“…In the past decades, several unfitted-mesh methods have been developed for solving Stokes interface problems, such as CutFEM [15], Nitsche's FEM [36], XFEM [9], fictitious domain FEM [31,34], to name only a few. The immersed finite element method (IFEM) [24,26,18,11,14,30] is a class of unfitted-mesh finite element methods for solving interface problems. The main idea of IFEM is to incorporate the interface jump conditions in the construction of IFE basis functions.…”