I have a disc that is rotating due to air being blown at its outer radius. The incoming relative velocity of the air is high, therefore the effect of friction supersedes the effect of conservation of angular momentum. The tangential portion of this velocity decreases due to the friction as it travels (swirls) towards the inner radius of the disc. When the tangential velocity reaches its minimum, the tangential velocity then begins to increase due to the conservation of angular momentum. How does tangential velocity increase due to conservation of angular momentum and not just stay at its minimum value? Thank you.