Nearly exact solution for coupled continuum/MD fluid simulation |
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Authors: | Ju Li Dongyi Liao and Sidney Yip |
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Affiliation: | (1) Department of Nuclear Engineering, Massachusetts Institute of Technology, Cambridge, MA, 02139, U.S.A |
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Abstract: | A general statistical approach is described to couple the continuum with molecular dynamics in fluid simulation. Arbitrary
thermodynamic field boundary conditions can be imposed on an MD system while minimally disturbing the particle dynamics of
the system. And by acting away from the region of interest through a feedback control mechanism, across a buffer zone where
the disturbed dynamics are allowed to relax, we can eliminate that disturbance entirely. The field estimator, based on maximum
likelihood inference, serves as the detector of the control loop, which infers smooth instantaneous fields from the particle
data. The optimal particle controller, defined by an implicit relation, can be proved mathematically to give the correct distribution
with least disturbance to the dynamics. A control algorithm compares the estimated current fields with the desired fields
at the boundary and modifies the action of the particle controller far way, until they eventually agree. This method, combined
with a continuum code in a Schwarz iterative domain-decomposition formalism, provides a mutually consistent solution for steady-state
problems, as particles in the MD region of interest have no way to tell any difference from reality. Finally, we explain the
importance of using a higher order single-particle distribution function, in light of the Chapman–Enskog development for shear
flow.
This revised version was published online in July 2006 with corrections to the Cover Date. |
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Keywords: | Buffer Continuum Feedback Inference Least disturbance Molecular dynamics |
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