When the radiation model can be used?

If the radiation heat flow is comparable with other heat flow, which is the main heat flow source in the problem (for example, convective heat flow), you have to use a radiation model.

The radiation heat flow can be evaluated based on temperature difference between surrounding environment and the body’s surface using the Stefan-Boltzmann's law:

rad eq 11

The formula above represents the low for the absolutely black body (Plankian radiator). For real bodies you have to multiply the value by emissivity factor.

rad eq 22

At present, usage of PrePostprocessor (PPP) is officially supported only for Windows. However, sometimes it is necessary to run PPP on Linux too. Customers of FlowVision have the ability to do so due to special software, like Wine, that allows running windows applications on Linux. Let us demonstrate how to run PPP on Linux using Wine-5.0 on Ubuntu 20.04.2, to show you just how easy it is. The software version used in this article is FlowVision 3.12.02.

What cells can be called Small cells

In FlowVision uses Cartesian grid that can be automatically locally downscaled. Grid cells intersecting computational domain boundaries and computational subregions are clipped by boundary surfaces.

fig1 cutcell

Fig.1. Splitting cells by geometry surface

After such clipping it is possible that size of new cells will be in many times smaller than initial cell:

fig2 smallcells

Fig. 2. Small cells