fluid-structure interaction

Increasing the cardiovascular disease had led to the researchers to investigate the blood flow more than before. In this article the effects of artery elasticity on hemodynamic parameters with concerning the interaction between blood and the vessel’s wall had been investigated. The wall shear stress had changed with different times and cannot send the congestion of the vessels. From this point the oscillatory shear index had been said the shear stress without the time average. In this study a 3D model from the left coronary bifurcation with 4 models of wall had been investigated. The result from a pulsatile flow from a non-newtonian flow with the method of two ways coupling by using the method of arbitrary Lagrangian–Eulerian had been calculated. The observation had showed a 13 percent decreasing in the profile of velocities at the bifurcation place in that in the hyperelastic model had the highest subtraction. Also by increasing the toughness of the wall the velocity profile and oscillator shear stress were increased. The average shear stress in the model of rigid had showed the 28 percent difference in comparison with the hyperelastic model. By comparing the results with clinical data showed that, the places with average shear stress 1.10 pa and less than that with presenting the oscillatory shear index is more than 0.3 that can be a potential dangerous places in forming atherosclerosis oscillatory shear index plaque especially in the posterior after the bifurcation. Meanwhile in the hyperelastic model the results are more precise than the other models.

Investigating the mechanical stimuli on stem cells under in vitro and in vivo conditions is a very important topic to achieve an ability to control the cellular responses like growth, proliferation and differentiation. Many investigations carried out about biomechanical factors involved in this phenomenon and nowadays, it is proved that some factors like as cell morphology, subcellular elements configuration, scaffold architecture, substrate stiffness and mechanical stimulation via substrate displacement or fluid flow, have got an important effect on cellular responses. In this study, we have tried to evaluate the responses of a stem cell to the stiffness and thickness of the substrate by the means of finite element method. For this purpose, we have used collagen-based scaffolds as the artificial ECM and a cell culture in a bioreactor with fluid flow was simulated.by use of fluid-structure interaction method and solving the equations in two-way coupling scheme, the results show that the increase in thickness and stiffness of the substrate will result in 15 percent change in cell-substrate stresses, respectively. Also, it was seen that the change of substrate stiffness only in the range of 0.1-100 KPa could affect the cell response to an external stimulation.These results, along with other similar investigations, could be used as an instructor by the researchers to optimize the stem cell’s microenvironment in vitro, and finally get the most out of their stem cell related Investigations.

Arterial stenosis and the consequent cardiovascular diseases such as atherosclerosis remain the major cause of mortality in the world. In this study, blood flow was analyzed in a three-dimensional model of stenosed carotid artery with asymmetric stenosis utilizing fluid-structure interaction method. The modeling was performed by ANSYS finite element software. To overcome the software inconsistency in FSI mode, a new code was designed in ANSYS multi-physics environment for coupling of solid and fluid domains via incremental boundary iteration method. The results indicated a considerable variation of local blood pressure, velocity and shear stress in stenosed artery, high pressure drop along stenosis, compressive stress and larger flow separation zone in the post-stenotic region as the result of increased eccentricity of stenosis. The results might be applied in evaluation of plaque severity, progression of disease, plaque growth and vulnerable regions of plaque to fracture.