Flow Past a Cylinder Using Lattice Boltzmann Method

Sehgal, A (2014) Flow Past a Cylinder Using Lattice Boltzmann Method. Masters thesis, Indian Institute of Technology.

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Abstract

In this thesis, an oscillatory flow over a rectangular cylinder has been investigated by varying the amplitude and frequency of the imposed flow. The region without reverse flow at the inlet of the computational domain is only considered. The objective of this thesis is to understand the formation of different vortex shedding modes and the transition from one mode to another as the frequency and amplitude ratio are varied. A lattice Boltzmann method is used in order to simulate this problem with non-uniform meshes.The problem considered in the thesis is an extremely difficult problem computationally as in order to get any accurate solution one has to use very fine mesh near the cylinder. In order to over come this difficulty, a non-uniform mesh has been used in the present LBM solver.For frequency ratio 0.7, it is found that for lower amplitude ratio the vortex-shedding pattern is antisymmetrical; for intermediate amplitude ratio chaotic mode is observed and symmetric shedding is found for higher amplitude ratio.For a fixed amplitude ratio 0.1, and varying the frequency ratio, we have not observed much difference in vortex shedding mode. Thus for getting different vortex shedding mode, one has to vary amplitude ratio’s. Hence probability of getting symmetric modes is for low frequency ratio and for a high range of amplitude ratio.

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