Question

255 Water flows at 20°C at 8 kg/s through the diffuser having 3 cm diameter at (7 the entrance and 7.0 cm diameter at its exit. The fluid Reynolds number at *: the inlet and exit of the diffuser are 339105, 146530 Not all the above 336105, 143530 338105, 145530 337105, 144530 A fan provides air speed upto 50 m/s, is used in low speed wind tunnel (8 with atmospheric air at 27°C. If this wind tunnel is used to study the boundary layer behaviour over a flat plate upto Re = 10^6. What should be the minimum plate length ? At what distance from the leading edge would * ? transition occur, if critical Reynolds number is (Re)critical = 5 x 1045 Not all the above 31.72 m, 0.159 m. 31.92 m, 0.159 m. 32 m, 0.17 m. 31.82 m, 0.159 m.

Answer 1

solution:- Given, T= 20°c in = 8pg/s di= = 3cm = 0.03m. d₂ = 7cm 0.07m now dynamic viscasity of water cet 2oc, pars M= now, diffuser inet seynold number is, RG = А. rum ЧX8 Rez (-:A, = Tai T di M A Xo 03 RB = 339530-54 | Ang 1 1-3 exit reynold number is, 488 rum Re = tda TXO.07 R2 = 145513 to and (6) Griven, U= 50m/s T = 27°C 1006 Rez 5 Reera 5x10

now, Imin for Rea 106 now, kinematic riscasity of water at 27°c is, v=11598105 m/s mow Re- Ulmin 10 500 lmin 1-57X16S min 0.318m Ang how dransition occur length Ly? Reen= Uhr 500g 5x10 7.59x105 = 0.15gm to Ang