The Research On Flow Past Cylinders Based On Improved IB-LBM

The flow around a circular cylinder has played a significant role in fluid mechanics, because there is some attractive regularity with the change of Reynolds number in this phenomenon.In the field of naval architecture and ocean engineering, complex offshore structures, such as pile structure and marine riser, have been increasing rapidly due to the development of the ocean exploration. It seems that cylindrical structures have become one of the most widely styles in the certain aspects and it has been the pressing issue to predict and curb the trend or problems from the flow around a circular cylinder or vortex-induced vibration.In this paper, an improved approach that is based on lattice Boltzmann method coupled with immersed boundary method has been represented. On the basis of this new numerical method,an enormous amount of research has been done, ranging from the flow around a circular cylinder, two-cylinder system to forced vortex-induced vibration. Analyzing those phenomena would enhance the understanding of complex fluid-structure interaction, and provide theoretical and technical support in the design of offshore platforms.Firstly, the theory of lattice Boltzmann method has been discussed in this paper, including how to get lattice Boltzmann equations (LBE) from kinetic theory, how to recover Navier-Stokes equations from LBE through Chapman-Enskog multi-scale analysis. It is clear that it has played an essential role in the following research.In addition, the boundary processing has been taken into consideration. The main reason that everyone can see is that it is a crucial part in numerical approaches. The complex surface boundaries are likely to be simulated exactly access to the immersed boundary method.Consequently, an improved immersed boundary-lattice Boltzmann method possesses not only the advantages of lattice Boltzmann method, but also the benefits of immersed method.Moreover, the model of two-cylinder system has been presented for the sake of researching the flow of multi-cylinder system. In this chapter, it has been observed that the change of vortex shedding as well as fluid force on circular cylinders stems from the change of the arrangement of solids,Reynolds number and the distance of solid center. It seems that the interaction between circular cylinders has been analyzed evenly.Finally, forced vortex-induced vibration has been considered. Perhaps, the main reason is that it has become the severe issue in the field of naval architecture and ocean engineering. In this chapter, it has been described that frequency and the amplitude exert impacts on the mode of vortex shedding. Clearly, it has exerted positive impacts on studying the fluid-structure interaction.