Selective control of Poiseuille Rayleigh Bénard flows instabilities by spanwise dielectric-barrier-discharge plasma actuation

Abstract

In this study, a body force model of dielectric barrier discharge plasma actuators is employed in Navier–Stokes computations to investigate the effect of the convective instability of Poiseuille Rayleigh Bénard (PRB) flow. We considered PRB flows (Pr = 2/3) in air in channels with an aspect ratio A = L/H = 20, with Reynolds numbers in the range of 10 ≤ Re ≤ 100 and a Rayleigh number of Ra = 104. The effect of flow Reynolds number, duty cycle, and burst frequency of plasma actuation on the PRB flows are studied. The results demonstrate that induced vortices near the plasma actuators enhance the development of thermoconvective transversal rolls, significantly improving heat transfer efficiency. At Reynolds number Re=25, the thermoconvective transversal roll region is extended by a factor of two, resulting in a threefold increase in heat transfer efficiency. As the Reynolds number increases, the influence of plasma-induced vortices on PRB flow field instability diminishes. When Re=100, plasma-induced vortices no longer change the flow field structure. The duty cycle significantly influences flow field instability, and the flow field structure varies greatly at different duty cycles, with higher duty cycles leading to larger heat transfer coefficients. In contrast, burst frequency has a relatively minor impact on flow field structure but results in increased heat transfer efficiency as frequency rises. Furthermore, by means of the Lagrangian method, we observe that the size and displacement of the induced vortex produced by the plasma actuator increase with the increasing duty cycle but decrease with increasing burst frequency.