An experimental study on the flow within two disks

摘要

The present experimental study concerns the flows generated within the gap of two parallel disks. For the sink-flow the reduction of the cross-sectional area along the flow direction drives the average velocity to increase which is accompanied by a static pressure drop. Due to the non-slip requirement on the upper and lower disks, a boundary layer forms. Increase of the local inertia to viscous forces ratio forces the radial velocity profile to flatten mid-channel. As the radius becomes smaller, the plateau progressively expands towards the wall. The source-flow in comparison to sink-flow, exhibits a reverse behavior of the pressure along the flow direction. However, there is a special phenomenon associated with this type of flow field, which is absent in the previous case. Fluid particles near the walls, moving within an adverse pressure gradient, experience a flow reversal. The later produces a vortex that is clearly evident in the pressure profile. The experimental pressure profiles for sink- and source-flows with swirl indicate a pressure variation qualitatively similar to that without swirl, but the generated strong vortex makes the drop more dramatic. Reasonable correlation for the inflow with the previously developed theory is apparent.