Computational Fluid Dynamics as good as it gets.

Prediction capability of RANS turbulence models for asymmetrically heated high-aspect-ratio duct flows

T. Kaller, S. Hickel, N.A. Adams (2020)  
AIAA Scitech paper 2020-0354. doi: 10.2514/6.2020-0354

We present well-resolved RANS simulations of a high-aspect-ratio generic cooling duct configuration consisting of an adiabatic straight feed line followed by a heated straight section ending with a 90° bend. The configuration is asymmetrically heated with a temperature difference of ∆T = 40 K. As fluid liquid water is used at a bulk Reynolds number of Reb = 110 000.

The setup follows an experimental reference case, which has also been investigated using a well-resolved LES. The current investigation focuses on the prediction capabilities of different RANS turbulence closure models for the duct flow field, defined by the interaction of secondary flows and turbulent heat transfer. In the straight duct only turbulence-induced secondary flow is present, which becomes weaker along the heated duct due to the viscosity reduction, leading in turn to a reduced mixing. In the curved section, the stronger pressure-induced secondary flow superimposes the turbulence-induced one increasing the mixing of hot and cold fluid. A well-resolved LES serves as comparison database for the straight duct results.

 

Setup of cooling duct simulations. The focus of this paper is on the straight part.

 

Secondary flow in the lower quarter of the adiabatic duct for (a) LES, (b) BSL EARSM, (c) BSL RSM and (d) SSG RSM models. Isolines are drawn from 0 to 2 in steps of 0.2.
Temperature increase ∆T = T − Tb in the lower quarter of the heated duct at x = 500 mm for (a) LES, (b) SST with Prt = 0.9, (c) BSL EARSM with Prt = 0.9, (d) BSL RSM with Prt = 0.9, (e) BSL RSM with the algebraic Younis model,(f) BSL RSM with additional PDEs for ui′h′, (g) SSG RSM with Prt = 0.9 and (h) SSG RSM with the anisotropic diffusion model. Isolines are drawn from 2.5 to 40 in steps of 2.5 K.

 

Publications