Quote:
Originally Posted by Ari
From my understanding skin dimpling, and shape are both trying to solve the same basic problem, laminar boundary separation. Dimpling helps by creating small vortexes above the object skin, producing a low pressure space between it and the laminar flow, causing it to be pushed against the skin longer creating a smaller wake. The effects of dimpling are most seen in fluids with high flow and low viscosity.
In just another look to nature moments, you will notice birds have rather rough surfaces with feathers covering their bodies, on the other hand many water dwelling creatures have smooth bodies covered in scales.
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It's all relative to viscosity and speed. In air a rough surface is better up to about 140 MPH. This is going to be different in other fluids. An engineer once related a study that indicated that at very high presures the resistance of hydraulic fluid in a pipe went down, but I was not present for the presentation of the study and it was many years ago that I heard about it.
A good, and common, example of skin dimpling is the golf ball,