RE: [Algorithms] Underwater Physics
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From: Charles B. <cb...@cb...> - 2004-05-28 18:27:30
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Very nice summary. The big thing that happens with CD is the transition from laminar to turbulent flow. At low Re, flow is laminar and CD is nearly inverse linear (hence drag is linear), at high Re, flow is turbulent and CD is nearly constant (hence drag is proportional to squared speed). You can exactly solve for CD at very low Re, this exercise is in most fluids books. At high Re with turbulence and boundary layers, you can't exactly solve for it analytically, and you must do numerical experiments or physical experiments to find CD. At the point of transition to turbulence CD does very strange things, so we just ignore that. Generally turbulent drag is much lower than laminar drag, which is why airplanes and such use needle-nozes to intentionally create turbulence and break the boundary layer, etc. ---------------------------------------------------- Charles Bloom email "cb" http://www.cbloom.com |