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On the Interaction of Separation Bubbles in the Near Wake of a Cylinder
Bimalendu Mahapatra, Sathyanarayana A., Venugopal Arumuru

Last modified: 2018-06-24

Abstract


The interaction of separation bubbles in the wake of a circular cylinder using 2D numerical simulations is presented in the current work. The focus of the study is to understand the dynamics of interaction between separation bubbles and the interaction between separation bubble and outer vortex. A separation bubble is induced by introducing a parallel slit in a cylinder. Six different slit widths with non-dimensional separation ratio, s/d = 0.05 - 0.3 are studied for a wide range of cylinder Reynolds number (Re = 100 – 600). At lower slit widths the characteristics of the flow and vortex formation mechanism is identical to the flow over a confined cylinder. At higher slit widths (s/d >1.5), a separation bubble from each of the inner surface is formed and oscillates with a phase difference with respect to the outer shed vortices.  It is found that the phase difference between the separation bubble oscillations & shedding of the outer vortex is a function of both s/d and Re. The strength of the primary or outer vortex is found to be affected by the interaction of the separation bubble through the transport of opposite sign vorticity from the separation bubble. Quantitative analysis shows that the dynamics of separation bubble also affects the lift and drag force acting on the bluff body. Such interactions of separation bubbles with the primary vortices could be utilized to improve the performance & design of various devices such as vortex flow meter, heat exchangers and VIVACE device to harvest clean energy from vortex induced vibrations.

 


Keywords


Vortex Shedding, Separation Bubble

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