Drag coefficient: Difference between revisions
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<div class="definition"><div class="short_definition">A dimensionless ratio of the component of force parallel to the direction of flow ([[drag]]) exerted on a body by a fluid to the [[kinetic energy]] of the fluid multiplied by a characteristic surface area of the body.</div><br/> <div class="paragraph">In symbols, the drag coefficient ''C''<sub>''D''</sub> is <div class="display-formula"><blockquote>[[File:ams2001glos-De46.gif|link=|center|ams2001glos-De46]]</blockquote></div> where ρ is the fluid [[density]], ''U'' the speed, and ''L'' a [[characteristic length]] of the body. [[Rayleigh's formula]] expresses the drag coefficient as proportional to a power of the [[Reynolds number]] (Re), <div class="display-formula"><blockquote>[[File:ams2001glos-De47.gif|link=|center|ams2001glos-De47]]</blockquote></div> For [[Couette flow]], ''n'' = | <div class="definition"><div class="short_definition">A dimensionless ratio of the component of force parallel to the direction of flow ([[drag]]) exerted on a body by a fluid to the [[kinetic energy]] of the fluid multiplied by a characteristic surface area of the body.</div><br/> <div class="paragraph">In symbols, the drag coefficient ''C''<sub>''D''</sub> is <div class="display-formula"><blockquote>[[File:ams2001glos-De46.gif|link=|center|ams2001glos-De46]]</blockquote></div> where ρ is the fluid [[density]], ''U'' the speed, and ''L'' a [[characteristic length]] of the body. [[Rayleigh's formula|Rayleigh's formula]] expresses the drag coefficient as proportional to a power of the [[Reynolds number]] (Re), <div class="display-formula"><blockquote>[[File:ams2001glos-De47.gif|link=|center|ams2001glos-De47]]</blockquote></div> For [[Couette flow]], ''n'' = -1 and the constant is 2. In most [[aerodynamic]] experiments ''n'' lies between -1/4 and -1/2. The drag coefficient for the force exerted by the [[atmosphere]] on the earth is called the [[skin-friction coefficient]].</div><br/> </div> | ||
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Latest revision as of 15:50, 25 April 2012
drag coefficient
A dimensionless ratio of the component of force parallel to the direction of flow (drag) exerted on a body by a fluid to the kinetic energy of the fluid multiplied by a characteristic surface area of the body.
In symbols, the drag coefficient CD is where ρ is the fluid density, U the speed, and L a characteristic length of the body. Rayleigh's formula expresses the drag coefficient as proportional to a power of the Reynolds number (Re), For Couette flow, n = -1 and the constant is 2. In most aerodynamic experiments n lies between -1/4 and -1/2. The drag coefficient for the force exerted by the atmosphere on the earth is called the skin-friction coefficient.
