Improved delayed detached-eddy simulations of sawtooth spoiler control before supersonic cavity

- IDDES assessment of a complex geometry cavity and multiple sawtooth control devices.
- The sawteeth lift up the shear layer and promote instability by spanwise structures.
- The spoiler's presence changes the cavity flow type from closed to open.
- Significant drag reduction and noise suppression are achieved by saw-tooth spoilers.
- Spoiler with height of boundary layer thickness and 90° tooth angle performs best.

Flows at Ma=1.5 over a cavity with different leading-edge sawtooth spoilers were numerically studied using improved delayed detached-eddy simulation based on the two-equation shear stress transport model, coupled with the adaptive dissipation scheme. Transonic flow past M219 cavity was chosen as the validation case for numerical methods and mesh convergence. Comparison of predicted sound pressure levels and spectra against the measurements has proved that the major oscillation dynamics inside the cavity is captured numerically. Five sawtooth spoilers were then evaluated before the leading edge of a complex irregular cavity in a supersonic flow. It is found that the spoiler lifts the shear layer, preventing its reattachment on the cavity floor, and completely changes the cavity flow type. The presence of sawtooth is necessary to promote instability more upstream. All spoilers show significant reduction in pressure fluctuation. Pressure decrease on the cavity floor and rear wall contributes to overall drag reduction, despite the extra drag by the spoiler. The spoiler with height equal to the local boundary layer thickness and a 90° tooth angle achieves optimal and balanced performance in both drag reduction and noise suppression among the evaluated spoilers.