Lockerby, Duncan A., Duque-Daza, Carlos A., Borg, Matthew K. and Reese, Jason M. (2013) Time-step coupling for hybrid simulations of multiscale flows. Journal of Computational Physics, Vol.237 . pp. 344-365. doi:10.1016/j.jcp.2012.11.032 ISSN 0021-9991.

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Abstract

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.

Item Type:	Journal Article
Divisions:	Faculty of Science, Engineering and Medicine > Engineering > Engineering
Journal or Publication Title:	Journal of Computational Physics
Publisher:	Academic Press Inc. Elsevier Science
ISSN:	0021-9991
Official Date:	2013
Dates:	Date Event 2013 Published
Volume:	Vol.237
Page Range:	pp. 344-365
DOI:	10.1016/j.jcp.2012.11.032
Status:	Peer Reviewed
Publication Status:	Published
Access rights to Published version:	Restricted or Subscription Access

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