A hybrid DSMC/Navier–Stokes frame to solve mixed rarefied/nonrarefied hypersonic flows over nano‐plate and micro‐cylinder

Abstract

SUMMARYWe extend a hybrid DSMC/Navier–Stokes (NS) approach to unify the DSMC and the NS simulators in one framework capable of solving the mixed non‐equilibrium and near‐equilibrium flow regions efficiently. Furthermore, we use a one‐way state‐based coupling (Dirichlet–Dirichlet boundary‐condition coupling) to transfer the required information from the continuum region to the rarefied one. The current hybrid DSMC–NS frame is applied to the hypersonic flows over nanoflat plate and microcylinder cases. The achieved solutions are compared with the pure DSMC and NS solutions. The results show that the current hybrid approach predicts the surface heat transfer rate and shear stress magnitudes very accurately. Some important conclusions can be drawn from this study. For example, although the shock wave region would be a non‐equilibrium region, it is not necessary to use a pure DSMC simulator to solve it entirely. This is important when the researchers wish to predict the surface properties such as velocity slip, temperature jump, wall heat flux rate, and friction drag magnitudes accurately. Our investigation showed that our hybrid solution time would be at least 40% (for the flat plate) and 35% (for the cylinder) of the time that must be spent by a pure DSMC solver to attain the same accuracy.Copyright © 2013 John Wiley & Sons, Ltd.

Heat transfer in rough microchannels under rarefied flow conditions

“…The choice of breakdown criterion and its threshold value, defining the size and position of kinetic domains, is important: an underestimated kinetic domain leads to incorrect numerical results [4,5], an overestimated one reduces the advantage in computational efficiency. The most robust and popular criterion is a local, gradient-length Knudsen number Kn GL (x) [3][4][5]:…”

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An open-source hybrid CFD-DSMC solver for high speed flows

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“…Since the DSMC method can become prohibitively computationally expensive as the characteristic Knudsen number of the flow decreases past 0.01 (either by having low density as in upper atmospheric conditions or very small characteristic lengths like in microchannels), there have been attempts to couple DSMC solvers with continuum Navier-Stokes solvers [79,80]. These hybrid schemes gain the accuracy of a DSMC simulation in the rarefied regions of the flowfield while keeping the lower computational expense of a continuum algorithm.…”