Flow Boundary Condition dialog box – Recirculation Loop options

Name
Name	Sets a name for the simulation object.Description opens an editor that lets you type a description for the boundary condition.
Destination Folder
Simulation Object Container	Specifies the folder in the Simulation Navigator in which the boundary condition will be stored. The list includes the root container and existing folders that you created using the New Folder command. Examples of a root container include Load Container, Constraint Container, and Simulation Object Container.
Folder Manager	Displays a hierarchical listing of existing folders. To create a new folder, right-click any level of the hierarchy and choose New Folder.
Extract Region or Return Region
Group Reference	Applies the boundary condition to the selected group.For more information, see Group Reference options.
Select Object (Extract Region)	Lets you select the face through which the fluid is extracted.Excluded lets you remove individual entities from within your selected object.
Select Object (Return Region)	Lets you select the face through which the fluid returns.Excluded lets you remove individual entities from within your selected object.
Stacked Smart Selector Methods	Opens the Smart Selector Methods dialog box where you can specify a progression of smart selection filters.For more information, see Smart Selector Methods dialog box.
Magnitude
Mode	Controls how you define the flow conditions at the extract and return openings.VelocityLets you specify the flow velocity at the extract region of the recirculation loop. The flow velocity is the speed of the fluid movement normal to the boundary condition surface. You enter a value in the Velocity box.Velocity VectorLets you specify the flow velocity vector components at the extract region of the recirculation loop. The components can either be constant, or vary with respect to time and spatial variables. You can use a formula field, a table of fields, or a 4D field to define how the flow velocity vector components vary with respect to time and spatial variables.To define constant velocity vector components, set the Velocity list to Expressions. You define the flow velocity vector components in the Vx, Vy, and Vz boxes using an expression. To define the velocity vector components using tabular data, set the Velocity list to Fields. You can define a formula field, a table of fields, or a 4D field. You can also define the Scale Factors for the flow velocity vector components in the Vx, Vy, and Vz boxes.Mass FlowLets you specify the mass flow per unit of time through the openings. Enter a value in the Mass Flow box.Volume FlowLets you specify the volume flow per unit of time through the openings. Enter a value in the Volume Flow box.Fan CurveLets you use a fan curve definition to specify the relationship between flow rate and static pressure rise across the openings in the Fan Curve box. In Simcenter 3D Electronic Systems Cooling, you can select a pre-defined fan curve from the manufacturing data when you click Fan Catalog. For more information, see Additional magnitude options.
Flow Extract
Head Loss	Appears only when Fan Curves is selected from the Mode list.Lets you define a pressure drop across the extract region due to a planar device, such as a screen or filter. Choose a previously defined Planar Head Loss modeling object from the list or click Create Modeling Object to create a new one. See Planar Head Loss.
Flow Return
Alignment	Specifies the general direction of the fluid flow.Normal to Face specifies that the fluid enters normal to the inlet. This is the appropriate alignment for most cases. Along Vector lets you specify a vector along which the fluid enters. This allows you to model the effect of devices that deflect the fluid flow, such as louvers on a fan or vent. Use the Specify Vector options to specify the direction of the flow.
Swirl	Appears when Alignment is set to Normal to Face.Models the effect of fan swirl. See Modeling fan swirl for more information.None specifies that there is no fan swirl effect.Fixed Angle specifies that the fluid rotates at the specified angle. You specify the fixed angle value in the Normal to Resultant Velocity Angle box. It is the angle between the device normal and the resultant fluid velocity vector. Radially Varying specifies that the fluid rotates at a varying angle. You specify the value for the rotational velocity of the device in the Rotational Velocity box.
Turbulence Characteristics	Specifies which method is used to specify turbulence in the flow at the return opening based on available data derived from experiment or standard references.AutomaticLets the solver compute automatically turbulence characteristics.Turbulence Characteristics modeling objectSpecifies the method for calculation initial turbulence quantities through the selected Turbulence Characteristics modeling object.You can also select a previously defined Turbulence Characteristics modeling object from the list or click Create Modeling Object to define a new modeling object.Click Edit to modify the specified modeling object.For more information, see Turbulence Characteristics.
Rotation Axis	Appears when Swirl is not set to None.Specifies the axis around which the fluid swirls when entering the flow domain.Global Cyclic AnalysisAppears if you defined the cyclic symmetry cylindrical coordinate system in the FEM. Swirls the fluid around the Z-axis of the cyclic symmetry cylindrical coordinate system. User-DefinedLets you specify the axis around which the fluid swirls. Use the Specify Vector options to specify the direction of revolution, and use the Specify Point options to specify the location of the axis.
Head Loss	Lets you define a pressure drop across the return due to a planar device, such as a screen or filter. Choose a previously defined Planar Head Loss modeling object from the list or click Create Modeling Object to create a new one. See Planar Head Loss.
Heat Exchange
Heat Exchange Type	Specifies the thermal change to the fluid between the extract and return openings.None is specifies that no thermal change occurs.Temperature Change specifies the temperature difference between the fluid at the extract and return openings. Enter a positive or negative value.Heat lets you specify the Heat Gain or Loss to the fluid.Convective measures the fluid's convective heat loss or gain. Enter a Heat Transfer Coefficient for convection, a Convecting Area, and a convective environment Temperature.See Modeling heat loss or gain in a recirculation loop for more information.
Fan Control
Controller Type	Specifies how the speed of the Flow Boundary Condition is controlled.None specifies that the speed at the boundary condition is not controlled.Thermostat lets you control the speed with a Thermostat modeling object. Choose a previously defined Thermostat modeling object from the list or click Create Modeling Object to create a new one. See Thermostat for more information.Speed Control lets you control the speed based on the temperature of a sensor. Choose a previously defined Fan Speed Controller modeling object from the list or click Create Modeling Object to create a new one. See Fan Speed Controller for more information.
Nominal Fan Speed	If you chose Velocity, Mass Flow, or Volume Flow from the Mode list, the Nominal Fan Speed value corresponds to the specified velocity or flow value (Qnominal). The software obtains the flow rate at a new temperature during the solve using this equation:Qnew = Qnominal × RPMnew / RPMnominalIf you chose Pressure Rise from the Mode list, the Nominal Fan Speed value corresponds to the specified pressure rise value (dPnominal). The software obtains the flow rate at a new temperature during the solve using this equation: dPnew = dPnominal × (RPMnew / RPMnominal)2 If you chose Fan Curve from the Mode list, the software uses the two equations above to compute the fan operating point.

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Create a Flow Boundary Condition

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Flow Boundary Condition

Flow Boundary Condition types

Working with fan curves

Modeling heat loss or gain in a recirculation loop

Modeling fan swirl

Flow boundary condition modeling

External Conditions

Planar Head Loss

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Flow Boundary Condition dialog box– Outlet Flow options

Flow Boundary Condition dialog box – Opening options

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Flow Boundary Condition dialog box– Static Pressure options

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Flow Boundary Condition dialog box– Flap options

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Flow Boundary Condition dialog box – Recirculation Loop options, Simcenter 3D 2021.1 Series

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