# 7.20. Bulk Nodes

This section is referenced in the following other sections

- Simulation Setup: Bulk Nodes

## 7.20.1. Bulk Fluid Element

Scope

  Aria Region, Equation System, Explicit Equation System, Root Finder Equation System

Summary

  Defines a bulk fluid element that can be used by a convective flux boundary condition.

Description

  Generally speaking, the reference temperature used in Newton’s Law of Cooling and is a known quantity because the fluid with which it is associated is modeled as an infinite reservoir. However, if the size of this reservoir is finite, then its temperature can be affected by the energy transfer across the surface in question. This situation can be modeled by the bulk fluid element, wherein the energy of the reservoir is determined by a finite volume conservation equation.

  For a bulk fluid element with a name specified as , the thermodynamic properties such as density, volume and temperature may be accessed via global variables. Density is accessed using _RHO, volume by _V, temperature at the current state by _T and temperature at the old state by _TOld.

    begin Bulk Fluid Element Name

       Bulk Coordinates {=} Parameters...

       Bulk Element Pressure {=} VolType [Parameters]...

       Bulk Element Volume {=} VolType [Parameters]...

       Bulk Eq EquationName For AssociatedDoF ([{of} SpeciesName]  | [{in} MaterialPhaseName]) Using ElementType With Terms...

       Bulk Source For EquationName {=} SrcType [Parameters]...

       Calculate Volume From Enclosing Surface

       Initial Pressure {=} p

       Initial Temperature {=} t

       Material {=} MatName

       Reinitialize Dof Name {=} value

       Temperature Is Celsius

       Update Bulk Volume Pressure [ Atmospheric {=} Value  ]

       Use Block BlockName

    end Bulk Fluid Element Name

### 7.20.1.1. Line Commands

###### Bulk Coordinates

Syntax

  Bulk Coordinates {=} Parameters…

Summary

  Specifies the physical coordinates for the bulk node.

Parameter | Value | Default
--- | --- | ---
{=} | {= | are | is} | –
Parameters | real… | –

###### Bulk Element Pressure

Syntax

  Bulk Element Pressure {=} VolType [Parameters]…

Summary

  Specifies the pressure of the bulk element with type Pressure Type (CONSTANT, USER) for bulk element defined by the specifications of the parameter list.

  This command should not be used when the bulk element is associated with a pressurization zone model since initial pressure will instead be associated with the pressurization zone as a whole.

Parameter | Value | Default
--- | --- | ---
{=} | {= | are | is} | –
VolType | string | –
Parameters | [string]… | –

###### Bulk Element Volume

Syntax

  Bulk Element Volume {=} VolType [Parameters]…

Summary

  Specifies the volume of the bulk element with type VolType (CONSTANT, USER) for bulk element defined by the specifications of the parameter list.

  For problems in which the mesh is deforming one should consider using CALCULATE VOLUME FROM ENCLOSING SURFACE instead.

Parameter | Value | Default
--- | --- | ---
{=} | {= | are | is} | –
VolType | string | –
Parameters | [string]… | –

###### Bulk Eq

Syntax

  Bulk Eq EquationName For AssociatedDoF ([{of} SpeciesName] | [{in} MaterialPhaseName]) Using ElementType With Terms…

Summary

  Specifies an equation to solve on the bulk node. User provides the degree of freedom associated with the equation, the element type, and the terms in the equation that are active.

Parameter | Value | Default
--- | --- | ---
EquationName | string | –
AssociatedDoF | string | –
{of} | {of | species} | –
SpeciesName | string | –
{in} | {in | material_phase} | –
MaterialPhaseName | string | –
ElementType | string | –
Terms | string… | –

###### Bulk Source For

Syntax

  Bulk Source For EquationName {=} SrcType [Parameters]…

Summary

  Indicates a source term of model type (i.e. CONSTANT, USER, CALORE_USER_SUB) and associated model Parameters for the given EquationName on the bulk element.

Parameter | Value | Default
--- | --- | ---
EquationName | string | –
{=} | {= | are | is} | –
SrcType | string | –
Parameters | [string]… | –

###### Calculate Volume From Enclosing Surface

Syntax

  Calculate Volume From Enclosing Surface

Summary

  Specifies that the volume of the bulk element is to be calculated at each timestep from an enclosing surface. The surface must be closed (although Aria currently does not currently check for this) and is defined by the extent of the flux boundary condition which uses this bulk element.

###### Initial Pressure

Syntax

  Initial Pressure {=} p

Summary

  Specifies the initial pressure of the bulk node.

  This command should not be used when the bulk element is associated with a pressurization zone model since initial pressure will instead be associated with the pressurization zone as a whole.

Parameter | Value | Default
--- | --- | ---
{=} | {= | are | is} | –
p | real | 0.0

###### Initial Temperature

Syntax

  Initial Temperature {=} t

Summary

  Specifies the initial temperature of the bulk node. If initial temperature values are supplied from file this value will be ignored and file value is used instead. If one wishes to override the file value or if the file does not contain the bulk node use REINITIALIZE DOF.

Parameter | Value | Default
--- | --- | ---
{=} | {= | are | is} | –
t | real | REAL_MAX

###### Material

Syntax

  Material {=} MatName

Summary

  Specifies that the material properties of the bulk element are defined in the material block named matName.

Parameter | Value | Default
--- | --- | ---
{=} | {= | are | is} | –
MatName | string | –

###### Reinitialize Dof

Syntax

  Reinitialize Dof Name {=} value

Summary

  Requests reinitialization of a bulk node DOF. This will allow override of the file supplied bulk node DOF value when using an initial condition from file. Here the initial value supplied from file will be replaced by a specified value. Likewise, if the initial condition file does not contain the bulk node this value is assigned as the initial condition.

Parameter | Value | Default
--- | --- | ---
Name | string | –
{=} | {= | are | is} | –
value | real | –

###### Temperature Is Celsius

Syntax

  Temperature Is Celsius

Summary

  Specifies the initial temperature of the bulk node is given in degrees Celsius. Internal to the code this is relevant only when performing updates of the bulk element pressure via an ideal gas law which requires an absolute temperature.

###### Update Bulk Volume Pressure

Syntax

  Update Bulk Volume Pressure [ Atmospheric {=} Value ]

Summary

  Reevaluate non-pressurization zone model bulk volume pressure.

Description

  If a bulk volume is filled with an ideal gas then the pressure can be calculated at each timestep provided that the initial temperature and pressure are given. Here it is assumed that the associated volume is closed and that the volume has been defined as constant or is being computed. If the bulk volume is being computed then one must also include the CALCULATE VOLUME FROM ENCLOSING SURFACE command line.

  By default the resulting update is an absolute pressure. If one wishes the update to reflect gauge pressure one must supply a reference pressure by adding an optional Atmospheric value syntax to the command line.

  This command should not be used when the bulk element is associated with a pressurization zone model since pressure is instead associated with the pressurization zone as a whole. The pressurization zone model also allows for gas models other than ideal gas.

###### Use Block

Syntax

  Use Block BlockName

Summary

  Specifies that the given element block should be used for the bulk node. The caveat here is that there must be only one element, one node and they must all satisfy the proper mesh object topologies. This option is used only if an element block for the bulk element is already present in the mesh. If the bulk element does not exist on the input mesh, the element block will be created and will exist on the output mesh.

Parameter | Value | Default
--- | --- | ---
BlockName | string | –

## 7.20.2. Bulk Nodes Ignore Restart

Syntax

  Bulk Nodes Ignore Restart

Summary

  Causes bulk nodes to ignore the restart file.

## 7.20.3. Bulk Node Coupling

Scope

  Aria Region, Equation System, Explicit Equation System, Root Finder Equation System

Summary

  Defines a coupling between equations on two bulk nodes.

Description

  This block command allows a user to couple equations on different bulk nodes to one another. For example, the density of gas on two bulk nodes can be coupled using a flow coefficient based on the relative pressure of the two bulk nodes. The same degree of freedom must be present on both bulk nodes, and both have to be in the same equation system in order for the coupling to be possible.

    begin Bulk Node Coupling Name

       Additional Parameter PropertyName {=} ModelName [Parameters]...

       Bulk Nodes {=} Names1 Names2...

       Couple DofName Model {=} ModelName [Parameters]...

    end Bulk Node Coupling Name

### 7.20.3.1. Line Commands

###### Additional Parameter

Syntax

  Additional Parameter PropertyName {=} ModelName [Parameters]…

Summary

  Declare an additional parameter for the coupling models present. For example, the “K_FACTOR_FLOW” model for density or species coupling requires that a “K_FACTOR” be provided using this line command.

Parameter | Value | Default
--- | --- | ---
PropertyName | string | –
{=} | {= | are | is} | –
ModelName | string | –
Parameters | [string]… | –

###### Bulk Nodes

Syntax

  Bulk Nodes {=} Names1 Names2…

Summary

  Specify the name of the bulk nodes involved in the coupling.

Parameter | Value | Default
--- | --- | ---
{=} | {= | are | is} | –
Names | string1 string2… | –

###### Couple

Syntax

  Couple DofName Model {=} ModelName [Parameters]…

Summary

  Specify what degree of freedom to couple between the bulk nodes, and what model to use for the coupling.

Parameter | Value | Default
--- | --- | ---
DofName | string | –
{=} | {= | are | is} | –
ModelName | string | –
Parameters | [string]… | –