Recommendations for future experimental work following this effort should consider emulating varying levels of freestream turbulence intensities in a single wind tunnel using a controlled turbulence generation instruments. Comparison with X-Foil trends confirm that higher freestream turbulence intensities promote an earlier onset of boundary layer transition. By comparison, DWT’s reaches its maximum lift at the αcrit and reduces beyond it. Beyond the critical angle, SDSU’s lift polar increases for two degrees before reaching the maximum lift and after which the lift gradually decreases. Increasing the freestream turbulence appears to promote earlier onset of the critical angle. However, the αcrit occurs at different values in SDSU’s experiment αcrit occurs at 8◦ whereas for DWT it occurs at 9.5◦. The lift and drag polars of both SDSU and DWT experiments show a sudden increase in the lift and decrease in the drag at a critical angle of attack, αcrit, at which the flow changes with increasing angle of attack from a laminar separated flow to a flow with a laminar separation bubble that transitions the laminar boundary layer to a turbulent boundary layer. China Clay is used to visualize the separation location in the SDSU experiment. Experimental lift and drag polars are measured with force balances, compared and verified against X-Foil computations for varying turbulence intensities and Reynolds numbers. The SDSU’s model has an aspect ratio of 12.6 while the DWT model is 12.9. Finite span wing models are fabricated independently and vertically centered with endplates in their respective wind tunnel test sections to mimic quasi-2D flow. The SDSU data is compared to a similar experiment conducted at the University of Southern California Dryden Wind Tunnel (DWT) which has notably lower turbulence intensity of 0.035%. Experiments are conducted at the San Diego State University (SDSU) Low-Speed Wind Tunnel with a turbulence intensity level of 0.27% in the test section. Flow over a NACA 65(1)-412 airfoil is studied for a moderate chord-based Reynolds number of 20,000 typically encountered in small-scale technologies such as micro-turbines and small unmanned air vehicles. Wonder how it did?Īlso of possible interest. Heard rumors he had the Patrol at a STOL contest recently. The 4 series has lower Reynolds #s than the 6s so don't know how it would compare side-by-side with a Cub of similar weight/power. Bob Barrows chose the Riblett GA35-413.5 for the Patrol which worked out pretty well from the reports I've read. I'm using the Riblett GA30A613.5 on my little bush plane project. I have Compufoil loaded in my computer and with it I can overlay two airfoils on top of the main airfoil. Don't see how one could go wrong with either airfoil. The Riblett GA30A613.5 should be just a tad bit better. The USA35B is a good airfoil, no question about it. I've read and utilized both and Riblett has his stuff wired. Later families, including the 6-Series, are. and it's a lot easier read than Abbott and Von Doenhoff's book: The Theory of Wing Sections. The early NACA airfoil series, the 4-digit, 5-digit, and modified 4-/5-digit, were generated using analytical equations that describe the camber (curvature) of the mean-line (geometric centerline) of the airfoil section as well as the sections thickness distribution along the length of the airfoil. The EAA sells a book (about $20) called GA Airfoils written by Harry Riblett which is a very informative book that the average aviator should have no problem understanding.
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