Application Of Immersion Boundary Method In Biological Fluid Mechanics

The research scope of biological fluid mechanics includes biofluid mechanics studies biological cardiovascular system,digestive and respiratory system,endocrine,swimming,flight and other mechanical problems related to hydrodynamics,aerodynamics,boundary layer theory and technology.The immersion boundary method(IBM)is developed rapidly as an important and effective way in recent years.It has been widely used in the fluid structure interaction problems involving complex geometry and irregular large deformation,such as blood flow in arteries and artificial heart valves,flight and swimming,and its core idea is to use the external equivalent body force to replace the force on the boundary of the immersed object in fluid field.The mesh can be quickly generated in this method when there are large irregular deformations and/or very complex shapes at the interface without generating completely body-fit mesh that conforms to the fluid-solid interface,effective flow solver can be used to solve the governing equations of fluid dynamics.Carotid is one of the focal regions prone to atherosclerosis.Previous studies have shown that hemodynamics plays an important role in the initiation and formation of atherosclerosis plaques.In this work,we numerically investigate the flow patterns in two carotids with different flares and proximal curvatures under inflows from three age groups with/without exercise.The simulation results show that the effects of exercising on the carotid flow and wall shear stress are different at different time instants and for different age groups.As for the oscillatory shear index,exercise does not have significant effects.The effects of inflow waveforms on the reversed flow volume are also examined.For the carotid C1 with low flare and high proximal curvature,it is found that exercising increases and decreases the reversed flow volume for young and senior people,respectively.For middle-aged people,on the other hand,the reversed flow volume is increased and decreased in the middle of the sinus and near the bifurcation,respectively,for the carotid C1.For the carotid C2 with high flare and low curvature,on the other hand,it is found that exercising increases the reversed flow volume for all age groups.This work suggests that the effects of exercise on atherosclerosis should be evaluated by fully considering patient-specific geometries and ages.The coupling of passive propulsion and stable motion of fish is an extremely complex problem of fluid mechanics and biology.According to the key characteristics of fish motion,this project will be simplified the passive propulsion of fish without any energy input into a tandem arrangement of a cylinder and a single elastic filament.For the flow around the cylinder and the filament,the fluid-structure ineraction is used to simulate the fish as a passively propulsive full-degree-freedom flexible filament to achieve a more realistic and effective simulation of the fish school swimming problem.The study found that when a vortex strip appeared in the wake of the cylinder due to the interaction between the filament and the flow field behind the cylinder,and it is found that the pressure at the leading edge of the filament that can move in the direction of the cylinder against the flow is lower than that at the trailing edge,while the pressure at the leading edge is greater than that at the trailing edge,the filament is rushed to downstream.the reason of the filament countercurrent motion is due to the energy obtained from the cylindrical wake.When considering the influence of Reynolds number on filament motion,it is also necessary to consider the distance between filament and cylinder.Biological and bionic fluid mechanics,as an interdisciplinary subject led by fluid mechanics,its basic task is to apply fluid mechanics to study the mechanical properties and behaviors of organisms and human bodies at the macro and micro scales,and to analyze the various processes that occur in the process of life activities.It is of great significance to reveal the laws of biological activities and to study the mechanism of fluid mechanics.