WOLFRAM SYSTEMMODELER

NominalTurbulentPipeFlow

NominalTurbulentPipeFlow: Quadratic turbulent flow in circular tubes for given nominal values

Wolfram Language

In[1]:=
SystemModel["Modelica.Fluid.Pipes.BaseClasses.FlowModels.NominalTurbulentPipeFlow"]
Out[1]:=

Information

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

TypeNameDescription
ReynoldsNumberRes[n] Reynolds numbers of pipe flow per flow segment
MassFlowRatem_flows_turbulent[n-1] mass flow rates at start of turbulent region for Re_turbulent=4000
AbsolutePressuredps_fg_turbulent[n-1] pressure losses due to friction and gravity corresponding to m_flows_turbulent

Parameters (18)

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: 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)

Inputs (9)

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

Components (2)

system

Type: System

Description: System properties

states

Type: ThermodynamicState[n]

Description: Thermodynamic states along design flow