Use the Convection and Diffusion node to define the fluid properties, velocity, diffusion coefficient, and dispersion model. This node as present by default.

The default Density ρ (SI unit: kg/m3) uses the value From material. For User defined enter a different value or expression.

The default Dynamic viscosity μ (SI unit: Pa·s) uses the value From material and describes the relationship between the shear rate and the shear stresses in a fluid. Intuitively, water and air have a low viscosity, and substances often described as thick, such as oil, have a higher viscosity.

Enter a value or expression for the Tangential velocity u (SI unit: m2/s). The default is 0 m2/s.

Enter a value or expression for the diffusion coefficient Dc (SI unit: m2/s). The default is 1 × 10-9 m2/s.

Select a Dispersion model — User defined (the default), Taylor (laminar, circular cross section), or Taylor (turbulent, circular cross section). For User defined, enter a value or expression for the Dispersion coefficient DD (SI unit: m2/s). The default is 0 m2/s. Find more detail in the theory section Dispersion.