Is it possible to calculate mean and prime2Mean values of U, P in OpenFOAM post-processing utility as I have already finished my simulations and forgot to include them as a function in controlDict ?
Unfortunately no, since it requires data from each individual time step. If you have saved a good amount of data, you may be able to get a sense of mean values, but I would not trust them in the same robust sense as the prime2Mean function.