Predicting the High Angle of Attack Characteristics of a Delta Wing at Low Speed
S. Seraj, and J. R. R. A. Martins
AIAA Aviation Forum, 2021
Ensuring the safe operation of new supersonic transport aircraft requires understanding their stability during takeoff and landing. These phases involve flying at subsonic speeds and high angles of attack, where the aerodynamics are characterized by unsteady vortical flow. In this work, we assess the accuracy of Reynolds-averaged Navier–Stokes (RANS) and delayed detached eddy simulations (DDES) at these flow conditions. We use a delta wing with an aspect ratio of 2 as a simplified representation of a supersonic transport wing and compare the predicted force and moment coefficients to experimental data for angles of attack from 0 to 40 degrees. We formulate a steadiness metric to distinguish between steady and unsteady angles of attack. We find that RANS accurately predicts vortex effects in the steady regime but is inaccurate at high angles of attack where the flow is unsteady. DDES is more reliable in the unsteady regime, but the computational cost is at least 100 times that of RANS. Predicting the pitching moment at the highest angles of attack is difficult even with DDES on a 69 million cell mesh. These results provide guidelines for choosing the appropriate fidelity depending on the flow characteristics, the required accuracy, and the computational budget.