Formation and Evolution of Rayleigh-Bénard Streaks in Rotating Cavities

Abstract

This paper presents numerical investigation into the phenomena of so-called Rayleigh-Bénard streaks inside rotating-cavities. Experimental data from the University of Sussex Multiple Cavity Rig (MCR) has been used as boundary conditions for Unsteady Reynolds-Averaged Navier-Stokes (URANS) calculation using the k-ω SST turbulence model on a three cavity model of the MCR. A four-point validation is presented using comparison to experimental and historical data sets and shows encouraging agreement. The Rayleigh-Bénard streaks develop along the periphery of the rotating cavity (shroud) and are only associated with flow involved in cyclonic circulation due to the circumferential pressure gradient. These streaks modify the local Nusselt number by as much as 40% above the surface average and, given the contribution of the shroud to the total heat transfer, upwards of 60%, may be a significant factor in further work concerning rotating cavities in aero-engines. However experimental confirmation is required to ratify the existence of the structures.