Dear Rob, nThe volume fraction of the diesel at the inlet is 1% . nI would say that in reality the diesel will form a stream, the smaller droplets will coalesce etc and in fact there will be a range of droplet diameters at the inlet. However, for the simulations we model different diameters (15, 30, 60, 100 microns) seperately to see how the hydrocyclone behaves across a range of conditions. nOk, yes that makes sense. Perhaps also the standard drag coefficient is not appropriate in this case?nCheersn