Question

Wind engineering

6.2 For a cylinder with the cross section shown the plots of the drag and lift coefficients as functions of angle of attack α are shown below. Based on the Glauert-Den Hartog criterion, can this cylinder experience galloping motions? Justify your answer. CL.C CORNER RADIUS .0.050 Co 0.5 10 20' -05 1.0

Answer 1

The drag co-efficient of the cylinder, e_D_eve = 1 reference area, A_CYL(S_CYL) = dh The drag co-efficient of the fairing, e_D_FAIR = 0.01 Reference area, S_EAIR(A_FAIR) = ch (As e = 10d given) = 10dh Both velocity of interest of cylinder and fairing = V_infinity Therefore Tge drag force of the cylinder D_CYL = e_D_CYL A_CYL rho V^2/2 = 1 times dh rho V^2/2 Therefore The drag force of the fairing D_FAIR = C_D_FAIR A_FAIR rho V^2/2 = 0.01 times 10dh rho V^2/2 Therefore The ratio i.e. D_CYL/D_FAIR = dh rho V^2/2/0.1 dh rho V^2/2 = 1/0.1 = 10: 1