Multi-scale Flow Field Simulation With Complex Boundary Based On IB-DUGKS

In order to accurately and effectively simulate multi-scale flow field with complex boundary,an improved IB-DUGKS is proposed based on the immersed boundary discrete unified gas kinetic scheme.In order to maintain the conservation of IB-DUGKS in the long simulation process,the conservation variables were updated synchronously while the velocity distribution function was updated.In order to avoid the occurrence of non-physical phenomena caused by negative values of the distribution function in the updating process,the interface distribution function was reconstructed using the higher-order MUSCL format with a positionpreserving limiter when calculating the interface flux.In order to capture the non-equilibrium effect more accurately,the direct discrete force scheme rather than the approximate equilibrium assumption is used to calculate the coupling force at the boundary.Aiming at the multi-scale flow problem with fixed curved boundary,The flow past a circular cylinder at different Reynolds numbers in continuous flow,the flow past a circular cylinder in different basins and the flow past double circular cylinder are simulated.By analyzing the stability of the fluid,the length of recirculation zone,the arrangement of the cylinders and variation of the drag coefficient and lift coefficient,the current IB-DUGKS is proved to be capable and superior of simulating curved boundary multi-scale flow field.For the multi-scale flow problem at the moving boundary,the oscillating cylinder turbulence with given particle trajectory in different basins is simulated,and the correctness of the improved IB-DUGKS simulation of multi-scale moving boundary is verified.The single particle drop due to gravity problem under the coupling action of particle and flow field is also studied,and the influence of particle density on sedimentation is analyzed,which further indicates the superiority of the present model in dealing with complex moving boundary problems.The results show that the current IB-DUGKS has high accuracy across the whole basin,has the ability to simulate complex boundary multi-scale field,and can meet the requirements in both accuracy and computational efficiency.