The flow characteristics and thermal performance of circular cylinders with V-shape slots are investigated numerically. The simulation is a two-dimensional incompressible flow that employs the semi-implicit finite volume multi-material algorithm MPM-ICE, which is a module of the Uintah framework. The normalized slot width s₂/D ranges from 0.1 to 0.2, and the corresponding increases in total surface area are from ~99% to ~70%, respectively. Compared to the solid cylinder, the slotted cylinder has the largest total drag reduction of ~67% at s₂/D of 0.2. Meanwhile, although the heat transfer is proportional with the surface area, the thermal performance of the V-shape slot first improves with the slot width, and then declines. The heat transfer improvement has an optimum value of ~192% at s₂/D of 0.15. The overall slot performance, defined by the ratio of the heat transfer to the drag force, is best at 0.175.

Gaseous flow in micro-scale systems comprised of moving components experience Fluid-Structure Interaction (FSI) and rarefaction when the length scales are small. While many commercial codes claim the ability to simulate FSI problems, such a combination is very challenging to model. Here we propose a momentum exchange coefficient model within the FSI algorithm, MPM-ICE, that enables the simulation of rarefied flow. The proposed model was derived using the Maxwell first-order velocity slip boundary condition. The model is verified using analytical solutions for pressure-driven Poiseuille and Couette planar flow. In addition, the model is validated using experimental pressure data of microchannel gas flow and DSMC simulation results. Unlike the previous model, the proposed model is more robust and is nearly insensitive to the grid size and the solid particle distribution around the surface. In addition, the model is universal since it is applicable for flow in the continuum and slip regimes.