INFLUENCE OF THE GRAVITY FIELD ON THE TURBULENCE SEEN BY HEAVY DISCRETE PARTICLES IN AN INHOMOGENEOUS FLOW

摘要

The motion of heavy discrete particles in a fully developed horizontal channel flow is investigated by means of direct numerical simulation (DNS). The paper explores the influence of the gravity field on the decorrelation time scales of the fluid seen by the discrete particles comparing to those obtained without external forces (Arcen et al., 2004). As expected, the crossing trajectory effect introduced by the presence of gravity induces a decrease of such time scales in all directions. The data extracted from DNS also enable to test the ability of the famous expressions proposed by Csanady (1963) to model the time scales of the fluid seen in an inhomogeneous flow, under conditions which are somewhat far from his theoretical analysis. It is demonstrated that the time scale decrease is about two times more important in the directions perpendicular to the mean relative velocity, a result which is qualitatively conform to Csanady's analysis although the mean relative velocity and the turbulent intensity are of the same order.