Numerical Analysis of Turbulent Heat Transfer in a Square Duct with One Rough Wall by Algebraic Turbulent Heat Flux Models.

Abstract

A numerical analysis has been performed for fully developed turbulent flow and heat transfer in a rectangular duct with smooth and rough walls by using algebraic Reynolds stress and turbulent heat flux models. The wall functions and the universal law of the wall, which are used as the boundary conditions of turbulent energy and dissipation, apply in the present analysis instead of taking shape of roughness element into account. Therefore, the roughness enters through the log law relating the velocity at the first grid point away from the wall with the friction velocity. In this numerical analysis, two kinds of turbulent heat flux models, i. e. Lumley-Launder model and Jones-Musonge model, are examined to compare the contour distributions of turbulent heat fluxes in three dimensions which have been measured in detail. In numerical analysis, convection and diffusion terms for the transport equation of turbulent heat flux are modelled as an algebraic turbulent heat flux model. From the comparison calculated results with the experimental data, it is found that two models can predict the mean temparature distributions which are distorted near the smooth wall located opposite to rough wall side. On top of that, Lumley-Launder model is able to better realize mean temperature near smooth and rough walls than Jones-Musonge model. As for comparison of the turbulent heat flux, calculated results suggest that two models predict characteristic features while two models have tendency to overestimate the experimental values.