UCLA AOS145 Jan 26

UCLA AOS145 Jan 26 - Jan 26 Growth velocity of droplets Use...

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Jan 26 Growth velocity of droplets Use the Köhler equation to find a p sat for the edge of the particle, plug pressure into ideal gas law to obtain concentration c s Then use = ∞- cr c Rpr ( ∞- ) c cs with c equal to ambient concentration to find concentration at surface of droplet Total flux to drop: = ( ∞- ) J 4πRpDg c cs dependent on the radius, larger droplets have larger flux. Consider a mass balance: = ( ) MWJ ρWddt 43πRp3 = ( ∞- ) dRpdt DgMWρpRp c cs Growth slows as droplet becomes larger. Cannot grow into raindrops by diffusion. At some point, R p is sufficiently large to reduce dR
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