New Export Format for CONVERGE Users

Just a few weeks ago, one of our col­leagues started a com­pre­hen­sive opti­miza­tion of an auto­mo­tive engine com­po­nent with CAESES®. More detailed, he had been inves­ti­gat­ing a piston bowl design. For the CFD analysis he used the sim­u­la­tion software CONVERGE from Con­ver­gent Science. As usual, he inte­grated the CFD software into CAESES® for automa­tion of the sim­u­la­tion task. Here is a screen­shot of the geometry model and the cor­re­spond­ing periodic control volume for the CFD (click on the images to enlarge them):

The entire opti­miza­tion process was robust and very effec­tive, and the design could be improved quite a bit (watch out for the upcoming case study on our website). However, when we looked into the details of his workflow, we dis­cov­ered that — for the geometry data exchange of the periodic control volume — he inte­grated a separate program as a workaround to convert the geometry from CAESES® into the pro­pri­etary CONVERGE format. Since the format itself is rather simple we decided to readily offer this export type to our users in the next release. The fol­low­ing sections describe how this new export func­tion­al­ity works in CAESES®.

Geometry Export

The CONVERGE geometry format is basi­cally an ASCII file with tes­sel­la­tion infor­ma­tion, includ­ing some kind of grouping mech­a­nism, to dis­tin­guish dif­fer­ent parts of the geometry. This new format can now be accessed through the file menu of CAESES®:

Input to this export type are tes­sel­lated surfaces i.e. triangle data. In CAESES® this means you can export any surface, as well as user-con­trolled triangle data, so-called trimeshes and breps with settings for the tes­sel­la­tion. However, you can also consider boundary infor­ma­tion — which is the inter­est­ing part now:

Assign­ing Boundary Information

For the sim­u­la­tion setup in CONVERGE, it is impor­tant to know which surface patches belong to which boundary. CAESES® has an intu­itive way to assign boundary ​“infor­ma­tion” by means of a user-defined color. This mech­a­nism is also used for other export types (STL, IGES, STEP — in these cases, the color name is taken for grouping). However, for the CONVERGE format, we now added unique IDs to all our colors which are auto­mat­i­cally written into the geometry file (for the grouping). We need such an ID because names are not sup­ported by this format. As a result, our users can export the geometry data plus the cor­re­spond­ing boundary information.

This is the pro­ce­dure: The user creates a new color and assigns a name to it (e.g. ​“inlet” or ​“peri­od­icwall” etc.). Such a color auto­mat­i­cally gets a unique ID, gen­er­ated by CAESES®. When using the new CONVERGE export, the IDs are trans­ferred into the geometry output file as group IDs, and hence the grouping is directly trans­ferred to CONVERGE.

The benefit of this mech­a­nism is that during auto­mated design studies and opti­miza­tions the IDs do not change, and the bound­aries can be ref­er­enced in CONVERGE and in all CONVERGE-related input files.

The fol­low­ing screen­shot shows the sit­u­a­tion in CONVERGE Studio after import­ing the geometry file from CAESES®. The boundary with the name ​“Peri­od­icA” (this was the color name in CAESES®) is directly shown in CONVERGE Studio and assigned to the cor­re­spond­ing patch.

Note that this setup was com­pletely created from within CAESES®, so there was no manual inter­ac­tion in the user inter­face of CONVERGE Studio! Exactly what we need to run auto­mated design studies … :-)

Sim­u­la­tion Setup

Hang on, this is not the whole story! There is some more added value to this new coloring and CONVERGE export mech­a­nism. As already briefly men­tioned, users can now also use this ID in other setup files for CONVERGE. In the next screen­shot, the software con­nec­tion in CAESES® is shown where the IDs are used by means of a template place­holder in a CONVERGE sim­u­la­tion setup file. In the auto­mated process such as an opti­miza­tion, CAESES® writes this file and includes the current color IDs of the geometry objects.

Even if the user changes the color of the geometry part, the correct ID will be auto­mat­i­cally written into all files due to the expres­sion mech­a­nism in CAESES® and the dynamic place­hold­ers of the CAESES® software con­nec­tor. BTW: Note that not only the color IDs are dynamic input to this file, but any other sim­u­la­tion control such as the tem­per­a­ture, as an example.

Image 4 actually shows the sit­u­a­tion after import­ing the geometry file and the sim­u­la­tion setup file from image 5. The widget on the right-hand side indi­cates that every­thing works well, without any error messages or warnings. Once again, the whole setup was created before in CAESES® without the need to open CONVERGE Studio at all.

In order to close this blog post, check out a final screen­shot which shows how it looks in the CAESES® user inter­face when you run CONVERGE for a design can­di­date. The task viewer on the right-hand side gives you status updates of the running CONVERGE com­pu­ta­tion, which is basi­cally a batch mode run of CONVERGE in the background.

More Infor­ma­tion

We hope that our ​“CAESES®-CONVERGE” users will like this tight data exchange, which makes it super easy now to combine these tools in auto­mated design processes. The new export is avail­able in versions > 4.1.2. In newer versions there is the pos­si­bil­ity to set custom names and custom IDs, to make things even more user-friendly!