Tomographic flow structures of a round jet in a crossflow

Abstract

Flow structures in the near wake of an elevated jet in a crossflow at a large jet‐to‐ crossflow momentum flux ratio are experimentally studied in a wind tunnel. A laser‐light sheet is employed to illuminate fine smoke tracers for flow visualization. A laser Doppler velocimeter is used to measure the velocity field. Flows on the vertical symmetry plane and three horizontal planes across jet‐wake, jet‐exit, and tube‐wake regions are investigated. Smoke patterns show qualitatively apparent differences in different regions of the flow field. The measured velocity fields present quantitative characteristics of the streamlines, vorticities, and topological features of the flow structures. The flow characteristics on the symmetry plane show two bifurcation lines separated by a source point in the jet and tube wakes, respectively. Upstream from the bifurcation lines, reverse flows are observed. While downstream from the bifurcation lines, flows go directly forward. The flow structures and vorticity distributions on the horizontal planes show non‐closed recirculation zones of different topological structures in different characteristic flow regions, i.e., jet‐wake, jet‐exit, and tube‐wake. Details of the flow structures and differences in the jet and tube wakes are presented and discussed.