Holman1992-Natural-Convection-System

Natural, or free, convection is observed as a result of the motion of the fluid due to density changes arising from the heating process.

The movement of the fluid in free convection, wheter it is a gas or liquid, results from the bouyancy forces imposed on the fluid when its density in the proximity of the heat-transfer surface is decreased as a result of the heating process.

The bouyancy forces would not be present if the fluid were not acted upon by some external force field such as gravity, although gravity is not only type of force field which can produce the free-convection currents; a fluid enclosed in a rotating machine is acted upon by a centrifugasl force field, and thus could experince free-convection currents if one or more of the surfaces in contact with the fluid were heated.

The bouyancy forces which give rise to the free-convection currents are called body forces.

4-bc's-from-Lu and Howarth (1996)

1.Dirichlet Boundary condition: all variables except pressure are specified at upstream of the flow domain.
2.No-slip condition at the solid wall is applied for velocities.
3.”Wall-functions’ are applied to describe the turbulent flow properties in near wall regions.
4.Neumann Boundary Conditions are applied at the outlet to satisfy the mass conservation law.
5.The most important information for particle transport is the initial conditions and physical state of the paticles.