Numerical Studies of the Influence of Strouhal Number on the Flow Characteristics of Synthetic Jet Impingement

In this work, the efficacy of synthetic jet impingement has been investigated for cooling applications. Numerical study is being carried out for two different Strouhal numbers (Sr) = 0.03 (low) and 0.43 (high) at constant Re = 3215 for 8 mm orifice diameter. In the present study, the SST k–ω model is used for the computational study along with the user-defined functions (UDF) to describe the movement of the diaphragm. The results showed that the jet’s Sr plays a significant role in the flow behaviour of SJ. At low Strouhal number (i.e., Sr = 0.03), the synthetic jet flow field is characterized by primary vortex ring followed by a trailing jet. Each vortex ring impinges on the surface separately due to the large wavelength between the coherent structures. However, high Sr jet flow field is exhibited by the train of primary vortices, which accumulate and even break up into smaller structures before impinging on the surface. At an intermediate surface spacing (z/d = 6), jet with high Sr exhibits a 9.9% higher heat transfer rate at the stagnation point than a low Sr jet. The intermittent vortex pairing in high Sr jet causes the breakdown of naturally occurring vortices and promotes a higher heat removal rate.