the most contact. In this thesis is described the design, calibration and operations planning for a new wind sensor for use on Mars. This sensor is lighter and smaller than previous Mars wind sensors. At the time of writing, the wind sensor is on its way to Mars as part of the science payload of Beagle 2, a small exobiology lander due to arrive in December 2003. The Beagle 2 wind sensor (B2WS) is a hot-film anemometer. Three platinum films are equally spaced around the surface of a vertical cylinder. A known current is dissipated in each film, heating the film 40-80°C above the ambient gas temperature. The film temperature is obtained by measuring its resistance. An effective heat transfer coefficient is then calculated for each film. A novel scheme has been developed which allows calculation of a wind vector from the differences between these heat transfer coefficients, rather than from their average. This makes the measured wind vector less prone to common-mode errors such as uncertainties in air temperature or sky temperature. The sensor was calibrated in a low density wind tunnel, optimised to provide stable winds of air or carbon dioxide at Martian pressures (5 – 10 mbar) and speeds (0.5 – 30 m/s). The flow field in the test section was calculated using analytical and finite element modelling techniques, and validated experimentally using a pitot probe. This facility’s stability and accuracy represent a significant improvement over previous calibration facilities. An analytical model of heat flow in the sensor has been developed in order to permit correction for conditions which may be encountered on Mars, but were not tested for in the wind tunnel. The wind sensor’s performance in a real Martian atmosphere is simulated using wind and temperature data from a previous Mars lander. The position of the wind sensor position at the end of Beagle 2's motorised arm allows several new possibilities for wind measurement on Mars that were unavailable in previous missions. The height of the wind and air temperature sensors can be adjusted to any height between 20 and 95 cm above the ground. The temperature sensor can be scanned horizontally and vertically above the lander to study convective updrafts above the heated lander. Planned operations sequences on Mars are discussed.
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Raabe, Armin, Katja Friedrich, and Holger Fritsch. "Vergleich beobachteter und aus parametrisierten Beziehungen berechneter Windreibungskoeffizienten während eines Sturmes an der Ostseeküste." Universitätsbibliothek Leipzig, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-213400.
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Beobachtete und über parametns1erte Beziehungen berechnete Windreibungs-koeffizienten werden für die Zeit eines Sturms, der in der Zeit zwischen dem 08.07.96 und 11.07.96 an der Ostseeküste tobte, verglichen. Die innerhalb der ufernahen Zone aus Windprofildaten ermittelten Reibungskoeffizienten lassen sich mit weniger als 20% Fehler auch über vorliegende parametrisierten Beziehungen aus einer standardisierten Windgeschwindigkeitsmessung berechnenA comparison between observed and calculated wind drag coefficients were investigated during a storm with wind speeds up to 20 m/s at the Baltic Sea coast between 3th July, 1996 and 1 lth July, 1996. The drag coefficient which was determined from observed wind speeds from wind profile measurements can also be predicted on behalf of parameterised relations with a random error less then 20%
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Fégeant, Olivier. "Noise from wind turbines." Doctoral thesis, KTH, Byggnader och installationer, 2001. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3100.
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A rapid growth of installed wind power capacity is expectedin the next few years. However, the siting of wind turbines ona large scale raises concerns about their environmental impact,notably with respect to noise. To this end, variable speed windturbines offer a promising solution for applications in denselypopulated areas like the European countries, as this designwould enable an efficient utilisation of the masking effect dueto ambient noise. In rural and recreational areas where windturbines are sited, the ambient noise originates from theaction of wind on the vegetation and about the listener's ear(pseudo-noise). It shows a wind speed dependence similar tothat of the noise from a variable speed wind turbine and cantherefore mask the latter for a wide range of conditions.However, a problem inherent to the design of these machines istheir proclivity to pure tone generation, because of theenhanced difficulty of avoiding structural resonances in themechanical parts. Pure tones are deemed highly annoying and areseverely regulated by most noise policies. In relation to thisproblem, the vibration transmission of structure-borne sound tothe tower of the turbine is investigated, in particular whenthe tower is stiffened at its upper end. Furthermore, sincenoise annoyance due to wind turbine is mostly a masking issue,the wind-related sources of ambient noise are studied and theirmasking potentials assessed. With this aim, prediction modelsfor wind-induced vegetation noise and pseudo-noise have beendeveloped. Finally, closely related to the effect of masking,is the difficulty, regularly encountered by local authoritiesand wind farm developers, to measure noise immission from windturbines. A new measurement technique has thus been developedin the course of this work. Through improving thesignal-to-noise ratio between wind turbine noise and ambientnoise, the new technique yields more accurate measurementresults. Keywords: Masking, vibration transmission, diffraction,ambient noise, pseudo-noise, cylindrical shell, perturbationmethods, structural mobility, acoustic outdoor measurement.QC 20100616
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Wang, Yu 1964. "Measurements and multifractal analysis of turbulent temperature and velocity near the ground." Thesis, McGill University, 1995. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=23433.
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High frequency turbulent temperature measurements were performed above clipped grass in the lower atmospheric surface layer in conjunction with three-dimensional turbulent velocities. Measurements were also made of turbulent temperature inside a corn canopy and at the canopy top. The 500Hz temperature time series were collected over periods of varying intervals, to a maximum of 24 hours.The multifractal analysis was performed on several datasets. First scaling properties of the temperature and the velocity fields were examined. Our results suggest that scaling is not observed throughout the entire range but on different regimes. The physically related regimes corresponding to the clipped grass experiment include the inertial subrange, the trend for diurnal peak, and a range between them, all together featuring the existence of the hourly gap. In the canopy experiment, except for the above feature, the effects of the presence of plant objects are also reflected by the presence of two regimes different from those for clipped grass field.
The double trace moment technique was performed on the inertial subrange of the temperature and velocity fields measured over clipped grass to obtain the parameters characterizing the multifractal fields. The variability of the parameters with the atmospheric stability was investigated and no apparent difference between stable and unstable conditions was found. The results reveal that those fields are universal multifractals with the characteristic parameters $ alpha$ near 1.7 and C$ sb1$ ranging from 0.04 to 0.12, implying that the fields can be modeled by a log-Levy process with unbounded singularities. We also found that the critical moment q$ rm sb{s}$ for the multifractal phase transition is close to 4.
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Kerze, David James. "Performance Characteristics of an Innovative Wind Power System." Cleveland State University / OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=csu1203808948.
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Li, Nan. "The methods of drag force measurement in wind tunnels." Thesis, Högskolan i Gävle, Akademin för teknik och miljö, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:hig:diva-13863.
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Horstmann, Jochen. "Measurement of ocean wind fields with synthetic aperture radar." [S.l. : s.n.], 2001. http://deposit.ddb.de/cgi-bin/dokserv?idn=965193853.
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Frame, David J. "Wind measurement and momentum balance in the southern mesosphere." Thesis, University of Canterbury. Physics, 1998. http://hdl.handle.net/10092/5938.
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This thesis makes use of diverse data sets in order to develop an understanding of the dynamics of the upper mesosphere in the region near Birdlings Flat, New Zealand.
Medium frequency radar data from the Birdlings Flat site were obtained for the period between May 1993 and December 1996. When analysed, the data reveal two distinct annually varying patterns of circulation, one of which corresponds to seasonal behaviour characteristic of the upper mesospheric, while the other is part of the lower thermospheric climatology. Time-series of wind data in the upper mesosphere also reveal the presence of a feature, recurring each winter, which appears to be the product of breaking gravity waves acting on the mesospheric jet.
Wind data from the Birdlings Flat radar were compared with wind measurements made by the High-Resolution Doppler Imager aboard the Upper Atmosphere Research Satellite. Data from the two instruments were compared on short time-scales and are discussed with reference to a number of physical parameters, especially proximity of measurement, data reliability and the local hour of observation. Although the small number of satellite overpasses limit the reliability of the conclusions of this comparison, proximity was found to be the most relevant of the three features. Data from the two instruments were also compared on longer time-scales with the intention of avoiding tidal contamination in the comparison. Two approaches to this problem are discussed. In one, the overpasses used in the individual comparisons are binned together according to season, while in the other, the longitudinal restriction was lifted from the satellite instrument, and a sampling period corresponding to a full 24 hours of local time was obtained for both the radar and satellite instruments. This approach gave at least as good agreement as the previous methods.
Radar wind data are also compared with wind data derived from the Improved Stratospheric And Mesospheric Sounder for the month of May 1992. The comparison between the two data sets, in conjunction with other material from this thesis, forms the basis of a study of the effects of gravity wave breaking on the momentum budget of the winter mesosphere in the mid-latitude Southern Hemisphere. Even when the maximum likely uncertainty is added to the magnitude of the monthly mean radar winds, there is still a significant discrepancy between observed and derived winds. This appears as unresolved-scale forcing terms in the atmospheric momentum equations. The unresolved-scale term in the zonal momentum equation is due primarily to the effects of breaking gravity waves, and was calculated to be D = 80 ± 40 ms-1d-1. The large and highly variable value of the unresolved-scale term in the meridional momentum equation, E = 88 ± 120 ms-1d-1 is more complicated, but is likely to incorporate a large contribution from the inter-play of various small-scale curvature terms.
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Osman, Kareem. "Multi-spacecraft measurement of turbulence in the solar wind." Thesis, Imperial College London, 2008. http://hdl.handle.net/10044/1/4258.
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A novel multi-spacecraft technique, applied to measurements made by the four Cluster spacecraft in the solar wind, is used to determine the field-aligned anisotropy of magnetohydrodynamic inertial range turbulence. Time-lagged two-point correlation functions are used to construct spatial auto-correlation functions. These are used in conjunction with a phenomenological elliptical scaling model to estimate the ratio of field-parallel to total correlation lengths, obtaining a mean value of 0.61 ± 0.02. A simulated turbulent field model is also fitted to the spatial auto-correlation functions in order to estimate the power in the 2D fluctuations, obtaining a mean value of (79 ± 3)%. The results obtained from both models, assuming a slab-2D paradigm, are consistent with solar wind fluctuations being anisotropic with energy mainly in wave vectors perpendicular to the mean magnetic field. Eight intervals of multi-point magnetic field data are analysed, and the degree of variation in the estimates of anisotropy about the mean is larger than expected for both models. This variation is not correlated with the solar wind velocity or the plasma beta. However, these anisotropy estimates are correlated between different field components, suggesting that the assumption of axisymmetry is valid. An alternative multi-spacecraft approach, where time-lagged second order structure functions are used to estimate the field-aligned anisotropy of the power levels and the spectral index, is also presented. The mean value obtained for the power in the 2D fluctuations, (93 ± 15)%, is consistent with the simulated turbulent field results, while the observed anisotropy in the spectral index suggests that multiple energy transfer mechanisms are present in solar wind turbulence. Results from all three analysis techniques are discussed and found to be correlated with each other. This suggests that the observed variation in the anisotropy estimates could be a physical effect that different data intervals exhibit different degrees of anisotropy.
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Wilberts, Frauke. "MEASUREMENT DRIVEN FATIGUE ASSESSMENT OF OFFSHORE WIND TURBINE FOUNDATIONS." Thesis, Uppsala universitet, Institutionen för geovetenskaper, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-337960.
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The installed capacity of offshore wind turbines in Europe is increasing with the monopile being the most common type of foundation. During its lifetime an offshore wind turbine is exposed to high dynamic loads which eventually can result in the fatigue of the substructure. This thesis will show how the linear damage accumulation approach based on the Miner’s rule can be used to estimate the damage induced on the substructure of an offshore wind turbine using measurements from strain gauges. Furthermore, the most important environmental influences will be illustrated and the different stress concentration factors and the size effect introduced in the industry guideline DNVGL-RP-C203 will be analysed towards their effect on the calculated lifetime.
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Hobbs, mark. "Aeroelastic analysis of a yacht rig." Thesis, University of Southampton, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.342816.
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Tetzlaff, Gerd, and Uwe Hoppmann. "Die Leistung von AEOLUS II in Abhängigkeit von mittlerem Windprofil und Turbulenz im Bereich der Rotorfläche." Universitätsbibliothek Leipzig, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-212831.
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Synchrone Messungen der Windgeschwindigkeit und die Leistung von Windkraftanlagen dienen der Ermittlung der Kennlinien der Anlagen. Die existierenden Vorschriften zur Vermessung enthalten bezüglich der Strömungseigenschaften des Windes nahezu keine Spezifikationen. Diese sind jedoch notwendig, um die erreichbare Genauigkeit und Repräsentativität der vermessenen Kennlinie zu quantifizieren. Messungen am Standort der AEOLUS II-Anlage in Wilhelmshaven dienten dazu, bei einer Anlagenvermessung die Eigenschaften der Strömung und die Kennlinie gemeinsam zu untersuchen. Es wurde gefunden, daß die Strömungseigenschaften wie die vertikale Windscherung, die Winddrehung über der Höhe, die turbulenten Schwankungen der Windgeschwindigkeit und der Windrichtung die Leistung von Windenergieanlagen bei gleicher mittlerer Windgeschwindigkeit erheblich verändern. Dabei wirken sowohl Standorteigenschaften als auch die Witterung auf die Ergebnisse der Vermessung. Am gleichen Standort können in anisotropem Gelände die Werte der Kennlinie auch bei mehrmonatigen Vermessungen wegen der Variabilität der Windrichtung Unterschiede von mehr als 10 % aufweisen. Der größte Einzeleffekt wird von der vertikalen Windscherung verursacht, die Wirkung der Drehung des mittleren Windvektors über der Rotorfläche ergab sich als kleinerer Effekt. Die Wirkung der turbulenten Schwankungen von Geschwindigkeit und Richtung weisen meist unterschiedliche Vorzeichen auf, so daß die Rolle dieser Schwankungen insgesamt meist klein bleibt. Die Vermessung einer Kennlinie mit einer kleineren systematischen Abweichung von im Mittel weniger als etwa 5 bis 10 % erfordert eine genaue Strömungsspezifikation sowohl für den Vermessungs- als für den Betriebsstandort, die bisher nicht in hinreichendem Maße in den entsprechenden Richtlinien und Vorschriften enthalten sindPower curves ofwind energy convetras need synchronous measurements of wind and power. The existing specification on the wind measurements are rather poor, however necessary. AEOLUS II-measurments and the wind measurments served to quantify the role of the different atmospheric parameters. Thus it was possible to define the influence on the power output of the machine as a function of the vertical wind shear, the wind veer with height, the turbulent fluctuations with the average wind speed being constant. As a consequence site properties and weather conditions both influence the measurements of the power curve. As a major result it was found that these factors may alter the power curve by as much as 10 %. The largest single effect is produced the effects of the vertical wind shear, The turbulent fluctuations are somewhat smaller in their effect, because speed and direction effects tend to compensate each other. lt may be concluded that a highly accurate power curve - meaning errors to be less than 10 % - requires a fully specified set of weather and site parameters
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Oram, C. E. "Aerodynamic surface pressure measurement in atmosphere and wind tunnel on a vertical axis wind turbine blade using pressure transducers." Thesis, Cranfield University, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.375937.
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Scott, Ryan. "Characterizing Tilt Effects on Wind Plants." PDXScholar, 2019. https://pdxscholar.library.pdx.edu/open_access_etds/5035.
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Tilting the nacelle of a wind turbine modifies entrainment into the wind plant and impacts total efficiency. Extreme angles can produce flying and crashing wakes where the wake either disrupts entertainment from the undisturbed flow above or is decimated on the ground. The effect of tilt angle on downstream wake behavior was investigated in a series of wind tunnel experiments. Scale model turbines with a hub height and diameter of 12 cm were arranged in a Cartesian array comprised of four rows of three turbines each. Nacelle tilt was varied in the third row from -15° to 15° in chosen 5° increments. Stereo PIV measurements of the instantaneous velocity field were recorded at four locations for each angle. Tilted wakes are described in terms of the average streamwise velocity field, wall-normal velocity field, Reynolds stresses, and mean vertical transport of kinetic energy. Conditional sampling is used to quantify the importance of sweep vs. ejection events and thus downwards vs. upwards momentum transfer. Additionally, wake center displacement and changes in net power are presented and compared to existing models. The results demonstrate large variations in wake velocity and vertical displacement with enhanced vertical energy and momentum transfer for negative tilt angles. Simulation models accurately predict wake deflection while analytic models deviate considerably highlighting the difficulties in describing tilt phenomena. Negative angles successfully produce crashing wakes and improve the availability of kinetic energy thereby improving the power output of the wind plant.
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Kumaraperumal, K. Ayyapan N. "Modelling and measurement of wind-driven rain on building facades." Thesis, Glasgow Caledonian University, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.517932.
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Jones, Gregory Stephen. "The measurement of wind tunnel flow quality at transonic speeds." Diss., Virginia Tech, 1991. http://hdl.handle.net/10919/39109.
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The measurement of wind tunnel flow quality for the transonic flow regime has been plagued by the inability to interpret complex unsteady flow field information obtained in the free stream. Traditionally hot wire anemometry and fluctuating pressure techniques have been used to quantify the unsteady characteristics of a wind tunnel. This research focuses on the application of these devices to the transonic flow regime.
Utilizing hot wire anemometry, one can decompose the unsteady flow field with a three sensor technique, to obtain fluctuations associated with the velocity, density, and total temperature. Implementing thermodynamic and kinematic equations, new methods for expanding the measured velocity, density, and total temperature fluctuations to obtain additional fluctuations are investigated. The derived static pressure fluctuations are compared to the static pressure fluctuations obtained with a conventional fluctuating static pressure probe. The results of this comparison are good, which implies that the individual velocity, density, and total temperature components are time accurate.
In the process of obtaining a high quality fluctuating flow field information, it was necessary to evaluate the calibration of the hot wire sensors. A direct calibration approach was compared to a conventional non-dimensional technique. These two calibration techniques should have resulted in the same hot wire sensitivities. There were significant differences in the hot wire sensitivities as obtained from the two approaches. The direct approach was determined to have less errors due to the added heat transfer information required of the indirect approach. Both calibration techniques demonstrated that the velocity and density sensitivities were in general not equal. This suggests that the velocity and density information cannot be combined to form a mass flow. A comparison of several hot wire techniques was included to highlight the errors obtained when assuming that these sensitivities are the same.
An evaluation of the free stream flow quality associated with a Laminar Flow Control experiment was carried out in the Langley Research Center 8-Foot Transonic Pressure Tunnel (8' TPT). The facility was modified with turbulence manipulators and a liner that provided a flow field around a yawed super-critical airfoil that is conducive to transition research. These devices are evaluated to determine the sources of disturbances associated with the LFC experiment.Ph. D.
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Sharp, David Brian. "Acoustic pulse reflectometry for the measurement of musical wind instruments." Thesis, University of Edinburgh, 1996. http://hdl.handle.net/1842/14396.
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The bore profile and input impedance of a musical wind instrument provide valuable information about its acoustical properties. The time domain technique of acoustic pulse reflectometry can be used to measure the input impulse response of a tubular object, such as a wind instrument, from which both its bore profile and input impedance can be calculated. In this thesis, after a discussion of the theory of acoustic pulse reflectometry, the operation of a practical reflectometer is described and measurements of input impulse response, bore profile and input impedance are investigated. In general, the experimentally measured input impulse response of a tubular object contains a DC offset which must be removed for accurate bore reconstruction. A new, faster method of determining the DC offset is introduced which doesn’t require prior knowledge of the object’s dimensions. The bore profile of a test object, calculated by applying a lossy reconstruction algorithm to its input impulse response (after removal of the DC offset), is found to agree with directly measured radii to within 0.05mm. Various brass instrument reconstructions of similar accuracy are presented. An input impedance curve, calculated from the input impulse response of the test object, is found to have peak frequencies which agree with those of a theoretical curve to within 0.7% (a considerably better agreement than when a standard frequency domain measurement technique is used). Impedance curves of various brass instruments are presented. Bore reconstructions are used to confirm the presence, and in certain cases, the positions of leaks in instruments. For the special case of a leaking cylinder, the impedance curve is successfully used to calculate the size of the leak. Finally, a method is investigated which allows the practical reflectometer to measure longer objects than previously possible.
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Hinneburg, Detlef. "The calculation of a wind climatology of the Erzgebirge." Universitätsbibliothek Leipzig, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-212336.
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Ausgangspunkt für die Berechnung klimatologisch gemittelter Windgeschwindigkeiten ist die mesoskalige Simulation atmosphärischer Strömungsereignisse, die von der geostrophischen Windgeschwindigkeit gesteuert werden. Der geostrophische Wind wird in 8 Richtungssektoren und Betragsklassen zu je 5m/s eingeteilt, so daß für jeden Sektor bis zu 7 Simulationen auszuführen waren. Die Simulationen wurden mit dem nicht-hydrostatischen Modell GESIMA für eine adiabatisch geschichtete Atmosphäre durchgeführt. Die statistische Mittelung der berechneten Werte erfolgte mit Hilfe einer 10-jährigen Häufigkeitsverteilung des 850hPa-Windes der Radiosondenmessungen von Prag. Ein Vergleich mit den Beobachtungswerten einiger Bodenstationen ergibt Abweichungen bis zu lm/s über höheren BergenStarting from the classification of the geostrophic wind into 8 sectors each of them splitted up into 7 classes by 5m/s, simulations with the non-hydrostatic mesoscale atmospheric model GESIMA were performed assuming adiabatic stratification of the atmosphere for each class. The climatologically averaged wind velocities are obtained by the folding with a ten-years frequency distribution of the geostrophic wind measured by the radio sonde station of Prague. Wind velocities observed at some surface stations indicate, that the simulated values can deviate from them by up to lm/s on high mountains
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Stober, Gunter, Christoph Jacobi, and Dierk Kürschner. "Mesopause region temperatures over Collm (51.3° N, 13° E)." Universitätsbibliothek Leipzig, 2017. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-221943.
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Seit August 2004 wird am geophysikalischen Observatorium Collm (51.3° N, 13° E) ein SKiYMET Meteor-Radar betrieben. Dieses liefert seitdem kontinuierliche Temperaturwerte und Windmessungen. Die Grundlage des Messverfahrens stellt ein stetiger Fluss von Meteoren dar, die in einer Höhe von 75-105 km verglühen. Aus den mit dem Radar bestimmten Positionen der Meteore können Temperaturen in der Mesopausenregion abgeschätzt werden. Für die Darstellung des Jahresganges wurden Tagesmittelwerte genutzt. Dabei tritt im Sommer ein Temperaturminimum mit ca. 170 K auf. Im Winter ist die Situation durch Temperaturen von 205 K und starker planetarer Wellenaktivität gekennzeichnet. Desweiteren konnte eine Klimatologie für die ganz-, halbtägigen und 8-stündigen Gezeiten erstellt werdenSince August 2004 a SKiYMET meteor-Radar is operated at the geophysical Observatory Collm, Germany (51.3° N, 13° E). The radar provides a continuous time series of temperature and wind measurements. The bases for this method is a steady flux of meteors entering the earth’s atmosphere. In an altitude between 75-105 km they form a cylindrical plasma trail, which reflects radar signals. Hence the system can determine the positions of the meteors, which are used to estimate mesopause region temperatures. For the diagram of the seasonal change we used daily mean temperatures. The summer shows a temperature minimum with 170 K. During the Winter we observed temperatures about 205 K and a stronger planetary wave activity. Another part was the generation of a climatology for the diurnal, semidiurnal und terdiurnal tide
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Fröhlich, Kristina, Alexander I. Pogoreltsev, Christoph Jacobi, and L. A. Nechaeva. "The influence of NCEP-data assimilated into COMMA-LIM on the 16-day wave." Universitätsbibliothek Leipzig, 2017. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-223197.
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The general circulation model COMMA-LIM solves the primitive equations on a sphere using gridpoints. The relative large interval between adjacent gridpoints (5° × 5.6° latitude versus longitude) causes an incorrect meridional temperature gradient in the coarsly resolved troposphere that leads to too weak winds there, particularly in the lower winter stratosphere above the polar region. By using the technique of nudging 11-year averaged NCEP zonal mean temperature data were assimilated into COMMA-LIM. This means that longitudinal dependent processes as calculated by the model still influence the atmosphere. The nudging method has improved not only the lower atmosphere, but also the middle atmospheric jets show a more realistic behaviour. A numerical experiment by forcing the 16-day wave was carried out in order to investigate the influence of an improved background circulation on the vertical propagation of planetary wavesDas globale Zirkulationsmodell COMMA-LIM berechnet die primitiven Gleichungen auf einem Kugelgitter. Der relativ große Gitterabstand von 5°× 5.6° in Breite und Länge und die grobe vertikale Auflösung führen zu einem inkorrekten meridionalen Temperaturgradienten in der Troposphäre, so dass die troposphärischen Jets und der polare Winterwirbel zu schwach ausgeprägt sind. Mit Hilfe der Methode des Nudging wurden in den unteren 30 km der Atmosphäre 11-Jahres gemittelte NCEP Reanalysedaten des Temperaturfeldes assimiliert. Dabei wurde nur der zonale Mittelwert der berechneten Temperatur an die Reanalysedaten relaxiert, so dass die Antriebsterme, die von COMMA-LIM berechnet werden, erhalten bleiben. Durch diese Methode wurden Wind- und Temperaturfeld sowohl in der Troposphäre als auch in der mittleren Atmosphäre verbessert. Ein Experiment zur Ausbreitung der 16-Tage Welle wurde unter den neuen Bedingungen durchgeführt, und der Einfluß der veränderten Atmosphäre auf die vertikale Wellenausbreitung wurde untersucht
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Butler, George D. Jr, and T. J. Henneberry. "Sweetpotato Whitefly: Flight Activity, Effects of Wind Velocity, and Precopulatory Pairing Activity Patterns." College of Agriculture, University of Arizona (Tucson, AZ), 1992. http://hdl.handle.net/10150/208650.
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Sweetpotato whitefly (SPW), Bemisia tabaci (Gennadius), exhibited high levels of flight activity during daylight hours from July to September. Flight activity in a fallow field in Arizona in late August began as early as 0600 h, peaked between 0800 and 0900 h, and decreased thereafter during the day. Flight activity in cultivated cotton, lettuce and alfalfa fields also occurred throughout the day in early and late September. Few SPW were caught between 1900 and 0700 h. Peak numbers were caught on sticky traps prior to 1200 h in Arizona and Israel. Numbers of adults caught on sticky traps decreased from 0700 to 1000 h and with increasing wind velocity. Precopulatory pairing behavior occurred as early as 0700 h and increased gradually to 0900 to 0920 h, when 48% of the adults observed were paired, and decreased thereafter.
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Mulkens, M. J. M. "Measurement of aerodynamic stability derivatives using a whirling arm facility." Thesis, Cranfield University, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.359563.
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Weithäuser, Ina, Gunter Stober, Kristina Fröhlich, and Christoph Jacobi. "Untersuchung der Quasi - 2 - Tage Welle im Sommer 2005." Universität Leipzig, 2007. https://ul.qucosa.de/id/qucosa%3A15568.
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Das seit Juli 2004 kontinuierlich arbeitende Meteorradar am Observatorium Collm (53,3°N, 13°E) der Universität Leipzig dient der Messung des horizontalen Windfeldes sowie der Temperatur in der Mesopausenregion. Neben der Betrachtung des jahreszeitlichen Verhaltens von Grund- und Gezeitenwind ist es möglich, die Aktivität planetarer Wellen zu untersuchen. Spezielles Interesse gilt dabei der Quasi-2-Tage Welle im Sommer 2005, da zu dieser Zeit sowohl eine Verschiebung der maximalen Amplituden hin zu kürzeren als auch zu längeren Perioden beobachtbar war. Als mögliche Ursache dafür werden nichtlineare Wechselwirkungen zwischen der Quasi-2-Tage Welle und planetaren Wellen mit größeren Perioden gesehen. Die Untersuchung derartiger Wechselwirkungen erfolgt mit Hilfe der Bispektralanalyse.Since July 2004 the meteor radar operates continuously at the Observatory (53,3°N, 13°E) of the University of Leipzig. It provides data of the horizontal wind field as well as the temperature of the mesopause region. In addition to the consideration of the seasonal behaviour of prevailing and tidal winds it is possible to examine the activity of planetary waves. Because of the shift of maximum amplitudes of the quasi-2-day wave in summer 2005 to shorter as well as longer periods the event has to be considered more in detail. Possible reasons for the displacements are nonlinear couplings between the quasi-2-day wave and planetary waves with longer periods. The examination of those couplings is performed using bispectral analyses.