Re: Wind and Dust
Posted by maddog_bill on January 07, 2003 at 21:33:06:
In Reply to: Wind and Dust posted by Harold Ericsson on January 07, 2003 at 10:55:01:
The pilots at China Lake have various indicators for guestimating the velocity of the wind. Just like if a wind sock is limp it is zero knots, half way extended, 15 kts, etc. The rule of thumb to move sand is 22 kts. But, this velocity is also subject to a lot of varibles, the biggest one being turbulence. According to fluid dynamics theory, in laminar flow (non turbulent), the velocity at the surface is always zero. Brush, trees, undulating terrain causes the turbulence to raise the sand and then the prevailing wind just merrily moves it along.
Dust is a whole different ball game. I have been in silt where just simply walking will raise a dust cloud 10 feet high.