IntroductionWhen a viscous fluid flows along a fixed impervious 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 point the surface is zero. The extent to which the condition changes the overall character of the flow depends on the viscosity of the fluid. If a body has an aerodynamic shape and the fluid flowing over the body has a small and non-negligible viscosity, the modifying effect appears confined to the narrower regions adjacent to the solid surfaces; these are called boundary layers. Within these layers a rapid change in velocity occurs which gives rise to a large velocity gradient normal to the boundary which produces a shear stress [1]. In the boundary layer where there is fluid flow on the surface of the body, the shear stress is not zero. However, outside the boundary layer there are negligible stresses, so the velocity of the fluid increases farther from 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 thickness of the boundary layer using the Blausius, parabolic and cubic velocity profile assumptions as well as to compare the results with the theoretical Navier-Stokes velocity profiles. Literature Review Low-Speed ​​Circulating Wind Tunnels Wind tunnels can be divided into three categories based on the air speed range. In the low air speed section of the wind tunnel, where the air speed varies from (0.1 to 1.5) m/s, there is a test section with a large cross-sectional area, used to generate a low velocity environment for anemometer calibration [3]. Occasionally, the low-speed wind tunnel contains…half the paper…turbulent boundary layer occurs at a 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 present downstream of the fluid flow. The critical position or distance along the plate xcr, approaches the leading edge of the plate as the free flow velocity increases [6]. The purpose of the boundary layer is for all fluid to change its velocity from the upstream value of U to zero at the surface [6]. Therefore, V=0 ay=0 and V=UÎ at the edge of the boundary layer with the velocity profile of u=u(x,y), bridging 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].