Numerical Study Of Flow And Heat Transfer For Multiphase Fluids

In this paper we numerically investigate flow, heat and mass transfer of multiphase fluids with different physical conditions such as infinite plate, rotating circular groove and pipe and so on. This research is interdisciplinary, involving a wide variety of fields in engineering thermophysics, fluid mechanics, applied mathematics and numerical computations. Nanofluids based on power-law fluids (solid-fluid two phase fluids), fluid-fluid two phase fluids with the same density and viscosity and fluid-fluid two phase fluids with different densities and viscosities are studied in this paper.For nanofluids based on power-law fluids and Cu nanoparticle, the governing equations are created based on conservation of mass, momentum and energy and so on. Heat and mass transfer of power-law fluids different from Newtonian fluid, non-uniform heat flux and non-uniform concentration flux on boundary, Brownian and thermophoresis are considered and it is numerically investigated from boundary layer and full flow field with similarity transformation, step-by-step shooting method, secant method, Newton method and finite element method. Influences of some important parameters are discussed on flow field, temperature field and the concentration of nanoparticles.We numerically investigate the fluid-fluid two phase fluids with phase filed model which is different from sharp interface based on Navier-Stokes-Cahn-Hilliard equations. General Navier Boundary Condition and no-slip boundary condition are used to study moving contact line with two phase fluids with the same density and viscosity and general two phase fluids with different densities and viscosities. Based on governing equations, the discrete energy law equation similar to the continuous energy law is obtained by choosing a special computation scheme. To our knowledge, no discrete energy law equation for moving contact line and the same governing equations is published before. They just make the energy stable or energy decrease, but they can not guarantee the amount of reducing of calculating energy is the same as the energy of original physical problems. Two immiscible fluids distributed at the left and right parts of a pipe and the droplet under the effect of pressure driven shear flow with the same density and viscosity, two kissing drop and rise of the droplet with different densities and viscosities are studied as numerical examples. This computation scheme preserving energy law can make the results under a coarse mesh agree well with results under a fine mesh published before and also can improve the efficiency. The numerical simulation of interface and the calculation of energy law can show the numerical stability of results and verify the existence of sharp-interface limit by changing the thickness of interface. That means we can simulate multiphase flows by reducing the thickness of interface but not to the nanoscale.