Dissipative particle dynamics simulation of flow in periodically grooved three-dimensional nano- and micro-channels

This paper was presented at the 3rd Micro and Nano Flows Conference (MNF2011), which was held at the Makedonia Palace Hotel, Thessaloniki in Greece. The conference was organised by Brunel University and supported by the Italian Union of Thermofluiddynamics, Aristotle University of Thessaloniki, University of Thessaly, IPEM, the Process Intensification Network, the Institution of Mechanical Engineers, the Heat Transfer Society, HEXAG - the Heat Exchange Action Group, and the Energy Institute.Nonequillibrium flow in three-dimensional grooved nano- and micro-channels is investigated using the Dissipative Particle Dynamics simulation method. Roughness is introduced by periodically placing rectangular protruding elements on the upper channel wall. The protrusion length and height are varied and their effect on the flow is examined. The computed macroscopic quantities of practical interest include density, velocity, pressure, and temperature profiles as well as relations between the friction factor and the Reynolds number. When compared to the smooth channel case, lower flow velocities are observed in the central part of the channel for all cases studied. This reduction of velocities becomes more pronounced as the protrusion height increases. For the micro-channel, density, pressure and temperature remain almost constant in the central part of the channel and their pattern near and inside the cavities depend on the protrusion shape. In the nanochannel case, lower temperatures and pressures are observed for all grooved channels relative to the smooth channel case. For all channel cases studied the calculated friction factor decreases as Reynolds number increases, following a power law relation

Monte-Carlo method for incompressible fluid flows past obstacles

We establish stochastic functional integral representations for incompressible fluid flows occupying wall-bounded domains using the conditional law duality for a class of diffusion processes. These representations are used to derive a Monte-Carlo scheme based on the corresponding exact random vortex formulation. We implement several numerical experiments based on the Monte-Carlo method without appealing to the boundary layer flow computations, to demonstrate the methodology.Comment: 60 figure

Lattice Boltzmann simulations of soft matter systems

This article concerns numerical simulations of the dynamics of particles immersed in a continuum solvent. As prototypical systems, we consider colloidal dispersions of spherical particles and solutions of uncharged polymers. After a brief explanation of the concept of hydrodynamic interactions, we give a general overview over the various simulation methods that have been developed to cope with the resulting computational problems. We then focus on the approach we have developed, which couples a system of particles to a lattice Boltzmann model representing the solvent degrees of freedom. The standard D3Q19 lattice Boltzmann model is derived and explained in depth, followed by a detailed discussion of complementary methods for the coupling of solvent and solute. Colloidal dispersions are best described in terms of extended particles with appropriate boundary conditions at the surfaces, while particles with internal degrees of freedom are easier to simulate as an arrangement of mass points with frictional coupling to the solvent. In both cases, particular care has been taken to simulate thermal fluctuations in a consistent way. The usefulness of this methodology is illustrated by studies from our own research, where the dynamics of colloidal and polymeric systems has been investigated in both equilibrium and nonequilibrium situations.Comment: Review article, submitted to Advances in Polymer Science. 16 figures, 76 page

Progress in particle-based multiscale and hybrid methods for flow applications

This work focuses on the review of particle-based multiscale and hybrid methods that have surfaced in the field of fluid mechanics over the last 20 years. We consider five established particle methods: molecular dynamics, direct simulation Monte Carlo, lattice Boltzmann method, dissipative particle dynamics and smoothed-particle hydrodynamics. A general description is given on each particle method in conjunction with multiscale and hybrid applications. An analysis on the length scale separation revealed that current multiscale methods only bridge across scales which are of the order of O(102)−O(103) and that further work on complex geometries and parallel code optimisation is needed to increase the separation. Similarities between methods are highlighted and combinations discussed. Advantages, disadvantages and applications of each particle method have been tabulated as a reference

Multiscale computational fluid dynamics

This is the final version. Available on open access from MDPI via the DOI in this recordComputational Fluid Dynamics (CFD) has numerous applications in the field of energy research, in modelling the basic physics of combustion, multiphase flow and heat transfer; and in the simulation of mechanical devices such as turbines, wind wave and tidal devices, and other devices for energy generation. With the constant increase in available computing power, the fidelity and accuracy of CFD simulations have constantly improved, and the technique is now an integral part of research and development. In the past few years, the development of multiscale methods has emerged as a topic of intensive research. The variable scales may be associated with scales of turbulence, or other physical processes which operate across a range of different scales, and often lead to spatial and temporal scales crossing the boundaries of continuum and molecular mechanics. In this paper, we present a short review of multiscale CFD frameworks with potential applications to energy problems

Influence of Fibrinogen Deficiency on Clot Formation in Flow by Hybrid Model

International audienceIn this work we develop the 2D model suggested in [32] in order to study the impact of fibrinogen concentration and the fibrin polymer production rate on clot growth in flow. The model is based on the method of Dissipative Particle Dynamics describing blood plasma flow and platelet suspension and on a system of partial differential equations describing blood coagulation regulatory network. We study the influence of parameters on clot development and on its final size

Modelling of platelet–fibrin clot formation in flow with a DPD–PDE method

International audienceThe paper is devoted to mathematical modelling of clot growth in bloodflow. Great complexity of the hemostatic system dictates the need of usage of themathematical models to understand its functioning in the normal and especially inpathological situations. In this work we investigate the interaction of blood flow,platelet aggregation and plasma coagulation. We develop a hybrid DPD–PDE modelwhere dissipative particle dynamics (DPD) is used to model plasma flow and platelets,while the regulatory network of plasma coagulation is described by a system of partialdifferential equations. Modelling results confirm the potency of the scenario of clotgrowth where at the first stage of clot formation platelets form an aggregate due toweak inter-platelet connections and then due to their activation. This enables the formationof the fibrin net in the centre of the platelet aggregate where the flow velocity issignificantly reduced. The fibrin net reinforces the clot and allows its further growth.When the clot becomes sufficiently large, it stops growing due to the narrowed vesseland the increase of flow shear rate at the surface of the clot. Its outer part is detachedby the flow revealing the inner part covered by fibrin. This fibrin cap does not allownew platelets to attach at the high shear rate, and the clot stops growing. Dependenceof the final clot size on wall shear rate and on other parameters is studied