.Modelica.Fluid.Types.Dynamics .Modelica.Fluid.Types.DynamicsEnumeration to define the formulation of balance equations (to be selected via choices menu):
| Dynamics. | Meaning |
|---|---|
| DynamicFreeInitial | Dynamic balance, Initial guess value |
| FixedInitial | Dynamic balance, Initial value fixed |
| SteadyStateInitial | Dynamic balance, Steady state initial with guess value |
| SteadyState | Steady state balance, Initial guess value |
The enumeration "Dynamics" is used for the mass, energy and momentum balance equations respectively. The exact meaning for the three balance equations is stated in the following tables:
| Mass balance | ||
| Dynamics. | Balance equation | Initial condition |
| DynamicFreeInitial | no restrictions | no initial conditions |
| FixedInitial | no restrictions | if Medium.singleState
then no initial condition else p=p_start |
| SteadyStateInitial | no restrictions | if Medium.singleState
then no initial condition else der(p)=0 |
| SteadyState | der(m)=0 | no initial conditions |
| Energy balance | ||
| Dynamics. | Balance equation | Initial condition |
| DynamicFreeInitial | no restrictions | no initial conditions |
| FixedInitial | no restrictions | T=T_start or h=h_start |
| SteadyStateInitial | no restrictions | der(T)=0 or der(h)=0 |
| SteadyState | der(U)=0 | no initial conditions |
| Momentum balance | ||
| Dynamics. | Balance equation | Initial condition |
| DynamicFreeInitial | no restrictions | no initial conditions |
| FixedInitial | no restrictions | m_flow = m_flow_start |
| SteadyStateInitial | no restrictions | der(m_flow)=0 |
| SteadyState | der(m_flow)=0 | no initial conditions |
In the tables above, the equations are given for one-substance fluids. For multiple-substance fluids and for trace substances, equivalent equations hold.
Medium.singleState is a medium property and defines whether the medium is only described by one state (+ the mass fractions in case of a multi-substance fluid). In such a case one initial condition less must be provided. For example, incompressible media have Medium.singleState = true.
type Dynamics = enumeration(DynamicFreeInitial "DynamicFreeInitial -- Dynamic balance, Initial guess value", FixedInitial "FixedInitial -- Dynamic balance, Initial value fixed", SteadyStateInitial "SteadyStateInitial -- Dynamic balance, Steady state initial with guess value", SteadyState "SteadyState -- Steady state balance, Initial guess value");