Implementation of Knudsen Layer Effects In Open Source CFD Solver for Effective Modeling of Microscale Gas Flows

We incorporate the power law (PL) based geometry de-\ud pendent mean free path (MFP) model into the open-source\ud computational fluid dynamics (CFD) software OpenFOAM.\ud As gas transport properties can be related to the mean\ud free path through kinetic theory, the Navier-Stokes-Fourier\ud constitutive relations are then modified in order to model\ud the flow behavior in the Knudsen layers close to surfaces.\ud The velocity slip and temperature jump boundary condi-\ud tions are also modified in the rhoCentralFoam solver. We\ud carry out numerical simulations in order to accuarately cap-\ud ture the knudsen-layer effect in microscale gas flows. Our\ud model implementation is validated against the direct sim-\ud ulation Monte-Carlo (DSMC) data. The modified rhoCen-\ud tralFOAM solver is applied to low and high mach number\ud velocity-driven (Couette) flow and Fourier heat transfer in\ud microchannels. The results show that our solver greatly im-\ud proves the near-wall accuracy of the Navier-Stokes-Fourier\ud equations, well beyond the slip-flow regime. The importance\ud of this paper stems from the numerical simulation point of\ud view, as OpenFOAM tool is open source, parallel-friendly,\ud and able to solve flows involving complex geometries and\ud unstructured mesh