CONVERGE CFD Software: Full Automa­tion with CAESES

With CAESES version 4.4.2, we intro­duced a set of new features to automate the CFD software CONVERGE for the purpose of con­duct­ing design explo­rations and shape opti­miza­tion. In recent posts about CONVERGE-related topics, we already talked about some of the existing features in CAESES and about some appli­ca­tions in more detail, such as piston bowl opti­miza­tion.

This short article gives you an update on the existing CAESES capa­bil­i­ties and their function in the context of using CONVERGE as your CFD software.

Iden­ti­fiers for Bound­aries in CONVERGE Setups

The CONVERGE setups contain iden­ti­fiers (IDs) for the dif­fer­ent bound­aries of a geometry. These numbers are ref­er­enced at dif­fer­ent loca­tions in dif­fer­ent CONVERGE input files. CAESES allows users to assign such an ID to a color, and then use this color during the geometry modeling process. This makes sure that the IDs of the CAESES geometry are always iden­ti­cal to the ones in the CONVERGE setup, even during auto­mated design variations.

Since CAESES also allows users to automate CFD runs using the software con­nec­tor, every­thing is then imme­di­ately ready for quick studies with the inte­grated opti­miza­tion strategies.

CONVERGE File Import

CAESES 4.4.2 comes with a new import for CONVERGE *.dat files. These geometry files contain the dif­fer­ent boundary IDs, from which CAESES auto­mat­i­cally creates colors. These colors are assigned to the imported geometry and hence give the dif­fer­ent patches their IDs.

Users can then quickly replace the geometry parts that need vari­a­tion or opti­miza­tion. All file depen­den­cies are pre­served in this process, when using the colors and their IDs for the patches. The auto­matic color creation and assign­ment mas­sively accel­er­ates the opti­miza­tion workflow and removes any manual interaction.

In addition to the colors and IDs, a scaling para­me­ter is created to scale the geometry up and down accord­ing to the units that are needed, e.g., meters or millimeters.

CONVERGE File Export

Once the faces are colored and hold a unique ID, users can export the geometry using the CONVERGE export in CAESES. During this export, the geometry is checked in terms of its face normal vectors. If they point to the outside of the geometry, there will be an auto­mated cor­rec­tion to let all normal vectors point inward. The export can be found in the menu > file > export > CONVERGE.

Tri­an­gu­la­tion Controls

CAESES lets you create para­met­ric models based on curves and surfaces. CONVERGE users can then control the tri­an­gu­la­tion of the final shape using the trimesh (i.e., the tri­an­gu­lated geometry) and BRep controls. The accuracy or the maximum edge length can be option­ally set to prepare the tri­an­gu­la­tion for the CONVERGE analysis. These settings are retained for each design can­di­date during auto­mated studies.

Trans­late Boundaries

In some sit­u­a­tions, such as the con­sid­er­a­tion of dif­fer­ent piston posi­tions, CAESES users can take one part of the full geometry and trans­late it, e.g., up or down, to another location without changing the general struc­ture of the tri­an­gu­la­tion (i.e. the number of tri­an­gles and their con­nec­tiv­ity). There is a new oper­a­tion in the trimesh object that trans­lates all patches that hold a spec­i­fied color.

This trans­la­tion capa­bil­ity is impor­tant since CONVERGE inter­nally moves the piston geometry up or down for the analysis. In order to avoid inter­sect­ing tri­an­gles, the CAESES geometry is typ­i­cally modeled at the top dead center, and trans­lated down to the bottom dead center before export­ing it.

Geometry Modeling

Aside from IDs, file handling and CONVERGE automa­tion, there are also geometry modeling capa­bil­i­ties that address the CONVERGE user group. There are new tuto­ri­als for piston bowl and port modeling, as well as ded­i­cated features to speed up the modeling process, e.g., to create a fillet between com­po­nents such as the intake port. The fol­low­ing ani­ma­tion shows the results of a geometry study where this fillet is applied without manual interaction:

More Infor­ma­tion

There is a webinar record­ing about CAESES and CONVERGE that gives a more com­pre­hen­sive intro­duc­tion to the coupling of these two software packages. 

Check out the blog post about the CONVERGE export of CAESES for more infor­ma­tion about coloring, IDs and CONVERGE setup files.

If you are inter­ested in piston bowl design, then check out this piston bowl opti­miza­tion blog post, which also comes with linking CONVERGE to CAESES.