WOLFRAM SYSTEM MODELER
NominalTurbulentPipeFlowNominalTurbulentPipeFlow: Quadratic turbulent flow in circular tubes for given nominal values |
SystemModel["Modelica.Fluid.Pipes.BaseClasses.FlowModels.NominalTurbulentPipeFlow"]
This information is part of the Modelica Standard Library maintained by the Modelica Association.
This model defines the pressure loss assuming turbulent flow for
specified dp_nominal
and m_flow_nominal
.
It takes into account the fluid density of each flow segment and
obtains appropriate pathLengths_nominal
values
for an inverse parameterization of the
TurbulentPipeFlow
model. Per default the upstream and downstream densities are averaged with the setting useUpstreamScheme = false
,
in order to avoid discontinuous pathLengths_nominal
values in the case of flow reversal.
The geometry parameters crossAreas
, diameters
and roughnesses
do
not effect simulation results of this nominal pressure loss model.
As the geometry is specified however, the optionally calculated Reynolds number as well as
m_flows_turbulent
and dps_fg_turbulent
become meaningful
and can be related to m_flow_small
and dp_small
.
Optional Variables if show_Res
Type | Name | Description |
---|---|---|
ReynoldsNumber | Res[n] | Reynolds numbers of pipe flow per flow segment |
MassFlowRate | m_flows_turbulent[n-1] | mass flow rates at start of turbulent region for Re_turbulent=4000 |
AbsolutePressure | dps_fg_turbulent[n-1] | pressure losses due to friction and gravity corresponding to m_flows_turbulent |
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: false 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 |
from_dp |
Value: momentumDynamics >= Types.Dynamics.SteadyStateInitial Type: Boolean Description: = true, use m_flow = f(dp), otherwise dp = f(m_flow) |
dp_nominal |
Value: Type: AbsolutePressure (Pa) Description: Nominal pressure loss (only for nominal models) |
m_flow_nominal |
Value: Type: MassFlowRate (kg/s) Description: Nominal mass flow rate |
m_flow_small |
Value: if system.use_eps_Re then system.eps_m_flow * m_flow_nominal else system.m_flow_small Type: MassFlowRate (kg/s) Description: Within regularization if |m_flows| < m_flow_small (may be wider for large discontinuities in static head) |
m_flow_turbulent |
Value: if system.use_eps_Re then 0.1 * m_flow_nominal else system.m_flow_small Type: MassFlowRate (kg/s) Description: Turbulent flow starting from |m_flows| > m_flow_turbulent (may be wider for large discontinuities in static head) |
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]) |
pathLengths_internal |
Default Value: pathLengths_nominal Type: Length[n - 1] (m) Description: pathLengths used internally; to be defined by extending class |
Res_turbulent_internal |
Default Value: Res_turbulent_nominal Type: ReynoldsNumber[n - 1] Description: Re_turbulent used internally; to be defined by extending class |
system |
Type: System Description: System properties |
|
---|---|---|
states |
Type: ThermodynamicState[n] Description: Thermodynamic states along design flow |