This page gathers other models implemented as source terms in the multiphase framework: analytical momentum/energy source terms and injected sources of mass.

Analytical source terms

Pressure term in the energy equation

This term arises from the averaging of the pressure-work term due to the transport of internal energy instead of enthalpy. It represents the pressure work associated with changes in the distribution of void fraction:

\[-P\left(\frac{\partial \alpha_k}{\partial t}+\nabla \cdot (\alpha_k v_k)\right) \]

It is implemented in Source_Travail_pression_Elem_base.

Gravity

Gravity is treated as a source term in Pb_Multiphase and cannot be handled as in the other TrioCFD/TRUST problems. The common way to add gravity is to add a source to the momentum equation; for example, with two phases:

source_qdm Champ_Fonc_xyz dom 6 0 0 0 0 -9.81 -9.81

When using a drift correlation, Gravite_Multiphase must be used to get gravity in the momentum equation.

Injected sources of mass

Injecting non-condensable bubbles is necessary to simulate bubble injectors (otherwise the flow boils); this was added to simulate the Gabillet test case.

Injection of mass

The model (Source_injection_masse_base) reads an injected-mass-flux field (one component per phase) and adds to the mass equation \(\texttt{secmem}\mathrel{+}=\rho_k f_{inj}\).

Momentum correction

When a fluid flow is injected through a wall with zero momentum via a Neumann boundary condition on the mass equation, the momentum equation must be corrected (Injection_QDM_nulle_PolyMAC_P0, default \(\beta=1\)). Two cases are handled:

Bubbles injected at the wall (not a boundary face): \(\texttt{f\_a\_masse}=\rho_g U_{inj}\), contributing \(-\texttt{surface}\times\texttt{f\_a\_masse}\times U^n\times\beta\) to secmem and \(+\texttt{surface}\times\texttt{f\_a\_masse}\times\beta\) to the velocity matrix.
Wall boiling (not a boundary face): \(G=\frac{q_p}{L_{vap}}\), with \(\texttt{f\_a\_masse}\mathrel{-}=\frac{G}{\texttt{surface}}\times\{1/\rho_g\text{ (gas)},\ -1/\rho_l\text{ (liquid)}\}\), contributing analogously to secmem and the velocity matrix.