Flow regime prediction of a self-oscillatory flow induced by a vertical jet in a heated cavity: Computational and analytical approach

Abstract

Interaction effects between the inlet Reynolds number (250≤ Rei ≤ 3000) and the heat flux of the impingement wall (0.5 ≤ qʹ ≤ 20 kW/m2) was investigated in a vertical self-excited oscillating jet confined by a heated cavity. The results revealed that some high amounts of qʹ stop oscillating flow. Thus, this study developed a new prediction method based on an analytical approach to identify the threshold of flow regime transition from oscillatory to non-oscillatory based on Rei. To this aim, a new dimensionless number named Non-dimensional Effective Number (NEN) was introduced. The proposed NEN index refers to the ratio of the thermal power applied on the impingement wall to the effective momentum power of the incoming jet. The performance of the proposed index was examined and compared in vertical upward and downward-facing chambers for different heat flux values. Investigations indicated that the proposed analytical method and the new NEN index have a much lower computational cost, despite the very high accuracy (about 95 %) compared to the numerical results extracted from the OpenFOAM code. The results also demonstrated that vertical downward self-excited jets maintain oscillatory behavior regardless of the amount of qʹ. In this case, the frequency of oscillations varied linearly with Rei for Rei > 2000.