High-order Large Eddy Simulations of Confined Rotor-Stator Flows

Abstract

In many engineering and industrial applications, the investigation of rotating turbulent flow is of great interest. In rotor-stator cavities, the centrifugal and Coriolis forces have a strong influence on the turbulence by producing a secondary flow in the meridian plane composed of two thin boundary layers along the disks separated by a non-viscous geostrophic core. Most numerical simulations have been performed using RANS and URANS modelling, and very few investigations have been performed using LES. This paper reports on quantitative comparisons of two high-order LES methods to predict a turbulent rotor-stator flow at the rotational Reynolds number Re=400000. The classical dynamic Smagorinsky model for the subgrid-scale stress (Germano et al., Phys Fluids A 3(7):1760-1765, 1991) is compared to a spectral vanishing viscosity technique (S\'everac & Serre, J Comp Phys 226(2):1234-1255, 2007). Numerical results include both instantaneous data and postprocessed statistics. The results show that both LES methods are able to accurately describe the unsteady flow structures and to satisfactorily predict mean velocities as well as Reynolds stress tensor components. A slight advantage is given to the spectral SVV approach in terms of accuracy and CPU cost. The strong improvements obtained in the present results with respect to RANS results confirm that LES is the appropriate level of modelling for flows in which fully turbulent and transition regimes are involved

Numerical Simulations of a Middle Gap Turbulent Taylor-Couette-Poiseuille Flow

“…The LES code developed by Viazzo et al [7] has been extended here to its multidomain version using the methodology described in [1]. This new approach has been fully validated against the velocity measurements of Nouri and Whitelaw [5] and the numerical results of Chung et al [2] in an opened Taylor-Couette system with an axial throughflow.…”

“…It has been recently validated in the case of turbulent rotor-stator flows in cylindrical coordinates by Viazzo et al [7]. The time advancement is second order accurate and based on the explicit Adams-Bashforth scheme for the convective terms and an implicit backward Euler scheme for the viscous ones.…”

Large eddy simulations of Taylor-Couette-Poiseuille flows in a narrow-gap system

“…It has been recently validated in the case of turbulent interdisk rotor-stator flows in cylindrical coordinates by Viazzo et al 18 but also for turbulent Taylor-Couette-Poiseuille flows in a middle-gap cavity by Oguic et al 19 The time advancement is second-order accurate and is based on the explicit Adams-Bashforth scheme for the convective terms and an implicit backward Euler scheme for the viscous terms. The derivatives are approximated using fourth-order compact formula in the radial and axial directions.…”

“…The classical Smagorinsky model appeared to be too dissipative in a previous work on turbulent rotorstator interdisk flows. 18 Thus, one chose to switch to the dynamic Smagorinsky model developed by Germano et al, 24 which overcomes some of the drawbacks of the classical Smagorinsky model: it suppresses its excessive dissipation, exhibits the correct behavior close to the walls and in laminar regions and does not formally prohibit energy backscatter from the small to the large scales. The constant C S is replaced by a coefficient C d , which is dynamically computed.…”

Effect of Axial Clearance on the Flow Structure around a Rotating Disk Enclosed in a Cylindrical Casing

“…including Kármán flow, Bödewadt flow and Taylor vortex flow, and they have engaged historical interests in theoretical, experimental and numerical studies. The cylindrical rotor-stator cavity flow is the flow between a rotating disk and a stationary disk enclosed by an outer casing, and it presents one of the three-dimensional cross flow models [1] [2]. The rotation of the disk makes an Ekman layer on the rotating disk and a Bödewadt layer on the stationary disk.…”