Duct Flow Boundary Conditions

Use the Duct Flow Boundary Conditions simulation object to model 1D fluid flow within a duct network. For example, you can use this simulation object to create pressure and temperature boundary conditions at the inlet or outlet to a duct network.

Duct Flow Boundary Conditions types

Duct Fan/Pump

Defines fluid movement in a duct network. Use the Duct Fan/Pump type to model fans, impellers, pumps, or openings with a known flow parameter.

Duct Opening

Applies constant or time varying pressure and temperature boundary conditions at the inlet or outlet of a duct network, that you define locally in the External Conditions group, or globally in the Solution dialog box. You can also specify a head loss as the fluid passes into or out of the system by creating a Duct Head Loss modeling object and applying it to the opening.

Note:

The solver treats any free end of a 1D duct element as a default Duct Opening with global ambient temperature and pressure values. To save time, you can omit the step of defining default duct openings for these elements.

You set the global ambient pressure and temperature values on the Ambient Conditions page in the Solution dialog box

Duct Total Pressure

Applies total gauge fluid pressure, on a point, mesh point, or node within the duct network. The total pressure is the sum of the static pressure and the dynamic pressure.

Duct Flow Properties

Defines and overrides the default roughness properties of the inside surface of the duct. You can apply the roughness properties to an individual duct element, or to curves or edges meshed with duct elements. Except for the Head Loss Override option, the solver uses the length of the duct elements as well as the perimeter and area of the flow section in conjunction with the values for Wall Friction to calculate the resistance to flow.

If your duct has a bend or a sudden contraction or expansion, the pressure losses due to these effects are not captured by the solver. You can model them in one of the following ways:

• Use the Head Loss Override option to add pressure losses through a Duct Head Loss modeling object.

• Use the Head Loss Multiplier option to add constant or velocity-varying flow resistance.

Duct to 3D Flow Connection

Models fluid flow between a duct network and a fluid domain. Using duct networks is an accurate and computationally efficient way to model 1D flow through ducts, pipes, and similar structures. If your model contains both complex 3D fluid volumes and simple 1D duct or pipe flow, you can use this boundary condition type to set up an interface between the duct network and the 3D flow domain.

Note:

The Duct to 3D Flow Connection type is not available when you are using the Simcenter 3D Space Systems Thermal or Simcenter 3D Multiphysics solver environments.

One-Sided Total Temperature Effects and Two-Sided Total Temperature Effects

Account for total temperature effects in convective heat transfer due to high speed rotating parts. The heat transfer can be from duct elements or duct with mass flow elements, to one or two walls. The total temperature accounts for the kinetic energy of the fluid. It is determined from the total enthalpy.

Note:

These types are available only when you are using the Thermal/Flow or Multiphysics solver environments.

Duct Label

Assigns a label ID to selected 1D duct elements, curves, or polygon edges. You can then reference these label IDs in the duct thermal-flow functions that you specify in expressions of convective boundary conditions. For more information, see Thermal-flow functions in expressions.

Note:

The Duct Label type is not available in the Simcenter 3D Space Systems Thermal solver environment.

Supported variables and functions

The following table lists the independent variables and auto-generated expressions for the Duct Flow Boundary Conditions quantities that you can define using fields and expressions.

Type	Quantity	Variables	Auto-generated expressions
Duct Fan/Pump	Velocity	TimeTemperature	fluid_temperatureheat_flow_ratemass_flow_ratenxnynzpressureradiusrotational_speedtemperaturetemperature_differencethermal_capacitancethicknesstimevelocity*volume_flow_ratexyz
Volume Flow Rate****Mass Flow	TimeTemperaturePressure
Pressure Rise	TimeTemperatureMass flow rateVolume flow rate
Duct Opening	External Temperature****External Total Pressure - Gauge	TimeSpatial variablesTime, spatial variables
Duct Total Pressure	Total Pressure - Gauge	TimeSpatial variablesTime, spatial variables
Duct Flow Properties	Head Loss Multiplier	Velocity
One-Sided Total Temperature Effects****Two-Sided Total Temperature Effects	Swirl VelocitySwirl RatioRelative Temperature Difference	TimeSpatial variablesTime, spatial variables
*Applicable to Duct Flow Properties only.

In expressions, you can also use all built-in functions that are listed in Mathematical functions in expressions and most built-in functions that are listed in Thermal-flow functions in expressions.

Where do I find it?

Application	Pre/Post
Command Finder	Duct Flow Boundary Conditions
Simulation Navigator	Right-click the Simulation Object Container node→New Simulation Object→Duct Flow Boundary Conditions

How do I

Create a duct flow network

Create a thick wall duct flow network

Create a duct flow network and model heat transfer using 2D shells

Connect the duct network to the 3D flow domain

Create a duct flow network and model heat transfer using 3D solid elements

Learn more

Duct Head Loss

Inputs to expressions

1D duct flow networks

Look up more details

Total temperature effects

Auto-generated expressions

Understanding ducts and area definition

Quick links

Simcenter 3D Thermal/Flow, Electronic Systems Cooling, and Space Systems Thermal boundary conditions

Thermal/Flow, Electronic Systems Cooling, and Space Systems Thermal

Command reference

Pre/Post video examples

Bulk Entry Descriptions

Simcenter 3D tutorials

Browse Simcenter 3D help by product area

Duct Flow Boundary Conditions, Simcenter 3D 2021.1 Series

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