WOLFRAM SYSTEM MODELER
PartialStaggeredFlowModelBase class for momentum balances in flow models |
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Wolfram Language
In[1]:=
SystemModel["Modelica.Fluid.Pipes.BaseClasses.FlowModels.PartialStaggeredFlowModel"]
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Information
This information is part of the Modelica Standard Library maintained by the Modelica Association.
This partial model defines a common interface for m=n-1 flow models between n device segments.
The flow models provide a steady-state or dynamic momentum balance using an upwind discretization scheme per default.
Extending models must add pressure loss terms for friction and gravity.
The fluid is specified in the interface with the thermodynamic states[n] for a given Medium model.
The geometry is specified with the pathLengths[n-1] between the device segments as well as
with the crossAreas[n] and the roughnesses[n] of the device segments.
Moreover the fluid flow is characterized for different types of devices by the characteristic dimensions[n]
and the average velocities vs[n] of fluid flow in the device segments.
See Pipes.BaseClasses.CharacteristicNumbers.ReynoldsNumber
for example definitions.
The parameter Re_turbulent can be specified for the least mass flow rate of the turbulent regime.
It defaults to 4000, which is appropriate for pipe flow.
The m_flows_turbulent[n-1] resulting from Re_turbulent can optionally be calculated together with the Reynolds numbers
Res[n] of the device segments (show_Res=true).
Using the thermodynamic states[n] of the device segments, the densities rhos[n] and the dynamic viscosities mus[n] of the segments as well as the actual densities rhos_act[n-1] and the actual viscosities mus_act[n-1] of the flows are predefined in this base model. Note that no events are raised on flow reversal. This needs to be treated by an extending model, e.g., with numerical smoothing or by raising events as appropriate.
Parameters (13)
| m |
Value: n - 1 Type: Integer Description: Number of flow segments |
|---|---|
| n |
Value: 2 Type: Integer Description: Number of discrete flow volumes |
| nParallel |
Value: Type: Real Description: Number of identical parallel flow devices |
| g |
Value: system.g Type: Acceleration (m/s²) Description: Constant gravity acceleration |
| allowFlowReversal |
Value: system.allowFlowReversal Type: Boolean Description: = true, if flow reversal is enabled, otherwise restrict flow to design direction (states[1] -> states[n+1]) |
| momentumDynamics |
Value: system.momentumDynamics Type: Dynamics Description: Formulation of momentum balance |
| m_flow_start |
Value: system.m_flow_start Type: MassFlowRate (kg/s) Description: Start value of mass flow rates |
| p_a_start |
Value: Type: AbsolutePressure (Pa) Description: Start value for p[1] at design inflow |
| p_b_start |
Value: Type: AbsolutePressure (Pa) Description: Start value for p[n+1] at design outflow |
| useUpstreamScheme |
Value: true Type: Boolean Description: = false to average upstream and downstream properties across flow segments |
| use_Ib_flows |
Value: momentumDynamics <> Types.Dynamics.SteadyState Type: Boolean Description: = true to consider differences in flow of momentum through boundaries |
| Re_turbulent |
Value: 4000 Type: ReynoldsNumber Description: Start of turbulent regime, depending on type of flow device |
| show_Res |
Value: false Type: Boolean Description: = true, if Reynolds numbers are included for plotting |
Inputs (7)
| pathLengths |
Type: Length[m] (m) Description: Lengths along flow path |
|---|---|
| states |
Type: ThermodynamicState[n] Description: Thermodynamic states along design flow |
| vs |
Type: Velocity[n] (m/s) Description: Mean velocities of fluid flow |
| crossAreas |
Type: Area[n] (m²) Description: Cross flow areas at segment boundaries |
| dimensions |
Type: Length[n] (m) Description: Characteristic dimensions for fluid flow (diameters for pipe flow) |
| roughnesses |
Type: Roughness[n] (m) Description: Average height of surface asperities |
| dheights |
Type: Length[n - 1] (m) Description: Height(states[2:n]) - Height(states[1:n-1]) |
Components (2)
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system |
Type: System Description: System properties |
|---|---|---|
 |
states |
Type: ThermodynamicState[n] Description: Thermodynamic states along design flow |
Extended by (2)
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Modelica.Fluid.Pipes.BaseClasses.FlowModels GenericPipeFlow: Pipe flow pressure loss and gravity with replaceable WallFriction package |
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Modelica.Fluid.Pipes.BaseClasses.FlowModels NominalLaminarFlow: Linear laminar flow for given nominal values |