Numerical Investigation of Flow Induced Vibration for the Triangular Array of Circular Cylinder

Abstract

Numerical Investigation of a Flow Induced Vibration in Cross Flow around Triangular Array of Circular Cylinders with two-degree of freedom, where the cylinder was allowed to vibrate in the transverse (cross- ow) and longitudinal directions. Computational Grid and Time step was optimized by performing Grid independent study and Time step independent study. The computations were carried out at Reynolds number range of 500, 1000, 2000, 5000 and 104 with multi-cylinder with change in upstream cylinder positions at 20o, 30o, 45o and 60o and varying p=D ratio of 1.5 and 2, using FLUENT (version 6.3). E ect of Reynolds num- ber on lift and drag force at various multi-cylinder arrangements were studied. The e ects of Reynolds number on ow parameters such as drag co-e cient, lift co-e cient, strouhal number, lift and drag force and vorticity were established. The seven di erent ow pat- terns (Single Blu Body (SBB), Base Bleed Flow (BBF), Shear Layer Re-attachment (SLR), Induced Separation (IS), Vortex Pairing and Enveloping (VPE), Vortex Pairing, Splitting and Enveloping (VPE), Periodic Gap Vortex Shedding (PGVS)) were identi ed from the present simulation. The FFT analysis were performed on all above mentioned con guration to establish strouhal frequency of ow induced vibration. The maximum displacement of cylinders due to ow induced vibration was calculated solving force vibration equation using Range-Kutta fourth order scheme. It was observed that at 0 = 45o and with p=D = 1:5, the amplitude of vibration (displacement) of cylinders was minimum with max vibration frequency (Strouhal frequency).