Natural convection study of brownian nano-size particles inside a water-filled cavity by lagrangian-eulerian tracking approach

Abstract

In this research Lagrangian method is employed to track the nanoparticles inside a differentially heated walls nanofluidfilled cavity in natural convective flow. The thermo-physical properties of the solid-liquid mixture is also included in Eulerian frame. There are multiple interactions between fluid and particles which turns the simulations for solid-liquid highly complicated. ANSYS FLUENT 15.0 was used in this research to model submicron particles. Moreover, important interaction forces are implemented in the software as a User Defined Function (UDF) to modify the Lagrangian model. Brownian movement of the particles is assumed as a diffusion force acting on each particle during small user defined time step. Pressure gradient, gravity, virtual mass and Thermophoresis forces have also added to the force balance equation. Electrostatic forces are the contributing factors for stability of the nanofluid which they are needed to be present in dynamic equation of the particles. The importance of the forces on distribution of the particles is compared. The results show that the presence of these forces has considerable impact on nanoparticles concentration profiles.