Re: [Phys-l] Fwd: So it is not vortex shedding?

[chuck britton <cvbritton@mac.com>]

I'd say that just because the Von Karman Street Formula might not 
match the observed resonant frequency of the bridge, that this does 
not rule out vortex shedding.

The Von Karman formula relates to a stationary object. Once a small 
displacement occurs (for whatever reason) the dynamics of the object 
will provide the positive feedback that gets the vortex shedding in 
synch with the bridge's resonant frequency.

(Or so it seems to me, and I'll not even comment on their spelling of 
Von Karman)
.
At 3:44 PM -0600 12/14/11, William Maddox wrote:
> From: WC  Maddox
>
> The part about the explanation for the torsional  motion not being the usual
> forced resonance discussed in physics classes is correct. This definition of
> aeronautical flutter from McGraw Hill Science & Technology Dictionary sounds
> like the explanations I have read: "An aeroelastic, self-excited vibration
> in which the external source of energy is the airstream and which depends on
> the elastic, inertial, and dissipative forces of the system in addition to
> the aerodynamic forces. Also known as flutter." See also Physics Teacher
> article: What to Say About the Tacoma Narrows Bridge to Your Introductory
> Physics Class by Bernard J. Feldman and Twin Views of Tacoma Narrows Bridge
> from http://www.aapt.org/Store/upload/tacoma_narrows2.pdf.
>
> End Message
>
> Read more: http://www.answers.com/topic/aeronautical-flutter#ixzz1gXxQTLoR