WMLES

The work from the workshops in 2022 and 2024 is continuing during monthly telecons.

Monthly videoconferences

Participants meet on the first Monday of every month at 12pm (noon) US Eastern Time. The Zoom link for these calls is https://umd.zoom.us/j/4487374796. If you want to receive very infrequent e-mail updates, please add your name to this Google sheet. The best way to stay up to date is to (a) check this website regularly and (b) subscribe to the Google calendar.

Notes from telecons (continued from the old page):

• 04/07/2025
• 03/03/2025
• 02/03/2025
• 01/08/2025 (in person at Scitech):
  • Let’s choose a time and meet in person for those that are there.
• 12/02/2024:
  • Preliminary agenda: more complete transition sensor results from Daluar, results with the new wall-model from the AFRL team.
• 11/04/2024:
  • Daluar Hussain has preliminary results with a transition sensor for the A-airfoil, seems to get transition at the right location. The hypothesis is that the nature of the flow (strong FPG first, then APG) forces this.
  • Siavash Toosi remarked that the cases with erroneously too thick boundary layer (due to errors at the leading edge) have a boundary layer with a larger-than-otherwise Rotta-Clauser parameter in the remainder of the airfoil, since the thickness increases while the wall stress decreases. His point being that this would make the boundary layer grow even more quickly and thus never recover from the initial error.
• 10/07/2024:
  • No updates.
• 09/03/2024 (moved to Tuesday due to Labor Day):
  • Timofey is experimenting with a transition sensor for the A-airfoil, seem to be getting transition in the right place. Will have more complete results next month.
  • Matt and Dan are also experimenting with transition for the A-airfoil, and are also re-running the smooth ramp case with different subgrid modeling treatment.
  • Johan has added his and Ivan’s smooth ramp results to the website.
• 08/05/2024 (cancelled due to vacations)
• 07/01/2024:
  • Discussed the A-airfoil. Johan showed additional numerical experiments aimed at the laminar region, with none really solving the problem. Dan showed numerical experiments where they tried different exchange location heights, and found different behaviors in the laminar region but low sensitivity in the turbulent region.
  • AFRL will re-visit the smooth ramp case with their new wall-model implementation and will also try different exchange locations for that case.
  • It was suggested that people try the A-airfoil with the WMLES grid but without the wall-model just to see what that looks like.
• 06/03/2024: (cancelled due to scheduling conflicts)
• 05/06/2024:
  • Johan presented numerical experiments for the A-airfoil where the wall shear stress was computed from Xfoil for the first 10% of the chord; this produced much better agreement with the reference WRLES.
  • Bala presented his ongoing simulations of the A-airfoil; he will start using the same grid as the UMD group and try with that.
  • David Flad presented his experiments on the smooth ramp problem where they get strange results when running with numerical dissipation but much better results without it.
  • David and Dan Garmann have both observed that their codes can produce fully laminar solutions when using the first grid point for the wall-model input but turbulent solutions when using the second or higher.
• 04/01/2024:
  • Timofey Mukha described his airfoil simulations and his a priori study of wall-model accuracy. An important point of the latter was how, for this particular case, choosing \( h_{\rm wm}(x) \approx 0.1 \delta_{99}(x) \) results in very good a priori accuracy due to luck.
  • Johan presented some numerical experiments of the smooth ramp problem where he increased the WENO fraction in the incoming boundary layer to produce different boundary layer states. Adding 1% WENO did not change much, but adding 4% WENO drastically reduced the separation bubble size. Not clear how to interpret these findings, though.
• 03/04/2024:
  • We agreed to slightly change the format going forward. The monthly telecons will continue (at noon US Eastern time on the first Monday of every month), but we will try to make these discussions more technical. The results comparisons will be updated on an ongoing basis rather than only once every two years. We will then meet formally or informally at every AIAA conference (Scitech and Aviation) for in-person discussions. In other words, we will function like an AIAA Working Group, which is essentially how this all started out.
  • ZJ Wang, Christoph Brehm, Dan Garmann and Timofey Mukha will re-run the airfoil case with identical wall-modeling exchange location (likely \(h_{\rm wm}/c = 0.001 \)) and without any special handling of the laminar/transitional region. The idea is to compare the different codes with identical, even if imperfect, settings.
  • Dan Garmann is taking the lead in putting together a paper for Aviation 2024 summarizing the January workshop. This paper won’t include updated results, but instead will provide a snapshot of the blind predictions at the workshop.