New airfoil website

Homebuilt Aircraft & Kit Plane Forum

Help Support Homebuilt Aircraft & Kit Plane Forum:

raytol

Well-Known Member
Supporting Member
Joined
Dec 17, 2021
Messages
206
Hi 3V152'
Could you please do some work in the Reynolds Number 2 million to 3 million range. Most of the aircraft we are talking about here are in that range unless they are gliders which in the .5 to one million range. NACA have their lowest range way above what is useful for us and if we use the NACA airfoils then we are really guessing how they perform at the lower numbers. It would be interesting to see how their performance degrades.
Ray
 
  • Like
Reactions: BJC

PiperCruisin

Well-Known Member
Supporting Member
Joined
Jan 17, 2017
Messages
469
Location
Idaho
Hi 3V152'
Could you please do some work in the Reynolds Number 2 million to 3 million range. Most of the aircraft we are talking about here are in that range unless they are gliders which in the .5 to one million range. NACA have their lowest range way above what is useful for us and if we use the NACA airfoils then we are really guessing how they perform at the lower numbers. It would be interesting to see how their performance degrades.
Ray
I don't think you are going to see a huge difference at 2.5e6 vs 2 or 3. Maybe 2.5 would be worth looking at, but 1e6 steps is probably sufficient. See example:
1643643386555.png
 

raytol

Well-Known Member
Supporting Member
Joined
Dec 17, 2021
Messages
206
Thank you PiperCruisin.
The Coefficient of Lift/ Angle of Attack is probably going to be more telling for the degredation due to lower Reynolds numbers.
Some airfoils you can actually feel it when you are landing eg RAF 48.
 

PiperCruisin

Well-Known Member
Supporting Member
Joined
Jan 17, 2017
Messages
469
Location
Idaho
For the other airfoils processed so far, the trends are the same - computer codes do a decent job on lift until near stall, and overpredict drag, except for XFOIL. Averaging JavaFoil/CFD and XFOIL data might do a better job of matching wind tunnel drag data across the angle of attack range.
Can Xfoil be modified or settings adjusted to yield smoother results? I feel Javafoil is somewhat inacurrate, but the plots are smooth and seems good enough for comparative analysis and estimates. Anyways, look forward to the results.
 
Joined
Jun 23, 2018
Messages
17
Location
SEATTLE WA
What's new at BigFoil:
I computed XFOIL data for each basic unflapped airfoil at ncrit=9 and Mach=0, 0.1, 0.25, 0.5.
The results are shown in the basic plots and data source comparison plots.

It is interesting to compare JavaFoil, XFOIL, CFD, and Wind Tunnel data. For this, airfoils such as NACA0012 and NACA23012 have large datasets.

Basic data plots now show only the Re=6M data traces by default to reduce clutter. To view other cases, click on the trace in the legend.
 

J.L. Frusha

Well-Known Member
Joined
Feb 17, 2006
Messages
1,043
Location
Luling, Texas
@3V152

Could you run the airfoil from the Gossamer Albatross to Ultralight speeds?
Max Straight and level: 54kts / 27.78 meters per second
Min Stall Speed: 12.07 meters per second

1662869412001.png
 
Joined
Jun 23, 2018
Messages
17
Location
SEATTLE WA
Hi J.L.,

For a 5 ft chord using the Re calculator BigFoil Re & Mach Calculator
27.78 m/s --> Re = 2.90M
12.07 m/s --> Re = 1.26M

The JavaFoil and XFOIL results for Re = 1M and Re = 3M are available at this link, and attached here as well.
BigFoil

Results for other Re are available through the "Find airfoil data" page.
 

Attachments

  • Cd vs Cl.png
    Cd vs Cl.png
    99.3 KB · Views: 0
  • LD vs alpha.png
    LD vs alpha.png
    115.1 KB · Views: 0
  • Cm vs alpha.png
    Cm vs alpha.png
    95.3 KB · Views: 0
  • Cd vs alpha.png
    Cd vs alpha.png
    105.2 KB · Views: 0
  • Cl vs alpha.png
    Cl vs alpha.png
    90 KB · Views: 0

J.L. Frusha

Well-Known Member
Joined
Feb 17, 2006
Messages
1,043
Location
Luling, Texas
Hi J.L.,

For a 5 ft chord using the Re calculator BigFoil Re & Mach Calculator
27.78 m/s --> Re = 2.90M
12.07 m/s --> Re = 1.26M

The JavaFoil and XFOIL results for Re = 1M and Re = 3M are available at this link, and attached here as well.
BigFoil

Results for other Re are available through the "Find airfoil data" page.
Thank you. I really don't know how to use those programs. Not anywhere near my areas of expertise. Hell, I even had to drop out of CAD when it was still only using plotters.

Considering scaling it to 48in for my UL design.

Jeff
 
Top