Sehgal, A
(2014)
Flow Past a Cylinder Using Lattice Boltzmann Method.
Masters thesis, Indian Institute of Technology.
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 nonuniform 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 nonuniform mesh has been used in the present LBM solver.For
frequency ratio 0.7, it is found that for lower amplitude ratio the vortexshedding 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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