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Posting-Version: version B 2.10.1 Fluke 8/7/84; site fluke.UUCP
Path: utzoo!watmath!clyde!burl!ulysses!mhuxl!houxm!houxz!vax135!cornell!uw-beaver!microsoft!fluke!marauder
From: marauder@fluke.UUCP (Bill Landsborough)
Newsgroups: net.cycle
Subject: Re: Aerodynamics of large vehicles
Message-ID: <1787@vax4.fluke.UUCP>
Date: Wed, 15-Aug-84 15:34:55 EDT
Article-I.D.: vax4.1787
Posted: Wed Aug 15 15:34:55 1984
Date-Received: Fri, 17-Aug-84 00:41:47 EDT
References: <1502@proper.UUCP>
Organization: John Fluke Mfg. Co., Everett, WA
Lines: 17
Keywords: wind currents,trucks (configuration)

You are right about shapes of the trucks and the turbulance they
create.  I have learned that the worst are big, tall, and square
corners all the way around, especially the back of the trailer.
The front first creates a high pressure area which pushes everything 
away from it.  Then the back, being big and square, creates a large
vacuum area which sucks everything back into it.
   The real condition which sets up the "big blast" when you are 
riding by is when the wind is blowing from your left side and the 
oncoming truck breaks that wind with a monsterous blast of pressure
then vacuum.  Your riding along leaning slightly to your left against
the normal crosswind when the truck goes by and triples the velocity.
You counteract by leaning harder to the left just as the truck gets
by and the vacuum pulls you violently to the left.  It becomes tough
to stay in your planned lane when the cross wind is around 30mph and
the trucks speed is at 70!  This is real common on two lane highways
in the deserts.  Oh well... just tuck down and hang on!