Development of a numerical tool to deal with complex fluid/structure interactions: applications in energy efficiency, biomechanics and marine propulsion

该研究计划的长期目标是开发一种新的数值CFD（计算流体动力学）工具，以研究涉及流体/结构相互作用的复杂流动系统。然后将其应用于能源效率、生物力学和船舶推进领域的四种具体情况。 在各种情况下，可以发现固体在叠加的流体流中移动。固体运动可以是规定的（《单向耦合》）或由流体流动引起的（《双向耦合》）。 2014年，开始开发一种基于格子玻尔兹曼方法的内部数值工具，并将其与浸没边界方法相结合，以考虑固体运动。这种耦合的方法有很多优点：自适应网格是不需要的，空间数值方案的准确性是保留，即使在墙壁和引入新的物理效应是很容易通过改变粘度和/或通过添加外部体力的玻尔兹曼方程。目前版本的代码能够模拟流配置，包括一个固体与施加的运动在两相分层流体介质的密度略有不同，并为任意（去）润湿条件。 在接下来的五年里，我的研究计划将集中在CFD工具的数值开发，以模拟更真实的流动配置，包括：非牛顿流体，湍流，流体/结构相互作用的“双向耦合”，多孔弹性壁和磁场的影响。这种新的CFD工具将应用于机械工程的三个战略研究领域： 1/用于优化两个制冷系统的能效：用于磁制冷的多孔再生器和用于冰浆的系统发生器/储罐。 2/在生物力学中，通过上皮表面纤毛的同步跳动来研究支气管粘液在人呼吸系统中的运输。 3/在船舶推进中使用Flettner转子。这些是高旋转圆柱体，利用马格努斯效应产生流向功率，能够节省船舶推进所需总能量的约25%。 该代码将是第一个允许在如此复杂的情况下模拟流体/结构相互作用的代码，同时保持移动壁上结果的准确性。除了该计划涵盖的四个应用外，这种独特的工具还将为许多其他应用打开大门：水力和风力涡轮机的几何优化，海洋动物纤毛运动的推进以及红细胞的运输等。六名高素质的人员不仅在数字开发中，而且在合作伙伴开发的真实的应用中，将在计划期间接受培训。

The long-term objective of this research program is to develop a new numerical CFD (Computational Fluid Dynamics) tool to investigate complex flow systems involving fluid/structure interactions. It will be then applied to four concrete situations in the fields of energy efficiency, biomechanics and marine propulsion. In various situations, one may find a solid body moving in a superimposed fluid flow. The solid body motion may be prescribed (« one-way coupling ») or induced by the fluid flow (« two-way coupling »). In 2014, the development of an in-house numerical tool based on the Lattice Boltzmann method and coupled to an immersed boundary method to take into account the solid body motion has been initiated. This kind of coupled approach has many advantages: adaptative mesh grids are not required, the accuracy of the spatial numerical schemes is preserved even at the walls and the introduction of new physical effects is achieved easily by changing viscosity and/or by adding external body forces in the Boltzmann equation. The present version of the code enables to simulate flow configurations including a solid body with an imposed motion in a two-phase stratified fluid medium with slightly different densities and for arbitrary (de)wetting conditions. In the next five years, my research program will focus on numerical developments of the CFD tool to simulate more realistic flow configurations, including: non-Newtonian fluids, turbulence, “two-way coupling” for the fluid/structure interaction, poro-elastic walls and effect of a magnetic field. This new CFD tool will be applied to three strategic research fields in mechanical engineering: 1/ in energy efficiency for the optimization of two refrigeration systems: a porous regenerator used in magnetic refrigeration and a system generator/storage tank for ice slurries. 2/ in biomechanics to study the transport of bronchial mucus in the human respiratory system by the synchronyzed beating of cilia at the epithelium surface. 3/ in marine propulsion by the use of Flettner rotors. These are high rotating cylinders using the Magnus effect to induce a streamwise power enabling to save about 25% of the total energy required for ship propulsion. This code will be the first to allow the simulation of the fluid/structure interactions in such complex situations while preserving the accuracy of the results on the moving walls. In addition to the four applications covered by the program, this unique tool will open the door with many other applications: the geometrical optimization of water and wind turbines, the propulsion by ciliary motion of marine animals and the transport of the red cells among other things. Six highly qualified personnel implied not only in the numerical developments but also in the real applications developed at the partners, will be trained during the program.