Radiative transfer effects in natural convection above fires—opaque approximation

In continuation of a previous paper on a similar subject, we examine here, in detail, the opaque approximation of the radiative transfer equation by retaining the vertical diffusivity term within the boundary layer theory. The results seem to indicate the presence of a layer very near the horizontal boundary of the plume where the radiation effects are dominant. The thickness of this layer tends to decrease with increasing absorption coefficient.