A Multiphase Mixture Theory for Fluid-Particle Flows

Publisher Summary This chapter presents a theory for suspension of particles in fluids based on the continuum theory of multiphase mixtures and it describes the application of the continuum mixture theory to the description of fluid–particle flows. The maximum concentration of particles can occur off the axis of symmetry because of a balance between lift forces and dynamic pressure forces. This provides a possible explanation of the Segre–Silberberg effect in the context of mixture theory. The classical theory of translational Brownian motion is concerned with the random migration of isolated colloidal particles in a suspending fluid. This random motion is a result of the collisions between the particles and the molecules of the fluid, which are undergoing thermal fluctuations. For neutrally buoyant particles, the particle flux, because of the fluctuating velocity field, is the same as that which can be produced by thermodynamic force acting on each particle. This thermodynamic force is equal to the gradient of the chemical potential of the particles.