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An experimental investigation of the mean flow field of a wavy cylinder at critical Reynolds numbers
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Fluid flow around a wavy cylinder geometry was investigated in the Texas A&M University 2'x3' wind tunnel. Tests consisted of mean surface static pressure and mean wake dynamic pressure measurements around two wavy cylinders of differing wavelength at a Reynolds number which produces laminar separation (ReD= 100,000), one producing turbulent separation (ReD= 400,000), and one transitional Reynolds number (ReD= 200,000). These tests revealed that similar characteristics exist between flow fields involving laminar and turbulent separation. The attachment line flow, and the existence of a highly three dimensional separation were characteristics found at all Reynolds numbers tested. Always characteristic of the separation were separation singularities which, at all Reynolds numbers tested, abnormally narrowed the near wake behind geometric nodes. Though these general flow characteristics were present at all Reynolds numbers tested, many other wavy cylinder flow field characteristics were found to change with a transition from laminar to turbulent separation. A state of turbulent separation caused the separation line to move downstream, greatly reducing secondary separation effects, and narrowing the wake. Movement of the separation line was small enough to indicate that its location was insensitive to the state of the boundary layer. The singularities, however, were more sensitive to the state of the boundary layer just prior to separation. The change to turbulent separation on the wavy cylinder was also found to add enough vorticity to the singularities through axial stretching to allow them to significantly influence surface flow well into the separated region of the cylinder. Not only was the separated region affected by singularities, but in some cases increased coherency of the singularities allowed them to influence the far wake as well. The far wake behind cylinder B (X/D = 2.4) was influenced by singularities which were coherent enough to withstand dissipation by the strain field in the wake. This was not the case with cylinder E (X/D = 1.2) where higher rates of model curvature caused large lateral strain fields in the wake which were capable of rapidly dissipating coherent singularities at all Reynolds numbers tested.
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Includes bibliographical references.
Damiana, Thomas Anthony (1994). An experimental investigation of the mean flow field of a wavy cylinder at critical Reynolds numbers. Master's thesis, Texas A&M University. Available electronically from
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