PartialStaggeredFlowModelBase class for momentum balances in flow models 
This information is part of the Modelica Standard Library maintained by the Modelica Association.
This partial model defines a common interface for m=n1
flow models between n
device segments.
The flow models provide a steadystate 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[n1]
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[n1]
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[n1] and the actual viscosities mus_act[n1] 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.
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 to allow flow reversal, false restricts 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 
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:n1]) 
system 
Type: System Description: System properties 


states 
Type: ThermodynamicState[n] Description: Thermodynamic states along design flow 
Modelica.Fluid.Pipes.BaseClasses.FlowModels GenericPipeFlow: Pipe flow pressure loss and gravity with replaceable WallFriction package 

Modelica.Fluid.Pipes.BaseClasses.FlowModels NominalLaminarFlow: Linear laminar flow for given nominal values 