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Phase Separation Behavior of Complex Fluids in Flow

Author: LiuLiJun
Tutor: WuShiShu；AnLiJia；ChenJiZhong
School: Jilin University
Course: Theoretical Physics
Keywords: Lattice Boltzmann method phase separation boundary condition cavitation channel
CLC: O35
Type: Master's thesis
Year: 2010
Downloads: 110
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Abstract

As a mesoscale simulation method, Lattice Boltzmann method is usually used to simulate kinetic behavior and phase separation behavior of the complex fluid. In this thesis, the derivation of the macroscopic fluid mechanics equation derived from Lattice Boltzmann equation is given in detail, and several kinds of basic models used in LBM as well as some common boundary conditions are introduced. We employ LBM to simulate Poiseuille flow, single component vapour-liquid separation, cavitation phenomena and binary blends fluid separation. Our studies focused on the separation of the binary fluids in a channel and we obtain the following conclusion:1. The simulation results of Poiseuille flow are consistent with theoretical results. The shape of velocity distribution of the fluid flowing in the channel is parabolic, in other words, the velocity achieves its maximum in the middle of the channel.2. With the same interaction strength, the simulation results of single component vapour-liquid separation show that the morphologies of the system dominated by the initial density of the system when the phase separation arrives at the equilibrium state. As the density increases, the size of the droplet increases while that of the bubble decreases.3. The simulation of cavitation shows that pressure difference between inside and outside of the bubble is the dominant factor to determine the critical radius of cavitation, and the growth of the bubble. Our results also show that the critical radius decreases as pressure difference between inside and outside the bubble increases.4. The simulation of binary blends fluid under periodic boundary condition shows that one component of the binary blends tends to form droplets when the system impends the equilibrium state, which is resulted from the minimized free energy.5. The simulation of the binary blends separation in the channel show that layered structure appears in the initial stage and in the intermediate stage of the phase separation, in which the initial density and relaxation time determine the length of time of layered structure. Though without small fluctuation of initial system density, the wall of channel can induce the phase separation and stable layered structures appear when the system arrives at its equilibrium state.

Phase Separation Behavior of Complex Fluids in Flow

Abstract

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