WOLFRAM SYSTEMMODELER

Dynamics

Enumeration to define definition of balance equations

Wolfram Language

In[1]:=
SystemModel["Modelica.Fluid.Types.Dynamics"]
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Information

This information is part of the Modelica Standard Library maintained by the Modelica Association.

Enumeration to define the formulation of balance equations (to be selected via choices menu):

Dynamics.Meaning
DynamicFreeInitialDynamic balance, Initial guess value
FixedInitialDynamic balance, Initial value fixed
SteadyStateInitialDynamic balance, Steady state initial with guess value
SteadyStateSteady 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.

Enumeration Literals (4)

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

Used in Examples (1)

IncompressibleFluidNetwork

Modelica.Fluid.Examples

Multi-way connections of pipes and incompressible medium model

Used in Components (10)

EquilibriumDrumBoiler

Modelica.Fluid.Examples.DrumBoiler.BaseClasses

Simple Evaporator with two states, see Astroem, Bell: Drum-boiler dynamics, Automatica 36, 2000, pp.363-378

BasicHX

Modelica.Fluid.Examples.HeatExchanger.BaseClasses

Simple heat exchanger model

WallConstProps

Modelica.Fluid.Examples.HeatExchanger.BaseClasses

Pipe wall with capacitance, assuming 1D heat conduction and constant material properties

System

Modelica.Fluid

System properties and default values (ambient, flow direction, initialization)

PartialTwoPortFlow

Modelica.Fluid.Pipes.BaseClasses

Base class for distributed flow models

PartialStaggeredFlowModel

Modelica.Fluid.Pipes.BaseClasses.FlowModels

Base class for momentum balances in flow models

PartialLumpedVolume

Modelica.Fluid.Interfaces

Lumped volume with mass and energy balance

PartialLumpedFlow

Modelica.Fluid.Interfaces

Base class for a lumped momentum balance

PartialDistributedVolume

Modelica.Fluid.Interfaces

Base class for distributed volume models

PartialDistributedFlow

Modelica.Fluid.Interfaces

Base class for a distributed momentum balance