A CBS-based partitioned semi-implicit coupling algorithm for fluid-structure interaction using MCIBC method

The characteristic-based split (CBS) scheme has been extensively utilized to address the fluid subproblem within fluid-structure interaction (FSI) analyses over the past decade. To cope with FSI, this article develops a CBS-based partitioned semi-implicit coupling algorithm where the CBS scheme serves not only for the fluid component but also for the entire coupling algorithm. At each time instant, the first step of the CBS scheme is explicitly treated together with the fluid mesh movement, while the remaining two steps are implicitly coupled with the structural motion on the fluid mesh frozen temporarily. To retrieve the semi-implicit coupling style, a mass source term is iteratively updated in the pressure Poisson equation for elements adhering to the fluid-structure interface. The present algorithm provides the stabilized solution of the Navier-Stokes equations and the computational reduction without stability drop, thus inheriting the virtues of the CBS scheme and the projection-based semi-implicit coupling method. Within our coupling algorithm, FSI is achieved by the modified combined interface boundary condition (MCIBC) method which is re-derived in a more concise fashion. A weak implementation of the MCIBC method is proposed to avoid deteriorating the numerical results. The MCIBC method rectifies the limitations of its original counterpart, making itself applicable to fluid-rigid/flexible body interaction. Flow-induced vibrations of various bluff bodies are analyzed to test the feasibility of the proposed methodology. The overall numerical results agree well with the existing data, demonstrating the validity and the applicability of the present approach.