A Mollified Sharp‐Interface Direct Forcing Method for Suppressing Spurious Oscillations in Moving Immersed Body Simulations

ABSTRACT The effects of complex boundary conditions on flows are represented by a volume force in the direct forcing method. This representation introduces spurious oscillations of the volume force in moving immersed body simulations. The present study focuses on the issues of spurious oscillations including pressure and force in the direct forcing method when encountering moving immersed body problems. In this study, the sources of the spurious pressure oscillations in the Cartesian fractional step framework are firstly analyzed theoretically, and then a novel smoothing method for the sharp‐interface direct forcing method is proposed, which could significantly suppress the spurious oscillations of the volume force and consequently the pressure field for simulating moving immersed body flow problems. Several canonical moving body flow cases are simulated as benchmarks to demonstrate the advantages of the present method for suppressing spurious pressure oscillations, while the results match remarkably well with previous experiments and numerical studies.