Stall Control of a NACA0015 Aerofoil at Low Reynolds Numbers

This thesis focuses on experiments for stall control by using boundary layer trips on a NACA0015 aerofoil wing at low Reynolds numbers. Some simulation for a 2D aerofoil simulation was studied. The NACA0015 aerofoil simulation with different numbers of node and turbulence models at an angle of attack of 6 degrees was investigated for grid independence study. Then the mesh of 400 nodes around the aerofoil was chosen in simulation at various angles of attack. For the experiments, a NACA0015 wing with and without boundary layer trip at Reynolds number of 78,000 was conducted to determine the aerodynamic characteristics of the aerofoil in both cases and to determine the optimized values of the size and location of the boundary layer trips.
The results show that the wing with no trip stalled at the angle of attack of 14 degrees with CLmax of 0.78. As a result of the roughness of the wing, the interference drag between the wing and the struts and the induced drag from wing tip vortices, the total drag coefficient values are higher than that of the aerofoil. When the boundary layer trips were added to the wing, the results showed that lift coefficients of every BLT height located at 50%c from the leading edge are highest when compared to other positions. The results state that 6 mm height BLT located at 50%c produced lowest CL while normal wing without BLT produced highest CL for angles of attack between 0⁰ and 14⁰. The BLT causes less severe stalling due to LSB reduction and reattachment resulting in more lift as the angle of attack increases to greater than 15⁰. Drag coefficients of BLT height of 6, 4, 3, and 1.5 mm located at 50%c from the leading edge were compared to the wing without BLT. The results indicate that 4 mm height BLT generated lowest CD compared to all cases both the normal wing and the wing with BLT.

For CFD simulations at Reynolds number of 650,000, the 2D NACA0015 aerofoil simulations with different turbulence models shows that the Cl slope is in good agreement with the 2D experimental results(NACA report No.586) from 0° to 9° of angle of attack. The obvious difference can be seen after 12°. Stall angle of the turbulence models are higher than that of the experiment due to the mesh construction and the sharp trailing edge of the aerofoil in CFD simulation that is sharper than the aerofoil model tested experimentally.