Second-order accurate immersed boundary-discrete unified gas kinetic scheme for fluid-particle flows

An immersed boundary-discrete unified gas kinetic scheme (IB-DUGKS) is developed in this paper for interface-resolved simulation of particle suspension flows. Compared with the conventional IB methods which consider the interface as a generator of external force, the no-slip boundary condition in the present scheme is implemented directly by correcting the distribution functions near the interface. Therefore, it makes good use of the intrinsic nature for the DUGKS as a kinetic method, and removes simultaneously the necessity to construct the models to evaluate and adsorb the external force in DUGKS. Furthermore, the present IB-DUGKS promotes the accuracy of the IB methods from first- to second-order, which is verified reasonably in the cylindrical Couette flow. After that, several well-established particle-fluid flows are simulated, including the motion of a neutrally buoyancy particle moving in the Poiseuille and Couette flows, and sedimentation of a particle in an enclosure. In all test cases, the results are in good agreement with the data available in the literature. The robust of the present IB-DUGKS is also demonstrated in the simulations.