IntroductionWhen a viscous fluid flows along a fixed impermeable wall, or beyond the rigid surface of an immersed body, an essential condition is that a velocity at any point on the wall or other fixed point on the surface is zero. The extent to which the condition changes the general character of the flow depends on the viscosity of the fluid. If a body has a streamlined shape and the fluid flowing over the body has a low viscosity that is not negligible, the modifying effect appears to be confined to the narrowest regions adjacent to solid surfaces; they 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 shear stress [1]. At the boundary layer where the fluid flow is located on the surface of the body, the shear stress is not zero. However, outside the boundary layer there are negligible stresses, so the fluid velocity increases further for the wall or boundary [2]. The objective is to study 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 the Blausius velocity profile assumptions, parabolic and cubic, as well as to compare the results with theoretical Navier-Stokes velocity profiles. Literature Review Low Speed ​​Circulating Wind Tunnels Wind tunnels can be divided into three categories based on the range. of air speed. In the low air speed section of the wind tunnel, where the air speeds vary from (0.1 to 1.5) m/s, a test section with a large cross-sectional area is adopted to generate a low-velocity environment for calibrating anemometers [3]. Sometimes the low speed wind tunnel contains...... middle of paper ...... a turbulent boundary layer occurs at a certain critical Reynolds number (Rex) on the order of 2 x 105 to 3 x 106 [6]. This depends on the roughness of the surface and the amount of turbulence that exists downstream of the fluid flow. The critical location or distance along the xcr plate approaches the leading edge of the plate as the free stream velocity increases [6]. The purpose of the boundary layer is to allow all 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), filling the thickness of the boundary layer [6]. This characteristic of the boundary layer 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].