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The dimensions of apparatus are determined according to MathCad calculations, we have two constraints of choosing the tube's length, the terminal velocity of the particle should be larger than both the capture velocity and the critical velocity in order to settle the big particle and prevent the small particles roll up, we also consider the length should be long enough to let the flow in the slanting tube could become fully developed flow; the relevant criteria being the length of both columnscan be found in our Mathcad file. MathCad file
Calculations were made using the following assumptions for simplification:
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