Flow structure identification and analysis in fin arrays produced by cold spray additive manufacturing

The focus of this work is the identification and analysis of the flow structures found in pyramidal pin fin arrays produced using the Masked Cold Gas Dynamic Spraying (MCGDS) additive manufacturing process. The observed flow structures are described, with classic double recirculation patterns being identified. The turbulence intensity levels of the flow in the axial flow channels was measured and it was found that although the flow rates considered in this work correspond to low Reynolds numbers (500-3000), significant turbulence intensity levels are found. Furthermore, these levels increase as the flow progresses downstream, even though the large scale flow structures are well established after a few rows (as little as two in this case). A slight misalignment of the axial and transverse flow channels resulting from imperfections in the masks caused a bypass flow structure to arise in the wake of the pin fins, replacing the double recirculation pattern observed when there is no such misalignment. A CFD model was used to investigate the effect of these misalignments on heat transfer efficiency and predicted that there would be no significant effect in the configurations studied. Finally, this work shows the importance of not only considering the flow structures in the fin's wake, but also the effect of these structures on the turbulence levels of the axial flow channels, which could significantly affect the thermal and hydrodynamic performance.