Switching Criteria for Hybrid Rarefied Gas Flow Solvers

Lockerby, Duncan A.; Struchtrup, Henning; Reese, Jason M.

doi:10.1063/1.3076516

Cited by 7 publications

(9 citation statements)

References 19 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…For each of the species, the density has been set such that the body-length Knudsen number Kn BL is 0.05. Studies on different breakdown parameters for similar test cases [36,37] show that the non-equilibrium originates from the Knudsen layer near the wall. For this reason, the CFD and DSMC domains are consider appropriate for the complete simulation, and will not be updated.…”

Section: Resultsmentioning

confidence: 97%

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

Espinoza

Casseau

Scanlon

et al. 2016

AIP Conference Proceedings

View full text Add to dashboard Cite

During re-entry, a spacecraft will experience flow conditions ranging from highly rarefied to continuum. To simulate regions in between, a hydrodynamic-molecular gas hybrid solver should be used to provide accuracy and effciency. Currently available hybrid codes are in-house codes or do not provide the capabilities to simulate all of the phenomena a spacecraft will experience during re-entry. An open-source CFD-DSMC hybrid code is being developed within the OpenFOAM framework, coupling the solvers dsmcFoam and hy2Foam. In this paper, comparison between the CFD, DSMC and hybrid codes have been performed for simple cases. The dsmcFoam and the hybrid code have shown to compare satisfactorily

show abstract

Section: Resultsmentioning

confidence: 97%

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

Espinoza

Casseau

Scanlon

et al. 2016

AIP Conference Proceedings

View full text Add to dashboard Cite

show abstract

“…Alternatively, some researchers have developed other formulations of continuum breakdown parameters by measuring the departure from hydrodynamic behavior. For example, Lockerby et al [19] proposed a new criterion based on the difference between the hydrodynamic near-equilibrium fluxes (the Navier-Stokes stress and Fourier heat flux) and the actual values of stress and heat flux (computed from molecular simulations or approximated through higher order constitutive relations); Meng et al [20] proposed a kinetic criterion based on the molecular distribution function to indirectly assess the errors introduced by the description using NSF equations. Their numerical tests demonstrated that the new criterion performs very well in both low-speed and high-speed flows.…”

Section: Continuum Breakdown Criterionmentioning

confidence: 99%

Particle-based hybrid and multiscale methods for nonequilibrium gas flows

et al. 2019

View full text Add to dashboard Cite

Over the past half century, a variety of computational fluid dynamics (CFD) methods and the direct simulation Monte Carlo (DSMC) method have been widely and successfully applied to the simulation of gas flows for the continuum and rarefied regime, respectively. However, they both encounter difficulties when dealing with multiscale gas flows in modern engineering problems, where the whole system is on the macroscopic scale but the nonequilibrium effects play an important role. In this paper, we review two particle-based strategies developed for the simulation of multiscale nonequilibrium gas flows, i.e., DSMC-CFD hybrid methods and multiscale particle methods. The principles, advantages, disadvantages, and applications for each method are described. The latest progress in the modelling of multiscale gas flows including the unified multiscale particle method proposed by the authors is presented.

show abstract

“…For problems such as this, where the degree of scale separation varies as the system evolves, we define a local scale-separation number (analogous to the local Knudsen number for rarefied gas flows, e.g., [7,8]) that compares the shortest relaxation time scale of the system (T micro ) with a time scale that characterises the evolution of the coupling variables:…”

Section: Example I: Step Response Of Coupled Odesmentioning

confidence: 99%

Time-step coupling for hybrid simulations of multiscale flows

Lockerby

Duque-Daza

Borg

et al. 2013

Journal of Computational Physics

Self Cite

View full text Add to dashboard Cite

A new method is presented for the exploitation of time-scale separation in hybrid continuum-molecular models of multiscale flows. Our method is a generalisation of existing approaches, and is evaluated in terms of computational efficiency and physical/numerical error. Comparison with existing schemes demonstrates comparable, or much improved, physical accuracy, at comparable, or far greater, efficiency (in terms of the number of time-step operations required to cover the same physical time). A leapfrog coupling is proposed between the ‘macro’ and ‘micro’ components of the hybrid model and demonstrates potential for improved numerical accuracy over a standard simultaneous approach. A general algorithm for a coupled time step is presented. Three test cases are considered where the degree of time-scale separation naturally varies during the course of the simulation. First, the step response of a second-order system composed of two linearly-coupled ODEs. Second, a micro-jet actuator combining a kinetic treatment in a small flow region where rarefaction is important with a simple ODE enforcing mass conservation in a much larger spatial region. Finally, the transient start-up flow of a journal bearing with a cylindrical rarefied gas layer. Our new time-stepping method consistently demonstrates as good as or better performance than existing schemes. This superior overall performance is due to an adaptability inherent in the method, which allows the most-desirable aspects of existing schemes to be applied only in the appropriate conditions

show abstract

Switching Criteria for Hybrid Rarefied Gas Flow Solvers

Cited by 7 publications

References 19 publications

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

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

Particle-based hybrid and multiscale methods for nonequilibrium gas flows

Time-step coupling for hybrid simulations of multiscale flows

Contact Info

Product

Resources

About