The study presents an experimental investigation of flow field, an elevated circular jet of aspect ratio of 9.0, exiting orthogonal to crossflow. The experiments are conducted in a recirculating low-speed water tunnel. Both flow visualization and time-averaged particle image velocimetry (PIV) measurements are conducted to capture the flow dynamics. The PIV technique is used for the measurement of mean velocities and turbulent kinetic energy in both the symmetric (XY) and wall-parallel (XZ) planes. The aim of the study is to analyze the jet and its wake at a velocity ratio (R) of 3.0 and Reynolds number (Re) of 1000. The jet shear layer exhibits anti-clockwise vortices on the windward side and clockwise vortices on the lee-side of the jet. Streamline plots reveal the presence of an unstable focus in the jet-wake region in the symmetric plane. A detailed sectional analysis at different XZ planes indicates the existence of two sets of vortex pairs in the mean spanwise velocity contour, located both upstream and downstream of the jet. These pairs suggest the separation of crossflow around the jet on the upstream side, while the shear layer enters the jet-wake region on the downstream side. The study finds that the turbulent kinetic energy and Reynolds shear stress are highest on the uppermost plane at y = 2.5, which is situated far from the free-end of the stack.

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Flow Field Measurements of an Elevated Circular Jet in Crossflow

  • Jyoti Gupta,
  • Arun K. Saha

摘要

The study presents an experimental investigation of flow field, an elevated circular jet of aspect ratio of 9.0, exiting orthogonal to crossflow. The experiments are conducted in a recirculating low-speed water tunnel. Both flow visualization and time-averaged particle image velocimetry (PIV) measurements are conducted to capture the flow dynamics. The PIV technique is used for the measurement of mean velocities and turbulent kinetic energy in both the symmetric (XY) and wall-parallel (XZ) planes. The aim of the study is to analyze the jet and its wake at a velocity ratio (R) of 3.0 and Reynolds number (Re) of 1000. The jet shear layer exhibits anti-clockwise vortices on the windward side and clockwise vortices on the lee-side of the jet. Streamline plots reveal the presence of an unstable focus in the jet-wake region in the symmetric plane. A detailed sectional analysis at different XZ planes indicates the existence of two sets of vortex pairs in the mean spanwise velocity contour, located both upstream and downstream of the jet. These pairs suggest the separation of crossflow around the jet on the upstream side, while the shear layer enters the jet-wake region on the downstream side. The study finds that the turbulent kinetic energy and Reynolds shear stress are highest on the uppermost plane at y = 2.5, which is situated far from the free-end of the stack.