# Two questions concerning flutter?

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 October 12, 2010, 15:03 Two questions concerning flutter? #1 Senior Member     Daniel WEI (老魏) Join Date: Mar 2009 Location: South Bend, IN, USA Posts: 688 Blog Entries: 9 Rep Power: 12 I have Two questions concerning flutter (external flow), 1. Suppose I have a flat plate parallel to the inflow direction in a wind tunnel, while keeping the wind speed constant at a certain value, what happens if the structure damping is zero? will flutter happen when the structural damping is zero? 2. What is the worst shape of a structure, which is the most unstable and has the lowest flutter point? (Structure, I mean rigid body here) Any ideas? Thanks, __________________ ~ Daniel WEI ------------- NatHaz Modeling Laboratory Department of Civil & Environmental Engineering & Earth Sciences University of Notre Dame, USA Email || My Personal CFD Blog

April 7, 2011, 07:15
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Wei Zhao
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Quote:
 Originally Posted by lakeat I have Two questions concerning flutter (external flow), 1. Suppose I have a flat plate parallel to the inflow direction in a wind tunnel, while keeping the wind speed constant at a certain value, what happens if the structure damping is zero? will flutter happen when the structural damping is zero? 2. What is the worst shape of a structure, which is the most unstable and has the lowest flutter point? (Structure, I mean rigid body here) Any ideas? Thanks,
Dear sir:

firstly, regarding to the structure damping is zero, you can refer to the plot of V-g curve, the real/ practical structure is not zero forever, which is a positive unknow values for which is changed as the velocity.
In computational method, we can judge the bundary of flutter velocity is at the point of the damp is zero. which is a conservative value, smaller than the real flutter velocity.

secondly, when the structure is located in the flutter, which notes the structer is in the harmonic motion, when the velocity is a little bigger, or the external energy put on the surface of the structure, the structure will locate in unstable motion.

 April 7, 2011, 09:28 #3 Senior Member     Daniel WEI (老魏) Join Date: Mar 2009 Location: South Bend, IN, USA Posts: 688 Blog Entries: 9 Rep Power: 12 Forget about my first question. I was wrong by asking that. Now, I am very interested in the second question, what kind of shape is the worst shape? I mean it will flutter very quickly at a low wind speed. __________________ ~ Daniel WEI ------------- NatHaz Modeling Laboratory Department of Civil & Environmental Engineering & Earth Sciences University of Notre Dame, USA Email || My Personal CFD Blog

April 7, 2011, 10:21
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Wei Zhao
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Quote:
 Originally Posted by lakeat Forget about my first question. I was wrong by asking that. Now, I am very interested in the second question, what kind of shape is the worst shape? I mean it will flutter very quickly at a low wind speed.
I have typed many explanations for you, sorry for the net problem, more information,you can contact with me zwseu2010@yeah.net, I can send you some PPT for you reference.
aeroelastic is a complicated and more interesting issue, which is worthy us further researching.
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