Spectral analysis on transport budgets of turbulent heat fluxes in plane Couette turbulence

TL;DR

This study investigates how turbulent heat fluxes are transported across scales in wall turbulence using spectral analysis of direct numerical simulation data of plane Couette flow, revealing similarities with Reynolds stress transport.

Contribution

It provides a detailed spectral analysis of turbulent heat flux transport in plane Couette flow, highlighting the roles of interscale transfer and spatial diffusion, which is a novel focus in heat transfer turbulence studies.

Findings

Spectral transport of temperature fluctuations resembles that of Reynolds stresses.

Inverse interscale transfer is observed in both heat flux and Reynolds stress transport.

Heat flux transport mechanisms are similar to those of turbulent energy in wall turbulence.

Abstract

In recent years, scale-by-scale energy transport in wall turbulence has been intensively studied, and the complex spatial and interscale transfer of turbulent energy has been investigated. As the enhancement of heat transfer is one of the most important aspects of turbulence from an engineering perspective, it is also important to study how turbulent heat fluxes are transported in space and in scale by nonlinear multi-scale interactions in wall turbulence as well as turbulent energy. In the present study, the spectral transport budgets of turbulent heat fluxes are investigated based on direct numerical simulation data of a turbulent plane Couette flow with a passive scalar heat transfer. The transport budgets of spanwise spectra of temperature fluctuation and velocity-temperature correlations are investigated in detail in comparison to those of the corresponding Reynolds stress spectra. The similarity and difference between those scale-by-scale transports are discussed, with a particular focus on the roles of interscale transport and spatial turbulent diffusion. As a result, it is found that the spectral transport of the temperature-related statistics is quite similar to those of the Reynolds stresses, and in particular inverse interscale transfer is commonly observed throughout the channel in both transport of the Reynolds shear stress and wall-normal turbulent heat flux