Berlin 2008 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 22: POSTERS Micro- and Nanofluidics

CPP 22.21: Poster

Wednesday, February 27, 2008, 16:00–18:30, Poster A

Lattice Boltzmann simulation of non ideal fluids — •Bin Wu, Fathollah Varnik, and Dierk Raabe — Max-Planck Institut für Eisenforschung, Max-Planck Straβe 1,40237 Düsseldorf, Germany

The basic idea of the Lattice Boltzmann(LB) Method is that the liquid approaches local equilibrium on each lattice site via collisions.The lattice Boltzmann dynamics is given by f_{σ i}( x+є e_iα,t+є) − f_{σ i}( x,t)=−1/τ[ f_{σ i}( x,t)−f_{σ i}^eq( x,t) ] with ∑f_ie_iαe_iβ=P_αβ+n u_αu_β.

For a liquid-gas system,the equilibrium properties can be described by the free energy, Ψ=∫_V(ψ_b(n)+κ/2(∂_αn)²)dV+∫_Sψ_c(n)dS.Minimizing the free energy gives P_αβ=κ∂_αn∂_βn+[n∂_nψ_b(n)−ψ_b(n)−κ/2(∂_αn)²−κ n△ n]δ_αβ.

The free energy enters the LB algorithm via the pressure tensor, P_αβ, which is so called free energy LB approach.

The free energy LB method can deal with Navier-Stokes level hydrodynamics at low Mach numbers. We simulate a droplet’s motion on a step-gradient substrate.Owing to different Laplace pressure, the droplet is driven to move on the substrate.Simulation of the droplets’ coalescence on substrates is also done by us and we fit the function between the width of bridge-neck and time.We find liquid droplet instability (evaporation) depends on the size of system.