The Numerical Research On Aerodynamic Efficiency And The Wake Vortex Structure Of Filament In Flow Field

Fluid-structure interaction is that aerodynamics force makes solid medium deformation and movement, at the same time, the deformation and movement of solid medium will have the opposite effect to flow field, making the distribution and size of aerodynamics force changed. Thus, the complex and changeable fluid-structure coupling phenomenon will be produced. the fluid-structure interaction phenomenon are existed extensively in nature and engineering. Therefore, the research is on numerical simulation of the coupling movement of filaments, to further exploring effective coupling phenomenon in the nature, as well as defense and t he application of engineering. Thus, the numerical and theoretical analysis methods of fluid-structure interaction will be provided theoretical basis and technical support.1. The immersed boundary method could treat the complex and moving boundaries using Cartesian grids, which is suitable for our purposes. We will use the immersed boundary method to simulate the movement of the flexible filaments, and investigate the aerodynamic forces and flow structures in flow field.2.In uniform flow field, the problems of the filament swinging wake region modal is studied. Increasing the Reynolds number, it appears that the Karman vortex streets change to the more complex vortex streets in the wake r egion. In the same bending stiffness, the trail of filament appears three kinds of modals, including small intensity of Karman vortex streets, irregular chaotic transition state and large intensity of Karman vortex streets. When bending strength is decreased, the conversion time of the three modes is shorter, and wake vortex intensity increasing.3.We study vortex structures and the propulsive performance of flexible flapping wing in uniform flow field. Increasing of Reynolds number, the vortex spacing changes from small to large extend in the wake of the flapping wing, at the same time, the dissipative speed of the vortex changes from slow to fast near the trailing edge and moves to downstream. As flapping amplitude increas ing, the intensive of vorticity becomes more intensive and produce reversed von Karman vortex streets. Further studies show that, the value of propulsive efficiency will reach the peak, and then decreased gradually, when the frequency increases.4. Discuss the different spacing parameters(include the horizontal spacing G and the vertical distance H) that it influences on the interaction between D-cylinder and filament. Increasing the horizontal spacing G, the drag coefficient of D-cylinder changes from small to large. increasing the vertical distance H, D-cylinder drag coefficient is also presented the law of diminishing.This paper is discussed three questions on fluid-structure interaction, including the movement and deformation of a single filament in the uniform flow field, the propulsive performance of the flexible airfoil flapping in the flow field, and the vortex structure and aerodynamic performance of the filaments behind D-cylinder, summarizing some characteristics about the vortex structures and the aerodynamic performance. We expect these results to be useful for studying the fluid-structure interaction and designing the micro air vehicles.