Sectional Flow Structures in Near Wake of Elevated Jets in a Crossflow

Abstract

Near-wake flow structures in the symmetry and horizontal planes of elevated jets in a crossflow are studied experimentally in a wind tunnel via a laser Doppler velocimeter. The measured velocity vector fields and the corresponding streamline patterns in the symmetry and several horizontal planes display tremendous variations in different characteristic regimes of jet-to-crossflow momentum flux ratios. They are typically termed crossflow-dominated, transitional, and jet-dominated regimes. The complex flow behaviors are the result of the interactions among the downwash effect, which is induced by the crossflow passing over the tube tip; the upshear effect induced by the issuing jet; and the wakes behind the jet and the tube. Topological flow patterns are proposed to delineate the measured flow structures. Impact effects of the crossflow on the jet are discussed in two aspects, that is, the geometry and the turbulence properties of the central streamline. The geometric characteristics of the deflected jet in different flow regimes are presented