In literature, the cost of a partitioned fluid-structure interaction scheme is typically assessed by the number of coupling iterations required per time step, while ignoring the internal iterations within the nonlinear subproblems. In this work, we demonstrate that these internal iterations have a significant influence on the computational cost of the coupled simulation. Particular attention is paid to how limiting the number of iterations within each solver call can shorten the overall run time, as it avoids polishing the subproblem solution using unconverged coupling data. Based on systematic parameter studies, we investigate the optimal number of subproblem iterations per coupling step. Lastly, this work proposes a new convergence criterion for coupled systems that is based on the residuals of the subproblems and therefore does not require any additional convergence tolerance for the coupling loop.

翻译：在文献中，分区流固耦合方案的计算成本通常通过每个时间步所需的耦合迭代次数来评估，而忽略了非线性子问题内部的迭代。在本工作中，我们证明了这些内部迭代对耦合模拟的计算成本具有显著影响。特别关注了限制每个求解器调用内的迭代次数如何能够缩短总体运行时间，因为这避免了使用未收敛的耦合数据优化子问题解。基于系统化的参数研究，我们探讨了每个耦合步骤中子问题迭代的最优次数。最后，本工作为耦合系统提出了一种新的收敛准则，该准则基于子问题的残差，因此不需要为耦合循环设置额外的收敛容差。