Question

please 3,4

hapter 9 External Flows The fixed keel of the sailboat is about 38 in. deep. The boat moves at a speed of 3 knots (i.c. 5.1 ft/s) in a lake with water temperature of 40°F. The keel can be approximated as a rectangular flat plate with an average length in flow direction / +(34+15)/2 = 24.5 in, and a depth of 38 inches. (Considering a laminar BL to turbulent BL transition happens at Red - 2x10° in this situation.) 1) (3 pts) What is the Reynolds number Res for flow over the plate? 2) (3 pts) What is the coefficient of drag for the plate, Cor? 3) (3 pts) What is the friction drag force on the keel? (notice there are two sides) 4) (1 pt) If the downstream keel flow BL transitions into turbulent BL, what is the effect of this on the overall skin friction drag? 134 in 38 in 15 in

Answer 1

First find out the reynolds number

Property of water at 4 of VE 1667x10 ftys S = 1b/ft at 4 of 62.42 V = 5.1 fills 38 in 15 im 51X 38/ 1667x108/12 -> VL Re .9.66105 Turbulent flow Cofficient of Draq 6 = 0.72 0.72 Vs (9.6x105) [co for Re72x108] → Co=0.045 FO - РАу'х, box 62.427 38 x15 x 65.1 x 6.045 Fó 144.68b/ft? 12 x12