Some Remarks on the Momentum Equation for Fast Transients

Abstract

A study of the effects of unsteadiness on flow characteristics is performed, showing that in fast transients both local inertia and friction forces are to be evaluated in a specific manner. Because these two effects are correlated and seem to depend on the same quantities, in this paper a single expression is proposed for both. This expression, in the form of an addition to the friction term, can be viewed as an improvement on a preceding expression by the writers already empirically validated. Column separation phenomena, which give rise to very fast transients when cavities collapse, are a specific case where the proposed expression should be used.