A ghost-cell immersed boundary method for unified simulations of flow over finite- and zero-thickness moving bodies at large Courant-Friedrichs-Lewy (CFL) numbers is presented. In order to handle such bodies in a unified manner, algorithms for interface construction and cell demarcation are proposed. The main challenge in treating zero-thickness bodies is to maintain sharpness and accuracy even at large CFL numbers with diminished spurious force oscillations. Thus, the effect of large CFL numbers on the solution accuracy of fluid-structure interaction (FSI) problems involving zero-thickness bodies is investigated and necessary treatments to preserve solution accuracy even at large CFL numbers are suggested. The present study suggests two treatments which are important in preserving the accuracy and stability of the solution: backward time integration for computational cells called ‘swept-cells’ and pressure boundary condition with mass conservation. Composite implicit time integration for the dynamic equation of a thin elastic structure is employed for a stable simulation of FSI at large CFL numbers. By using large time step sizes, the present method not only enhances computational efficiency, but also suppresses spurious force oscillations while maintaining the sharpness of an infinitesimally thin body. The efficacy and accuracy of the present method are examined through numerical examples.

提出了一种在大库仑-弗里德里希斯-路易​​（CFL）数下有限厚度和零厚度运动体上流动的统一模拟的重影单元浸入边界方法。为了统一处理这些主体，提出了用于接口构造和小区划分的算法。处理零厚度物体的主要挑战是即使在CFL数量较大且杂散力振荡减小的情况下也要保持清晰度和准确性。因此，研究了大的CFL数量对涉及零厚度物体的流固耦合问题（FSI）的求解精度的影响，并提出了即使在大的CFL数量下也要保持求解精度的必要处理方法。本研究提出了两种对保持溶液的准确性和稳定性很重要的处理方法：称为“后掠单元”的计算单元的后向时间积分和具有质量守恒的压力边界条件。薄弹性结构动力学方程的复合隐式时间积分用于在大CFL数下稳定模拟FSI。通过使用大的时间步长，本方法不仅提高了计算效率，而且在保持无限薄的物体的清晰度的同时抑制了杂散力振荡。通过数值实例检验了本方法的有效性和准确性。通过使用大的时间步长，本方法不仅提高了计算效率，而且在保持无限薄的物体的清晰度的同时抑制了杂散力振荡。通过数值实例检验了本方法的有效性和准确性。通过使用大的时间步长，本方法不仅提高了计算效率，而且在保持无限薄的物体的清晰度的同时抑制了杂散力振荡。通过数值实例检验了本方法的有效性和准确性。