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

这一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)工具来研究涉及流体/结构相互作用的复杂流动系统。然后将其应用于能源效率、生物力学和海洋推进领域的四个具体情况。 在各种情况下，人们可能会发现固体在叠加的流体中运动。固体的运动可以是规定的(单向耦合)，也可以是由流体流动引起的(双向耦合)。 2014年，已经启动了基于格子Boltzmann方法并结合浸没边界方法来考虑固体运动的内部数值工具的开发。这种耦合方法具有许多优点：不需要自适应网格，空间数值格式的精度即使在壁面上也保持不变，通过改变粘性和/或在Boltzmann方程中添加外体力，可以很容易地引入新的物理效应。当前版本的程序能够模拟流动结构，包括在密度略有不同的两相分层流体介质中具有外加运动的固体，以及任意(去)润湿条件。 在接下来的五年里，我的研究计划将重点放在CFD工具的数值开发上，以模拟更真实的流动形态，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。这一新的CFD工具将应用于机械工程的三个战略研究领域： 1/1能效，用于优化两个制冷系统：用于磁制冷的多孔式再生器和用于冰浆的系统发电机/储存罐。 2/在生物力学中，通过纤毛在上皮表面的同步敲击，研究呼吸道粘液在人体呼吸系统中的运输。 在使用Flettner转子的船舶推进中。这些是高旋转气缸，利用马格努斯效应产生顺流功率，能够节省大约25%的船舶推进所需的总能量。 该代码将第一次允许在这种复杂情况下模拟流体/结构相互作用，同时保持移动墙壁上结果的准确性。除了该计划涵盖的四个应用外，这一独特的工具还将为许多其他应用打开大门：水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。六名高素质的人员将在计划期间接受培训，这些人员不仅在数字开发中，而且在合作伙伴开发的实际应用中也是如此。

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.