Wake Interaction Using Lattice Boltzmann Method

Wake Interaction Using Lattice Boltzmann Method

K. Karthik Selva Kumar (National Institute of Technology, India) and L. A. Kumaraswamidhas (Indian Institute of Technology (ISM), India)
Copyright: © 2018 |Pages: 39
DOI: 10.4018/978-1-5225-4760-0.ch007
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In this chapter, a brief discussion about the application of lattice Boltzmann method on complex flow characteristics over circular structures is presented. A two-dimensional computational simulation is performed to study the fluid flow characteristics by employing the lattice Boltzmann method (LBM) with respect to Bhatnagar-Gross-Krook (BGK) collision model to simulate the interaction of fluid flow over the circular cylinders at different spacing conditions. From the results, it is observed that there is no significant interaction between the wakes for the transverse spacing's ratio higher than six times the cylinder diameter. For smaller transverse spacing ratios, the fluid flow regimes were recognized with presence of vortices. Apart from that, the drag coefficient signals are revealed as chaotic, quasi-periodic, and synchronized regimes, which were observed from the results of vortex shedding frequencies and fluid structure interaction frequencies. The strength of the latter frequency depends on spacing between the cylinders; in addition, the frequency observed from the fluid structure interaction is also associated with respect to the change in narrow and wide wakes behind the surface of the cylinder. Further, the St and mean Cd are observed to be increasing with respect to decrease in the transverse spacing ratio.
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Fluids, such as air and water, are frequently met in our daily life. Physically, all fluids are composed of a large set of atoms or molecules that collide with one another and move randomly. Interactions among molecules in a fluid are usually much weaker than those in a solid, and a fluid can deform continuously under a small applied shear stress. Usually, the microscopic dynamics of the fluid molecules is very complicated and demonstrates strong in homogeneity and fluctuations. On the other hand, the macroscopic dynamics of the fluid, which is the average result of the motion of molecules, is homogeneous and continuous. Therefore, it can be expected that mathematical models for fluid dynamics will be strongly dependent on the length and time scales at which the fluid is observed. Generally, the motion of a fluid can be described by three types of mathematical models according to the observed scales, i.e. microscopic models at molecular scale, kinetic theories at mesoscopic scale, and continuum models at macroscopic scale. The lattice Boltzmann method (LBM) has found applications in fields as diverse as quantum mechanics and image processing, it has historically been and predominantly remains a computational fluid dynamics method. This is also the spirit of this book in which we largely develop and apply the LBM for solving fluid mechanics phenomena.

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