.TRANSFORM.Types.Dynamics .TRANSFORM.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 transient behavior initializations such as mass, energy and momentum balances. The exact meaning of the three balance equations is stated in the following tables using fluid flow as an example:
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");