Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Turning flow through rotor blades

Turning flow through rotor blades

Turning flow through rotor blades


As I am not much of a helicopter guy, I thought I'd turn to the helo forum for help.

I am doing work on a vehicle with a rotor mounted at a 45 deg. angle relative to horizontal.  I have a lifting surface less than one rotor diameter down stream of the rotor, and I need to calculate the angle of attack on this surface.

I understand that there is a vector sum between the forward flight velocity and the velocity induced by the rotor, however through the research I have been doing, I see this as an inflow angle to the rotor.  What I want to know is how much the flow is turned through the rotor?

Ideally, the flow is turned the full 45 degrees, but I don't believe this to be the case in the real world.

Can anyone shed some light on this question?

Aerospace Engineer

Replies continue below

Recommended for you

RE: Turning flow through rotor blades

A good start is to estimate total required lift and drag of system. Lift will result in a change in vertical momentum. Drag will result in a change in horizontal momentum. The air effected will be an approximate elliptical tube, entering the profile of the rotor assy depending on flight direction. Basically it is very unlikely that the downwash will be at 45', except at specific flight regimes.

I couldn't work out what you meant by rotor at 45'. Is this 45' forwards to create thrust and lift, or 45' rearwards to autorotate and generate lift? I assume you are really discussing a ducted fan, with a rear stator?

In either case the downwash rotor whirl will complicate matters, but fortunately is likely to be a fixed rotational velocity. Also the downwash is highly unlikely to be evenly distrubited across rotor (this has been the source of a recent interesting discussion).

Hope this helps...


Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members! Already a Member? Login


Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close