Bioreactor help

[nur1234]

Hi If anyone can help me answer the following questions below, it would be a great help. Its about bioreactors, turbulence

1. Why does the power requirement for a bioreactor increase when flooding ( when the cavities in the bioreactor hae merge together and beome large) occurs to the bioreactor? Shouldn't it have a lower power requirement since the agitators are practically spinning air and air much is less dense than liquid.

2. Why is tip speed of the agitator related to having the highest shear force in a bioreactor?