Search found 10 matches

by Steven.Fahey
Thu Apr 05, 2012 11:28 am
Forum: Structural Analysis
Topic: Mass Imbalance
Replies: 3
Views: 3328

Re: Mass Imbalance

I'm a little concerned that you are not stepping away from the FEA to do the hand-calculations properly. As I pointed out, it is a statics and vectors problem. You can feed the resulting conditions into the FEA when you know them, but a "reality check" is also needed. I fear that I've misu...
by Steven.Fahey
Thu Apr 05, 2012 12:02 am
Forum: Structural Analysis
Topic: calculating truss tower stiffness
Replies: 2
Views: 3775

Re: calculating truss tower stiffness

Sorry but I don't believe the simple 3-leg approach will give a close enough number for a meaningful result in subsequent analysis. I would work out the tower's stiffness by FEM, however I wouldn't be daunted by that project, because there are some s/w packages on the internet that make it quite eas...
by Steven.Fahey
Wed Apr 04, 2012 11:50 pm
Forum: Structural Analysis
Topic: Mass Imbalance
Replies: 3
Views: 3328

Re: Mass Imbalance

This should be simple to work out. The center of gravity of the rotor with the one overweight blade will be offset by half a meter from the axis of rotation! It sounds terrifying to me. I hope they mean it as a "fail-safe design limit". The turbine must be shut down by its accelerometers w...
by Steven.Fahey
Mon Jan 16, 2012 10:35 pm
Forum: General
Topic: Blade Failure
Replies: 3
Views: 33862

Re: Blade Failure

It's not basic at all. Your question goes to one of the fundamental changes of focus in a number of industries: how to translate knowledge of the bulk properties of a material into the detail behaviour of its fine structure, and how to do this with complex materials such as composites. Your literatu...
by Steven.Fahey
Thu Dec 16, 2010 10:12 am
Forum: Rotor Aerodynamics
Topic: Induced flow estimation in BEM
Replies: 16
Views: 10706

Re: Induced flow estimation in BEM

Marco,
I think you answered your own question. Yes, aerodynamic coefficients, particularly airfoil drag, vary with Reynold's number. Also consider the effect of Re on the slope of the lift-curve. This will have an effect on the induced flow velocity.
by Steven.Fahey
Fri Dec 03, 2010 1:11 pm
Forum: Testing
Topic: Aerodynamic loads on blade & conversion into test loads.
Replies: 4
Views: 9142

Re: Aerodynamic loads on blade & conversion into test loads.

Hi Shankar, I doubt I could find much that would be directly useful to you, if that's what you mean. My involvement in certification tests for wing extensions and external equipment on aircraft was the basis of my earlier comments. The aerodynamics and behaviour of wings and rotor blades are similar...
by Steven.Fahey
Fri Dec 03, 2010 12:39 pm
Forum: Rotor Aerodynamics
Topic: Induced flow estimation in BEM
Replies: 16
Views: 10706

Re: Induced flow estimation in BEM

Talk of the vortex-ring state brings me back to school days when helicopter flight theory was being discussed. Opened up old Shapiro's book to refresh my memory and though the bias of the subject matter is for helicopter rotors, there is a lot of discussion in practical terms of the transitions to t...
by Steven.Fahey
Fri Oct 29, 2010 4:53 pm
Forum: Computer-Aided Engineering Software Tools
Topic: Low-complexity static model
Replies: 4
Views: 1991

Re: Low-complexity static model

Do I read correctly that you are only interested in the "shutdown" condition? If that's the case, then you only need to calculate forces of drag. Vortex shedding can be guess-timated if you get the Strouhal number from a fluid-dynamics textbook like Hoerner. Natural frequency of the blades...
by Steven.Fahey
Wed Sep 01, 2010 11:27 am
Forum: Testing
Topic: Aerodynamic loads on blade & conversion into test loads.
Replies: 4
Views: 9142

Re: Aerodynamic loads on blade & conversion into test loads.

Though not on wind turbine blades per se, I've carried out structural tests on aircraft external structures. Perhaps my experience is relevant to you. A lot is published about aerodynamic load test practices on aircraft structures, especially on helicopter rotor blades for example, which you might a...
by Steven.Fahey
Tue Aug 31, 2010 10:24 am
Forum: Rotor Aerodynamics
Topic: Re variation over span
Replies: 9
Views: 15338

Re: Re variation over span

Perhaps it's of no use to post to such an old thread, but in case this question comes up on a search (like it did for me), I'd like to suggest going back to the basics. To me the obvious starting point is NACA test reports for their airfoils. This is public domain data which can be searched and down...

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