Two-phase Numerical Simulation Of Blood Flow In Thoracic Aortic Dissection

Thoracic aortic dissection is a cardiovascular disease,which is a serious hazard to human health.Thoracic endovascular aortic repair(TEVAR)can reduce the mortality of aortic dissection and has become the preferred way to treat the disease in recent years.Previous studies have shown that even after TEVAR treatment,vascular rupture and visceral artery ischemia are still the main causes of death in patients.However,there is still a lack of sufficient understanding for the mechanism of aortic dissection occurrence,development and rupture.This has brought great difficulties to clinical treatment.To deeply investigate this issue,this project proposes to apply the non-Newtonian two-fluid model for two-phase blood flow.The arbitrary Lagrange-Euler method will be incorporated to deal with the interactions between fluid and complex boundaries.This method could make up for the deficiencies in previous studies which treated the blood as single-phase Newtonian fluid and treated the vessel wall as rigid wall.This paper aims to simulate blood flow and obtain a series of hemodynamic parameters like flow velocity and wall shear stress.The results will be analyzed to quantify the relationship between hemodynamics and thombosis as well as false lumen remodeling,so that we can provide data for the prediction of dissection development and the evaluation of TEVAR.The main work includes the following three parts:In the first part,CT tomography images were processed to establish a real 3D aortic dissection model firstly.Then two validation cases were carried out and the results show that the two-fluid model can accurately simulate the blood two-phase flow.After that,we coupled the two-fluid model and ALE method to simulate blood flow in a Stanford B thoracic aortic dissection model.The results showed that the average wall shear stress calculated by the fluid-solid interaction model was lower than that of the rigid wall model,the maximum difference was 18.4%.The second part is a study of preoperative and postoperative blood flow simulation in an acute dissection case with left subclavian artery(LSA)closure.It was found that blood flow rate in the true lumen and aortic arch increased significantly after TEVAR,the flow rate ratio increased from 11.15%and 14.85%to 51.49%and 37.32%respectively,indicating that TEVAR can improve the blood supply function of true lumen and branching vessels.By simulating a LSA non-occluded model,we also found that LSA occlusion had little effect on upper limb blood supply and most of the patients can survive well with LSA occlusion.The third part is a study of preoperative and postoperative blood flow simulation in a chronic aortic dissection whose false lumen has expanded.It was found that the blood flow in postoperative descending aorta are more stable,the turbulence intensity and OSI value are much lower than preoperative.TEVAR can effectively avoid the risk of false lumen rupture,improve the stability of blood flow in true lumen and distal blood supply.