Mirkhani Nima, Davoudi Mohammad Reza, Hanafizadeh Pedram, Javidi Daryoosh, Saffarian Niloofar
Center of Excellence in Design and Optimization of Energy Systems, School of Mechanical Engineering, College of Engineering, University of Tehran, Tehran, Iran.
Biomedical Engineering, Katholieke Universiteit Leuven, Louvain, Belgium.
Cardiovasc Eng Technol. 2016 Sep;7(3):223-37. doi: 10.1007/s13239-016-0265-y. Epub 2016 May 10.
Numerical simulation of the bileaflet mechanical heart valves (BMHVs) has been of interest for many researchers due to its capability of predicting hemodynamic performance. A lot of studies have tried to simulate this three-dimensional complex flow in order to analyze the effect of different valve designs on the blood flow pattern. However, simplified models and prescribed motion for the leaflets were utilized. In this paper, transient complex blood flow in the location of ascending aorta has been investigated in a realistic model by fully coupled simulation. Geometry model for the aorta and the replaced valve is constructed based on the medical images and extracted point clouds. A 23-mm On-X Medical BMHV as the new generation design has been selected for the flow field analysis. The two-way coupling simulation is conducted throughout the accelerating phase in order to obtain valve dynamics in the opening process. The complex flow field in the hinge recess is captured precisely for all leaflet positions and recirculating zones and elevated shear stress areas have been observed. Results indicate that On-X valve yields relatively less transvalvular pressure gradient which would lower cardiac external work. Furthermore, converging inlet leads to a more uniform flow and consequently less turbulent eddies. However, the leaflets cannot open fully due to middle diffuser-shaped orifice. In addition, asymmetric butterfly-shaped hinge design and converging orifice leads to better hemodynamic performance. With the help of two-way fluid solid interaction simulation, leaflet angle follows the experimental trends more precisely rather than the prescribed motion in previous 3D simulations.
双叶机械心脏瓣膜（BMHVs）的数值模拟因其预测血流动力学性能的能力而受到许多研究人员的关注。许多研究试图模拟这种三维复杂流动，以分析不同瓣膜设计对血流模式的影响。然而，使用的是简化模型和预设的瓣叶运动。本文通过全耦合模拟在一个真实模型中研究了升主动脉位置的瞬态复杂血流。基于医学图像和提取的点云构建了主动脉和置换瓣膜的几何模型。选择了一款23毫米的On-X医用双叶机械心脏瓣膜作为新一代设计进行流场分析。在整个加速阶段进行双向耦合模拟，以获得瓣膜开启过程中的动力学。精确捕捉了所有瓣叶位置时铰链凹槽内的复杂流场，并观察到了回流区域和剪切应力升高区域。结果表明，On-X瓣膜产生的跨瓣压力梯度相对较小，这将降低心脏的外部做功。此外，收敛的入口导致流动更加均匀，从而减少湍流涡旋。然而，由于中间扩散器形孔口，瓣叶无法完全打开。此外，不对称蝶形铰链设计和收敛孔口导致更好的血流动力学性能。借助双向流固相互作用模拟，瓣叶角度比之前三维模拟中的预设运动更精确地遵循实验趋势。
