SL-08-017 -- Coarse-Grid CFD: The Effect of Grid Size on Data Center Modeling PDF

A substantial reduction in analysis time would greatly aid the proliferation of CFD-based modeling tools which, in turn, would reduce IT equipment operating temperatures and energy consumption. As solution time is dominated by total grid count, an obvious question is: how coarse can the grid be made while retaining meaningful accuracy? This paper exams the effect of grid size on solution time and accuracy. Ten data center layouts, based on actual facilities, are analyzed over a range of approximately-uniform grid sizes with a commercially available CFD package. Accuracy improves significantly as average grid size is reduced to about six inches. As grid size is further reduced from six to two inches, results improve only marginally while solution time increases by about a factor of 50. Finally, an example in which the local grid size near IT racks is varied independently from the global (room) grid suggests that substantially coarser grids may be used for much of the data center so long as the grid is more refined in key areas of interest.

Units: I-P