Numerical investigations of transonic flow over a hemisphere-on-cylinder turret based on Reynolds-averaged Navier–Stokes/large eddy simulation hybrid methods

In this paper, three Reynolds-averaged Navier–Stokes/large eddy simulation (RANS/LES) hybrid methods, detached-eddy simulation–Spalart–Allmaras (DES–SA), improved delayed DES (IDDES), and stress-blended eddy simulation (SBES), are employed to investigate unsteady transonic flows on a hemisphere-on-cylinder turret. A detailed comparison of the three hybrid methods is performed in terms of transient pressure coefficients, vortex structures, and aero-optic effects. Additionally, in-depth analyses are performed on the high-frequency pressure fluctuations at the pressure peaks and the disappearance of local shock wave at the turret top. The results show that the SBES method better describes the flow structure details in the necklace vortex region and the separated shear layer region. For the simulation of shock wave positions, the average shock positions of IDDES and SBES are more upstream than those of DES–SA. Meanwhile, the SBES and IDDES methods can capture the phenomenon of shock wave disappearance more clearly. In the simulation of aero-optic effects, when the beam is directed toward the leeward side, the time-averaged Zernike polynomial coefficients of the SBES method after the 10th term are higher than those of the other two methods, indicating that the SBES method has a better ability to resolve small-scale vortex structures and high-order optical aberrations than the other two methods. Moreover, a detailed analysis is provided for the severe high-order optical distortions that occur at the angle of 90°.