Experimental Study On Fluid-structure Interaction Of Aneurysm Based On Pulsatile Flow

Intracranial aneurysm is a pathological dilation of the arterial wall,which is the main cause of subarachnoid hemorrhage(SAH),with a very high disability and mortality rate.Hemodynamic factors are considered to be one of the important factors in the occurrence,development and rupture of aneurysms.Blood flow is a periodic pulsating flow,which will cause the radial and axial movement of blood vessel wall.Therefore,it is of great significance to explore the interaction between elastic blood vessels and blood flow to analyze the causes of aneurysm occurrence,growth and rupture.Based on the in vitro experiments of the elastic vascular model,we analyzed the deformation characteristics of aneurysms under different pulsating flow conditions by fluid-structure interaction(FSI)method,and compared the effects of different aspect ratios(Aspect Ratio,AR)on the deformation of the aneurysm.In addition,the numerical FSI calculation of blood flow in the aneurysm was carried out in this paper to compare with and verify the experimental results,the flow characteristics inside the aneurysm were further obtained.Finally,the effects of vascular stenosis and intracranial aneurysm on the blood flow regulation of the bifurcated vessels downstream of the aneurysm were analyzed through numerical simulation,so as to explain the mechanism of intracranial aneurysm from a more macroscopic perspective.This research set up an in vitro experimental platform,which mainly consists of a selfdesigned pulsating cycle mechanism,a peristaltic pump and a height-adjustable outlet tank.With the help of 3D printing technology,a flexible silicone aneurysm model was produced.By adjusting the pulsating flow condition,this work first explored the deformation characteristics of an idealized aneurysm by the laser displacement sensors.The results show that the deformation of the aneurysm is closely related to the pulsating flow conditions,the deformation at aneurysm dome gradually increase with the increase of pulsation frequency and terminal resistance.In addition,the vortex motion in the aneurysms has been observed in the CFX numerical simulation.And the trajectory of the vortex center has a high time correlation with the deformation waveform of the aneurysm.The numerical results also reflect the pressure change in the aneurysm.As the pulsation frequency and the terminal resistance increase,the pressure in the aneurysm also increases,which explains the aneurysm deformation characteristics observed in the experiment based on different flow conditions.Furthermore,based on the medical image data of aneurysm,this paper reconstructed the internal carotid aneurysm model using SIMPLEWARE,which is a three-dimensional reconstruction software.Through experimental and numerical methods,the characteristics of patient-specific model deformation were explored.In terms of the influence of pulsating flow conditions on the aneurysm deformation,the results of the patient-specific study were basically consistent with the idealized results.In this study,11 groups of aspect ratio(AR)sizes were set between 0.3-1.9,and the aneurysm deformation was measured under the same pulsating flow condition.The results show that when the AR<1.0,the aneurysm deformation decreases with the increase of the AR.When the AR>1.0,the aneurysm deformation gradually increases with the increase of the AR.Especially,when the AR>1.5,the increasing tendency of aneurysm deformation is more obvious than that when 1.0<AR<1.5.Aiming at the bifurcation patient-specific model,the morphological characteristics of stenosis with different degrees and aneurysms with different aspect ratio were added to the upstream of the bifurcation respectively,and the flow distribution changes between the two bifurcated vessels downstream of the aneurysm were compared.The results showed that the regulation effects of stenosis and intracranial aneurysm on outlet blood flow were completely opposite.Within the appropriate aspect ratio range,the appearance of intracranial aneurysm can regulate the adverse blood flow changes caused by stenosis.