Experimental and Numerical Study on Boundary Layer Growth in Wind Tunnel

Abstract

When a real fluid flow passes over the surface of a flat plate, the velocity of the fluids on the surface of the object becomes same as that of the object. If object is at rest, the fluid will also have zero velocity because of no slip condition at the boundary. Away from the boundary the velocity increase gradually and reaches to free stream velocity and hence there exists a region closed to the object where velocity gradient exists, this region is known as boundary layer region. The flow in the boundary layer is viscous and rotational. Due to viscous effect shear stress is developed inside the boundary layer, above the boundary layer region the flow is non viscous. Study of boundary layer is vital for design of streamline bodies such as air foil. Generally most of wind tunnel is mainly designed for the study of aeronautic action with laminar flow and produces low depth of boundary layer due to lack of turbulence intensity in test section of wind tunnel.
This thesis describes how thick boundary layer can be produced in a short wind tunnel. Several type of thickening (passive) devices are used to increase the boundary layer growth in low speed wind tunnel. This project is a study of four different passive devices (spire, mat, square and diamond blocks) separately and in various combination so that boundary layer can be increased and analyzes the effect of these roughness elements on boundary layer parameter using velocity profile at various free stream velocity at various sections in wind tunnel. This thesis is also used to simulate the atmospheric boundary layer in wind tunnel with a short test section (8m ×.6m×.6m). This project presents the design, computation analysis and experimental study of passive device of different configuration.