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h2. Equations still to be made pretty and alpha or 'a' written as symbol

A common parameter in describing used to describe sedimentation is the capture velocity. Capture velocity is the velocity of the floc that is only barely settled-out, or "captured", during the sedimentation process. To gain a more profound understanding of this crucial parameter, we will walk through the derivation of the capture velocity equation.

The figure below illustrates the longest path that a floc is able to travel in a sedimentation tube and still be captured.

Below is the equation for capture velocity: Figure 1. Longest possible path of a floc through a sedimentation tube.

The capture velocity is the velocity that the particle must travel to fall a distance 'x' (see figure above) in the same amount of time that a particle traveling at Va will travel L + btana.

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Solving for the capture velocity by equating the first and third expressions, we find that:

Where L is the length of the tube, d is the inner diameter of the tube, Vup is the vertical velocity through one tube, and alpha a is equal to sixty degrees.

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