On the flow topology of swirl jets upon impingement

TL;DR

This study investigates the flow topology of swirl jets impinging on a flat surface, combining experimental PIV data and numerical simulations to analyze flow structures, turbulence, and heat transfer implications at various distances and Reynolds numbers.

Contribution

It provides new insights into the flow structures and turbulence characteristics of swirl jet impingement, supported by combined experimental and numerical analysis, focusing on the effects of impingement distance.

Findings

Turbulence is more intense at smaller jet-plate distances (H/D ≤ 2).

Proper Orthogonal Decomposition reveals dominant coherent structures vary with impingement distance.

Flow topology and turbulence characteristics influence heat transfer efficiency.

Abstract

Jet impingement enhances heat transfer and is characterised by the complex flow patterns formed when a jet impacts a plate aligned normal to it. While traditional round jet impingement has been extensively studied to understand flow and associated heat transfer, there is still room for research in investigating flow structures in swirl jet impingement. This paper focuses on the flow topology of swirl jets generated by a 45-degree vane swirler, impinging on a flat plate studied at dimensionless jet-plate distances (H/D=1-4) and Reynolds numbers (Re = 16600 and 23000). The flow structures, mean velocity components, and turbulence characteristics are presented using a 2D Particle Image Velocimetry (PIV) experiment at the front and top planes. Furthermore, results from the 3D numerical simulations are presented to support the results where the PIV study had experimental limitations. The effect of impingement distance or jet-plate distance on the mean flow properties and turbulence parameters is discussed. A Proper Orthogonal Decomposition (POD) analysis has been performed to understand the dominant coherent structures in different cases of impingement distance. We show that the turbulence parameters are more pronounced at smaller jet-plate distances $(H/D \leq 2)$, which could explain the enhanced heat transfer for these jets.