FDS Mesh
Enter the x, y, z dimensions (meters) and your expected HRR
NOTE: The calculator presented below is only indicative mesh size, and a grid sensitivity analysis should be used to verify the mesh size used. 

For simulations involving buoyant plumes, a measure of how well the flow field is resolved is given by
the non-dimensional expression
D*/δx, where D* is a characteristic fire diameter:


and δx is the nominal size of a mesh cell. The quantity, Q˙, is the total heat release rate of the fire. If it changes over time, you should consider the corresponding change in resolution. The quantity D*/δx can be thought of as the number of computational cells spanning the characteristic (not necessarily the physical) diameter of the fire. The more cells spanning the fire, the better the resolution of the  calculation. It is better to assess the quality of the mesh in terms of this non-dimensional parameter, rather than an absolute mesh cell size. For example, a cell size of 10 cm may be 'adequate,' in some sense, for evaluating the spread of smoke and heat through a building from a sizable fire, but may not be appropriate to study a very small, smouldering source.

There are a number of special output quantities that provide local measures of grid resolution which should be considered in addition to the quantity above. They are listed below.


 A Posteriori Mesh Quality Metrics

  • Measure of Turbulence Resolution

  • Wavelet Error Measure

  • Local Cell Reynolds Number

  • Near-Wall Grid Resolution


This application was developed based on the information provided in the FDS User Guide (NIST Special Publication 1019 Sixth Edition).