I am using parallel fluent and using a cluster of three PC's. When I made a comparison of time taken to execute same number of iterations for same problem, I was astonished to note that cluster of three PCs take more time as compared to a single PC. What is the problem? Thanks

There may not be a problem at all. If the case is only small then fluent spends more time communicating between processors than it does solving the equations. We have a four processor unit here and more often than not it is quicker to run the solution on two processors than on four. It is possible to increases the number of iterations between communications but we have found that this can lead to erroneous solutions at the joining of the partitions.

Stuart