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ACRO E-mail Archive Thread: [Acro] RE: Gnats

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ACRO E-mail Archive Thread: [Acro] RE: Gnats


Thread: [Acro] RE: Gnats

Message: [Acro] RE: Gnats

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From: "Seppanen, Kari J" <kari.j.seppanen at>

Date: Tue, 18 Jun 2002 01:04:56 UTC


  Are you sure the wind is "blowing" where the gnats are? Is the dam
deflecting the wind hitting it  and producing an area of detached flow? Next
time stop and throw some light weight dirt or something into the air the
gnats are flying in and see if it blows away. 

Large scale aerodynamics can be fun and useful. On the Washington State
Ferries, there is a stagnation point just below the wheelhouse. If you stand
there, you feel no relative wind. Move a few feet to either side and you get
wind chill. A good trick to know on those cool NW days.

Kari J. Seppanen
Flight Test Engineering Analysis 
Aerodynamic Performance Group
kari.j.seppanen at
Phone 206-655-3356
Fax 206-655-5321
M/S 14-KF

-----Original Message-----
From: Michael Cook [mailto:michael.cook at]
Sent: Monday, June 17, 2002 7:01 AM
Subject: [Acro] Gnats

I have witnessed a phenomena that defies my understanding.

I ride my bike around our city lake. It is pretty open with a raised dam on
the north side. Virtually every time I ride the wind is blowing from 12-20
mph across the lake from the south. On the road over the dam I encounter
swarms of gnats.

Here is the amazing thing. These gnats, who weigh 1/12 th of a newt, are
able to say in a swarm ball in winds of 20 mph. How can they do this? Logic
would tell you that the wind would carry them away. Yet they stay in this
swarm for a long time.

Surely there will be someone on this forum that can understand the
aerodynamics and propulsion of the Gnat.

Michael Cook
Edmond, OK


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