Experiments in Near-Field of Turbulent Jets into a Crossflow

Abstract

Low-speed wind tunnel experiments were conducted to examine the effects of jet exit behavior on the near-field characteristics of jets in crossflow. To better understand this problem, a row of six square jets were perpendicularly injected into the main turbulent flow. The jet-to-crossflow velocity ratios examined were 0.25, 0.5 and 1.0, while the jet spacing to jet diameter was 3.0. No significant temperature differences between the jet and the crossflow were introduced. The analysis of the vertical structure of the transverse jets, including focusing on the jet shear layer and the vorticity dynamics of the exiting jets, is complicated. The vorticity around the circumference of the jets was tracked to identify its relative contributions to the nascent streamwise vortices, which evolve eventually into kidney vortices downstream. The mean velocities and the six turbulent stresses were measured using a dual-sensor probe (X-array wire). Comparisons between the present work in the measurement sections with previous experimental data show reasonably good agreement. In this paper, the flow statistics are reported in the form of vector plots, contours and X-Y graphs, showing the velocity vectors, turbulence intensities and Reynolds stresses.