Transition scenario of the round jet in crossflow topology at low velocity ratios

TL;DR

This study experimentally investigates the transition of the round jet in crossflow topology at low velocity ratios, revealing new flow regimes and the conditions under which classical and deformed topologies occur.

Contribution

It provides the first detailed transition scenario of JICF topology at low velocity ratios, identifying a new transition at R<0.3 and characterizing the deformation of classical flow structures.

Findings

Discovered a new transition at R<0.3.

Revealed the deformation of classical JICF topology at intermediate R.

Identified the threshold R>1.25 for classical topology recovery.

Abstract

We study experimentally a round Jet In CrossFlow (JICF) at low values of the jet to-crossflow velocity ratio R using instantaneous and time-averaged three-dimensions three-components (3D3C) velocimetry. The difference between instantaneous and time-averaged swirling structures of the JICF is emphasized. Through the analysis of spatial distribution of instantaneous transverse and longitudinal vortices the main transitions of the JICF are characterized for 0.15 < R < 2.2. A new transition at very low velocity ratio is found (R < 0.3). When R is large enough (R > 1.25), the classic JICF topology is recovered. In between, a deformation of the classical JICF topology is observed consisting in a progressive disappearance of the leading-edge vortices, a bending of the jet trajectory and thus a strengthened interaction with the boundary layer. toward the wall. Thanks to a state-of-the-art review on the JICF topology and using visualizations of the flow structures extracted from our experimental volumetric velocimetry measurements, this article provides a complete transition scenario of the JICF topology from the high velocity ratios to the lowest ones, and gives the topological transition threshold associated with each kind of vortex.