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Observations of Laminar Surface Shear Stress Patterns on the Sidewall of a Rectangular, Mach 3 Quiet Tunnel Using Liquid Crystal CoatingsA shear-stress--sensitive liquid crystal coating (LCC) was used to visualize the surface shear stress distribution on the flat sidewall of the MSU quiet supersonic tunnel as a function of flow stagnation pressure. Under conditions of quiet operation, the LCC color-change response indicated the existence of a nonuniform surface shear stress distribution. This shear pattern was characterized by an elongated, down st ream-point ing triangular region of relatively low shear, with its apex on and its axis coincident with, the sidewall centerline. This low-shear zone was bounded symmetrically by two regions of relatively higher shear; these high-shear zones originated within the concave-curvature portion of the nozzle, in the corners between the flat sidewall and the contoured upper and lower nozzle surfaces. A 3-D Navier-Stokes code was used to compute the pressure and surface shear distributions on the sidewall. Flow-expansion-induced transverse pressure gradients on the nozzle sidewall generated symmetric inflows from the corners towards the sidewall centerline; these inflows caused a thickening of the sidewall boundary layer along the centerline, resulting in lower shear stresses consistent with the liquid crystal results. Peripherally nonuniform laminar boundary layer development, and the associated stability of such complex 3-D flows, must be considered in quiet-tunnel applications using rectangular nozzles. A color video will be shown.
Document ID
20010114152
Acquisition Source
Ames Research Center
Document Type
Preprint (Draft being sent to journal)
Authors
Reda, D.
(NASA Ames Research Center Moffett Field, CA United States)
King, L.
(NASA Ames Research Center Moffett Field, CA United States)
Date Acquired
August 20, 2013
Publication Date
May 16, 1994
Subject Category
Fluid Mechanics And Thermodynamics
Meeting Information
Meeting: Fluid Dynamics
Location: Atlanta, GA
Country: United States
Start Date: November 20, 1994
End Date: November 24, 1994
Funding Number(s)
PROJECT: RTOP 505-59-50
CONTRACT_GRANT: NAC2-659
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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