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Holloway, Simon, Hugo Ricketts, and Geraint Vaughan. "Boundary layer temperature measurements of a noctual urban boundary layer." EPJ Web of Conferences 176 (2018): 06004. http://dx.doi.org/10.1051/epjconf/201817606004.
A low-power lidar system based in Manchester, United Kingdom has been developed to measure temperature profiles in the nocturnal urban boundary layer. The lidar transmitter uses a 355nm diode-pumped solid state Nd:YAG laser and two narrow-band interference filters in the receiver filter out rotational Raman lines that are dependent on temperature. The spectral response of the lidar is calibrated using a monochromator. Temperature profiles measured by the system are calibrated by comparison to co-located radiosondes.
Mamtaz, Farhana, Ahammad Hossain, and Nusrat Sharmin. "Solution of Boundary Layer and Thermal Boundary Layer Equation." Asian Research Journal of Mathematics 11, no. 4 (December 19, 2018): 1–15. http://dx.doi.org/10.9734/arjom/2018/45267.
Atmospheric Boundary Layer (ABL) is the lowest part of the troposphere. The main feature of the Atmospheric Boundary Layer is the turbulent nature of the flow. The thickness of the boundary layer, formed by flowing air friction on the earth’s surface under various conditions move in quite a wide range. ABL is generally defined as being 0.5 km above the surface, although it can extend up to 2 km depending on time and location. The flow properties are most important over the surface of solid objects, which carry out all the reactions between fluid and solid.
Müller, Bernhard M. "Boundary‐layer microphone." Journal of the Acoustical Society of America 96, no. 5 (November 1994): 3206. http://dx.doi.org/10.1121/1.411273.
In this thesis we describe various regimes of practical and theoretical significance that arise in the laminar two-dimensional flow of a layer of an incompressible viscous fluid over a solid surface at high Reynolds number. In Part I we consider steady flows over a distorted rigid surface. Almost uniform flows are considered first, when the distortion is sufficient to provoke a viscous-inviscid interaction, and therefore boundary-layer separation. The two cases of supercritical and subcritical flow have quite distinct features, and are discussed separately. The governing equations in each case require a numerical treatment in general, but analytical progress has been made in certain important regimes e. g. when the distortion is relatively small and linearisation of the problem is possible. Next, the grossly separated motion of fully-developed flows over large obstacles, with dimensions of the order of the depth of the liquid layer, is studied on the basis of inviscid Kirchhoff free-streamline theory. Some comparisons of the theory with recent experiments are also given. In Part II we discuss unsteady and instability aspects of two-dimensional flow over a flat surface. It is shown that viscous and mean flow effects can combine to give instability in some cases, whereas previous studies have only found viscous effects to be stabilising. Unsteadiness of a two-layer fluid flow, with fluids of different viscosity and density, and incorporating surface tension effects, is also discussed. In Part III, deviating from the above theme slightly, we discuss briefly the steady, high-Reynolds-number flow in an asymmetric branching channel, again in the context of viscous-inviscid interactions. The asymmetry is found to force a large-scale response both up- and downstream of the start of the bifurcation. The aim is to find the pressure distributions on the channel walls and on the dividing body. This requires the use of a Wiener-Hopf technique in view of the mixed boundary conditions.
Yuile, Adam. "Swept boundary layer transition." Thesis, University of Liverpool, 2013. http://livrepository.liverpool.ac.uk/14613/.
Boundary layer transition has been investigated for incompressible three-dimensional mean flows on a flat plate with a 60° swept leading edge for a nominally zero, a positive, and a negative pressure gradient for three freestream turbulence intensities using a low speed blower tunnel with a 1.22 x 0.61 m working section at the University of Liverpool. The freestream turbulence intensities were generated using grids upstream of the leading edge, producing turbulence levels of approximately 0.2 %, 1.25 % and 3.25 %. For each of these nine (3 x 3) test cases detailed boundary layer traverses were obtained at ten streamwise measurement stations, at a fixed spanwise location, using single-wire constant temperature hot-wire anemometry techniques and digital signal processing. The location for the onset and end of transition was obtained for each case, in terms of distance from the leading edge and local momentum thickness Reynolds number. These results are compared with the 2-D unswept empirical transition correlations of Abu-Ghannam and Shaw (1980) and the differences in the results between the two flows are highlighted. It was found that transition starts and ends earlier than for similar unswept flows, complementing the transition observations of Gray (1952) for swept wings. Further to this the receptivity of the swept boundary layers to freestream turbulence (in the bypass transition regime) was determined by comparing near wall and local freestream spectra, for the pre-transitional boundary layers. These experimental results were compared with numerical predictions from a fourth order accurate computational fluid dynamics method which considered a multitude of perturbation waveforms. This numerical approach was also able to identify the waveform frequency and orientation combinations which drive receptivity in swept boundary layer transition and indicate the manner in which receptivity scales with momentum thickness Reynolds number. It was found that the most receptive waveforms correspond to the streamwise streaks which are frequently observed in flow visualisations and direct numerical simulation studies of pre-transitional boundary layers. Additionally it was also found that the numerical receptivities to freestream turbulence were highest for the positive pressure gradient and, in contrast, lowest for the negative pressure gradient – a similar finding to that in 2-D boundary layers. Transition was seen to commence prior to the advent of the intended non-zero pressure gradients in the experiments and thus direct comparisons are not strictly available. The results obtained, and synthesis undertaken for this thesis, contribute towards an improved understanding of the transition process, particularly with respect to receptivity, in regard to flat plates with swept leading edges in various pressure gradients and highlight the differences between swept and unswept flows. Furthermore, additional avenues have been identified for future work on more complicated topologies where potential problems have also been highlighted.
Kral, Linda Dee. "Numerical investigation of transition control of a flat plate boundary layer." Diss., The University of Arizona, 1988. http://hdl.handle.net/10150/184621.
A numerical model has been developed for investigating boundary layer transition control for a three-dimensional flat plate boundary layer. Control of a periodically forced boundary layer in an incompressible fluid is studied using surface heating techniques. The spatially evolving boundary layer is simulated. The Navier-Stokes and energy equations are integrated using a fully implicit finite difference/spectral method. The Navier-Stokes equations are in vorticity-velocity form and are coupled with the energy equation through the viscosity dependence on temperature. Both passive and active methods of control by surface heating are investigated. In passive methods of control, wall heating is employed to alter the stability characteristics of the mean flow. Both uniform and nonuniform surface temperature distributions are studied. In the active control investigations, temperature perturbations are introduced locally along finite heater strips to directly attenuate the instability waves in the flow. A feedback control loop is employed in which a downstream sensor is used to monitor wall shear stress fluctuations. Passive control of small amplitude two-dimensional Tollmien-Schlichting waves and three-dimensional oblique waves are numerically simulated with both uniform and nonuniform passive heating applied. Strong reductions in both amplitude levels and amplification rates are achieved. Active control of small amplitude two-dimensional and three-dimensional disturbances is also numerically simulated. With proper phase control, in phase reinforcement and out of phase attenuation is demonstrated. A receptivity study is performed to study how localized temperature perturbations are generated into Tollmien-Schlichting waves. It is shown that narrow heater strips are more receptive in that they maximize the amplitude level of the disturbances in the flow. It is also found that the local temperature fluctuations cause mainly a strong normal gradient in spanwise vorticity. Control of the early stages of the nonlinear breakdown process is also investigated. Uniform passive control is applied to both the fundamental and sub-harmonic routes to turbulence. A strong reduction in amplitude levels and growth rates results. In particular, the three-dimensional growth rates are significantly reduced below the uncontrolled levels. Active control of the fundamental breakdown process is also numerically simulated. Control is achieved using either a two-dimensional or three-dimensional control input.
An experimental investigation of transition in boundary layer flows under the influence of various freestream conditions is described. Velocity profiles are obtained automatically by means of a stepper-motor driven traverse mechanism which carries a hot wire probe connected to a constant temperature anemometer and associated instrumentation. This was achieved by use of a data acquisition and control facility centred around a microcomputer with a Eurocard rack mounted extension. The automatic boundary layer traverse is software controlled and the data obtained is stored in a disc file for subsequent analysis and graphical display. As an integral part of this facility a successful method of obtaining reliable intermittency values from a hot wire signal was developed. The influence of freestream turbulence and pressure gradient upon transition within a boundary layer developing on a flat plate is elucidated by a series of controlled experiments. From the data accumulated, the concept of statistical similarity in transition regions is extended to include moderate non-zero pressure gradients, with the streamwise mean intermittency distribution described by the normal distribution function. An original correlation which accounts for the influence of freestream turbulence in zero pressure gradient flows, and the combined influence of freestream turbulence and pressure gradient in adverse pressure gradient flows, on the transition length Reynolds number R, is presented. (The limited amount of favourable pressure gradient data precluded the extension of the correlation to include favourable pressure gradient flows). A further original contribution was the derivation of an intermittency weighted function which describes the development of the boundary layer energy thickness through the transition region. A general boundary layer integral prediction scheme based on existing established integral techniques for the laminar and turbulent boundary layers with an intermittency modelled transition region, has been developed and applied successfully to a range of test data.
AbstractThe Prandtl’s equations for laminar boundary layer are obtained via dimensional analysis. The case of the flat plate is treated as a suitable example for the development of the boundary layer on a simple geometry. Various thicknesses are introduced. The integration of Prandtl’s equation across the boundary layer produces the von Kármán integral equation which allows the elaboration of the approximate von Kármán-Pohlhausen method where the velocity profile is given as a polynomial. The use of a third degree polynomial for the flat plate demonstrates the feasibility of the approach.
Schlichting, Herrmann, and Klaus Gersten. "Unsteady Boundary Layers." In Boundary-Layer Theory, 349–75. Berlin, Heidelberg: Springer Berlin Heidelberg, 2000. http://dx.doi.org/10.1007/978-3-642-85829-1_13.
Schlichting, Hermann, and Klaus Gersten. "Unsteady Boundary Layers." In Boundary-Layer Theory, 349–75. Berlin, Heidelberg: Springer Berlin Heidelberg, 2016. http://dx.doi.org/10.1007/978-3-662-52919-5_13.
Schlichting, Herrmann, and Klaus Gersten. "Boundary—Layer Equations in Plane Flow; Plate Boundary Layer." In Boundary-Layer Theory, 145–64. Berlin, Heidelberg: Springer Berlin Heidelberg, 2000. http://dx.doi.org/10.1007/978-3-642-85829-1_6.
Schlichting, Hermann, and Klaus Gersten. "Boundary–Layer Equations in Plane Flow; Plate Boundary Layer." In Boundary-Layer Theory, 145–64. Berlin, Heidelberg: Springer Berlin Heidelberg, 2016. http://dx.doi.org/10.1007/978-3-662-52919-5_6.
Schlichting, Herrmann, and Klaus Gersten. "Some Features of Viscous Flows." In Boundary-Layer Theory, 3–27. Berlin, Heidelberg: Springer Berlin Heidelberg, 2000. http://dx.doi.org/10.1007/978-3-642-85829-1_1.
Schlichting, Herrmann, and Klaus Gersten. "Thermal Boundary Layers with Coupling of the Velocity Field to the Temperature Field." In Boundary-Layer Theory, 231–89. Berlin, Heidelberg: Springer Berlin Heidelberg, 2000. http://dx.doi.org/10.1007/978-3-642-85829-1_10.
Schlichting, Herrmann, and Klaus Gersten. "Boundary-Layer Control (Suction/Blowing)." In Boundary-Layer Theory, 291–320. Berlin, Heidelberg: Springer Berlin Heidelberg, 2000. http://dx.doi.org/10.1007/978-3-642-85829-1_11.
Schlichting, Herrmann, and Klaus Gersten. "Axisymmetric and Three-Dimensional Boundary Layers." In Boundary-Layer Theory, 321–47. Berlin, Heidelberg: Springer Berlin Heidelberg, 2000. http://dx.doi.org/10.1007/978-3-642-85829-1_12.
Schlichting, Herrmann, and Klaus Gersten. "Extensions to the Prandtl Boundary-Layer Theory." In Boundary-Layer Theory, 377–411. Berlin, Heidelberg: Springer Berlin Heidelberg, 2000. http://dx.doi.org/10.1007/978-3-642-85829-1_14.
"Effects of boundary layer bleed on swept-shock/boundary layer interaction." In 23rd Fluid Dynamics, Plasmadynamics, and Lasers Conference. Reston, Virigina: American Institute of Aeronautics and Astronautics, 1993. http://dx.doi.org/10.2514/6.1993-2989.
BARNHART, P., I. GREBER, and W. HINGST. "Glancing shock wave-turbulent boundary layer interaction with boundary layer suction." In 26th Aerospace Sciences Meeting. Reston, Virigina: American Institute of Aeronautics and Astronautics, 1988. http://dx.doi.org/10.2514/6.1988-308.
de Graffenried, Albert. "Boundary-Layer-Growth Suppression." In 18th Applied Aerodynamics Conference. Reston, Virigina: American Institute of Aeronautics and Astronautics, 2000. http://dx.doi.org/10.2514/6.2000-4512.
CUTLER, A., and P. BRADSHAW. "Vortex/boundary layer interactions." In 27th Aerospace Sciences Meeting. Reston, Virigina: American Institute of Aeronautics and Astronautics, 1989. http://dx.doi.org/10.2514/6.1989-83.
Keady, John. "Plasma Boundary Layer Propulsion." In 33rd Plasmadynamics and Lasers Conference. Reston, Virigina: American Institute of Aeronautics and Astronautics, 2002. http://dx.doi.org/10.2514/6.2002-2142.
Haas, Martin, Ray-Sing Lin, and Tory Brogan. "Boundary Layer Separation Control." In 1st Flow Control Conference. Reston, Virigina: American Institute of Aeronautics and Astronautics, 2002. http://dx.doi.org/10.2514/6.2002-2947.
CHOU, J., and M. CHILDS. "The passive control of compressible boundary layer growth by boundary layer trips." In Shear Flow Control Conference. Reston, Virigina: American Institute of Aeronautics and Astronautics, 1985. http://dx.doi.org/10.2514/6.1985-561.
CHOUDHARI, MEELAN, and CRAIG STREETT. "Boundary layer receptivity phenomena in three-dimensional and high-speed boundary layers." In 2nd International Aerospace Planes Conference. Reston, Virigina: American Institute of Aeronautics and Astronautics, 1990. http://dx.doi.org/10.2514/6.1990-5258.
Mart, Steven R., and Stephen T. McClain. "Protuberances in a Turbulent Thermal Boundary Layer." In ASME 2011 Turbo Expo: Turbine Technical Conference and Exposition. ASMEDC, 2011. http://dx.doi.org/10.1115/gt2011-45180.
Recent efforts to evaluate the effects of isolated protuberances within velocity and thermal boundary layers have been performed using transient heat transfer approaches. While these approaches provide accurate and highly resolved measurements of surface flux, measuring the state of the thermal boundary-layer during transient tests with high spatial resolution presents several challenges. As such, the heat transfer enhancement evaluated during transient tests are presently correlated to a Reynolds number based either on the distance from the leading edge or on the momentum thickness. Heat flux and temperature variations along the surface of a turbine blade may cause significant differences between the shapes and sizes of the velocity and thermal boundary layer profiles. Therefore, correlations are needed which relate the states of both the velocity and thermal boundary layers to protuberance and roughness distribution heat transfer. In this study, a series of three experiments are performed for various freestream velocities to investigate the local temperature details of protuberances interacting with thermal boundary layers. The experimental measurements are performed using isolated protuberances of varying thermal conductivity on a steadily-heated, constant flux flat plate. In the first experiment, detailed surface temperature maps are recorded using infrared thermography. In the second experiment, the unperturbed velocity profile over the plate without heating is measured using hot-wire anemometry. Finally, the thermal boundary layer over the steadily heated plate is measured using a thermocouple probe. Because of the constant flux experimental configuration, the protuberances provide negligible heat flux augmentation. Consequently, the variation in protuberance temperature is investigated using the velocity boundary layer parameters, the thermal boundary layer parameters, and the local fluid temperature at the protuberance apices. A comparison of results using plastic and steel protuberances illuminates the importance of the shape of the thermal and velocity boundary layers in determining the minimum protuberance temperatures.
Звіти організацій з теми "Boundary layer":
Nayfeh, Ali H. Laminar Boundary-Layer Breakdown. Fort Belvoir, VA: Defense Technical Information Center, July 1992. http://dx.doi.org/10.21236/ada254489.
Kimmel, Roger L., Matthew P. Borg, Joseph S. Jewell, James H. Miller, and Dinesh Prabhu. HIFiRE-5 Boundary Layer Transition and HIFiRE-1 Shock Boundary Layer Interaction. Fort Belvoir, VA: Defense Technical Information Center, October 2015. http://dx.doi.org/10.21236/ada623564.
Dimotakis, Paul, Patrick Diamond, Freeman Dyson, David Hammer, and Jonathan Katz. Turbulent Boundary-Layer Drag Reduction. Fort Belvoir, VA: Defense Technical Information Center, May 2003. http://dx.doi.org/10.21236/ada416331.