Introduction
When a viscous fluid flows along a fixed impermeable wall, or past the rigid surface of an immersed body, an essential condition is that a velocity at any point on the wall or other fixed surface is zero. To the extent to which the condition modifies the general character of the flow is dependent on the viscosity of the fluid. If a body has a streamlined shape and the fluid flowing over the body has a small viscosity that is not negligible, the modifying effect appears to be confined to the narrowest regions adjacent to the solid surfaces; these are called boundary layers. Within these layers, there is a rapid change in velocity which gives rise to a large velocity gradient normal to the boundary which produces a shear stress [1]. At the boundary layer where the flow of fluid at the surface of the body is where the shearing stress is not zero. However, outside the boundary layer there are negligible stresses therefore the fluid velocity increases further away for the wall or boundary [2].
The objective is to investigate the velocity profile and boundary layer in the test section of the UJ low-speed wind tunnel as well as to calculate the boundary layer thickness using Blausius, parabolic and cubic velocity profile assumptions as well as to compare results to with theoretical Navier-Stokes velocity profiles.
Literature Review
Low-speed Circulating wind tunnels
Wind tunnels can be divided into three categories according to the range of air speed. In the low air speed section of the wind tunnel where air speeds range from (0.1 – 1.5) m/s, has a test section with large cross-sectional area, is adopted to generate a low-speed environment for calibration of anemometers [3]. Occasionally, the low-speed wind tunnel contains ...
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...ayer to a turbulent boundary layer happens at some critical Reynolds number (Rex) in the order of 2 x 105 to 3 x 106 [6]. This depends on the on the roughness of the surface and the amount of turbulence there is downstream of the fluid flow. The critical location or distance along the plate xcr, comes closer to the leading edge of the plate as the free-stream velocity increases [6].
The purpose of the boundary layer is to all the fluid to change its velocity from the upstream value of U to zero on the surface [6]. Therefore, V=0 at y=0 and V=UÎ at the edge of the boundary layer with the velocity profile of u=u(x,y), bridging the boundary layer thickness [6]. This boundary layer characteristic is true for a variety of different flow situations [6].
Figure 6: Boundary layer thickness (a) standard boundary layer thickness, boundary layer displacement thickness [6].
3. Identify the layers of the Earth shown in the diagram to the right. (S6E5a)
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We must first begin the today’s lab by connecting the thermometer that digitally detects surrounding temperature to the Lab Pro Interface located on the computer via...
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chamber used as a control will be used to measure any changes due to air
As the air flows over the wing producing lift, it grabs onto the wings surface and causes drag. Drag can be measured by the equation D=Cd 1/2 (pV2)S, much like the lift equation. The drag coeficent Cd is found, again, by determining ...
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