PIV analysis of confined multiple jets impinging on a step surface

Abstract

Forced convection by submerged multiple jet impingement for cooling applications is widely implemented in several industrial sectors. However, the complexity of the flow makes this process difficult to control. Therefore, it is important to conduct an in-depth study in order to characterize the flow field and this is possible through Particle Image Velocimetry (PIV) technique. PIV allows the measurement of the velocity field and information regarding flow vorticity and turbulence intensity can be obtained. To conduct the PIV measurements, an experimental setup was specially built to analyze the flow dynamics of multiple air jets impinging on a surface with a step. In PIV, the selection of the most appropriate tracer particles is crucial to ensure accurate measurements. In that sense, this work comprises an analysis of different seeding particles produced by a Concept Smoke Aerotech system. The measurement region consists of an array of multiple air jets spaced 3 D (jet diameters) between them according to a staggered configuration. The jets are confined and a distance between the nozzle plate and the target surface of 2 D is applied. The central, back, and front rows are analyzed in order to determine the effect of the jet’s interactions on the velocity fields and heat transfer. The results show that the complexity of the flow is increased by the implementation of a non-flat surface. The step induces a strong flow reversal that affects the jet flow development over the surface. Moreover, the measured data highlights the complex interactions between jets and confirm that PIV is able to capture the large-scale structures induced in the vicinity of the target plate, as well as the strong fountain flows generated between the adjacent jets. Furthermore, the results show that the combination of PIV and heat flux sensors is appropriate to characterize the jet’s flow dynamics and the heat transfer of multiple jets impinging on a surface, providing relevant insights for several engineering applications. This study underlines the advantages of the PIV system for a detailed characterization of a multiple jet impingement flow and the importance of a proper definition of the experimental condition to ensure the accuracy of the measurements.