Interface Turbulence Damping

At a liquid-gas interface with a high relative velocity between the phases, the large gradients in the boundary layer near the free surface can cause significant turbulence fluctuations. The Interface Turbulence Damping model accounts for this in VOF multiphase simulations.

A symmetric damping procedure is used to model the interface as a moving wall for both of the phases in the interface region ([517], [506]).

K-Omega Model

The damping procedure introduces a reduction of the destruction term, − β ρ ω 2 , in the turbulent specific dissipation rate equation of the K-Omega model, Eqn. (1216). A positive term with a similar form is added:

Figure 1. EQUATION_DISPLAY
S ω = I ( α ) Δ n β ρ ω w 2
(2635)

where:

  • I ( α ) is the interface area density (in units of m − 1 )

  • Δ n is the grid size in the interface region

  • β is a K-Omega model coefficient.

  • ω w ⁢ =   B 6 μ β * ρ Δ n 2 is modelled on the asymptotic value of ω at the wall with B the damping coefficient.

    β * is a K-Omega model coefficient.

    See Model Coefficients.

K-Epsilon and Reynolds Stress Transport Models

For the K-Epsilon and Reynolds Stress Transport models, a corresponding source term is added:

Figure 2. EQUATION_DISPLAY
S ϵ = I ( α ) Δ n C ϵ 2 ρ ϵ w 2 k
(2636)

where:

  • ϵ w = B ˜ 2 ν k Δ n 2 , based on the wall-cell dissipation ϵ = 2 ν k y 2 for low-y+ wall treatment with B ˜ the tuning parameter.

  • C ϵ 2 is a K-Epsilon model coefficient.

    See Model Coefficients.