WOLFRAM SYSTEM MODELER
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
The geometry is specified with the
pathLengths[n-1] between the device segments as well as
crossAreas[n] and the
roughnesses[n] of the device segments.
Moreover the fluid flow is characterized for different types of devices by the characteristic
and the average velocities
vs[n] of fluid flow in the device segments.
for example definitions.
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.
m_flows_turbulent[n-1] resulting from
Re_turbulent can optionally be calculated together with the Reynolds numbers
Res[n] of the device segments (
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.
Value: n - 1
Description: Number of flow segments
Description: Number of discrete flow volumes
Description: number of identical parallel flow devices
Type: Acceleration (m/s²)
Description: Constant gravity acceleration
Description: = true to allow flow reversal, false restricts to design direction (states -> states[n+1])
Description: Formulation of momentum balance
Type: MassFlowRate (kg/s)
Description: Start value of mass flow rates
Type: AbsolutePressure (Pa)
Description: Start value for p at design inflow
Type: AbsolutePressure (Pa)
Description: Start value for p[n+1] at design outflow
Description: = false to average upstream and downstream properties across flow segments
Value: momentumDynamics <> Types.Dynamics.SteadyState
Description: = true to consider differences in flow of momentum through boundaries
Description: Start of turbulent regime, depending on type of flow device
Description: = true, if Reynolds numbers are included for plotting
Type: Length[m] (m)
Description: Lengths along flow path
Description: Thermodynamic states along design flow
Type: Velocity[n] (m/s)
Description: Mean velocities of fluid flow
Type: Area[n] (m²)
Description: Cross flow areas at segment boundaries
Type: Length[n] (m)
Description: Characteristic dimensions for fluid flow (diameters for pipe flow)
Type: Roughness[n] (m)
Description: Average height of surface asperities
Type: Length[n - 1] (m)
Description: Height(states[2:n]) - Height(states[1:n-1])