DPW 4 Wind Tunnel Data

 

 

National Transonic Facility Wind Tunnel Data for the NASA Common Research Model (CRM)

17 June 2011

Revision 0

Case 1 – Grid Convergence and Downwash Studies:

1.     Grid Convergence study at Mach = 0.85, CL = 0.500 (0.001)

 

Configuration

Alpha

CD

CM

iH

WB

2.791

0.02489

-0.06313

NA

WBH iH =  -2

3.296

0.02879

  0.16218

-2.000

WBH iH =   0

3.028

0.02672

  0.03987

 0.000

WBH iH = +2

2.752

0.02594

-0.07797

 2.000

Trimmed

2.937

0.02631

  0.00000

 0.668

Downwash

2.791

0.02597

-0.06170

 1.719

Notes:

For all of the untrimmed cases, the process was as follows:

    1. Grab the closest data point to CL=0.5 and its two neighboring points, for each of the 3 or 4 repeat runs.

2.     Perform a least-squares quadratic curve-fit on the data.  Here CL (or CL^2) is a function of the other parameters.

3.     Use quadratic formula to extract the interpolated quantities for CL=0.50.

4.     Plot these interpolated values along with the scatter data to verify that all interpolations went well.

5.     Compare the least-squares fit with the experimental data to quantify uncertainties/scatter of data about the fit.

 

To trim the WBH, the following process was used:

    1. Cross-plot all of the CL=0.5 data against tail setting (iH).
    2. Determine iH from the CM quadratic-curve.
    3. Determine CD and Alpha by interpolating on the trimmed iH value.
    4. Plot derived data against interpolated CL=0.5 data to ensure everything went well.

 

To calculate the downwash, the following process was used:

1.     Get the tail setting which gives zero lift on the tail when the WBH is at CL=0.5 by matching Alpha of the WB and backed-out an iH of 1.719 deg.

2.     Use the quadratic curve-fits to extract CD and CM at this iH.

 

2.     Downwash Study at Mach = 0.85


Case 2 (Optional) – Mach Sweep Study:

Drag Polars at:
- Mach = 0.70, 0.75, 0.80, 0.83, 0.85, 0.86, 0.87
- Drag Rise curves at CL = 0.400, 0.450, 0.500 (0.001 or extracted from polars)
- Untrimmed, Tail Incidence angle, iH = 0

- Medium grid
- Chord Reynolds Number 5x106 based on cREF = 275.80 in

- Reference Temperature = 100F

Case 3 (Optional) – Reynolds Number Study:

Reynolds Number study at Mach = 0.85, CL = 0.500 (0.001)


Notes: