Aeronautical Engineering/rotor wake modelling

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Expert: - 3/15/2010


Question

rotor wake
Dear sir,
I am implementing a software code for modeling the wake of a hovering rotor by coupling free wake method and vortex lattice method.In the result I have some problems and it is difficult to me find solutions for these issues. My main problem is that near the root of blade the wake has tendency of lifting the wake. I have shown this issue by the image attached. Also end of the wake there is a tendency of lifting the wake. these effects finally leads to up lift the wake.But wake roll up effect on near the tip can be seen successfully. So please kind me to give some reasons for my issues.
Nalaka Samaraweera
University of Moratuwa
SriLanka

Answer
Wake roll up at a blade tip occurs because the high pressure air on the lower surface tends to flow around the tip to the low pressure area on the upper surface.  This does not happen on a wing because the fuselage blocks the flow.  But on a rotor, there is no fuselage to block the root wake from rolling up toward the upper surface in the same way as the flow does at the tip.  There will be some blockage from the rotor shaft and pitch hardware.  But some roll up is possible - your solution may be correct.

Paul Soderman

Expertise

Aeronautics, Fluid Mechanics, Aeroacoustics, Noise Control, Muffler Design, Wind Tunnel Research.... I know nothing about India - do not ask about schools, jobs, application requirements, career choices, etc. for India. Please, no text message verbiage; I prefer full words in full sentences. Thanks.

Experience

38 years as research engineer at NASA

Publications
AIAA, NASA

Education/Credentials
B.S. and M.S. Aeronautical Engineering - U. of Washington Graduate work Standford U.

Awards and Honors
AIAA Associate Fellow (American Institute of Aeronautics and Astronautics)

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