Abstract
The method of multi-particle collision dynamics (MPCD) and its different implementations are commonly used in the field of soft matter physics to simulate fluid flow at the micron scale. Typically, the coarse-grained fluid particles are described by the equation of state of an ideal gas, and the fluid is rather compressible. This is in contrast to conventional fluids, which are incompressible for velocities much below the speed of sound, and can cause inhomogeneities in density. We propose an algorithm for MPCD with a modified collision rule that results in a non-ideal equation of state and a significantly decreased compressibility. It allows simulations at less computational costs compared to conventional MPCD algorithms. We derive analytic expressions for the equation of state and the corresponding compressibility as well as shear viscosity. They show overall very good agreement with simulations, where we determine the pressure by simulating a quiet bulk fluid and the shear viscosity by simulating a linear shear flow and a Poiseuille flow.
Highlights
Since their introduction in 1999,1 algorithms belonging to the method of multi-particle collision dynamics (MPCD) have become a standard tool to simulate fluid flows in the field of soft matter physics.2–4 In particular, MPCD algorithms have commonly been used to model solvent dynamics in the context of microswimmers,5–18 where we can only cite a few examples
Germany a)Author to whom correspondence should be addressed: holger.stark@tu-berlin.de
The collision rules for the coarse-grained fluid particles are well suited for the implementation on parallel computer hardware39,40 so that extensive simulations can be performed on desktop computers with graphic cards
Summary
Since their introduction in 1999,1 algorithms belonging to the method of multi-particle collision dynamics (MPCD) have become a standard tool to simulate fluid flows in the field of soft matter physics. In particular, MPCD algorithms have commonly been used to model solvent dynamics in the context of microswimmers, where we can only cite a few examples. MPCD methods are often used to simulate the dynamics of incompressible solvents, one has to be aware that the coarse-grained fluid particles follow the equation of state of an ideal gas.. For the MPCD fluid with its ideal-gas equation of state, this can be achieved by increasing the number n0 of fluid particles per collision cell and thereby density.. Our approach extends ideas of Tüzel, Ihle, and collaborators, who included geometric properties of hard-core particles in two dimensions into the collision rule to control momentum transport in the fluid.. Our approach extends ideas of Tüzel, Ihle, and collaborators, who included geometric properties of hard-core particles in two dimensions into the collision rule to control momentum transport in the fluid.42,43 This approach has been extended to the simulation of fluid mixtures..
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