  Grid independent is associated with the accuracy or even rationality of
numerical results. This paper takes two-dimensional steady heat transfer for
example to reveal the effect of grid resolution on numerical results. The law
of grid dependence is obtained and a simple mathematical formula is presented.
The production acquired here can be used as the guidance in choosing grid
density in numerical simulation and get exact grid independent value without
using infinite fine grid. Through analyzing grid independent, we can find the
minimum number of grid cells that is needed to get grid-independent results.
Such strategy can save computational resource while ensure a rational
computational result.
