Airfoil operating in reverse airflow

[Intermesher]

Does anyone know of any sources of information related to the, lift, drag, center of pressure etc. on airfoils when the airfoil is being subjected to reverse airflow. I.e. where the air stream is flowing from the [labeled] trailing edge to the [labeled] leading edge.

Thanks

 

[TheRaptor]

Where exactly is such a design used?

 

[verymadmac]

HI

The best source of that type of information is from wind turbine data. The likes of Wind Engineering journal

Here's a link to a paper covering three airfoil's

http://www.ecn.nl/docs/library/report/2001/rx01004.pdf

Duncan

 

[rb1957]

maybe someone from the helicopter field has something to add ?

 

[Sparweb]

The guys at Sandia National Labs did this kind of research.

http://www.sandia.gov/wind/topical.htm#VAWTARCHIVE

Steven Fahey, CET

 

[Intermesher]

The Raptor,

It isn't used ~ yet.
This link is to work I am doing, in the hope of developing the concept for future rotorcraft use.

http://www.UniCopter.com/B473.html

verymadmac and SparWeb,

Thanks for the references. Something to read over a coffee.

rb1957,

Very little (public) work has been done on this subject. However, I believe that if pure rotorcraft are to have a future and achieve faster forward velocities, they must utilize the reverse velocity airflow on the retreating side of slowly rotating rotors.


Dave

 

[Sparweb]

...they must utilize the reverse velocity airflow on the retreating side of slowly rotating rotors.

Have you noticed how much the drag jumps up when you do this? Have you converted this drag into horsepower?



Steven Fahey, CET

 

[Intermesher]

Steven,

No the drag has not been looked into yet. I am trying to assimilate any pertinent information first. It has been mentioned that someone had done it for the NACA 0012 and thinner airfoils.

A couple of positive features are that the airspeed will be less on the retreating side and that the drag on the retreating side will contribute to the rotation of the rotor.

Dave