| Fluid structure interaction problems are very pervasive in industrial engineering and production practice. With the development of theory for fluid structure interaction and computational science, numerical simulation of fluid structure interaction become a hot topic in field of fluid dynamics. However, due to its nonlinear and uncertainties of the interface, its simulation puts a great challenge to numerical techniques. Recently, there has been much progress in developing both methods Lattice Boltzmann Method (LBM) and Immersed Boundary Method (IBM). The proposed method called Immersed Boundary-Lattice Boltzmann Method (IB-LBM), which is employed to solve complex fluid dynamic systems. The author studied some improved models of IB-LBM, and proved the method is effective through discussions of flows around stational cylinder. The main contents and conclusions are as follows.(1) Brief discussion for fundamental theories of LBM and IBM.(2) Velocity correction method is an improved model of IB-LBM. Simulation of flows around stational cylinder is in the framework of velocity correction theory. Since the non-slip condition is accurately satisfied, no flow penetration can be found in the present results. Compared with the traditional IB-LB Method, quality is conservation.(3) Application of multi-block approach in LBM. To demonstrate the present approach, cavity flow with different Reynolds number is selected. Compared with uniform grid method, flow field characteristics are represented more precisely with low Reynolds number, and the method can overcome high grid solution near the boundary. Fine mesh covers the blocks only in which the gradients are large. Owing to this improvement, multi-block strategy can substantially improve the accuracy and computational efficiency for viscous flow computations.(4) Feed back law is introduced into IB-LBM, that is, the force term in Boltzmann equation is feed back force, and we called this strategy feed back method. The simulation of flows around stational cylinder in two-dimensional flow field is carried out to exhibit the capability of present approach. The streamline figures show that this method can guarantee non-slip condition so as to ensure mass conservation. The numerical simulation results, such as drag coefficients, lift coefficients, vorticity are in good agreement with literatures. In other words, the feed back method can not only inherit the advantages of IB-LBM, but also calculate easily. (5) A red cell in poiseille flows and a slender elastic body flapping in the wake of a cylinder are simulated by IB-LBM in this paper. IBM is adopted as the boundary condition to describe the interaction between fluid and object. Numerical results point out:as time step goes by, shape of the red cell in the vessel is different, the results have good agreement with thoese in previous literatures, and the flexible elastic object swings with the oscillating wake,at the same time, the vortex structure is influenced by the object. It was found that IB-LBM can be modified by improving of accuracy of force term. The capability of this improved method is suitable for intense fluid structure interaction problems with rapid boundary motion and large pressure gradient. |
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