Understanding the flow behavior around spheres is of great importance when it comes to improving the efficiency of any industrial application involving multiphase flow systems. The purpose with this study is to continue the work and further investigate the wake dynamics behind interacting spheres under steady and periodic free-stream conditions. Both single and dual sphere configurations are considered, focusing on Reynolds number at values around which, flow transitions have been found to occur.

The results shows that "lock on" to the free-stream flow frequency is more likely to occur for free-stream frequencies greater than the frequency associated with the natural vortex shedding. The appearance of a low frequeny mode can often be related to a swirling motion of the wake. Also, the vortex shedding for tandem config-urations is delayed at short inter-particle distances and the vorticle strucctures in the flow field of two spheres in tandem are different as compared to those observed for a single sphere