Title page for ETD etd-10597-134454


Type of Document Master's Thesis
Author Madden, Michael Mark Jr.
Author's Email Address m.m.madden@worldnet.att.net
URN etd-10597-134454
Title Octant Analysis of the Reynolds Stresses in the Three Dimensional Turbulent Boundary Layer of a Prolate Spheroid
Degree Master of Science
Department Aerospace and Ocean Engineering
Advisory Committee
Advisor Name Title
Simpson, Roger L. Committee Chair
Devenport, William J. Committee Member
Neu, Wayne L. Committee Member
Keywords
  • aeropsace
  • boundary layer
  • prolate spheroid
  • octant analysis
Date of Defense 1997-07-24
Availability unrestricted
Abstract
The Reynolds stresses in a three-dimensional turbulent

boundary layer were examined using octant analysis. The

representative flow was a pressure driven, three-dimensional

turbulent boundary layer on the leeside

(x/L=0.76-0.78, f=105°-130°) of a 6:1 prolate spheroid at

10° angle of attack. The Reynolds number for the flow was

Re=4.2x10E+6. The LDV data of Chesnakas, Simpson, and Madden

(1994) were the basis of examination. This data set employed

a post-processing technique for refining the radial location

of the measurments. A least-squares fit of the Spalding wall

law was used to both correct the measurement locations and

estimate the wall shear stress. This paper presents a

previously unpublished assesment of the techinque. Octant

analysis was performed on the corrected data under

free-stream and wall-collateral coordinates. (The wall-collateral

coordinate system is aligned with the mean tangential

velocity in the buffer-layer.) The octant analysis led to

the development of a structural model that extends the

sweep/ejection process to three dimensions. Ejections and

sweeps produce w' through the same mechanism that produces

u'; they transport fluid across a spanwise velocity

gradient. The model's results remain consistent with

coordinate rotation. The model also describes the

asymmetries that evolve between ejections and sweeps with

spanwise fluctuations (w') of opposite sign. These

asymmetries cause non-zero u'w' and v'w' in the buffer

layer. Comparison of the two coordinate systems reveals

that wall-collateral coordinates provides a simpler

foundation for octant analysis. The sweep and ejection

octants maintain a nearly equal distribution of velocity

events throughout the buffer and lower log layers. Also, the

spanwise velocity profile monotonically decreases to a

constant value at the boundary layer edge, simplifying

application of the sweep/ejection model to spanwise

fluctuations. Comparison with other 3DTBL experiments

suggests that the wall-collateral coordinates are more

closely aligned with the quasi-streamwise vortex structures

than free-stream coordinates. The octant analysis also

reveals structural behavior consistent with the four

mechanisms revealed by the direct numerical simulation of

Sendstad and Moin (1992).

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