In this work is presented particles size analyses techniques under turbulent flow using the equivalent sphere diameter (Re > 3000) where the Newton law is applied. In the case of intermediary flow (0,2 < Re < 3000) it can be used for example Abraham's equation, which gives excellent results until Re = 5000. But it is necessary to use a drag coefficient that depend on Reynolds number and the Reynolds number depends on particle settling velocity. This calculation should be done by iterative process like the one presented in appendix. It is presented also corrections because of particles concentration and the influence of particle shape on terminal falling velocity of those particles.
settling; particles in viscous fluid; drag force
