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, C_L = 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 C_L=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 C_L (or C_L^2) is a function of the other parameters.

3.     Use quadratic formula to extract the interpolated quantities for C_L=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 C_L=0.5 data against tail setting (i_H).
2. Determine i_H from the C_M quadratic-curve.
3. Determine C_D and Alpha by interpolating on the trimmed i_H value.
4. Plot derived data against interpolated C_L=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 C_L = 0.400, 0.450, 0.500 (±0.001 or extracted from polars)
- Untrimmed, Tail Incidence angle, i_H = 0°

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

- Reference Temperature = 100°F

Case 3 (Optional) – Reynolds Number Study:

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

Notes:

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