Papers by Keyword: Bio-Fluid Mechanics

Abstract: The purpose of this study is to accumulate data to predict the ruptures of aneurysms on the bifurcation of the middle cerebral arteries at the base of the brain. Particular stress is laid on understanding the elemental nature of branch flows with/without an aneurysm. Therefore, “flow patterns” and “wall shear stress”, which are important factors for the causes of ruptures, are investigated by the three-dimensional experiments in vitro and the two-dimensional numerical simulations with simplified models. In the branch arteries without an aneurysm, there is a possibility of growing aneurysms at the location slightly away from a stagnation point. If an aneurysm forms into a centrosymmetric shape for the inlet axis, it is considered that they tend to grow further in a symmetrical plane. From the viewpoint of the risk of ruptures, recirculation flows become problematic with the lower Reynolds number, while the influence of wall shear stress becomes larger with the higher Reynolds number.

Abstract: Recently for the treatment of aneurysms, endovascular therapy with microcoils and stents has started. This study explores the design of better stents by means of numerical computations from the viewpoint of the fluid mechanics. Two-dimensional flows are numerically solved for a stented duct with a model of an aneurysmal sac by changing the distribution of stent filaments under the constraint of a constant porosity for the neck. Stents are assessed by whether the wall shear stress (WSS) on the aneurismal wall and the shear rate (SR) within the aneurysm are made lower. Barometers for the allocation of filaments are sought, and resultant optimized stents are those where filament(s) should be attached to both the distal and proximal wall of the neck, with more filaments to the distal wall, to make the WSS low, and filaments should be appropriately distributed in the off-wall portion of the neck to make the SR low.

Abstract: Recently, the intravascular therapy using microcoils and stents to treat aneurysms has attracted researcher’s interest. In this study, in order to evaluate the effects of the stents, a numerical simulation of two-dimensional flows has been carried out for a pipe with a model of an aneurismal sac. Using aneurismal models with different inclined angles to the pipe, inflow conditions with steady states or pulsations have been applied in the range of Reynolds number in human blood flows. First, the computational results are compared with experiments under the steady inflow condition, which has shown the reliability of the numerical simulation. Furthermore, the mechanism of flows with an aneurismal model is discussed in the case with or without a stent, and consequently the effect of the stent is clarified.