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research-article

Large-eddy simulation of buoyancy-induced flow in a sealed rotating cavity

[+] Author and Article Information
Diogo Berta Pitz

Thermo-Fluid Systems University Technology Centre, Department of Mechanical Engineering Sciences, University of Surrey, Guildford, United Kingdom; CAPES Foundation, Ministry of Education of Brazil, Brasília, Brazil
d.bertapitz@surrey.ac.uk

Dr. John W. Chew

Thermo-Fluid Systems University Technology Centre, Department of Mechanical Engineering Sciences, University of Surrey, Guildford, United Kingdom
j.chew@surrey.ac.uk

Olaf Marxen

Thermo-Fluid Systems University Technology Centre, Department of Mechanical Engineering Sciences, University of Surrey, Guildford, United Kingdom
o.marxen@surrey.ac.uk

1Corresponding author.

ASME doi:10.1115/1.4041113 History: Received July 03, 2018; Revised July 15, 2018

Abstract

Buoyancy-induced flows occur in the rotating cavities of gas turbine internal air systems, and are particularly challenging to model due to the inherently unsteadiness of these flows. While the global features of such flows are well documented, detailed analyses of the unsteady structure and turbulent quantities have not been reported. In this work we use a high-order numerical method to perform large-eddy simulation (LES) of buoyancy-induced flow in a sealed rotating cavity with either adiabatic or heated disks. New insight is given into long-standing questions regarding the flow characteristics and nature of the boundary layers. The analyses focus on showing time-averaged quantities, including temperature and velocity fluctuations, as well as on the effect of the centrifugal Rayleigh number on the flow structure. Using velocity and temperature data collected over several revolutions of the system, the shroud and disk boundary layers are analysed in detail. The instantaneous flow structure contains pairs of large, counter-rotating convection rolls, and it is shown that unsteady laminar Ekman boundary layers near the disks are driven by the interior flow structure. The shroud thermal boundary layer scales as approximately Ra^-1/3 , in agreement with observations for natural convection under gravity.

Copyright (c) 2018 by ASME
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