7.18. Advective Bar

This section is referenced in the following other sections

Simulation Setup: Advective Bars

7.18.1. Advective Bar Network

Scope: Aria Region, Equation System, Explicit Equation System, Root Finder Equation System
Summary: Defines an advective bar that can be used by a convective flux boundary condition.
Description: Newton’s law of cooling specifies that the heat flux normal to a surface is proportional to the difference between the unknown temperature of the surface and some reference temperature of the fluid in which the surface is immersed: $q_n=h(T-T_r)$ . The convection coefficient, $h$ , and the reference temperature, $T_r$ , may be specified in several ways. Of particular interest is the situation where the fluid flow can be reduced to a simple 1D flow. In this case, heat transfer between the surface and the fluid is modeled with an advective bar model where each segment on the bar and each facet on the surface assumes a constant heat flux based on a constant $h$ , $T$ and $T_r$ .

begin Advective Bar Network Name

   Add Volume Parameters...

   Annulus Diameter Ratio Function {=} Function

   Annulus Diameter Ratio Threshold {=} Threshold

   Coordinate Reference {=} Nodelist Component {s | x | y | z}

   Entrance Effect Starting Node Id {=} NodeID [ Offset {=} Value  ]

   Flow Cross Section Area {=} Value

   Flow Cross Sectional Area Function {=} Function

   Fluid Density {=} Value

   Fluid Density Function {=} Function

   Hydraulic Diameter Function {=} Function

   Initial Temperature {=} t

   Mass Flow Rate {on} Nodelist {=} Value

   Mass Flow Rate Function {on} Nodelist {=} Function

   Maximum Search Tolerance {=} Tolerance

   Search Interval {=} Interval

   Velocity Bc {on} Nodelist {=} Velocity

   Visualization {off | on}

   Wetted Perimeter Function {=} Function

end Advective Bar Network Name

7.18.1.1. Line Commands

Add Volume

Syntax: Add Volume Parameters…
Summary: Adds bar element volumes, by name, to a boundary condition’s extent.

Parameter	Value	Default
Parameters	string…	–

Annulus Diameter Ratio Function

Syntax: Annulus Diameter Ratio Function {=} Function
Summary: Specifies the name of a user tabular function for annulus diameter ratio.

Parameter	Value	Default
{=}	{= \| are \| is}	–
Function	string	–

Annulus Diameter Ratio Threshold

Syntax: Annulus Diameter Ratio Threshold {=} Threshold
Summary: Specifies the minimum value for annulus diameter ratio. This is used with both automatic calculation as well as user tabular function.

Parameter	Value	Default
{=}	{= \| are \| is}	–
Threshold	real	0.05

Coordinate Reference

Syntax: Coordinate Reference {=} Nodelist Component {s | x | y | z}
Summary: Specifies the reference nodelist and direction for bar coordinates.

Parameter	Value	Default
{=}	{= \| are \| is}	–
Nodelist	string	–
xyzs	{s \| x \| y \| z}	–

Entrance Effect Starting Node Id

Syntax

Entrance Effect Starting Node Id {=} NodeID [ Offset {=} Value ]

Summary

Specifies the node in the advective bar that corresponds to the position where entrance effects begin with pipe and annular flow correlations (Types 23, 25, 72-74).

Description

Pipe and annular flow correlations support an entrance effect correction factor that will adjust the local heat transfer coefficient based on how far a point is from the inlet of the pipe or annulus. By default the inlet of the pipe is assumed to be at the first node of the advective bar. This option allows the user to specify a different node ID as the pipe entrance for calculating the entrance effect. This node ID must be part of the advective bar network.

Optionally, in cases where the entrance effect begins at a point not exactly aligned with the STARTING NODE one may specify an offset that will align the entrance effect to the correct coordinate. Here the offset is defined in the COORDINATE REFERENCE direction.

Parameter	Value	Default
{=}	{= \| are \| is}	–
NodeID	integer	0

Flow Cross Section Area

Syntax: Flow Cross Section Area {=} Value
Summary: Specifies a constant cross section area.

Parameter	Value	Default
{=}	{= \| are \| is}	–
Value	real	–

Flow Cross Sectional Area Function

Syntax: Flow Cross Sectional Area Function {=} Function
Summary: Specifies the name of a user tabular function for cross-sectional flow area.

Parameter	Value	Default
{=}	{= \| are \| is}	–
Function	string	–

Fluid Density

Syntax: Fluid Density {=} Value
Summary: Specifies bar fluid density.

Parameter	Value	Default
{=}	{= \| are \| is}	–
Value	real	–

Fluid Density Function

Syntax: Fluid Density Function {=} Function
Summary: Specifies the name of a user tabular function of temperature for density.

Parameter	Value	Default
{=}	{= \| are \| is}	–
Function	string	–

Hydraulic Diameter Function

Syntax: Hydraulic Diameter Function {=} Function
Summary: Specifies the name of a user tabular function for hydraulic diameter.

Parameter	Value	Default
{=}	{= \| are \| is}	–
Function	string	–

Initial Temperature

Syntax: Initial Temperature {=} t
Summary: Specifies the initial temperature of the bulk node.

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

Mass Flow Rate

Syntax: Mass Flow Rate {on} Nodelist {=} Value
Summary: Specifies the mass flow rate at a node.

Parameter	Value	Default
{on}	{@ \| at \| for \| in \| on \| over}	–
Nodelist	string	–
{=}	{= \| are \| is}	–
Value	real	–

Mass Flow Rate Function

Syntax: Mass Flow Rate Function {on} Nodelist {=} Function
Summary: Specifies the mass flow rate as a function of time at a node with a user function.

Parameter	Value	Default
{on}	{@ \| at \| for \| in \| on \| over}	–
Nodelist	string	–
{=}	{= \| are \| is}	–
Function	string	–

Maximum Search Tolerance

Syntax

Maximum Search Tolerance {=} Tolerance

Summary

Specifies the maximum search tolerance for bar/facet geometric coupling search and this must be between 0 and 1. For an idealized case of a curved bar with a constant curvature (R) and a facet that is at a distance (d) from the bar, the analytical solution tolerance is given by

$tol = \frac{d}{2R}$

Note that for a straight bar with infinite radius of curvature, this gives a tolerance of 0.

Parameter	Value	Default
{=}	{= \| are \| is}	–
Tolerance	real	0.5

Search Interval

Syntax: Search Interval {=} Interval
Summary: Specifies the number of search intervals for bar/facet geometric coupling search. This is used in conjunction with the maximum search tolerance to generate search tolerances from 0.0 to the maximum search tolerance specified. Must be greater than 0

Parameter	Value	Default
{=}	{= \| are \| is}	–
Interval	integer	5

Velocity Bc

Syntax: Velocity Bc {on} Nodelist {=} Velocity
Summary: Specifies bar inlet velocity.

Parameter	Value	Default
{on}	{@ \| at \| for \| in \| on \| over}	–
Nodelist	string	–
{=}	{= \| are \| is}	–
Velocity	real	–

Visualization

Syntax: Visualization {off | on}
Summary: Specifies Exodus output toggling of the created subsetted surfaces which are directly affected by the bulk nodes on the advective bar.

Parameter	Value	Default
OnOff	{off \| on}	Off

Wetted Perimeter Function

Syntax: Wetted Perimeter Function {=} Function
Summary: Specifies the name of a user tabular function for wetted perimeter.

Parameter	Value	Default
{=}	{= \| are \| is}	–
Function	string	–