Lattice Boltzmann Simulations Of Fluid-solid Interaction For Viscous Flow Past Flat Plates

Fluid-solid interaction (FSI) is of significance in funfamentals and applications. In this dissertation, the Lattice-Boltzmann method (LBM) is used to investigate fluid-solid interaction for viscous flow past flat plates. The results and conclusions are described briefly as follows:(1) Route from steady to chaotic state for flow past a swing flat plate has been investigated. When the flat plate is fixed, the chaotic flow regime may be reached through the sequential occurrence of successive period-doubling bifurcations and various incommensurate bifurcations. As the flat plate is allowed to swing freely, the chaotic state in this system may be reached through one Hopf bifurcation and the sequential occurrence of successive period-doubling bifurcations.(2) Self-propulsion of a passive flapping flat plate has been studied to analyze the states of movement, the influence of torsional flexibility, dynamical behaviors and vortical structures. Two typical flow states including a periodic and a non-periodic flow state are revealed. Then, in the periodic flow regime, two dynamical responses of the passive flapping plate, i.e. the forward and backward horizontal movement, are disclosed and depend only on the frequency ratio F of the natural frequency of the system and the vertical oscillating frequency. It is also found that the plate will take the forward movement when F > 1 and the backward movement when F≤1. The torsional flexibility of plate can remarkably enhance the propulsion performance. The results obtained are reasonably consistent with the observations and measurements of swimming and flying animals, and provide physical insight into the understanding of the locomotion properties and propulsion mechanisms of the flapping wings and fins in swimming and flying animals.(3) Aerodynamic performance due to the fore-plate and hind-plate interaction in uniform flow has been investigated. Results show that the interactions between fore-plate and hind-plate effectively enhance the total lift force and reduce the drag force and the force fluctuations on the plates. The interaction mechanism may be associated with the triangular camber effect by modulating the relative arrangement of the two plates. The results provide physical insight into the understanding of aerodynamic behaviors for gliding dragonfly flight.(4) Flow over two passive flapping flat plates in a side-by-side arrangement has been investigated. Two typical phase differences between the two flapping flat plates, i.e., in-phase and anti-phase flapping movements, are considered. The torsional flexibility of plate and the effect of lateral interference between the flat plates on the forces, power consumption, propulsive efficiency, and vortical structures are analyzed. It is revealed that the lateral interference is of benefit to saving the power consumption in the in-phase case and enhancing the forces and propulsive efficiency in the anti-phase case. The results provide physical insight into the understanding of the tail fin swimming actions and hydrodynamic behaviors in fish schooling.