Numerical analysis of the interaction mechanism between Rayleigh-Bénard convection and oscillatory flow

In the present study, effects of oscillatory driven flow on Rayleigh – Benard convection are investigated numerically in a two-dimensional shallow enclosure. The enclosure is isothermally heated from the bottom surface and top surface is kept at isothermal initial temperature. Two side walls are thermally insulated. Pure Rayleigh-Bénard convection and pure oscillatory flows have been the subject of several investigations by using both experimental and theoretical methods. To our best knowledge, the influence of vibrating side wall on classical Rayleigh-Bénard convection has not been studied. The aspect ratio of enclosure (L/H) is considered as four and enclosure is filled with air, Pr number is 0.71. Simulations were performed for various Rayleigh numbers. Fully compressible form of the Navier-Stokes and energy equations are considered to compute the interaction of oscillatory and gravitational flow fields. A control-volume method based, explicit time-marching Flux-Corrected Transport (FCT) Algorithm is used to simulate the transport phenomena in the enclosure. The oscillatory motion of air is driven by the harmonic vibration of the left wall at various frequencies and amplitudes. The frequency of the vibrating left wall was chosen as to create a standing wave motion at first fundamental mode in the enclosure. The results of test case for pure Rayleigh-Bénard convection and pure oscillatory flow with unheated enclosure are compared with the existing literature for the validation of the algorithm utilized. It is found that the oscillatory fluid motion significantly changes the transient behavior of the thermal transport in the enclosure compared to the pure Rayleigh-Bénard convection.