Numerical study of the effect of geometric scaling of a fluidic oscillator on the heat transfer and frequency of impinging sweeping jet

Abstract

In this research, the effects of a new approach of geometric scaling on the heat transfer rate of a hot plate impinged by a sweeping jet were investigated numerically. In this approach, the throat of the fluidic oscillator is constant while the geometry is scaled. Ansys Fluent 2020R2 was used to solve unsteady Reynolds-averaged Navier–Stokes (URANS) equations with a k-ω SST turbulence model inside and outside the fluidic oscillator with four scaling factors of 0.33, 0.5, 1, and 1.3 at three distance to throat diameter ratios of 4.5, 5.5, and 7.5 to analyze their effects on the heat transfer rate. The results indicated that the frequency of the sweeping jet increases by decreasing the scale factor due to shrinking the separation bubble, which increases the heat transfer rate of the hot plate. The maximum Nusselt number occurred for the scale factor of 0.33, which was 13% higher than that for the baseline geometry. Furthermore, the effect of changing the Reynolds number on the frequency of the self-sustained oscillating jet was numerically studied for the different scaled geometries to obtain a new general definition for the Strouhal number. The formation of the oscillating jet was correlated with the evolution of the separation bubble in the mixing chamber, and an appropriate length scale associated with the oscillation frequency was determined. An in-depth study demonstrated that the Strouhal number based on the new definition remained constant for the various scaled geometries.