Evaluation of Aerodynamic and Stability Performance Parameters of High Wing Piston Engine Aircraft

Abstract

Aerodynamic performance and stability parameters of high wing piston engine aircraft were evaluated using Computational Fluid Dynamics and validated against wind tunnel test and analytical solution. The results were calculated at various angles of attack and angles of sideslip at standard sea level conditions and at 121 Kts. Aircraft geometry was scanned with scanner and meshing was carried out using hexagonal mesh elements with growth ratio of 1.2. SA turbulence model was used in commercially available software Fluent®. Boundary layer effects were modeled using prism elements with y+ value of 35 and standard wall functions. Convergence was achieved in around 12000 iterations using 6.34 million volume mesh. It was found that gradient of pitching moment coefficient with angle of attack was -0.003 rad-1 which showed longitudinal stable behavior. However, the trim angle of attack was obtained as -2o therefore aircraft needs to be trimmed at positive angle of attack for steady and level flight. It is also found that tendency of instability is caused mainly by swirl effect of propeller. Rolling and yawing moment coefficients showed that aircraft not only underwent positive yaw but also rolled towards right. This yaw-roll coupling was computationally captured, however magnitude of yaw-roll coupling was found to be very small due to the swept forward wings and high wing configuration. Wind tunnel tests were carried out at 121Kts and lift and drag coefficients were compared with CFD results. Wind tunnel tests over predicted coefficient of lift at all angles of attack, however it under predicted coefficient of drag at all angles of attack. Most probable cause of this deviation seems to be more turbulence and vibration level of wind tunnel. The Zero lift drag coefficient of aircraft was found to be higher as compared to other similar aircraft like Cessna 172.