Using Particle Image Velocimetry to Visualize Jet Impingement Flow Mechanics on Modified Surfaces

In this effort, particle image velocimetry (PIV) flow visualization was utilized to examine the effects of cone and rib surface structures applied to the impingement surface under a submerged water jet array with a flat and angled confining wall. Key flow interactions, including the interactions between adjacent jets and fountains, were examined in two regions of interest with the intent to enable desirable fluid motion that is known to promote effective heat dissipation. The angled wall provides space for spent fluid to reach the outlet without affecting the performance of downstream jets, mitigating detrimental crossflow effects. Cone structures were placed underneath each nozzle. While these increased surface area in the stagnation region, slight misalignment caused uneven deflection of fluid, inhibiting fountain development. These cones are promising in hotspot applications but could cause problems with distributed heating. Triangular rib modifications were examined between the rows of jets. When oriented normal to the flow direction, reduced space between the ribs and a flat confining wall caused the flow to impact the downstream jet, effectively magnifying crossflow. However, these ribs replaced weak fountain interactions with oblique impingement of the wall jets on the rib face, which can provide far more effective thermal performance. Orienting the ribs parallel to the outflow direction enabled more effective deflection of spent fluid from the surface.