Difference between revisions of "Contrib/CompressibleMixingPhaseChangeFoam"
Mkraposhin (Talk | contribs) (→Model Equations Derivation) |
Mkraposhin (Talk | contribs) (→Model Equations Derivation) |
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* '''Energy equation''' | * '''Energy equation''' | ||
− | Energy equation for mixture temperature obtained from sum of energy equations for each phase. Consider energy equation for phase-1: | + | Energy equation for mixture temperature obtained from sum of energy equations for each phase. Consider internal energy equation for phase-1: |
<math> | <math> | ||
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\nabla \cdot \left ( \alpha_1 \rho_1 e_1 \textbf{U} \right ) + \nabla \cdot \textbf{q}_1 | \nabla \cdot \left ( \alpha_1 \rho_1 e_1 \textbf{U} \right ) + \nabla \cdot \textbf{q}_1 | ||
= | = | ||
− | -\alpha_1 p \nabla \cdot \textbf{U} | + | -\alpha_1 p (\nabla \cdot \textbf{U} - \dot m_1 / \rho_1) |
+ | + | ||
\dot m_1 e_1 | \dot m_1 e_1 | ||
</math> | </math> | ||
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− | + | By combining equations of phases, we get internal energy balance for mixture in temperatures: | |
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− | By combining equations of phases, we get energy balance for mixture: | + | |
<math> | <math> | ||
\frac{\partial T}{\partial t} + \nabla \cdot \left ( T \textbf{U} \right ) - T \nabla \cdot \textbf{U} | \frac{\partial T}{\partial t} + \nabla \cdot \left ( T \textbf{U} \right ) - T \nabla \cdot \textbf{U} | ||
− | -\frac{1}{\rho_1 C_{ | + | -\frac{1}{\alpha_1 \rho_1 C_{v,1} + \alpha_2 \rho_2 C_{v,2}} (\nabla \cdot \kappa_1 \nabla T + \nabla \cdot \kappa_2 \nabla T) |
= | = | ||
</math> | </math> | ||
<math> | <math> | ||
− | \left ( \frac{ | + | -\left ( \nabla \cdot \textbf{U} - \left(\frac{1}{\rho_1}-\frac{1}{\rho_2}\right) \dot m_1 \right ) |
− | + | \frac{p}{\alpha_1 \rho_1 C_{v,1} + \alpha_2 \rho_2 C_{v,2}} | |
− | + \ | + | - \left ( \frac{\partial L}{\partial t} + \nabla \cdot (\textbf{U} L) - L \nabla \cdot \textbf{U} \right ) |
+ | \frac{\alpha_2 \rho_2}{\alpha_1 \rho_1 C_{v,1} + \alpha_2 \rho_2 C_{v,2}} | ||
</math> | </math> | ||
+ | |||
+ | Where <math> L </math> - latent heat of evaporation | ||
* '''Linking liquid volume transport to pressure equation''' is done by introducing <math>+\alpha_1 \nabla \cdot \textbf{U}</math> and <math>-\alpha_1 \nabla \cdot \textbf{U}</math> at r.h.s of volume fraction balance equation. Then, <math>-\nabla \cdot \textbf{U}</math> replaced by value from pressure equation | * '''Linking liquid volume transport to pressure equation''' is done by introducing <math>+\alpha_1 \nabla \cdot \textbf{U}</math> and <math>-\alpha_1 \nabla \cdot \textbf{U}</math> at r.h.s of volume fraction balance equation. Then, <math>-\nabla \cdot \textbf{U}</math> replaced by value from pressure equation | ||
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* Phase change model | * Phase change model | ||
+ | Schnerr-Sauer | ||
== Model Equations Summary == | == Model Equations Summary == |
Revision as of 15:31, 6 August 2013
Solver for two fluids with phase change (for example - water <---> steam), pressure and temperature density dependence
1 Model Equations Derivation
- Equation of state
Low-compressible fluid:
Ideal gas:
By combining this equations, we can get general relation:
where computed with respect to previous formulations
mixture density calculated as
Here, and afterthere indices:
1,l,f - for liquid (heavy media with low compressibility)
2,g,s - for gas (light media (like steam) with big compressibility)
without index - mixture variable (or all variables local to some phase)
- Liquid volume transport
Let us consider transport of liquid (heavy phase) volume fraction :
By converting to volume fluxes we get:
Using equation of state, we can reformulate substantial derivative for density in terms of pressure for any phase:
- General rule for converting from mass to volume fluxes in transport equation
- Momentum equation (velocity prediction)
by substituting piezometric pressure we get:
- Pressure equation obtained by summation of equation for volume phase fraction of liquid and gas phases:
- Energy equation
Energy equation for mixture temperature obtained from sum of energy equations for each phase. Consider internal energy equation for phase-1:
By combining equations of phases, we get internal energy balance for mixture in temperatures:
Where - latent heat of evaporation
- Linking liquid volume transport to pressure equation is done by introducing and at r.h.s of volume fraction balance equation. Then, replaced by value from pressure equation
- Phase change model
Schnerr-Sauer
2 Model Equations Summary
3 Tutorial cases
- Case #1 - Water Evaporation in Cavity