Research On Vortex-induced Vibration And Heat Transfer Characteristics Of Circular Cylinder Using Lattice Boltzmann Method

The flow around cylinders is a common phenomenon in the practical engineering,which is widely existed in the fields of ships, aerospace, and water conservancy machinery. When a certain relative velocity exists between the cylinder structure and the flow field (water or air), the structure and the fluid flow have a strong coupling effect, forming an inverse pressure gradient region on the surface of the structure which can induce fluid force. A vortex is produced behind the structure. With the periodic separation and shedding of the fluid boundary layer near the surface, the fluid force in the form of periodic fluctuation is formed that leads to the vibration of the structure along the transverse and longitudinal directions(i.e., the vortex induced vibration), and then induce the resonance or the structural fatigue damage.In fact, compared to the flow around a single column, it is more traditional that the coexistence of multiple columns with the same structure in practical applications. There is a mutual influence between them which makes the whole fluid-structure interaction process more complicated. Especially, when the heat exchange between the columns or between the column and the flow field(such as reactors, heat exchange in the tube bundle) are considered, the question in the research is more difficulty, though the research content is closer to the actual physical problems. This fluid-structure interaction process is a transient process involving moving boundaries,multiple interfaces and multiple physical fields. Though, there have been many researches on a single problem in the fluid-structure interaction till now, systematic studies which can consider all the problems in the coupling process are still less.According to the above problems,the lattice Boltzmann method (LBM) based on the microscopic statistical mechanics is used to study the vortex induced vibration of two degrees of freedom for the columns, the interaction between the columns and the heat transfer characteristics. The main research contents in the present shown as:Aiming at the model of vortex induced vibration,a novel of lattice Boltzmann treatment of moving boundries is proposed by considering the additional mass effect.To ensure that the boundary treatment is accurate to meet the law of Galileo's invariance,the relative velocity of the moving boundary is introduced, based on the non-equilibrium extrapolation and spatial interpolation methods. At the same time, in order to improve the computational efficiency of the program and take the parallel advantages of the lattice Boltzmann method, the OpenMP multi-core parallel computing technology is introduced.According to the similarity theory of fluid mechanics, the main dimensionless parameters including the fluid correlation parameters, the structure parameters and coupling motion parameters are determined and the corresponding analytical models are established. The effects of structural mass, damping and response frequency on the vibration characteristics of a single cylinder in the flow field are discussed in detail.And the additional mass produced in the flow field is analyzed.On the basis of that, static-static, static-move and move-move coupling models are established. The influence of the initial relative position on the flow field structure, the movement characteristic and the load characteristic of the column is investigated systematically. And, the power efficiency of the vibrating cylinder in different models is analyzed.A thermal lattice Boltzmann equation is introduced, and the temperature field model is established to match with the original velocity field. The temperature field and the heat transfer characteristics of a single column and double columns coupled vibration are studied respectively. It found that the vibration of a circular cylinder is helpful to the heat transfer of solid wall surface.