Practical indicators for assessing the magnitudes of wall radiative flux and of coupling effects between radiation and other heat transfer modes on the temperature law-of-the wall in turbulent gaseous boundary layers

•Radiation effects in gaseous turbulent boundary layers are characterized.•Non-coupled 1D simulations are validated against coupled DNS/Monte Carlo results.•The impact of system size, Reynolds number, wall emissivity and pressure is studied.•Cases where the temperature law-of-the-wall is modified by radiation are identified.