Three-Dimensional Plasma-Based Stall Control Simulations with Coupled First-Principles Approaches.

摘要

Numerical simulations are employed to understand the mechanisms by which asymmetric dielectric barrier discharges operating at radio frequencies reduce or eliminate stall. The specific focus is on a NACA 0015 wing section at a nominal Reynolds number of 45,000 and 15 degree angle-of-attack. The body force is obtained separately from both phenomenological and first-principles based models. To overcome the daunting complexity of the latter approach, a procedure to couple unsteady force fields obtained from multi-fluid models to very high-fidelity implicit large-eddy simulations is developed, implemented and evaluated for a 5kHz signal. The paper discusses results with both approaches to understand the effect of Reynolds number, angle of attack, actuator strength and location as well as unsteadiness of actuation through radio frequency excitation and duty cycle variation. The results are assimilated in the context of the combined impact of near wall momentum enhancement and transition to turbulence. It is shown that force fluctuations at radio frequencies result in the development of a rich turbulence structure downstream of actuation. These observations, as well as details of the acoustic signal, cannot be obtained from the simplified steady force model. For higher Reynolds numbers and relatively lower actuation forces, mechanisms that enhance turbulence development are the dominant consideration. These include not only radio-frequency force variations but also streamwise vorticity generation through edge effects associated with finite-span actuation and wide-spectrum input associated with switch-on/switch-off inherent in duty cycles.