Mesoscopic simulation of binary immiscible fluids flow in a square microchannel with hydrophobic surfaces

Abstract

The mesoscopic simulation for fluids flow in a square microchannel is investigated using dissipative particle dynamics. The velocity distribution for single fluid in a square channel is compared with the solutions of CFD solver, which is found to be in good agreement with each other. The no-slip boundary condition could be well held for the repulsive coefficient ranged from 9.68 to 18.0. For the same range of repulsive coefficient, various wettabilities could be obtained by changing the repulsive coefficient for binary immiscible fluids, in which the immiscible fluids are achieved by increasing the repulsive force between species. The typical motion of the DPD particle might be described as Brownian, which is similar to MD simulation results. The DPD simulated fluid/fluid interfacial tension is in accord with theoretical prediction. For the same repulsive parameters, the fluid/solid interfacial tension is always greater than the fluid/fluid interfacial tension. The DPD simulated static contact angles are in good agreement with Young's equation even though some differences exist due to thermal fluctuation. For moving contact line, the advancing and receding contact angles are different with each other. It is found that the cross-section area of hydrophobic fluid retracts towards the central part of the square microchannel and forms a cir cle. The retraction extent of the hydrophobic fluid is dependant on the velocity itself. For immiscible fluid, the moving velocities of fluid A in a microchannel could be increased by increasing the repulsive coefficient between fluid A and walls, and larger static angle may produce larger moving velocity. Copyright © 2007 Tech Science Press.