ライブラリ登録: Guest
TSFP DL Home アーカイブ 執行委員会

FLOW AROUND NONPARALLEL TANDEM CYLINDERS

Md. Yamin Younis
Institute for Turbulence-Noise-Vibration Interaction and Control Shenzhen Graduate School, Harbin Institute of Technology Shenzhen, 518055, China

Md. Mahbub Alam
Department of Mechanical Engineering, The Hong Kong Polytechnic University Hung Hum, Kowloon, Hong Kong; Institute for Turbulence-Noise-Vibration Interaction and Control Shenzhen Graduate School, Harbin Institute of Technology Shenzhen, 518055, China

Yu Zhou
Department of Mechanical Engineering, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong; Institute for Turbulence-Noise-Vibration Interaction and Control Shenzhen Graduate School, Harbin Institute of Technology Shenzhen, 518055, China

要約

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*.