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4th AIAA CFD High Lift Prediction Workshop

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Logo 1 for HLPW-4


Q1: Why is HLPW-4 being conducted differently than previous high-lift workshops?

A1: Bottom line: to try to get more out of the workshop. In an attempt to accelerate the rate of progress, and to take better advantage of the collective brain-power focused on enhancing CFD prediction capability for practical high-lift aerodynamics, the committee decided to try something new for HLPW-4. Rather than working individually, active participants are asked to join one or more Technology Focus Groups during the months leading up to the workshop. Also, HLPW is again co-locating with the Geometry and Mesh Generation Workshop (GMGW) because of the important interplay of the technologies. We are hoping that the new way of operating the workshop will enhance this collaboration. As a side note, starting with HLPW-4 we are changing the workshop acronym from HiLiftPW to HLPW. However, the workshop's website name still uses "hiliftpw".


Q2: What are Technology Focus Groups, and how will they work?

A2: A Technology Focus Group (TFG) is made up of ACTIVE PARTICIPANTS working (remotely) together in a specific area, to try to answer questions related to CFD prediction of high-lift flows. These specific areas are currently defined to be the following: Each member of a TFG will contribute to team activities, as delineated by the TFG leaders. These activities will likely involve performing CFD or meshing work, and sharing it with the TFG team. (It is possible that each TFG may be conducted somewhat differently.) At the HLPW-4 workshop itself, each TFG will present a summary of its results. In other words, HLPW-4 is similar to previous workshops in that active participants will still perform research/work on their own. However, it is different in the following ways:
  1. The work is now part of a broader team's collective efforts.
  2. Rather than reporting results individually at the workshop, active participants are interacting regularly with their TFG, and sharing their results with the TFG in the months prior to the workshop. Individual active participants are no longer responsible for making a presentation at the workshop.
  3. Instead, the TFGs are responsible for summarizing their collective results and presenting them at the workshop.
It is hoped that this new experimental way of conducting the workshop will lead to (1) more up-front learning and (2) more time for discussions and rapid dissemination of ideas at the workshop.


Q3: How can I attend the workshop if I am not presenting my own work in an individual presentation?

A3: It is hoped that organizations will still encourage their employees to attend the workshop in order to see all of the TFG summaries given by the TFG organizers, and to participate in the workshop discussions.


Q4: Do I have to join a TFG to attend HLPW-4?

A4: No. If you are not a member of a TFG, then your status is OBSERVER. Observers are free to run the test cases, use the grids, etc. But their results will not be included in the collective summaries presented at the workshop. Observers can also do nothing - just observe, because they are interested. Like everyone else, observers can attend the HLPW-4 workshop and join in the discussions there. In other words: Anyone, including active participants and observers, may attend HLPW-4 (subject to possible space availability/restrictions).


Q5: What do I need to do to attend the workshop?

A5: To attend the workshop, both active participants and observers must register for HLPW-4 with AIAA. AIAA will also give details regarding travel and accomodations, visas, etc. Note that registering for the AIAA Aviation conference alone does not give you access to HLPW-4 (and vice versa). You must specifically register for HLPW-4, and pay its additional registration fee.


Q6: How might COVID-19 affect HLPW-4?

A6: Unknown at this time. The workshop dates are set for June 5-6, 2021. As the time approaches, a decision will be made regarding whether to hold the workshop in person, hold it remotely (on-line), or delay it. In any case, all preparatory work/research is continuing as planned.


Q7: What happened at the first three high-lift prediction workshops?

A7: The first HiLift workshop took place in June 2010. See Webpage for HiLiftPW-1 for detailed information. The second HiLift workshop took place in June 2013. See Webpage for HiLiftPW-2 for detailed information. The third HiLift workshop took place in June 2017. See Webpage for HiLiftPW-3 for detailed information.


Q8: By what date will CFD results need to be completed?

A8: Because this workshop is being conducted so differently from the previous ones, this is a difficult question to answer. We now have the TFGs bringing participants together to collaborate well ahead of the workshop date. Each TFG has its own unique challenges, so may operate somewhat differently (and on potentially different schedules) from the others. However, all TFGs will no doubt require results from its members at intervals between now and June 2021. They will likely evaluate how things are going via regular team meetings, and will work interactively with all its members to answer a set of "key questions" prior to the workshop.


Q9: What should I do if I find "problem areas" in the geometry files?

A9: If you encounter any problems/issues as you build grids using the geometry files, please make your own fixes, DOCUMENT everything done, and plan to share your fixes with the workshop committee. Note that the geometry includes regions that may be very difficult to grid (and possibly solve), including very thin gaps at the bottom/inside edge of the slats. These were present in the wind tunnel configuration, so they were left in. It is up to you how to handle such areas; this is part of the challenge of the workshop. Again, be sure to document every assumption/change/fix that you make, as your grids are created.


Q10: It is confusing that the free-air test cases use full-scale geometry yet wind-tunnel-scale Reynolds number (Re). Then, the test case with wind tunnel walls uses model-scale geometry (and again wind-tunnel-scale Re). How do I reconcile this, and how do I set Re if my code does not have Re as an input?

A10: It is particularly important that you set conditions to match the prescribed Reynolds number and Mach number of the test cases. These two parameters uniquely define the flow conditions. If your CFD code does not take Reynolds number (Re) as an input, then (preferably) kinematic viscosity should be adjusted in order to achieve the precise Re requested in the Test Cases Document. The Re is given based on mean aerodynamic chord (MAC): ReMAC=5,490,000. The MAC is 275.8 inches (full scale). Thus, when you run your CFD code on a grid based on the full scale configuration, the Re per inch should come out to ReMAC/275.8 = 19,905.7288. (If you had to scale the grid by 10% so that the configuration is at model scale instead, then the MAC would be one-tenth as large: 27.58 inches. The ReMAC would still be exactly the same, at 5,490,000, but now the Re per inch would be 199,057.288.)


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Recent significant updates:
10/21/2020 - Added Q10
10/20/2020 - Added Q9

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Responsible NASA Official: Christopher Rumsey
Page Curator: Christopher Rumsey
Last Updated: 10/21/2020