## Search found 10 matches

Thu Apr 05, 2012 11:28 am
Forum: Structural Analysis
Topic: Mass Imbalance
Replies: 3
Views: 3705

### 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...
Thu Apr 05, 2012 12:02 am
Forum: Structural Analysis
Topic: calculating truss tower stiffness
Replies: 2
Views: 4092

### 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...
Wed Apr 04, 2012 11:50 pm
Forum: Structural Analysis
Topic: Mass Imbalance
Replies: 3
Views: 3705

### 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...
Mon Jan 16, 2012 10:35 pm
Forum: General
Replies: 3
Views: 34196

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...
Thu Dec 16, 2010 10:12 am
Forum: Rotor Aerodynamics
Topic: Induced flow estimation in BEM
Replies: 16
Views: 11766

### 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.
Fri Dec 03, 2010 1:11 pm
Forum: Testing
Replies: 4
Views: 9947

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...
Fri Dec 03, 2010 12:39 pm
Forum: Rotor Aerodynamics
Topic: Induced flow estimation in BEM
Replies: 16
Views: 11766

### 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...
Fri Oct 29, 2010 4:53 pm
Forum: Computer-Aided Engineering Software Tools
Topic: Low-complexity static model
Replies: 4
Views: 2399

### 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...
Wed Sep 01, 2010 11:27 am
Forum: Testing
Replies: 4
Views: 9947