Command Reference

This chapter contains explanations for all the commands usable in the SIMULIA Tosca Fluid parameter file.

This page discusses:

<ALGO_SET_TOPO_OC>

This command defines the used parameters that are specific for the topology optimization algorithm based on the optimality criterion.

It is not mandatory and normally there is no need to set any of its parameters.

Item name

Type (Default)

Remark

<ID_NAME>

[STRING]

Name for this command item.

<BACKFLOW_TOLERANCE>

[REAL]

(0.5)

Defines the amount of backflow that should be allowed by the optimizer.

Value between 0.0 and 1.0 (minimum and maximum tolerance)

Note: This value can be modified for a restart of SIMULIA Tosca Fluid.
Example 

<ALGO_SET_TOPO_OC>
  <ID_NAME>ALGO_OC_1</ID_NAME>
  <BACKFLOW_TOLERANCE>0.75</BACKFLOW_TOLERANCE>
</ALGO_SET_TOPO_OC>

<DRESP>

The design response defines a system response for the current analysis model. At least one must be regarded in the objective function. It is defined for either a surface or element group.

Item name

Type (Default)

Remark

<ID_NAME>

[STRING]

Name for this command item.

<FACE_GROUP>

<INFLOW>, <OUTFLOW>

[STRING]

[STRING]

Surface groups for which this response is defined.

Depending on the type of the design response, a single face group or a combination of inflow and outflow face groups must be given.

<ELEMENT_GROUP>

[STRING]

Element group this design response is defined.

<TYPE>

[ENUM]

<BACKFLOW, PRESSURE_DROP, VOLUME>

Type of the design response.

For the optimization strategy TOPO_OC, only the type BACKFLOW can be used in the objective function. The other types can be used in the <MONITOR> command.

Remarks

  1. Multiple design responses can be defined using multiple <DRESP> commands. They can be combined with the use of the <OPERATOR> command.

Example


<DRESP>
  <ID_NAME>DRESP_1</ID_NAME>
  <INFLOW>INLET_1</INFLOW>
  <OUTFLOW>OUTLET_1</OUTFLOW>
  <TYPE>BACKFLOW</TYPE>
</DRESP>

<DV>

Definition of the design variables for the optimization. For topology optimization, the design variables are elements. They are defined by means of an element group.

Item name

Type (Default)

Remark

<ID_NAME>

[STRING]

Name for this command item.

<ELEMENT_GROUP>

[STRING]

(ALL_CELLS)

Name of the design element group.

Default is to use all elements in the model for optimization.

Remarks

  1. An element group may be defined by giving the name of an element group in the model. Alternatively one of the automatically defined groups can be used like ALL_CELLS, for example.

Example


<DV>
  <ID_NAME>DV_1</ID_NAME>
  <ELEMENT_GROUP>ALL_CELLS</ELEMENT_GROUP>
</DV>

<FLOW_PATHS>

Definition of the flow paths to consider in the optimization. Multiple flow paths may be defined using several <PATH> commands. A path is defined by two boundary surfaces. An inflow and an outflow.

Item name

Type (Default)

Remark

<ID_NAME>

[STRING]

Name for this command item.

<PATH>

[STRING]

Names of the inflow and outflow boundaries for this flowpath separated by a comma

Remarks

  1. It is recommended to use all possible flow paths that result from all possible inflow/outflow combinations

Example


<FLOW_PATHS>
  <ID_NAME>FLOWPATHS_1</ID_NAME>
  <PATH>Inflow_1,Outflow_1</PATH>
  <PATH>Inflow_1,Outflow_2</PATH>
</FLOW_PATHS>

<MODEL_INPUT>

Specifies the CFD model and CFD solver for the optimization.

Item name

Type (Default)

Remark

<ID_NAME>

[STRING]

Name for this command item.

<FILE>

[STRING]

The name of the CFD model, which is read by SIMULIA Tosca Fluid.

For FLUENT®, the case file must be specified.

Example: duct.cas

For STAR-CCM+®, the model file name must be specified.

Example: backstepflow.sim

<SOLVER>

[STRING]

Name of a configured CFD solver to use for the optimization.

Note: The specified CFD solver must be compatible to the specified CFD model.

Example

STAR-CCM+®:


<MODEL_INPUT>
  <ID_NAME>MODEL_INPUT_1</ID_NAME>
  <FILE>star.sim</FILE>
  <SOLVER>starccmp-7.02.008</SOLVER>
<MODEL_INPUT>

<MONITOR>

Defines a monitor for the given design response, which can be either displayed in the Tosca Fluid.gui or read from a .tjmd file after the optimization.

Item name

Type (Default)

Remark

<ID_NAME>

[STRING]

Name for this command item.

<DRESP>

[REFERENCE]

<DRESP>

The design response that is referenced by this monitor.

Remarks

  1. Monitors should be used with caution as their values do not reflect the physical correct solution. They are no replacement for a validation run with the optimized geometry.
  2. The use of monitors is not recommended as they can slow down the optimization. They should only be used when really necessary.
  3. Multiple different monitors can be defined. They need to be referenced in the <OPTIMIZE> command.

Example


<MONITOR>
  <ID_NAME>MONITOR_1</ID_NAME>
  <DRESP>DRESP_1</DRESP>
</MONITOR>

<OBJ_FUNC>

Defines the objective function for the optimization. An objective function definition refers to a single design response (<DRESP>) or an operator (<OPERATOR>) in the case of multiple design responses to be optimized at once. It also specifies an optimization target.

Item name

Type (Default)

Remark

<ID_NAME>

[STRING]

Name for this command item.

<DRESP>

[REFERENCE]

<DRESP>

The design response that is referenced by the objective function.

<OPERATOR>

[REFERENCE]

<OPERATOR>

The operator that is referenced by the objective function.

<TARGET>

[ENUM]

MIN

(MIN)

MIN: Target is to minimize the list of design responses.

Remarks

  1. Currently, the only possible target is minimization (MIN).
  2. For TOPO_OC, the referenced <DRESP> or <OPERATOR> must be of the type BACKFLOW.

Example


<OBJ_FUNC>
  <ID_NAME>OBJ_FUNC_1</ID_NAME>
  <DRESP>DRESP_1</DRESP>
  <TARGET>MIN</TARGET>
</OBJ_FUNC>

<OPERATOR>

Defines an operator response that combines multiple design responses (<DRESP>) and can be used to specify a certain ratio between them.

Item name

Type (Default)

Remark

<ID_NAME>

[STRING]

Name for this command item.

<DRESP>

[REFERENCE]

<DRESP>

A design response that is referenced by this operator.

Several design responses may be specified by using multiple <DRESP> command items that refer to different <DRESP> commands.

<OPERATOR>

[REFERENCE]

<OPERATOR>

An operator that is referenced by this operator.

Several operators may be specified by using multiple <OPERATOR> command items that refer to different <OPERATOR> commands.

<WEIGHT>

[INTEGER]

(1)

A weighting factor that can be used to set a specific ratio between the used design responses or operators

Remarks

  1. An operator is always needed if a model has multiple flowpaths and more than one of them should be optimized.

Example


<OPERATOR>
  <ID_NAME>OPERATOR_1</ID_NAME>
  <DRESP>DRESP_1</DRESP>
  <DRESP>DRESP_2</DRESP>
</OPERATOR>

<OPTIMIZE>

Defines the optimization problem by referencing a set of commands, namely design variables <DV>, an objective function <OBJ_FUNC>, optimization parameters <OPT_PARAM>, and a stop condition <STOP>.

Item name

Type (Default)

Remark

<ID_NAME>

[STRING]

Name for this command item.

<DV>

[REFERENCE]

<DV>

Reference to a <DV> entry defining the design region for the optimization problem.

<OBJ_FUNC>

[REFERENCE]

<OBJ_FUNC>

Reference(s) to the objective function(s) for the optimization problem.

<STRATEGY>

[ENUM]

TOPO_OC

(TOPO_OC)

Definition of the optimization strategy.

Possible values:

TOPO_OC: Topology optimization approach based on an optimality criterion

<OPT_PARAM>

[REFERENCE]

<OPT_PARAM>

Reference to the optimization parameters applied to the problem.

If the command is omitted, the default set of parameters is applied.

<PRE_PARAM>

[REFERENCE]

<PRE_PARAM>

Reference to a parameter set that is applied for the preparation run of SIMULIA Tosca Fluid.

If the command is omitted, the default stop condition is applied.

<ALGO_SET_TOPO_OC>

[REFERENCE]

<ALGO_SET_TOPO_OC>

Reference to the optimization parameters that are specific for the algorithm TOPO_OC.

If the command is omitted, a default set of parameters is applied.

<STOP>

[REFERENCE]

<STOP>

Reference to the stop condition applied to this problem.

If the command is omitted, the default stop condition is applied.

<MONITOR>

[REFERENCE]

<MONITOR>

Reference to an optional monitor.

Multiple monitors can be referenced here.

Example


<OPTIMIZE>
  <ID_NAME>OPTIMIZE_1</ID_NAME>
  <DV>DV_1</DV>
  <OBJ_FUNC>OBJ_FUNC_1</OBJ_FUNC>
  <OPT_PARAM>OPT_PARAM_1</OPT_PARAM>
  <STOP>STOP_1</STOP>
OPTIMIZE>

<OPT_PARAM>

Defines parameters to control the optimization run.

Item name

Type (Default)

Remark

<ID_NAME>

[STRING]

Name for this command item.

<RESULT_STORE_INTERVAL>

[INTEGER LIST]

Controls the storage of optimization results. This is independent from the creation of intermediate output during the optimization.

Example:

100-1000:100

Results are saved every 100th iteration starting with iteration 100 until the iteration 1000 is reached.

Note: This value can be modified for a restart of SIMULIA Tosca Fluid.

<OPT_START>

[INTEGER]

(300)

Defines the starting iteration for the optimization. When the specified iteration is reached, SIMULIA Tosca Fluid starts the optimization process.

Note: The optimization process should start when the CFD solution has reached a reasonable quality.

Remark

  1. Default only the solution of the last optimization iteration is saved.
  2. Needed if post/smooth results are desired after the successfully finished optimization for iterations other than the last one.
  3. Depending on the model size, storing results can lead to large file sizes. Therefore, results should only be stored if really needed.

Example


<OPT_PARAM>
  <ID_NAME>OPT_PARAM_1</ID_NAME>
  <RESULT_STORE_INTERVAL>100-800:100</RESULT_STORE_INTERVAL>
  <OPT_START>500</OPT_START>
</OPT_PARAM>

<OUTPUT>

Defines intermediate runtime result output that is generated during the optimization run.

Item name

Type (Default)

Remark

<ID_NAME>

[STRING]

Name for this command item.

<FILENAME>

[STRING]

(optresult)

Base name for the generated output file(s).

File names are generated in the following way:

<FILENAME>_<Result specific extension>.<Format_extension>

Note: The result specific extension has the general format:

<iteration>_<value>

Note: The extension indicating the file format like .wrl, for example, must not be specified. The appropriate extension is added automatically.

<FORMAT>

[ENUM]

WRL

(WRL)

File format for the output file.

Possible values:

WRL: Virtual reality modeling language

<ITERATION>

[INTEGER_LIST]

Optimization iteration(s) in which the output is to be written.

Examples:

1) Single iteration:

<ITERATION>500</ITERATION>

Write results in iteration 500

2) Multiple iterations:

<ITERATION>100-1000:100</ITERATION>

Write results every 100th iteration between iteration 100 and 1,000 i.e. in iterations 100, 200, … , 1,000

Note: In case of multiple iterations, a separate output file for each iteration is written.

<RESULT>

[ENUM]

MATERIAL, PTRACK, VELOCITY

(MATERIAL)

The kind of result values that should be used for the result determination.

MATERIAL: Cell sedimentation factor.

PTRACK: Result based on the calculation of particle tracks.

VELOCITY: Cell velocity data.

<CUTOFF>

[REAL_LIST]

Definition of CUTOFF value(s).

Examples:

1) Single output:

<CUTOFF>0.2</CUTOFF>

2) Multiple outputs:

<CUTOFF>0.2-0.6:0.1</CUTOFF>

Write five output files for using cutoff values 0.2, 0.3, 0.4, 0.5, 0.6

<DESIGN_ONLY>

[ENUM]

YES, NO

(NO)

Write only design cells to the output file.

Remark

  1. The command item <CUTOFF> is mandatory if the result type velocity is selected.
  2. The result extraction (especially PTRACK:) can be time consuming. Therefore, it is recommended to use it only if it is really necessary.

Example


<OUTPUT>
  <ID_NAME>my_output</ID_NAME>
  <FILENAME>cellresult</FILENAME>
  <FORMAT>WRL</FORMAT>
  <ITERATION>100-1000:100</ITERATION>
  <RESULT>VELOCITY</RESULT>
  <CUTOFF>0.1</CUTOFF>
</OUTPUT>

<PRE_PARAM>

Defines parameters to control the preparation run performed by SIMULIA Tosca Fluid.

Item name

Type (Default)

Remark

<ID_NAME>

[STRING]

Name for this command item.

<PTRACK_PRIMARY_VRML>

[ENUM]

YES, NO

(YES)

Create the VRML output that shows the primary particle tracks.

Example


<PRE_PARAM>
  <ID_NAME>PRE_PARAM_1</ID_NAME>
  <PTRACK_PRIMARY_VRML>YES</PTRACK_PRIMARY_VRML>
</PRE_PARAM>

<STOP>

Defines a STOP condition for an optimization problem.

Item name

Type (Default)

Remark

<ID_NAME>

[STRING]

Name for this command item.

<ITER_MAX>

[INTEGER]

The absolute number of iterations to process.

Note: This value is modifiable for a restart of SIMULIA Tosca Fluid.

Remarks

  1. For more information on the <STOP> command and the choice of a maximum number of iterations, please consult the User Manual.

Example


<STOP>
  <ID_NAME>STOP_1</ID_NAME>
  <ITER_MAX>1000</ITER_MAX>
</STOP>