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Tenth International Symposium on Turbulence and Shear Flow Phenomena
July, 7-9, 2017 , Swissotel Chicago, Chicago, Illinois, U.S.A.

DOI: 10.1615/TSFP10

FLOW AROUND NONPARALLEL TANDEM CYLINDERS

pages 191-197
DOI: 10.1615/TSFP10.340
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RÉSUMÉ

Flow around two nonparallel tandem cylinders is investigated experimentally to understand the associated fluid dynamics at a Reynolds number Re = 5.6 × 104. Two cylinders of identical diameter D are oppositely inclined by 7.5° measured from the normal to the free stream direction, which leads to an included angle of 15° between the cylinders. Strouhal number (St) and time-mean and instantaneous flow field measurements for L* (= L/D = 1 - 4.05, where L is the cylinder center-to-center spacing) leads to identification of three distinct flows: alternating reattachment flow (regime I, 1 ≤ L* < 2.15), bi-stable flow (regime II, 2.15 ≤ L* ≤ 3.1), and coshedding flow (regime III, 3.1 < L* ≤ 4.05). Regime I is further subdivided into regimes IA and IB contingent on shear layer reattachment and its influence on quasi-steady vortex in the gap and wake. The three flow regimes are totally different from those for parallel cylinders. A spiral vortex forming in the gap that varies along the cylinder span is responsible for making the difference. The sporadic presence of reattachment and coshedding flows results in a jump in St at regime II. In contrast to parallel cylinders, nonparallel cylinders experience another jump in St associated with the coshedding flow at L* = 2.5 in regime II. A wake-flow bifurcation at L* = 2.5 is responsible for the jump, separating the wake flow turning towards the small L* and towards the large L*.

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