Numerical simulation of fluid-fluid and solid-fluid interactions: a lattice Boltzmann strategy

Asadi, Mohammad Bagher (2021) Numerical simulation of fluid-fluid and solid-fluid interactions: a lattice Boltzmann strategy. Doctoral (PhD) thesis, Memorial University of Newfoundland.

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Abstract

It is crucial to obtain a better understanding of fluid-fluid and solid-fluid interactions with several applications in science and engineering disciplines. Associating fluids such as water, alcohols, asphaltene might exist in many processes. Modeling associating fluids to explore phase equilibrium behaviors is required for proper design, operation, and optimization of various chemical and energy processes. Pseudopotential lattice Boltzmann method (LBM) can be a promising and capable mesoscopic approach to study phase transition and thermodynamic behaviors of complex fluid systems. Results of integrating the cubic equations of state (EOSs) with LBM showed a considerable deviation from experimental data for associating fluids. Cubic-plus-association (CPA) EOS is utilized in the LBM to increase the accuracy of modeling associating fluids. A global optimization approach is applied to determine the optimum association parameters of CPA EOS for water and primary alcohols in the lattice units. Maxwell equal area construction is used to verify the thermodynamic consistency. By increasing the isotropy order of gradient operator, the spurious velocities are decreased, and an extended form of CPA EOS is introduced to find proper initial densities, which increase the stabilities at low reduced temperatures. Simulating fluid flow at high Reynolds number is another aspect of an LBM study that needs further improvement. In fluid flow in porous media, specifically at tight gas reservoirs, a high flow rate might happen at pore throat. Therefore, to increase the stability of the model at high Reynolds number, the central moments collision operator is implemented in the LBM. The advantages of central moments collision operator are shown by comparing with multi relaxation time (MRT) collision operator in the double shear layers test. It is found that using a higher order of isotropy in the gradient operator can lead to a 34% reduction in spurious velocities. From the thermodynamic consistency point of view, it is concluded that collision operators can also have an impact on the consistency of the model. Furthermore, the model validation is performed by observing a straight line in the Laplace law test. Surface wettability is known as an important concept to achieve a better understanding of fluid flow and distribution in both porous and non-porous systems. Improving the solid-fluid interaction can help to have a better understanding of thermodynamics of curved interfaces. The contact angle is an important parameter to study the multiphase fluid flow in various systems such as porous media and membranes. It helps to design better production, separation, treatment, and reaction processes in different applications. In order to increase the accuracy and reliability of the model for simulation of the surface wettability and absorption, a new solid-fluid interaction in the pseudopotential approach is introduced. Usually, the surface wettability is reported by the contact angle, which is measured by fitting a circle on the drop. Because the circle is a constant curvature shape, it is not suitable to consider the disjoining pressure. A new strategy is presented based on the Smoothing Splines to measure the contact angle without considering a constant curvature shape of the interface profile. The new solid-fluid interaction exhibits the capability of simulating extreme non-wetting surfaces without detaching the drop. The probability histogram of the density domain appears to be a reliable tool to measure the phase density in the presence of a surface. The results of the current research have a wide range of applications in energy and environment, such as simulation of fluid flow in porous systems (e.g., shale reservoirs and membranes). Pores and fractures are large in conventional permeable media and pressure-drive convective flow is applicable in the framework of continuum flow. Shale reservoir have fine grains and pores in the range on nanometer where fluid molecular distribution is inhomogeneous and surface adsorption may be significant. Coupling the introduced method with nucleation theory provide a powerful tool to simulate asphaltene precipitation in the porous media. The presence of water component as an associating fluid in some biological processes such as blood coagulation makes the presented model an effective tool to simulate those processes.

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