Experimental study of Counter-Rotating Vortex Pair Trajectories induced by a Round Jet in Cross-Flow at Low Velocity Ratios

TL;DR

This study experimentally investigates the trajectories of counter-rotating vortex pairs generated by a round jet in cross-flow at low velocity ratios, introducing a new momentum-based scaling law that improves trajectory collapse.

Contribution

It introduces a novel momentum ratio scaling law for CVP trajectories in jet in cross-flow experiments, enhancing the understanding of vortex behavior at low velocity ratios.

Findings

The new scaling law improves trajectory collapse quality.

The study quantifies the influence of velocity ratio, jet diameter, and boundary layer thickness.

A rigorous scaling quality factor Q is used to evaluate scaling effectiveness.

Abstract

Circular flush Jets In Cross-Flow were experimentally studied in a water tunnel using Volumetric Particle Tracking Velocimetry, for a range of jet to cross-flow velocity ratios, r, from 0.5 to 3, jet exit diameters $d$ from 0.8 cm to 1 cm and cross-flow boundary layer thickness delta from 1 to 2.5 cm. The analysis of the 3D mean velocity fields allows for the definition, computation and study of Counter-rotating Vortex Pair trajectories. The influences of r, d and delta were investigated. A new scaling based on momentum ratio r_m taking into account jet and cross-flow momentum distributions is introduced based on the analysis of jet trajectories published in the literature. Using a rigorous scaling quality factor Q to quantify how well a given scaling successfully collapses trajectories, we show that the proposed scaling also improves the collapse of CVP trajectories, leading to a final scaling law for these trajectories.