The unsteady nature of vortex structures has been investigated by a large eddy simulation (LES) in a propeller fan with a shroud covering only the rear region of its rotor tip. The simulation shows that the tip vortex plays a major role in the structure and unsteady behavior of the vortical flow in the propeller fan. The spiral-type breakdown of the tip vortex occurs near the midpitch, leading to significant changes in the nature of the tip vortex. The breakdown gives rise to large and cyclic movements of the tip vortex, so that the vortex impinges cyclically on the pressure surface of the adjacent blade. The movements of the tip vortex cause the leading edge separation vortex to oscillate in a cycle, but on a small scale. The movements of the vortex structures induce high-pressure fluctuations on the rotor blade and in the blade passage.

Issue Section:
Technical Papers
Keywords:
rotors, aerodynamics, vortices, numerical analysis, flow simulation, flow separation, laser Doppler anemometry
Topics:
Blades, Flow (Dynamics), Pressure, Propellers, Rotors, Vortex flow, Vortices, Wake turbulence
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Copyright © 2001
 by ASME
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