Misbehaving Impingement Jets - Low-frequency lift-off and jet interaction revealed by LES

Abstract

Impingement cooling provides high heat-transfer rates but creates local hot spots due to strongly unsteady jet behavior. RANS typically predicts steady, symmetric jets because unsteadiness is absorbed by the turbulence model, while experiments show jet deflection, oscillation and interaction driven by cross-flow and shear-layer instabilities. In this work, nine round jets impinging on a uniformly heated target plate in a square channel are simulated using TRACE-LES with the WALE subgrid model and compared against high-speed PIV measurements. The LES reveals low-frequency bursts, intermittent jet lift-off and wall-jet collisions, which cause fluctuating Nusselt footprints and intermittent hot zones. These insights support cooling designs targeting jet stability and more uniform thermal loading, including stabilization concepts such as the ArcConic turbulator.