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GEOMETRY FILES

4th AIAA CFD High Lift Prediction Workshop

and

3rd Geometry and Mesh Generation Workshop


 
 
Logo 1 for HLPW-4

 
 

NASA High Lift Common Research Model (CRM-HL):


Test Article Definition:

A general description of the CRM-HL can be found in AIAA Paper 2020-2771 (Lacy & Clark).

Specifically, the particular geometry definition provided here represents the NASA 10%-scale semispan CRM-HL test article, as tested in the QinetiQ wind tunnel in 2019 (AIAA Paper 2020-2770 (Evans et al.). Future CRM-HL wind tunnel models will be designed and built according to a reference configuration geometry specification, which is slightly different than the geometry used to design and build the NASA 10%-scale model.

The following geometry files for this configuration are provided in full-scale inches. The geometry files are provided in both IGES and STEP formats. There are three landing configurations included. The first is the nominal configuration, with inboard flap angle of 40 degrees and outboard flap angle of 37 degrees. The second and third configurations have modified flap settings: one at 37/34 degrees, and the other at 43/40 degrees. The Test Cases for HLPW-4 are posted on the Test Cases page.

The V2 geometry is different from V1 in the following way. Pinch-points (where a CAD face has a very cusp-like corner where two curves meet at nearly 0 degrees) were adjusted on the flap-bracket connections to the flap underside, and on the outer WUSS end-wall. The adjustment made the angle slightly more pronounced where the curves meet, and this corrected some very slight overlaps detected between these curves as they approached the corner. This fix helps avoid some grid generation issues and also helps to insure consistency among all grids (many grid generators were found to require adjustments in these regions).

If you encounter any problems/issues as you build grids using the V2 geometry, 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.

NOTE: STEP files only support SI units. For the purposes of this workshop, the subject model is in inches. The conversion based unit (#614316 in the file) should be used by a STEP reader to convert the model on import. In this case, units of CM were chosen with a conversion factor of 2.54 (again the STEP file includes this conversion constant). In the end, be sure to check that your final size agrees with the numbers below (e.g., full-scale wing semi-span should be 1156.75 inches).


 

Farfield Definition:

If possible, for consistency between grids, it is recommended that the following geometry definition for the freestream (farfield) boundary along with symmetry plane be used:
 

CRM-HL Boundary-Layer Tripping Information from QinetiQ Test:


 

Geometric Reference Parameters for the NASA CRM-HL (full scale inches):

If you are generating your own meshes for the CRM-HL configuration instead of using the provided baseline meshes, you should try to follow the gridding guidelines found on the Grids page, and the final grids must be made available to the HLPW Committee.


 

QinetiQ Wind Tunnel Geometry Files:

Note that the wind tunnel geometry has been scaled up to match the full scale CRM-HL geometry. I.e., the tunnel is being represented as 10 times its actual size. When the tunnel geometry is loaded together with the CRM-HL full scale geometry, the model is positioned appropriately in the tunnel test section, at zero degrees angle of incidence. Instructions for rotating to a different angle of incidence are included in the pdf file below. (The rotation centerline is parallel to the Y axis at X=1227.5, Z=198.0.) Note that using full scale CRM-HL geometry may require adjustments to the fluid properties in order to match Reynolds number; as with the free air cases, adjusting the kinematic viscosity is the preferred approach (see Q10/A10 on the FAQs page). An alternate approach would be to scale the entire geometry set by 0.10, and run with real air specifications.

Files:

(X,Y,Z) Tunnel Probe Locations (full-scale-model inches):

Typical CFD Iterative Procedure for Running in the Wind Tunnel:
  1. Use inviscid thermodynamic relations with the desired reference Mach number (Mach=0.2) to obtain total pressure (Pt) and total temperature (Tt) (relative to the reference static pressure and reference static temperature, respectively) at the tunnel inlet. Apply an appropriate inlet BC that fixes these total values; this inlet BC remains unchanged throughout the iterative procedure.
  2. Set static pressure BC at tunnel outflow boundary. (A typical starting value might be slightly lower than that required for an empty tunnel; see AIAA-2017-4126 for an example in a different wind tunnel. In the QinetiQ tunnel geometry, the area ratio between the test section and downstream boundary is approximately Amin/Aexit = 0.474.

    An estimated starting back pressure for the provided QinetiQ tunnel configuration is Pexit/Pref ≈ 1.02.

  3. Run CFD solver.
  4. Use temperature (average of 4 probe locations), pressures, and total pressure computed by CFD at the tunnel probe locations, along with the tunnel calibrations (described in above Q5m_Tunnel_Modeling_V01.pdf file) to calculate q/Pt and Mach in the CFD run. Note, in an empty tunnel, the computed Mach should also be achieved (seen) at the tunnel's calibration reference location ((X,Y,Z)=(1227.5, 791.7717, 198.00) in the provided scale). However, when a test article is present in the tunnel, the computed Mach value is based on the calibration only.
  5. Iterate steps 2-5 until the computed Mach is within a desired tolerance (preferably within 0.195 - 0.205); i.e., if the computed Mach number comes out too high, then raise the back pressure, if too low then lower the back pressure. You may need to experiment to determine the effect, and use linear interpolation to determine the next back pressure to try (for example, if p_back1 yields M1 and p_back2 yields M2 (and neither M1 nor M2 is close enough to the goal of M=0.2), then try p_back = p_back1 + [(0.2 - M1)*(p_back2 - p_back1)/(M2 - M1)]). Note that this iterative procedure can take time. Once converged, other conditions, particularly Re, should also be checked using inviscid thermodynamic relations.
  6. Note that the required back pressure may be different for every case (it could be affected by the grid and the angle of incidence of the model in the tunnel).
(This method is sometimes automated. See, e.g., NASA/TM-2018-219812.)

Note: one can solve for the flow in the tunnel using the tunnel coordinate system fixed (rotating the model to different angles of incidence), or using the airplane coordinate system fixed (rotating the tunnel around it). If the latter method is used, be sure to also rotate all of the Tunnel Probe Locations.
 
 

Other Geometry Files:

Some of the TFGs are making use of other geometries beside CRM-HL as part of their research for HLPW-4. These include:
 

Please check periodically for updates, and/or get on the email distribution list by request to hiliftpw@gmail.com to be notified directly of any updates/changes.


 

Link to: Grids Page

Link to: Test Cases Page


 

Return to: High Lift Prediction Workshop Home Page


 

Recent significant updates:
02/18/2021 - Added estimated starting back pressure setting for in-tunnel iterative procedure
01/25/2021 - Added Tunnel Probe Locations and typical CFD procedure for running in tunnel
12/18/2020 - Added QinetiQ Wind Tunnel geometry files and information
12/17/2020 - Added clarification regarding use of MAC as the length to nondimensionalize the pitching moment
11/18/2020 - Added link to NASA wall-mounted hump website
10/20/2020 - Added additional suggestions in red regarding problems/issues
10/13/2020 - Posted V2 geometry files and farfield/symmetry plane definition
09/25/2020 - Added tripping information from QinetiQ test
09/24/2020 - Added links to other geometry files
09/09/2020 - Updated note regarding STEP file details

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Responsible NASA Official: Christopher Rumsey
Page Curator: Christopher Rumsey
Last Updated: 02/20/2021