Hydraulic Comparison of Single and Multiple-Jet Impingement on a Flat Plate

Abstract

Jet impingement onto a solid boundary is of practical interest in a variety of engineering applications. The novelty of the current work is in the comparison of the single and multiple inline jets, the latter being more prevalent in application but less examined in the literature. The study focuses explicitly on the incompressible, hydraulic comparison, by performing experiments near room temperature and low speeds. Three round jets of diameter 22.23 mm are placed inline and 2 diameters apart on the ceiling of the test section. The jets issue vertically downward into a pseudo-unconfined domain whose bottom surface is 9.8 diameters from the jet outlets, acting as the plate. Three distinct flow rates are measured via Stereoscopic Particle Image Velocimetry (S-PIV) for both the single jet and triple jet geometries, where for the latter, each outlet is set to an equivalent flow rate. Several reference parameters further delineate fluid properties in the test section and ambient environment. The investigation begins with evaluation of the single jet, comparing first and second order turbulence statistics with existing literature. The triple jet cases are then presented, showing dramatically different behavior. The results of each configuration, inlet profiles, reference parameters, and uncertainty quantification are provided to embolden future work in computational fluid dynamics (CFD). The investigation concludes with the promotion of several comparisons of the single and triple jet setup and is meant to provide insight into the expected dynamic response of the fluid near and along the solid boundary.

Low Speed Wind Tunnel Flow Diagnostics and Benchmark Cases for Thermal Fluids CFD Validation Efforts

“…The top (ceiling) incorporates a large square cutout with a side length of 317.5 mm. The ceiling cutout is meant to provide a flexible "adapter" plate to other test section inserts and experiments such as the turbulent jet investigations of Reed et al [18] and Lewandowski et al [19]. All test section wall and window interfaces have been carefully machined and properly sealed to prevent unwanted boundary layer interactions or leakages from the system, while minimizing optical inaccessibility.…”