Physical study of radiation effects on the boundary layer structure in a turbulent channel flow

Abstract

A complete numerical coupling between radiation and turbulent convection in a channel gas flow has been performed for different temperature, optical thickness (pressure) and wall emissivity conditions. In this model, radiation is treated from the CK approach and a Monte Carlo transfer method; the flow by a Direct Numerical Simulation. Both the effects of turbulence on radiation fields and of radiation on turbulent fields are accounted for.Gas–gas and gas–wall radiation interactions generate antagonist effects on the temperature and flux fields. The first one tends to increase wall conductive flux while the second one to decrease it. Consequently, the structure of the temperature field and the wall conductive flux often strongly differ from results without radiation. Classical wall log-laws for temperature are then strongly modified by the global radiation effects. Many conditions encountered in applications are discussed in the paper. The observed modifications depend on all the set of conditions (temperature level, wall emissivity, pressure, Reynolds number), i.e. on the relative magnitudes of radiation gas–gas and gas–wall phenomena and of global radiation flux and conductive flux without radiation.