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1
Yanovych, Viatlii, and Daniel Duda. "Using ARAMIS system for measurement of structural stability of running wind tunnel." MATEC Web of Conferences 328 (2020): 01003. http://dx.doi.org/10.1051/matecconf/202032801003.
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Wind tunnels are popularly used to study various aerodynamic phenomena. Their design significantly influences the quality of the created airflow. During the flow generation, the construction parts of the wind tunnel to get deformed due to pressure variations. This phenomenon significantly complicates the creation of high-level laminar flow and worsens the results of experimental studies. The main purpose of this work is to investigate the effect of a sharp change in flow velocity on the structural stability of parts of a wind tunnel with a capacity of 55 kW. For experimental studies, we used the ARAMIS optical measurement system. Using it, we estimated the amount of deformation and mutual displacement of parts of the running wind tunnel at a flow rate of 76 m·s-1.
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Liu, Shanhe, Zhiwen Luo, Keer Zhang, and Jian Hang. "Natural Ventilation of a Small-Scale Road Tunnel by Wind Catchers: A CFD Simulation Study." Atmosphere 9, no. 10 (October 20, 2018): 411. http://dx.doi.org/10.3390/atmos9100411.
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Providing efficient ventilation in road tunnels is essential to prevent severe air pollution exposure for both drivers and pedestrians in such enclosed spaces with heavy vehicle emissions. Longitudinal ventilation methods like commercial jet fans have been widely applied and confirmed to be effective for introducing external fresh air into road tunnels that are shorter than 3 km. However, operating tunnel jet fans is energy consuming. Therefore, for small-scale (~100 m–1 km) road tunnels, mechanical ventilation methods might be highly energetically expensive and unaffordable. Many studies have found that the use of wind catchers could improve buildings’ natural ventilation, but their effect on improving natural ventilation in small-scale road tunnels has, hitherto, rarely been studied. This paper, therefore, aims to quantify the influence of style and arrangement of one-sided flat-roof wind catchers on ventilation performance in a road tunnel. The concept of intake fraction (IF) is applied for ventilation and pollutant exposure assessment in the overall tunnel and for pedestrian regions. Computational fluid dynamics (CFD) methodology with a standard k-epsilon turbulence model is used to perform a three-dimensional (3D) turbulent flow simulation, and CFD results have been validated by wind-tunnel experiments for building cross ventilation. Results show that the introduction of wind catchers would significantly enhance wind speed at pedestrian level, but a negative velocity reduction effect and a near-catcher recirculation zone can also be found. A special downstream vortex extending along the downstream tunnel is found, helping remove the accumulated pollutants away from the low-level pedestrian sides. Both wind catcher style and arrangement would significantly influence the ventilation performance in the tunnel. Compared to long-catcher designs, short-catchers would be more effective for providing fresh air to pedestrian sides due to a weaker upstream velocity reduction effect and smaller near-catcher recirculation zone. In long-catcher cases, IF increases to 1.13 ppm when the wind catcher is positioned 240 m away from the tunnel entrance, which is almost twice that in short-catcher cases. For the effects of catcher arrangements, single, short-catcher, span-wise, shifting would not help dilute pollutants effectively. Generally, a design involving a double short-catcher in a parallel arrangement is the most recommended, with the smallest IF, i.e., 61% of that in the tunnel without wind catchers (0.36 ppm).
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Nosek, Štěpán, Zbyněk Jaňour, David Janke, Qianying Yi, André Aarnink, Salvador Calvet, Mélynda Hassouna, Michala Jakubcová, Peter Demeyer, and Guoqiang Zhang. "Review of Wind Tunnel Modelling of Flow and Pollutant Dispersion within and from Naturally Ventilated Livestock Buildings." Applied Sciences 11, no. 9 (April 22, 2021): 3783. http://dx.doi.org/10.3390/app11093783.
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Ammonia emissions from naturally ventilated livestock buildings (NVLBs) pose a serious environmental problem. However, the mechanisms that control these emissions are still not fully understood. One promising method for understanding these mechanisms is physical modelling in wind tunnels. This paper reviews studies that have used this method to investigate flow or pollutant dispersion within or from NVLBs. The review indicates the importance of wind tunnels for understanding the flow and pollutant dispersion processes within and from NVLBs. However, most studies have investigated the flow, while only few studies have focused on pollutant dispersion. Furthermore, only few studies have simulated all the essential parameters of the approaching boundary layer. Therefore, this paper discusses these shortcomings and provides tips and recommendations for further research in this respect.
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Meyer, O., W. Nitsche, and I. Futterer. "Numerical and experimental investigations on the reduction of wind tunnel wall interference by means of adaptive slots." Aeronautical Journal 105, no. 1052 (October 2001): 571–80. http://dx.doi.org/10.1017/s0001924000012513.
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Abstract The flow in many wind tunnel experiments is affected by the presence of test section walls. The resulting interference can be minimised by correcting the measured model pressures, or by influencing the model flow directly with the use of ventilated or adaptive test section walls. The objective behind the latter technique is to guide the flow in the test section to achieve low interference (i.e. free flow) condition at the model. The most successful technique of flexible, adaptive walls is still restricted to small research wind tunnels due to its mechanical complexity. However, a very promising alternative is the use of adaptive slots in the test section walls. This concept combines the method of passive slotted walls, as they are already implemented in many large wind tunnels, and flexible walls. Additionally, this technique presents the opportunity of full 3D adaptations because the slots can be situated in all four test section walls. This paper presents preliminary experimental results and the latest numerical calculations on the effectiveness of adaptive slots. The experiments were conducted under high subsonic flow conditions in the new slotted test section of the transonic wind tunnel at TU Berlin’s Aeronautical Institute (ILR). The numerical results presented are focussed on the 2D slot adaptation of a 2D-model (CAST7 aerofoil) and the 3D slot adaptation of a body of revolution (3D-ETB). In addition, basic studies were made of the flows associated with a single slot on one wall and a bump on the other. The numerical and the first experimental investigations have shown the potential of adaptive slots to reduce wall interferences effectively. The adaptation accuracy of the investigated slot configurations deviated not more than 3% from the reference case (2D-wall adaptation).
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Mwachugha, Alfred Gift, Jean Byiringiro, Harrison Ngetha, Thomas Carolus, and Kathrin Stahl. "Experimental Investigation of a Prandtl Probe Fabricated Using Desktop Stereolithography Technology." European Journal of Engineering Research and Science 5, no. 10 (October 30, 2020): 1274–80. http://dx.doi.org/10.24018/ejers.2020.5.10.2202.
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A Prandtl probe is one of the standard instruments used for flow characterization in wind tunnel facilities. The convectional fabrication method of this instrument requires skilled artisanship, precision drilling, lathing and soldering of its several parts. This reflects into high costs of production in turn making wind energy studies expensive. With the adoption of additive manufacturing, the tooling costs, skills required and design to manufacture constraints can be addressed. This research presents a Prandtl probe that was designed using NX™ software, fabricated by desktop stereolithography additive manufacturing platform and validated in a wind tunnel for velocity range of 0 m/s to 51 m/s. This research attested the option of fabricating relatively cheap functional Prandtl probe with desktop stereolithography technology which can be used for accurate determination of flow quality in wind tunnels experiments. This provides various learning and research institution in developing countries that have already invested in additive desktop manufacturing technology certainty and a cheaper option to fabricate wind research instruments for use at their laboratories. Moreover, fabrication and validation of a 5-hole Prandtl probe can also be examined.
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Wang, Yansen, Jonathan Decker, and Eric R. Pardyjak. "Large-Eddy Simulations of Turbulent Flows around Buildings Using the Atmospheric Boundary Layer Environment–Lattice Boltzmann Model (ABLE-LBM)." Journal of Applied Meteorology and Climatology 59, no. 5 (May 2020): 885–99. http://dx.doi.org/10.1175/jamc-d-19-0161.1.
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ABSTRACTA three-dimensional, prognostic Atmospheric Boundary Layer Environment–Lattice Boltzmann Model (ABLE-LBM) using the multiple-relaxation-time lattice Boltzmann method was developed for large-eddy simulation of urban boundary layer atmospheric flows. In this article we describe the details of the ABLE-LBM for urban flow, its implementation of complex boundaries, and the subgrid turbulence parameterizations. As a first validation of this newly developed model, the simulation results were evaluated with two wind-tunnel datasets that were collected using particle image velocimetry and Irwin probes, respectively. The ABLE-LBM simulations use the same building layout and Reynolds numbers used in the laboratory wind tunnels. The ABLE-LBM simulations compare favorably to both laboratory studies in terms of the mean wind fields. The turbulent fluxes simulated by the model in the observational planes also agreed reasonably well with the laboratory results. The model produced urban canyon flows and vortices on the lee side and over the building tops that are similar to those of the laboratory studies in strength and location. This validation study using laboratory data indicates that our new ABLE-LBM is a viable approach for modeling atmospheric turbulent flows in urban environments. A numerical implementation using a graphics processing unit shows that real-time simulations are achieved for these two validation cases.
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Flay, R. G. J., and P. S. Jackson. "Flow simulations for wind-tunnel studies of sail aerodynamics." Journal of Wind Engineering and Industrial Aerodynamics 44, no. 1-3 (October 1992): 2703–14. http://dx.doi.org/10.1016/0167-6105(92)90064-h.
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Ohya, Y., M. Tatsuno, Y. Nakamura, and H. Ueda. "A thermally stratified wind tunnel for environmental flow studies." Atmospheric Environment 30, no. 16 (August 1996): 2881–87. http://dx.doi.org/10.1016/1352-2310(95)00256-1.
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Wagner, Alexander, Erich Schülein, René Petervari, Klaus Hannemann, Syed R. C. Ali, Adriano Cerminara, and Neil D. Sandham. "Combined free-stream disturbance measurements and receptivity studies in hypersonic wind tunnels by means of a slender wedge probe and direct numerical simulation." Journal of Fluid Mechanics 842 (March 13, 2018): 495–531. http://dx.doi.org/10.1017/jfm.2018.132.
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Combined free-stream disturbance measurements and receptivity studies in hypersonic wind tunnels were conducted by means of a slender wedge probe and direct numerical simulation. The study comprises comparative tunnel noise measurements at Mach 3, 6 and 7.4 in two Ludwieg tube facilities and a shock tunnel. Surface pressure fluctuations were measured over a wide range of frequencies and test conditions including harsh test environments not accessible to measurement techniques such as Pitot probes and hot-wire anemometry. A good agreement was found between normalized Pitot pressure fluctuations converted into normalized static pressure fluctuations and the wedge probe readings. Quantitative results of the tunnel noise are provided in frequency ranges relevant for hypersonic boundary-layer transition. Complementary numerical simulations of the leading-edge receptivity to fast and slow acoustic waves were performed for the applied wedge probe at conditions corresponding to the experimental free-stream conditions. The receptivity to fast acoustic waves was found to be characterized by an early amplification of the induced fast mode. For slow acoustic waves an initial decay was found close to the leading edge. At all Mach numbers, and for all considered frequencies, the leading-edge receptivity to fast acoustic waves was found to be higher than the receptivity to slow acoustic waves. Further, the effect of inclination angles of the acoustic wave with respect to the flow direction was investigated. An inclination angle was found to increase the response on the wave-facing surface of the probe and decrease the response on the opposite surface for fast acoustic waves. A frequency-dependent response was found for slow acoustic waves. The combined numerical and experimental approach in the present study confirmed the previous suggestion that the slow acoustic wave is the dominant acoustic mode in noisy hypersonic wind tunnels.
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Tesař, Václav. "Wind tunnel for studies of latent heat storage." EPJ Web of Conferences 180 (2018): 02108. http://dx.doi.org/10.1051/epjconf/201818002108.
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When a heated solid body temperature reaches the melting point, temperature stops increasing and remains constant until the whole body is completely molten. The heat input during this melting is spent on freeing the body molecules. This latent heat of melting remains inside the body and may be released when the body is cooled and solidifies. This heat was suggested, already several decades ago, for storing thermal energy. The advantage it offers is avoiding high temperature differences - which otherwise decrease effectiveness of storage (by inevitable heat escape by conduction). Also the mass of the body needed to store a given amount of heat is much smaller. For investigations of the melting and solidification processes a special wind tunnel has been designed and is being built in this study. The tested sample of phase change material, encapsulated in a spherical shell, will be exposed in the tunnel to recirculating hot air flow in a 140 mm x 140 mm test section. Sudden decrease in air flow temperature is made by shifting away the whole closed-circuit part of the tunnel and exposing the test section to flow of cold (room temperature) air.
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SKEWS, B. W. "Three-dimensional effects in wind tunnel studies of shock wave reflection." Journal of Fluid Mechanics 407 (March 25, 2000): 85–104. http://dx.doi.org/10.1017/s002211209900765x.
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This paper concentrates on establishing the three-dimensional flow geometry associated with studies of shock wave reflection between two symmetrical wedges in supersonic flow. It considers the issue of hysteresis in such flows, and draws a distinction between three different aspects of hysteresis, associated with: ideal two-dimensional flow, flow with noise, and three-dimensional effects. The three-dimensional nature of the flow field is elucidated by the use of oblique shadowgraph photography where the optical axis of the shadowgraph system passes at an oblique angle, of as much as 55°, through the test section. The traces of the wave system reflecting off the tunnel window are identified and are used to assist in identification of wave profiles. The nature of the approach of the peripheral Mach reflections collapsing towards the centre of the flow becomes evident, as does the mechanism of transition from Mach reflection to regular reflection. Distinct evidence of the effects of flow perturbations at the mechanical equilibrium transition point are presented, as are changes in the rate of growth of the Mach stem near this point.It is shown that three-dimensional effects can have a major effect on the wedge angle for transition. In the present tests, at Mach 3.1 and a wedge aspect ratio of 0.5, this occurs at a wedge angle of about 5° higher than the theoretical maximum for the corresponding two-dimensional flow, where the dual solution domain extends over only two degrees.
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Bienkiewicz, B., and J. E. Cermak. "A flow visualization technique for low-speed wind-tunnel studies." Experiments in Fluids 5, no. 3 (1987): 212–14. http://dx.doi.org/10.1007/bf00298465.
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Weber, Johannes, Sebastian Riedel, Julian Praß, Andreas Renz, Stefan Becker, and Jörg Franke. "Effect of Boundary Layer Tripping on the Aeroacoustics of Small Vertical Axis Wind Turbines." Advanced Engineering Forum 19 (October 2016): 3–9. http://dx.doi.org/10.4028/www.scientific.net/aef.19.3.
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Small wind turbines are investigated as a possible solution for using wind energy at small scales in urban and suburban areas. Most turbines are suffering from a low aerodynamic performance due to turbulent and complex wind situations in cities. Therefore, increasing aerodynamic performance and reducing noise is an important factor to design small wind turbines. In order to optimize such turbines with respect to noise and efficiency it is important to understand the physical mechanisms. Measuring acoustic in urban environment it is hardly possible to obtain reproducible results, which are necessary for a comprehensively and profoundly investigation. Therefore, experimental studies have to been performed in anechoic wind tunnels. Those tunnels are mostly limited in size, which makes it quite difficult to investigate full small wind turbine models. Hence a model scale has to be used in order to measure the power and acoustic performance. For comparing the model scale results with original turbines, the same flow conditions around the airfoils are necessary. Due to the smaller size of the model scale the relative velocities of the blades are less, which can result in a laminar boundary layer. In order to force transition from laminar to turbulent, boundary layer trips can be used. The focus of this study is to examine and quantify the effect of boundary layer tripping on the aeroacoustics in case of small vertical axis wind turbines.
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Roach, P. E. "A new boundary layer wind tunnel." Aeronautical Journal 92, no. 916 (July 1988): 224–29. http://dx.doi.org/10.1017/s000192400001616x.
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Summary The procedures employed for the design of a closed-circuit, boundary layer wind tunnel are described. The tunnel was designed for the generation of relatively large-scale, two-dimensional boundary layers with Reynolds numbers, pressure gradients and free-stream turbulence levels typical of the turbomachinery environment. The results of a series of tests to evaluate the tunnel performance are also described. The flow in the test section is shown to be highly uniform and steady, with very low (natural) free-stream turbulence intensities. Measured boundary layer mean and fluctuating velocity profiles were found to be in good agreement with classical correlations. Test-section free-stream turbulence intensities are presented for grid-generated turbulence: agreement with expectation is again found to be good. Immediate applications to the tunnel include friction drag reduction and boundary layer transition studies, with future possibilities including flow separation and other complex flows typical of those found in gas turbines.
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Al-Nehari, Hamoud A., Ali K. Abdel-Rahman, Abd El-Moneim Nassib, and Hamdy M. Shafey. "DESIGN AND CONSTRUCTION OF A WIND TUNNEL FOR ENVIRONMENTAL FLOW STUDIES." JES. Journal of Engineering Sciences 38, no. 1 (January 1, 2010): 177–93. http://dx.doi.org/10.21608/jesaun.2010.123800.
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Uzu-Kuei, Hsu, Tai Cheng-Hsien, HSU Chia-Wei, and Miau Jiun-Jih. "Numerical Studies on a NACA0018 Airfoil Blade HAWT with Trailing Edge Jet Flow." E3S Web of Conferences 64 (2018): 07008. http://dx.doi.org/10.1051/e3sconf/20186407008.
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This study analyzed an airfoil blade for a horizontal-axis wind turbine (HAWT) with a trailing-edge jet flow design. This design was realized by drilling a hole in the trailing edge of an NACA0018 blade of a conventional HAWT to serve as a pressure injection nozzle. Five inflow wind speeds and three trailing-edge jet flow conditions were examined in the test. The results revealed the efficiency differences between a HAWT with the new jet flow design and conventional HAWTs. The experimental methods employed involved a wind tunnel experiment and a computational fluid dynamics (CFD) simulation. The results revealed that when the inflow wind speed was low, the trailing-edge jet flow accelerated the initiation phase and increased the rotating speed of the HAWT; however, when the inflow wind speed was high, damping occurred and the rotating speed of the turbine blades decreased.
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Hung, Nguyen Manh, and Hoang Thi Bich Ngoc. "Experimental study of laminar separation phenomenon combining with numerical calculations." Vietnam Journal of Mechanics 33, no. 2 (June 10, 2011): 95–104. http://dx.doi.org/10.15625/0866-7136/33/2/41.
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The separation is much more sensitive for laminar flow than for turbulent flow. These remarks have been attested for both subsonic and supersonic flows. However, they are not applicable to transonic flows when there are interactions between boundary layer and shock wave. Along with the Reynolds number, the Mach number is a necessary dimensionless parameter for the condition and the mechanism of separations. The report presents one part of studies on laminar separation with Mach number of incompressible flow. The laminar regimes correspond to flows through wind turbine blades. Our experimental work for laminar separation phenomenon was carried out in a subsonic open circuit wind tunnel by taking photographs. The accuracy of experimental results basically depends on the accuracy of wind tunnel and the quality of smoke on density and constitutive materials. Experimental results permit to determine the position of separation and the form of turbulent region followed from the separation point. Numerical studies were simultaneously realized. Based on obtained experimental and numerical results, the report presents also the comparison between the laminar separation and the turbulent separation.
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Groth, Johan, and Arne V. Johansson. "Turbulence reduction by screens." Journal of Fluid Mechanics 197 (December 1988): 139–55. http://dx.doi.org/10.1017/s0022112088003209.
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Turbulence suppression by use of screens was studied in a small wind tunnel especially designed and built for the purpose. Wide ranges of mesh sizes and wire-diameter Reynolds numbers were covered in the present investigation, enabling the study of sub- and super-critical screens under the same, well-controlled, flow conditions. For the latter type small-scale fluctuations, produced by the screen itself, interact with the incoming turbulence. In the immediate vicinity of the screen the turbulence was found to be highly anisotropic and the intensities were higher than on the upstream side. Downstream of a short initial decay region, where the intensities decrease rapidly, the return to isotropy was found to be much slower than for the unmanipulated turbulence. The latter was generated by a square rod grid, and was shown to become practically isotropic beyond a distance of roughly 20 mesh widths from the grid. The role of the turbulence scales for the overall reduction effectiveness, and for the optimization of screen combinations for application in low-turbulence wind tunnels was studied.
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Veghova, Ivana, and Olga Hubova. "Influence of the near standing hall for wind flowing around group of circular cylinders." MATEC Web of Conferences 310 (2020): 00013. http://dx.doi.org/10.1051/matecconf/202031000013.
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This article deals with experimental investigation of air flow around in – line standing circular cylinders and influence of nearby standing hall on external wind pressure distribution. The wind pressure distribution on the structures is an important parameter in terms of wind load calculation. For vertical circular cylinders in a row arrangement only wind force coefficient is possible find in Eurocode. 1991-1-4. External wind pressure coefficient depends on wind direction and the ratio of distance and diameter b. Influence of nearby standing structure is not possible find in Eurocode. The series of parametric wind tunnel studies was carried out in Boundary Layer Wind Tunnel (BLWT) STU to investigate the external wind pressure coefficient in turbulent wind flow. Experimental measurements were performed in BLWT for 2 reference wind speeds, which fulfilled flow similarity of prototype and model. We have compared the results of free in - line standing 3 circular cylinder and influence of hall on distribution of wind pressure at 3 height levels in turbulent wind flow and these results were compared with values in EN 1991-1-4.
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Bullough, W. A., J. H. Hart, and S. B. Chin. "Comparative Studies: CFD, Experimental and Analytical Techniques in the Fluids Laboratory." International Journal of Mechanical Engineering Education 31, no. 2 (April 2003): 150–59. http://dx.doi.org/10.7227/ijmee.31.2.7.
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This task is concerned with the recovery of pressure in a fluid as it flows through various conical diffusers of the same inlet (d) and outlet (D) diameters, but with different included angles (2θ). In particular, it involves comparison of the measured and computational fluid dynamics (CFD) predicted pressure recovery coefficients (PRC) and, for modelling purposes only, illustrating the effect of the choice of boundary conditions, pressure recovery patterns along the diffusers and the use of PreBFC. The fluid is air (density ρ and dynamic viscosity μ); the test rigs available are existing open-circuit wind tunnels.
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Hastings, R. C., and B. R. Williams. "Studies of the flow field near a IMACA 4412 aerofoil at nearly maximum lift." Aeronautical Journal 91, no. 901 (January 1987): 29–44. http://dx.doi.org/10.1017/s0001924000016079.
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Summary Measurements made at a Mach number of 0.18 and a chord-based Reynolds number of 4·2 x 106 on a constant-chord model having a NACA 4412 aerofoil section are described and compared with the results of flow field calculations. Both the experimental arrangement and the difficulties initially experienced in achieving an adequate approximation to two-dimensional flow above the wing are briefly outlined. The measurements include static pressure distributions on the wing surface and on the wind-tunnel walls above and below the mid-span section of the wing. The main emphasis in the experiment was, however, on defining the development of the upper surface boundary layer through separation (at about 20% chord ahead of the trailing-edge) and on into the wake, making extensive use of laser anemometry to measure mean velocities. In addition, Reynolds stresses were measured in certain parts of the flow field by hot-wire anemometry. The flow field calculations are of the semi-inverse kind in which an inverse momentum-integral treatment of the shear flow, used to avoid difficulties at separation, is coupled to a direct solution of the inviscid flow problem. The main features of the method are outlined.
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Garman, K. E., K. A. Hill, P. Wyss, M. Carlsen, J. R. Zimmerman, B. H. Stirm, T. Q. Carney, R. Santini, and P. B. Shepson. "An Airborne and Wind Tunnel Evaluation of a Wind Turbulence Measurement System for Aircraft-Based Flux Measurements*." Journal of Atmospheric and Oceanic Technology 23, no. 12 (December 1, 2006): 1696–708. http://dx.doi.org/10.1175/jtech1940.1.
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Abstract Although the ability to measure vertical eddy fluxes of gases from aircraft platforms represents an important capability to obtain spatially resolved data, accurate and reliable determination of the turbulent vertical velocity presents a great challenge. A nine-hole hemispherical probe known as the “Best Air Turbulence Probe” (often abbreviated as the “BAT Probe”) is frequently used in aircraft-based flux studies to sense the airflow angles and velocity relative to the aircraft. Instruments such as inertial navigation and global positioning systems allow the measured airflow to be converted into the three-dimensional wind velocity relative to the earth’s surface by taking into account the aircraft’s velocity and orientation. Calibration of the aircraft system has previously been performed primarily through in-flight experiments, where calibration coefficients were determined by performing various flight maneuvers. However, a rigorous test of the BAT Probe in a wind tunnel has not been previously undertaken. The authors summarize the results of a complement of low-speed wind tunnel tests and in-flight calibrations for the aircraft–BAT Probe combination. Two key factors are addressed in this paper: The first is the correction of systematic error arising from airflow measurements with a noncalibrated BAT Probe. The second is the instrumental precision in measuring the vertical component of wind from the integrated aircraft-based wind measurement system. The wind tunnel calibration allows one to ascertain the extent to which the BAT Probe airflow measurements depart from a commonly used theoretical potential flow model and to correct for systematic errors that would be present if only the potential flow model were used. The precision in the determined vertical winds was estimated by propagating the precision of the BAT Probe data (determined from the wind tunnel study) and the inertial measurement precision (determined from in-flight tests). The precision of the vertical wind measurement for spatial scales larger than approximately 2 m is independent of aircraft flight speed over the range of airspeeds studied, and the 1σ precision is approximately 0.03 m s−1.
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Yang, Qing, J. J. Li, Y. N. Yang, and Z. Y. Ye. "Experimental and Computational Studies of Twin-Vertical-Tail Buffet." Advanced Materials Research 33-37 (March 2008): 1241–46. http://dx.doi.org/10.4028/www.scientific.net/amr.33-37.1241.
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Characteristics and mechanism of twin-vertical-tail buffet response on airplane configuration with wing root leading edge extension (LEX) were studied by both experiment and computation. Low-speed wind tunnel experiments were carried out to measure the root bending moment and tip acceleration of vertical tail. Vortical flow patterns were visualized via laser light sheet technique. Three-dimensional computation was performed to solve the unsteady Euler equations on rigid model. The results indicate that (1) bursting of vortices emanating from LEX is the main source of twin-vertical-tail buffet; (2) the Euler equations is able to predict the general characteristics of vertical-tail buffet response reasonably.
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Karwa, Rajendra, B. K. Maheshwari, and Nitin Karwa. "Flow visualization and local mass transfer studies for turbulent flow in a wind tunnel with chamfered ribs." Journal of Visualization 11, no. 3 (September 2008): 205–12. http://dx.doi.org/10.1007/bf03181708.
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Allarton, Richard, Jun Yao, Tyler Clifford, Benjamin Hitchborn, Liam J. Parker, and Joshua Shaw. "Surface flow modification of aerofoils for automotive racing car applications." International Journal of Modern Physics B 34, no. 14n16 (April 20, 2020): 2040096. http://dx.doi.org/10.1142/s0217979220400962.
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An aerofoil commonly used in aerospace engineering to produce lift is also employed in the motor sport industry to produce downforce for improving traction during cornering. This paper investigates aerofoil surface modification through ‘golf ball dimpling’, used to reduce flow separation behind a golf ball. The studies of other researchers have shown that this type of design can have a positive effect on improving aerofoil performance. However, no optimization information of dimple sizing is given in literature. Therefore, three types of dimpling sized at 5, 10 and 15 mm are applied to the surface of a NACA 6615 wing at 25% chord length from the leading edge in this study using Computational Fluid Dynamics (CFD) as an initial design process. Then a physical model, made through 3D printing additive manufacturing (AM), is tested at angles of attack (AoA) ranging from [Formula: see text] to [Formula: see text] and wind speed up to 30 m/s in a subsonic wind tunnel. Experimental and CFD results show that the smallest dimple size provides the most significant increase on lift to drag ratio at high AoA above [Formula: see text]. This ratio increases further with the wind speed, indicating that a high AoA wing favors down force to improve drag reduction performance.
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Musa, Mohamad Nor, Samion Syahrullail, and Fairuz Zainal Abidin. "Aerodynamic Analysis on Proton Preve by Experimental." Applied Mechanics and Materials 773-774 (July 2015): 575–79. http://dx.doi.org/10.4028/www.scientific.net/amm.773-774.575.
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The purpose of this study is to determine the coefficient drag, CD of the Proton PREVẾ by experimental method using Low Speed Wind Tunnel. All the relevant data are collected through the literature reviews from books and journals. First, the basic thing in aerodynamic is studied. There are two things are concern when studies aerodynamics. They were air flow and vehicle shape which we regard as aerodynamics factor that determine aerodynamic of the vehicle. Fundamental of air flow and vehicle shape is reviewed includes the relationship between air speed with pressure, boundary layer, Reynolds number, drag, lift drag and shape optimization. Wind tunnel is also studied before the experiment. Five selected speed were been tasted during the experiment to determine the CD value.
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Colban, W. F., A. T. Lethander, K. A. Thole, and G. Zess. "Combustor Turbine Interface Studies—Part 2: Flow and Thermal Field Measurements." Journal of Turbomachinery 125, no. 2 (April 1, 2003): 203–9. http://dx.doi.org/10.1115/1.1561812.
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Most turbine inlet flows resulting from the combustor exit are nonuniform in the near-platform region as a result of cooling methods used for the combustor liner. These cooling methods include injection through film-cooling holes and injection through a slot that connects the combustor and turbine. This paper presents thermal and flow field measurements in the turbine vane passage for a combustor exit flow representative of what occurs in a gas turbine engine. The experiments were performed in a large-scale wind tunnel facility that incorporates combustor and turbine vane models. The measured results for the thermal and flow fields indicate a secondary flow pattern in the vane passage that can be explained by the total pressure profile exiting the combustor. This secondary flow field is quite different than that presented for past studies with an approaching flat plate turbulent boundary layer along the upstream platform. A counter-rotating vortex that is positioned above the passage vortex was identified from the measurements. Highly turbulent and highly unsteady flow velocities occur at flow impingement locations along the stagnation line.
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Jeon, Wonyoung, Jeanho Park, Seungro Lee, Youngguan Jung, Yeesock Kim, and Youngjin Seo. "Performance prediction of loop-type wind turbine." Advances in Mechanical Engineering 12, no. 2 (February 2020): 168781401984047. http://dx.doi.org/10.1177/1687814019840472.
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An experimental and analytical method to evaluate the performance of a loop-type wind turbine generator is presented. The loop-type wind turbine is a horizontal axis wind turbine with a different shaped blade. A computational fluid dynamics analysis and experimental studies were conducted in this study to validate the performance of the computational fluid dynamics method, when compared with the experimental results obtained for a 1/15 scale model of a 3 kW wind turbine. Furthermore, the performance of a full sized wind turbine is predicted. The computational fluid dynamics analysis revealed a sufficiently large magnitude of external flow field, indicating that no factor influences the flow other than the turbine. However, the experimental results indicated that the wall surface of the wind tunnel significantly affects the flow, due to the limited cross-sectional size of the wind tunnel used in the tunnel test. The turbine power is overestimated when the blockage ratio is high; thus, the results must be corrected by defining the appropriate blockage factor (the factor that corrects the blockage ratio). The turbine performance was corrected using the Bahaj method. The simulation results showed good agreement with the experimental results. The performance of an actual 3 kW wind turbine was also predicted by computational fluid dynamics.
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Khalid, Mahmood, Khalid A. Juhany, and Salah Hafez. "Computational modeling of the flow in a wind tunnel." Aircraft Engineering and Aerospace Technology 90, no. 1 (January 2, 2018): 175–85. http://dx.doi.org/10.1108/aeat-05-2016-0072.
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Purpose The purpose of this paper is to use a computational technique to simulate the flow in a two-dimensional (2D) wind tunnel where the effect of the solid walls facing the model has been addressed using a porous geometry so that interference arriving at the solid walls are duly damped and a flow suction procedure has been adopted at the side wall to minimize the span-wise effect of the growing side wall boundary layer. Design/methodology/approach A CFD procedure based on discretization of the Navier–Stokes equations has been used to model the flow in a rectangular volume with appropriate treatment for solid walls of the confined volume in which the model is placed. The rectangular volume was configured by stacking O-Grid sections in a span-wise direction using geometric growth from the wall. A porous wall condition has been adapted to counter the wall interference signatures and a separate suction procedure has been implemented for reducing the side wall boundary layer effects. Findings It has been shown that through such corrective measures, the flow in a wind tunnel can be adequately simulated using computational modeling. Computed results were compared against experimental measurements obtained from IAR (Institute for Aerospace, Canada) and NAL (National Aeronautical Laboratory, Japan) to show that indeed appropriate corrective means may be adapted to reduce the interference effects. Research limitations/implications The solutions seemed to converge a lot better using relatively coarser grids which placed the shock locations closer to the experimental values. The finer grids were more stiff to converge and resulted in reversed flow with the two equation k-w model in the region where the intention was to draw out the fluid to thin down the boundary layer. The one equation Spalart–Allmaras model gave better result when porosity and wall suction routines were implemented. Practical implications This method could be used by industry to point check the results against certain demanding flow conditions and then used for more routine parametric studies at other conditions. The method would prove to be efficient and economical during early design stages of a configuration. Originality/value The method makes use of an O-grid to represent the confined test section and its dual treatment of wall interference and blockage effects through simultaneous application of porosity and boundary layer suction is believed to be quite original.
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Michaux, J. L., F. Naaim-Bouvet, M. Naaim, M. Lehning, and G. Guyomarc’h. "Effect of unsteady wind on drifting snow: first investigations." Natural Hazards and Earth System Sciences 2, no. 3/4 (December 31, 2002): 129–36. http://dx.doi.org/10.5194/nhess-2-129-2002.
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Abstract. Wind is not always a steady flow. It can oscillate, producing blasts. However, most of the current numerical models of drifting snow are constrained by one major assumption: forcing winds are steady and uniform. Moreover, very few studies have been done to verify this hypothesis, because of the lack of available instrumentation and measurement difficulties. Therefore, too little is known about the possible role of wind gust in drifting snow. In order to better understand the effect of unsteady winds, we have performed both experiments at the climatic wind tunnel at the CSTB (Centre Scientifique et Technique des Bâtiments) in Nantes, France, and in situ experiments on our experimental high-altitude site, at the Lac Blanc Pass. These experiments were carried out collaboratively with Cemagref (France), Météo-France, and the IFENA (Switzerland). Through the wind tunnel experiments, we found that drifting snow is in a state of permanent disequilibrium in the presence of fluctuating airflows. In addition, the in situ experiments show that the largest drifting snow episodes appear during periods of roughly constant strong wind, whereas a short but strong blast does not produce significant drifting snow. Key words. Drifting snow, blowing snow, gust, blast, acoustic sensor
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Peltola, Olli, Karl Lapo, Ilkka Martinkauppi, Ewan O'Connor, Christoph K. Thomas, and Timo Vesala. "Suitability of fibre-optic distributed temperature sensing for revealing mixing processes and higher-order moments at the forest–air interface." Atmospheric Measurement Techniques 14, no. 3 (March 26, 2021): 2409–27. http://dx.doi.org/10.5194/amt-14-2409-2021.
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Abstract. The suitability of a fibre-optic distributed temperature sensing (DTS) technique for observing atmospheric mixing profiles within and above a forest was quantified, and these profiles were analysed. The spatially continuous observations were made at a 125 m tall mast in a boreal pine forest. Airflows near forest canopies diverge from typical boundary layer flows due to the influence of roughness elements (i.e. trees) on the flow. Ideally, these complex flows should be studied with spatially continuous measurements, yet such measurements are not feasible with conventional micrometeorological measurements with, for example, sonic anemometers. Hence, the suitability of DTS measurements for studying canopy flows was assessed. The DTS measurements were able to discern continuous profiles of turbulent fluctuations and mean values of air temperature along the mast, providing information about mixing processes (e.g. canopy eddies and evolution of inversion layers at night) and up to third-order turbulence statistics across the forest–atmosphere interface. Turbulence measurements with 3D sonic anemometers and Doppler lidar at the site were also utilised in this analysis. The continuous profiles for turbulence statistics were in line with prior studies made at wind tunnels and large eddy simulations for canopy flows. The DTS measurements contained a significant noise component which was, however, quantified, and its effect on turbulence statistics was accounted for. Underestimation of air temperature fluctuations at high frequencies caused 20 %–30 % underestimation of temperature variance at typical flow conditions. Despite these limitations, the DTS measurements should prove useful also in other studies concentrating on flows near roughness elements and/or non-stationary periods, since the measurements revealed spatio-temporal patterns of the flow which were not possible to be discerned from single point measurements fixed in space.
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Salinas, Manuel Flores, Ruxandra Mihaela Botez, and Guy Gauthier. "New Numerical and Measurements Flow Analyses Near Radars." Applied Mechanics 2, no. 2 (May 25, 2021): 303–31. http://dx.doi.org/10.3390/applmech2020019.
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An experimental and numerical investigation of the flow near a blunt body has been conducted in this study. Most experimental methods of flow studies use flow visualization and probes introduction into the flow field. The main goal of this research was the development of a new methodology to analyze flows, and to measure flow characteristics without taking into account the distorting effects of measuring probes. A series of experiments were performed on a ground surveillance radar in the Price-Païdoussis subsonic wind tunnel. Forces and moments were measured as functions of wind speeds and angular positions by the use of a six-component aerodynamic scale. A Computational Fluid Dynamics three-dimensional model was employed to analyze the wake region of the ground surveillance radar. A turbulence reduction system was proposed and analyzed in this research. The use of the proposed turbulence reduction system was found to be an effective way to reduce turbulent flow intensity by 50%, drag coefficients by 9.6%, and delay the flow transition point by 7.6 times.
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Schottler, Jannik, Jan Bartl, Franz Mühle, Lars Sætran, Joachim Peinke, and Michael Hölling. "Wind tunnel experiments on wind turbine wakes in yaw: redefining the wake width." Wind Energy Science 3, no. 1 (May 16, 2018): 257–73. http://dx.doi.org/10.5194/wes-3-257-2018.
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Abstract. This paper presents an investigation of wakes behind model wind turbines, including cases of yaw misalignment. Two different turbines were used and their wakes are compared, isolating effects of boundary conditions and turbine specifications. Laser Doppler anemometry was used to scan full planes of wakes normal to the main flow direction, six rotor diameters downstream of the respective turbine. The wakes of both turbines are compared in terms of the time-averaged main flow component, the turbulent kinetic energy and the distribution of velocity increments. The shape of the velocity increments' distributions is quantified by the shape parameter λ2. The results show that areas of strongly heavy-tailed distributed velocity increments surround the velocity deficits in all cases examined. Thus, a wake is significantly wider when two-point statistics are included as opposed to a description limited to one-point quantities. As non-Gaussian distributions of velocity increments affect loads of downstream rotors, our findings impact the application of active wake steering through yaw misalignment as well as wind farm layout optimizations and should therefore be considered in future wake studies, wind farm layout and farm control approaches. Further, the velocity deficits behind both turbines are deformed to a kidney-like curled shape during yaw misalignment, for which parameterization methods are introduced. Moreover, the lateral wake deflection during yaw misalignment is investigated.
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Wang, Qian, Qing Hao Meng, Yan Peng Man, Jia Ying Wang, Ming Zeng, and Wei Li. "Simulation of Outdoor Near-Surface Airflows Based on a Wind Tunnel with Multiple Actively-Controlled Fans." Advanced Materials Research 807-809 (September 2013): 102–5. http://dx.doi.org/10.4028/www.scientific.net/amr.807-809.102.
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In this paper, multiple actively-controlled fans generate outdoor near-surface airflow in a wind tunnel with once-through openings. The wind tunnel system consists of 6 groups of fans installed on rotatable plates in a rectangular inlet. We use a stochastic strategy to control the fans and the rotatable plates to regulate wind speed and direction that fluctuate according to the pattern of outdoor near-surface airflow. We utilize the statistics and multi-scale methods to analyze the effectiveness of the strategy for simulating the outdoor near-surface airflow. We provide comparison studies on the multi-scale entropy of wind speed, wind stability, and the standard deviation of directions between out-door wind and the tunnel generated wind. Results show that a flow field akin to the near-surface airflow in outdoor environments can be produced by the wind tunnel using the stochastic control strategy, which can be considered as a reliable experiment environment for gas pollution source localization research in outdoor near-surface breeze conditions.
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Kellnerová, Radka, Klára Jurčáková, Pavel Procházka, and Václav Uruba. "Vorticity in the turbulent flow above variously rough surfaces." EPJ Web of Conferences 213 (2019): 02039. http://dx.doi.org/10.1051/epjconf/201921302039.
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Highly turbulent flows above variously rough surfaces were investigated by means of Time-Resolved Particle Image Velocimetry in a wind tunnel. Proper Orthogonal Decomposition was applied to both velocity and vorticity data in order to detect dominant features in the flow based on turbulent kinetic energy and enstrophy, respectively. While both the shape and location of the POD patterns exhibited similarity with other studies, a systematic inconsistency in terms of contribution from the features to the enstrophy between the previously published papers and our results were found.
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Gong, W., Peter A. Taylor, and Andreas Dörnbrack. "Turbulent boundary-layer flow over fixed aerodynamically rough two-dimensional sinusoidal waves." Journal of Fluid Mechanics 312 (April 10, 1996): 1–37. http://dx.doi.org/10.1017/s0022112096001905.
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Results from a wind tunnel study of aerodynamically rough turbulent boundary-layer flow over a sinusoidal surface are presented. The waves had a maximum slope (ak) of 0.5 and two surface roughnesses were used. For the relatively rough surface the flow separated in the wave troughs while for the relatively smooth surface it generally remained attached. Over the relatively smooth-surfaced waves an organized secondary flow developed, consisting of vortex pairs of a scale comparable to the boundary-layer depth and aligned with the mean flow. Large-eddy simulation studies model the flows well and provide supporting evidence for the existence of this secondary flow.
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Wu, Shenghao, Jiming Chen, Qin Chen, and Haitao Pei. "Measurementimprovement of flow quality of slotted test section in transonic wind tunnel." Xibei Gongye Daxue Xuebao/Journal of Northwestern Polytechnical University 39, no. 3 (June 2021): 660–67. http://dx.doi.org/10.1051/jnwpu/20213930660.
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Experimental studies were carried out in the 0.6 m×0.6 m continuous transonic wind tunnel of CARDC in order to investigate the flow characteristics of the slotted test section. Experimental results show that the root-mean-square deviation of axial Mach number in the model area is above 0.01 when the test section Mach number is above 1.0.Numerical simulation under the same conditions to investigate the flow characteristics of the slotted section, together with the experimental studies indicate tow phenomena may directly cause the Mach number fluctuation. Firstly, a straight section was installed to connect the nozzle and the test section in the wind tunnel. Weak shock waves due to the curvature discontinuity at the joint of the test section and the straight section contribute to Mach number fluctuation. Secondly, the open-area ratio of both the upper and lower wall of test section, each with 8 slots, is of 10%. The larger porosity leads to stronger expansion waves in the acceleration zone located at the inlet of the test section. The flow was over accelerated because of the stronger expansion wave and thus fluctuate the flow field severely. Two measures were taken to improve the flow quality of the slotted test section based on the above-mentioned analysis: ①Flexible plate instead of solid straight plate was installed to bridge nozzle and test section to eliminate the curvature discontinuity; ②Decreasing the open-area ratio of the upper and lower test section wall to 6% and the number of slots to 6. Numerical and experimental results show that the Mach number fluctuation in the model area was suppressed to a satisfactory degree.
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Uehara, Kiyoshi, Shinji Wakamatsu, and Ryozo Ooka. "Studies on critical Reynolds number indices for wind-tunnel experiments on flow within urban areas." Boundary-Layer Meteorology 107, no. 2 (May 2003): 353–70. http://dx.doi.org/10.1023/a:1022162807729.
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Kramer, C., H. J. Gerhardt, and L. J. Janssen. "Flow studies of an open jet wind tunnel and comparison with closed and slotted walls." Journal of Wind Engineering and Industrial Aerodynamics 22, no. 2-3 (June 1986): 115–27. http://dx.doi.org/10.1016/0167-6105(86)90078-4.
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Gai, S. L., M. Roberts, A. Barker, C. Kleczaj, and A. J. Riley. "Vortex interaction and breakdown over double-delta wings." Aeronautical Journal 108, no. 1079 (January 2004): 27–34. http://dx.doi.org/10.1017/s0001924000004966.
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Modern high-speed aircraft, especially military, are very often equipped with single or compound delta wings. When such aircraft operate at high angles-of-attack, the major portion of the lift is sustained by streamwise vortices generated at the leading edges of the wing. This vortex-dominated flow field can breakdown, leading not only to loss of lift but also to adverse interactions with other airframe components such as the fin or horizontal tail. The wind tunnel and water studies described herein attempt to clarify the fluid mechanics of interaction between the strake and wing vortices of a generic 76°/40° double-delta wing leading to vortex breakdown. Some studies of passive control using fences at the apex and kink region are also described. Various diagnostic methods-laser sheet flow visualisation, fluorescent dyes, and pressure sensitive paints have been used.
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Khrapunov, Evgenii, and Sergei Solovev. "Advantages of modeling ABL properties to determine wind loads on structures." MATEC Web of Conferences 245 (2018): 09007. http://dx.doi.org/10.1051/matecconf/201824509007.
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In present paper we introduce the main advantages of modeling atmospheric boundary layer (ABL) properties for determination of mean and peak wind loads on structures. Experimental tests were carried out using wind tunnel with uniform velocity profile and new Landscape Wind tunnel (LWT) of Krylov State Research Centre. General characteristics of simulated boundary layer (such as mean velocity profile and turbulence intensity profile) are presented. For wind loads measurements model of Silsoe cube in a scale of 1:15 was used. Comparison of the data obtained at both test rigs with data published in early studies is performed. New data about aerodynamic forces acting on the model in range of angles of oncoming flow are presented. Algorithm for determination of peak wind loads is discussed.
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MAEDA, Takao, Yasunari KAMADA, Yusaku SAKAI, and Naoki TAKAHARA. "Experimental Study on Flow around Blades of Horizontal Axis Wind Turbine in Wind Tunnel (2nd Report, Studies on the Flow around Blade Based on Pressure Distribution)." Transactions of the Japan Society of Mechanical Engineers Series B 71, no. 705 (2005): 1383–89. http://dx.doi.org/10.1299/kikaib.71.1383.
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SARMENTO, C. V. S., A. O. C. FONTE, L. J. PEDROSO, and P. M. V. RIBEIRO. "From numerical prototypes to real models: a progressive study of aerodynamic parameters of nonconventional concrete structures with Computational Fluid Dynamics." Revista IBRACON de Estruturas e Materiais 13, no. 3 (June 2020): 628–43. http://dx.doi.org/10.1590/s1983-41952020000300012.
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Abstract The practical evaluation of aerodynamic coefficients in unconventional concrete structures requires specific studies, which are small-scale models evaluated in wind tunnels. Sophisticated facilities and special sensors are needed, and the tendency is for modern and slender constructions to arise with specific demands on their interaction with the wind. On the other hand, the advances obtained in modern multi-core processors emerge as an alternative for the construction of sophisticated computational models, where the Navier-Stokes differential equations are solved for fluid flow using numerical methods. Computations of this kind require specialized theoretical knowledge, efficient computer programs, and high-performance computers for large-scale calculations. This paper presents recent results involving two real-world applications in concrete structures, where the aerodynamic parameters were estimated with the aid of computational fluid dynamics. Conventional quad-core computers were applied in simulations with the Finite Volume Method and a progressive methodology is presented, highlighting the main aspects of the simulation and allowing its generalization to other types of problems. The results confirm that the proposed methodology is promising in terms of computational cost, drag coefficient estimation and versatility of simulation parameters. These results also indicate that mid-performance computers can be applied for preliminary studies of aerodynamic parameters in design offices.
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Hashempour, Javad, and Ahmad Sharifian. "Optimizing the Coupling of a Firebrand Generator to a Horizontal Wind Tunnel." Advanced Materials Research 726-731 (August 2013): 971–76. http://dx.doi.org/10.4028/www.scientific.net/amr.726-731.971.
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Australia is considered as the most fire-prone country in the world. Spotting ignition by lofted firebrands is the main mechanism of fire spread. Many experimental studies have been conducted to evaluate the effect of the firebrand attacks on structures and to identify possible solutions. The experimental facility consists of a firebrand generator coupled to a wind tunnel. The wind speed in the firebrand generator is relatively low, in order to assure a quality continuous flow of glowing firebrands. On the contrary, the wind speed in the wind tunnel is high to duplicate actual firebrand attacks. Previous works show a highly turbulent region above the entrance of firebrands to the wind tunnel which is formed because of the velocity difference and penetration of firebrand entrance hose into the wind tunnel. The penetration is required to provide a uniform firebrand distribution along the height of the test section. In this computational work, the influence of the height of the entrance hose, its orientation respect to the tunnel and the distance between the coupling port and the test section are analyzed. The optimized results are presented and discussed for a variety of wind speeds within the wind tunnel and the firebrand generator.
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Sarkar, Md Rasel, Sabariah Julai, Mst Jesmin Nahar, Moslem Uddin, Mahmudur Rahman, and Md Riyad Tanshen. "Experimental Study of Vertical Axis Wind Turbine Performance under Vibration." International Journal of Robotics and Control Systems 1, no. 2 (June 16, 2021): 177–85. http://dx.doi.org/10.31763/ijrcs.v1i2.335.
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An experimental study was conducted to study the effects of flow uniformity on vibration and power generation of a small vertical axis wind turbine (VAWT). Previous studies have confirmed that one of the sources of vibration in the turbine is due to aerodynamic forces, which are due to incident wind. Firstly, understanding vibration is essential before proceeding to the measurements. In this experiment, further understand the vibrations of the turbine in operation, the operating deflection shape (ODS) technique was used. A wind tunnel and flow conditioner were fabricated. Experimental modal analysis (EMA) was conducted, and the dynamic characteristics are gathered. The ODS was conducted for operating the turbine at different speeds, with and without the flow conditioner. Results from EMA and ODS are correlated to explain the behavior of structures. In conclusion, the flow conditioner tested did have a big impact on the response of the structure in terms of vibration up to 30% indifference, but not so much in power generated about 2% indifference.
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Rtischeva, A. S. "Gas Dynamic Design and Numerical Study of Supersonic Circuit of Wind Tunnel." Herald of the Bauman Moscow State Technical University. Series Mechanical Engineering, no. 1 (136) (March 2021): 68–84. http://dx.doi.org/10.18698/0236-3941-2021-1-68-84.
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For an advanced trisonic wind tunnel of a straight-flow type with a test section size of 1.2 × 1.2, intended for ground tests of rocket-space and aviation aircraft models, we implemented a gas-dynamic design of the circuit and did numerical simulation of the flow for the main supersonic regimes (M = 2, M = 4). The gas-dynamic design of the wind tunnel circuit was carried out on the basis of techniques developed at TsAGI and operating experience of existing facilities. The study considers both traditional configurations of the duct with the bending of the walls of all elements, i.e., nozzle, test section and diffuser in the XY plane, and alternative design developments with the bending of the diffuser walls in the XZ plane. When carrying out numerical studies in all areas of the wind tunnel, the ANSYS Fluent software package was used to solve the Navier --- Stokes equations for viscous and heat-conducting air using the turbulence model, i.e., Spalart --- Allmaras, SST. The paper investigates the effect of the wall opening angle, compensating the increasing thickness of boundary-layer longwise displacement, on the flow characteristics; shows the possibilities of obtaining a sufficiently uniform flow with the Mach number accuracy ΔM = ± 0.005 in the area of the model, and analyzes the influence of geometric parameters and boundary conditions on the efficiency of the supersonic diffuser
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Chen, Zengshun, Yemeng Xu, Hailin Huang, and Kam Tim Tse. "Wind Tunnel Measurement Systems for Unsteady Aerodynamic Forces on Bluff Bodies: Review and New Perspective." Sensors 20, no. 16 (August 17, 2020): 4633. http://dx.doi.org/10.3390/s20164633.
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Wind tunnel tests have become one of the most effective ways to evaluate aerodynamics and aeroelasticity in bluff bodies. This paper has firstly overviewed the development of conventional wind tunnel test techniques, including high frequency base balance technique, static synchronous multi-pressure sensing system test technique and aeroelastic test, and summarized their advantages and shortcomings. Subsequently, two advanced test approaches, a forced vibration test technique and hybrid aeroelastic- force balance wind tunnel test technique have been comprehensively reviewed. Then the characteristics and calculation procedure of the conventional and advanced wind tunnel test techniques were discussed and summarized. The results indicated that the conventional wind tunnel test techniques ignored the effect of structural oscillation on the measured aerodynamics as the test model is rigid. A forced vibration test can include that effect. Unfortunately, a test model in a forced vibration test cannot respond like a structure in the real world; it only includes the effect of structural oscillation on the surrounding flow and cannot consider the feedback from the surrounding flow to the oscillation test model. A hybrid aeroelastic-pressure/force balance test technique that can observe unsteady aerodynamics of a test model during its aeroelastic oscillation completely takes the effect of structural oscillation into consideration and is, therefore, effective in evaluation of aerodynamics and aeroelasticity in bluff bodies. This paper has not only advanced our understanding for aerodynamics and aeroelasticity in bluff bodies, but also provided a new perspective for advanced wind tunnel test techniques that can be used for fundamental studies and engineering applications.
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Cheng, K. C., and Y. W. Kim. "Flow Visualization Studies on Vortex Instability of Natural Convection Flow Over Horizontal and Slightly Inclined Constant-Temperature Plates." Journal of Heat Transfer 110, no. 3 (August 1, 1988): 608–15. http://dx.doi.org/10.1115/1.3250536.
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Flow visualization experiments were performed in a low-speed wind tunnel to study vortex instability of laminar natural convection flow along inclined isothermally heated plates having inclination angles from the horizontal of θ = 0, 5, 10, 15 and 20 deg. The temperature difference between plate surface and ambient air ranged from ΔT = 15.5 to 37.5°C and the local Grashof number range was Grx = 1.02×106 to 2.13×108. Three characteristic flow regimes were identified as follows: a two-dimensional laminar flow, a transition regime for developing longitudinal vortices, and a turbulent regime after the breakdown of the longitudinal vortices. Photographs are presented of side and top views of the flow and of cross-sectional views of the developing views of the developing secondary flow in the postcritical regime. Instability data of critical Grashof number and wavelength are presented and are compared with the theoretical predictions from the literature.
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Veghova, Ivana, and Olga Hubova. "Influence of near standing cylindrical structures on wind pressure distribution on the multispan roofs of halls." MATEC Web of Conferences 313 (2020): 00048. http://dx.doi.org/10.1051/matecconf/202031300048.
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This article deals with experimental investigation of a wind pressure distribution on multispan roofs of halls. The wind pressure distribution on the structures is an important parameter in terms of wind load calculation. For multispan roofs it is possible to find these values in Eurocode 1991-1-4, but without an influence of surrounding structures. The series of parametric wind tunnel studies was carried out in BLWT to investigate the effects of in-line standing cylinders near the hall. Measurements were made in turbulent wind flow for two reference wind speeds and varying wind directions. The experimentally obtained cpe values were compared with the conservative values in EN 1991-1-4 for multispan roofs.
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Prakash, R., N. Karthiek, P. Ashwath, H. Anand, and G. Adithya. "Numerical Study on a Conical Diffuser with Inlet Swirl." Applied Mechanics and Materials 852 (September 2016): 688–92. http://dx.doi.org/10.4028/www.scientific.net/amm.852.688.
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One of the major components of axial-flow compressors and turbines are the diffusers, employed for the conversion of fluid velocity to pressure. They are used in gas turbines, pumps, wind tunnels and other fluid flow devices. Diffusers are used in jet engines, aircraft engines for various purposes. Usually a diffuser is considered as an isolated component for the ease of computation. However, when there is upstream machinery, the effect of flow separation cannot be neglected and hence considering a diffuser as an isolated component would not suffice. The effect of swirl on the performance of a conical diffuser is taken into consideration. Pressure recovery co-efficient indicates the performance of the system and its values are studied under various inlet condition still ideal case is reached and various flow parameters for this ideal case are noted. Ideal condition is the one in which the energy losses along the sections of a diffuser are minimum. This paper provides a holistic view of the flow through a diffuser, laying primary emphasis on the effect of inlet swirl.