Active Flow Control with Thermoacoustic Actuators

摘要

We numerically examine the effectiveness of thermoacoustic actuators that locally introduce high-intensity acoustic waves for active flow control. In this investigation, we perform LES of flow control with acoustic waves motivated by the recent development in manufacturing graphene/carbon nanotube- based surface compliant loud speakers. The interaction of the acoustic waves and turbulent flow structures is analyzed with high-fidelity LES for compressible flow over a wall-mounted hump at a Reynolds number of 0.5x1000000 and Mach number of 0.25. In the computations, we consider the use of high- frequency actuation at Helmholtz number of 3 based on performance characteristics of the graphene-based thermoacoustic actuators. We observe that the actuation is able to introduce small-scale perturbation to the shear layer in the separated flow and delay the formation of large-scale spanwise vortices. This hence elongates the recirculation zone and shifts the low-pressure region downstream of the hump. As a consequence, the drag on the hump is reduced by approximately 5% for the threedimensional calculation and up to 10% in the two- dimensional flow. The mechanism of drag reduction is different from the one using synthetic jets, which relies on reducing the size of the recirculation zone.