Structure of turbulent natural convection in a heated rapidly rotating inter-disk cavity with near-axis heat sinks

Abstract

The paper presents the results of implicit LES numerical analysis of natural convection developing in a rapidly rotating inter-disk cavity with the width-to-radius aspect ratio equal to 0.13. The convection under study is developed under conditions of a prescribed temperature distribution over the disk surfaces and heat removing action of two near-axis volume sinks of a proper intensity. The thermal conditions are defined on the base of experimental data available in the literature for the prototype case of mixed-convection flow in a cavity heated from the side of the disk surfaces with axial throughflow of cooling air. The computations were carried out for the Ekman layer equal to 0.28· 10−4, if evaluated with the cavity width. Using the closed-cavity model with near-axis heat sinks, principal features of the flow structure and heat transfer, revealed previously for the prototype case of mixed convection have been reproduced successfully, including formation of a pair of global cyclonic/anticyclone vortices and a cold flow core of nearly constant temperature. It is shown also that each near-disk shear layer can be subdivided into a relatively thin highly gradient “internal” Ekman-type layer and a much thicker “outer” layer, which thickness is of the same order as the thermal layer thickness. For the case considered, groups of elongated regular structures occur within the outer layer that can be detected by analyzing the low-speed fluid motion in the axial direction. Further studies are needed to reveal physical reasons of occurring these structures.