Swirl cooling enhancement via fluidic oscillators: Cross-flow suppression and sweeping jet dynamics

For swirl cooling systems that employ multiple inlet jets, the cross-flow generated by upstream inlets gradually forces the downstream jets to deviate, resulting in significant deterioration of heat transfer over the latter portion of the chamber. To overcome this limitation, the present study introduced a swirl cooling configuration that employed fluidic oscillators as jet nozzles for the first time. With steady inlet conditions, the fluidic oscillators could self-induce and sustain periodic sweeping jets without any moving parts, continuously agitating the near-wall fluid. An unsteady numerical investigation using URANS simulations with the SST k - ω turbulence model was conducted to examine the flow characteristics, vortex dynamics, and heat transfer performance of the oscillating swirl cooling configuration, with comparisons made against a smooth swirl chamber. The results demonstrated that the sweeping jets effectively suppressed cross-flow-induced jet deflection and maintained vigorous Görtler vortex activity along the entire chamber, even at the downstream locations where the vortex structures were nearly completely suppressed in the smooth chamber. At Re = 52,500, the peak circumferentially-averaged Nusselt number near the 5th nozzle reached approximately 190 for the oscillating configuration, while that of the smooth chamber droped to only about 55. The thermal performance factor increased from 1.27 at Re = 10,500 to 2.79 at Re = 52,500, consistently exceeding unity across the entire range, confirming that the improved thermal performance compensates for the additional frictional losses. The oscillating swirl cooling configuration achieved significant heat transfer enhancement with favorable overall thermal performance, providing a new strategy for swirl cooling designs.