An experimental investigation of the surface flow and wake dynamics associated with transverse flow over wavy cylinders
Fluid flow over wavy and right circular cylinders was investigated experimentally in the TAMU 2' x 3' wind tunnel and 2' x 3' water tunnel. Surface-pressure and three-component laser-Doppler-velocimetry measurements were obtained at a Reynolds number of 20,000 based on mean diameter. Flow-visualization tests were conducted for right circular cylinders at Reynolds numbers from 330 to 21,000 and for wavy cylinders at Reynolds numbers of 5,000, 10,000 and 20,000. These tests revealed new information concerning the secondary streamwise vortical structures (ribs) in the immediate wake of a right circular cylinder. The formation of the ribs was observed to be linked to an interaction between the near-surface flow on the leeward side of the cylinder and each von Karman vortex as it advected from the vortex-formation region. The spanwise spacing of the ribs in the immediate wake was independent of Reynolds number over the range of Reynolds numbers tested. The ribs significantly affected the von Karman vortices at the upstream end of each braid and rapidly distorted stream surfaces as they were entrained into the wake. The wavy-cylinder flow field exhibited streamwise trailing vortices originating at the boundary-layer separation lines near the geometric nodes. The trailing vortices caused the width of the wake to shrink behind the geometric nodes and expand behind the geometric saddles. The behavior of these structures, in response to the von Karman vortex shedding, indicated that pairing of counter-rotating streamwise vortices can be suppressed by the application of an axial strain field. The wavy-cylinder geometry had no significant effect on the spanwise spacing or the spatial locations of the rib structures. Despite large spanwise variations in the vortex-formation region, the velocity and Reynolds shear-stress fields in the wake of a wavy cylinder rapidly approached a state of spanwise uniformity.
- Research Organization:
- Texas A and M Univ., College Station, TX (United States)
- OSTI ID:
- 7115509
- Country of Publication:
- United States
- Language:
- English
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