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Turbulence Modeling for Unsteady Transonic FlowsConditionally sampled, ensemble-averaged velocity measurements, made with a laser velocimeter, were taken in the flowfield over the rear half of an 18% thick circular arc airfoil at zero incidence tested at M = 0.76 and at a Reynolds number based on chord of 11 x 10(exp 6). Data for one cycle of periodic unsteady flow having a reduced frequency f of 0.49 are analyzed. A series of compression waves, which develop in the early stages of the cycle, strengthen and coalesce into a strong shock wave that moves toward the airfoil leading edge. A thick shear layer forms downstream of the shock wave. The kinetic energy and shear stresses increase dramatically, reach a maximum when dissipation and diffusion of the turbulence exceed production, and then decrease substantially. The response lime of the turbulence to the changes brought about by the shock-wave passage upstream depends on the shock-wave strength and position in the boundary layer. The cycle completes itself when the shock wave passes the midchord, weakens, and the shear layer collapses. Remarkably good comparisons are found with computations that employ the time-dependent Reynolds averaged form of the Navier-Stokes equations using an algebraic eddy viscosity model, developed for steady flows.
Document ID
19980213316
Acquisition Source
Ames Research Center
Document Type
Reprint (Version printed in journal)
Authors
Marvin, J. G. (NASA Ames Research Center Moffett Field, CA United States)
Levy, L. L., Jr. (NASA Ames Research Center Moffett Field, CA United States)
Seegmiller, H. L. (NASA Ames Research Center Moffett Field, CA United States)
Date Acquired
September 6, 2013
Publication Date
May 1, 1980
Publication Information
Publication: AIAA Journal
Publisher: American Inst. of Aeronautics and Astronautics
Volume: 18
Issue: 5
Subject Category
Fluid Mechanics And Heat Transfer
Report/Patent Number
AIAA Paper 79-0071
NAS 1.15:208062
NASA/TM-1979-208062
Meeting Information
Meeting: Aerospace Sciences
Location: New Orleans, LA
Country: United States
Start Date: January 15, 1979
End Date: January 17, 1979
Sponsors: American Inst. of Aeronautics and Astronautics
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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