Flow-induced vibration of tandem circular cylinders with selective roughness: Effect of spacing, damping and stiffness

摘要: Abstract Flow Induced Vibrations (FIV), and particularly Vortex (VIV) galloping, of two locally rough, rigid, circular cylinders in tandem are studied by varying the stiffness supporting springs, linear viscous damping, cylinder spacing. The test parameters are: mass ratio set to 1.34, center-to-center spacing 1.57, 2.0 2.57 diameters; spring-stiffness 400 N/m ∼ 1200 N/m, damping-ratio 0 . 02 ζ 26 , Reynolds number 30,000 ⩽ Re 120,000, which falls TrSL3 flow regime. virtual spring-damping system Vck developed Marine Renewable Energy Laboratory (MRELab) enables embedded computer controlled change viscous-damping for fast mathematically correct oscillator realization, without including hydrodynamic force closed control loop. Experimental measurements oscillatory response both cylinders, reveal interaction upstream downstream cylinders. All experiments were conducted Low Turbulence Free Surface Water (LTFSW) Channel MRELab University Michigan. main findings (1) In range tested, all values K cylinder’s amplitude is enhanced due presence cylinder. This effect very strong galloping. (2) With exception initial branch VIV, also but with higher standard deviation oscillating (3) Three oscillation patterns identified galloping: In-phase, out-of-phase, alternating between a given experiment. (4) Four interactive zones identified.