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

Jaiswal, S and Dongari, Nishanth (2015) Implementation of Knudsen Layer Effects In Open Source CFD Solver for Effective Modeling of Microscale Gas Flows. In: Proceedings of the 23rd National Heat and Mass Transfer Conference and 1st International ISHMT-ASTFE Heat and Mass Transfer Conference (IHMTC), 17-20 December, 2015, Thiruvananthapuram, India.

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Abstract

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

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