I'm trying to learn friction (only - nothing else - just skin friction) on a surface as it moves through water. I'm hoping to find a working formula, including all necessary units, in terms of wetted area, viscosity, and velocity (while, along the way, absorbing the subject well).
More than twice now, I've encountered almost-perfect papers, except for this critical weirdness:-
3.5. Experimental condition The experiments were conducted as follows. The towing speeds were set at U0 = 0.25, 0.5, 0.75, 1.0, 1.125, 1.25, 1.375, 1.5, 1.625, 1.75, 1.875, 2.0 m s−1 For each speed, the draft was varied among h = 0.590, 0.635, 0.700, 0.785 m, where h is defined as the distance from the bottom of the plate to the water surface. The total drag was measured under the same conditions for plate A (L = 3.3 m) and plate B (L = 4.3 m). Wetted surface area S is defined as L ×h. The Reynolds number ReL varied from 8×10 to 10 .
A flat plate has two sides - so "Wetted surface area" should be 2* L * h.
The paper goes on using this mistake, complete with comparisons to other tables and so on... thus, either I'm missing something important in my comprehension, or, someone somewhere made that mistake and now it's become the standard, or more than a few papers are both wrong, and fudging their results to match reference tables ?
For those curious, I'm working on examining the difference between rotating a propeller inside a fixed shroud, as opposed to rotating a propeller that is physically attached to the shroud (i.e. rotating the shroud too)
I am aware that skin friction formulas are abundant, and that there's two (one for slow, one for fast), however, they're typically all missing units, making them not practically useful.