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We have developed a lattice-Boltzmann simulation capability for modeling the behavior of microscale fluid systems. Complex fluid dynamics problems in this size range currently are not amenable to being modeled by conventional simulation methods. These methods do not properly account for the importance of surface forces at fluid-gas, fluid-fluid and fluid-solid interfaces. However, our lattice-Boltzmann modeling capability overcomes these limitations. It is critically important to support the design and testing of MICRO-CATS.
One major advantage of the lattice-Boltzmann method is the ability to incorporate surface energy terms into the equations of motion. A non-ideal equation of state may be specified which is used to represent a fluid-vapor interface, forming individual bubbles or droplets that are free to move through the lattice grid. A similar approach has also been demonstrated for simulating immiscible fluids. A fluid-solid interaction potential is used to incorporate an external chemical potential that is a function of the material properties of the solid boundary. These terms are used to represent the wettability or non-wettability of a solid surface. The usefulness of the lattice-Boltzmann method has been demonstrated by simulating a number of microfluid systems, including the stability of the fluid-fluid interface in a micromachined contactor with precision-engineered pores and chemical separations using a liquid-liquid extraction device.
In our recent work we have focused on coupling thermal effects to a multiphase model of fluid behavior. This can be used to model heat transfer in multiphase flow and the dynamics of thermally limited phase changes. For instance it can be used to do a calculation of condensation in a pore.
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