Just to the point How to calculate Re number? in example for calculating Re number at diffrent points in a boat. How turbulence affect drag? I know simply turbulence will increase the drag but, to what extent; or simply, the formula connecting both. Comparing the drag between turbulence and laminar flow. Sorry as I am not sure if this is the correct place for this topic. I just looks and it says aerospace, so some one here, I assume, must be familiar with fluid dynamic. thank you.