Question

Problem: For completely rough flat plates (i.e., plate surfaces on which urk,/v> 70), Schlichting developed conrelations for skin-friction, ef, and (one-sided) drag. Co. coefficients, viz. -2.5 -2.5 c 2.87+1.58 log1o and Cp1.891.62 log1o 10g10 k where a is distance along the plate, L is plate length and k, is surface-roughness height. For the rudder of a motorboat, compute cyat the trailing edge and C using the smooth-surface formulas, given below, and the Schlichting formulas. The boat is moving at 16 knots, and v= 10-5 ft2 sec. Approximate the rudder as a rectangular flat plate of length 2 ft and of width (depth in the water) 4 ft. Also, assume the surface roughness is 0.0048 in. How much larger are cf and CD when we account for k,? The smooth surface formula for skin friction is. cf = 0.0576 Rex Answer: Smooth, c, 0.0026, CD-0.0033. Rough, c, -0.00446, CD 0.00573

Answer 1

击, yo ks G+ lpe7 }.se )。9..(2보 o 0048 C 0.oou4 (D= 0.005732 27 008 x 2 Jo-s VL Reynold's N. Re C}= 0, 0571 (Rex) .. 0, 00 259

e how velacily 7006,() d lo-5 CD 105,081 where L=2 00014891 x 5 x (2)% CD= 0,00325