Three-dimensional Flow Dynamics Research Articles

Mesoscopic solvent simulations: multiparticle-collision dynamics of three-dimensional flows.

A recently developed mesoscopic solvent model with multiparticle-collision dynamics is applied to three-dimensional solvent flows in a channel with and without a spherical obstacle. The advantage of a gravitationally driven flow of the solvent over the flow induced by a pressure gradient in the calculation of the solvent viscosity is demonstrated. Three different algorithms for stochastic collision steps are investigated and compared. In particular, we have examined an alternative algorithm with relative velocities drawn from a Maxwell-Boltzmann distribution at each collision step. This algorithm increases the numerical efficiency of the mesoscopic model for solvent flows with low and intermediate Reynolds numbers. Our simulation results for the recirculation length of stationary vortices behind a spherical obstacle are in good agreement with the previous experimental measurements.

Flow visualization studies of a swirling flow in a cylinder

The three-dimensional flow dynamics of a cylindrical cyclone with tangential inlet and tangential exit with an aspect ratio of 2 and 4 was studied using flow visualization. Photographs of circular and longitudinal cross sections of the cylinder revealed stable three-dimensional flow structure in the cylinder. The primary flow was observed to follow a helical pattern that surrounded a secondary flow. The secondary flow was characterized by a single vortex that circulated around the cylinder axis and occupied a large fraction of the cylinder diameter. The secondary flow was seen to include two cells of rotation in skewed planes for an aspects ratio of 2 and four cells for an aspect ratio of 4. Qualitatively, no change in flow structure was seen for a Reynolds number of 15,000–60,000.