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Analysis of the Slat at 12 Degrees


First the disclaimer: there are not enough pressure ports or films on the slat to give a great deal of confidence in the analysis. The attachment line locations as predicted from the experimental pressure ports are estimated to be located at:


 
eta
 S, attachment
 Xn, attachment
 Zn, attachment
 Effective Sweep, degrees
 Rbar
0.17
 0.029
 9.71 -0.354
 44.5
 265
0.41
 -0.52
 23.72
 -0.713 38.4
 239
0.65
 -0.67
 37.60
 -0.685
 33.7
 222
0.85
 -0.67
 49.05 -0.593
 34.4
 224
0.95
 -0.19
 		54.38
 		-0.372
 		40.2
 		145

The above is FINAL DATA
The rough estimation of the uncertainty in the attachment line location is discussed here. If we assume that the best estimate is that made when using a CFD solution that closely matches the pressure ports, then the uncertainty in the location is approximately 5% of the slat chord (cs = 5 inches). As shown in the discussion though, poorly place ports can result in a difference of 10%cs. The effect of the location of the attachment line and the number and placement of the pressure ports is discussed here. As indicated there can be a large uncertainty in the calculation of Rbar.

At 12 degrees the value of Rbar on the slat indicates that the attachment line is laminar.


Film Object 37 on the upper surface of the slat indicates that the flow is laminar on the forward section of the upper surface, i.e., in front of film object 37. Near the end of the film object at a location of Xn = 31.1, Yn = 42.0, and Zn = 1.2, the films indicate the possible start of transition. A very high frequency disturbance arises in the spectra between 60 - 70 kHz and grows in frequency band with distance Xn downstream. These are very small scale disturbances and may not be real, i.e., they may be too small with regard to the noise floor of the instrument to be rationally discussed. The other film object on the upper surface of the slat is located near the tip of the slat and indicates laminar flow.

The lower surface of the slat has three main objects covering the portion of the slat under surface upstream of the cusp. These objects show the slat to be mainly laminar with slight disturbances growing as the flow proceeds downstream toward the cusp.