Question

Experiments show that the coefficient of drag C=F/(1/2ApV^2) for smooth spheres should only be a function of a Reynold's number.

8. Experiments show that the coefticient of drag Cp F(Ap) for smooth spheres should only be a function of a Reynold's number, Re PVD/μ). I lere F is the total drag force of the fluid on the sphere, and includes all the viscous and pressure forces, and A is the frontal area A D"4. The drag force ơn small spheres in air (l) 0.2 cm) sphere in air at V 12 m/s is to be predicted using experimental results for a larger sphere (D0.6 cm) in water. (a) What experimental water spced is required; (b) what will be the ratio of drag forces (Fwater/Fair) ? (c) for very small spheres it is known that Cp 24/Re . I is observed that two very small rain drops falling in air have a terminal spced ratio of V2V4. What would be the ratio of the rain drop diameters (D-/D) ? note: the terminal speed is reached when the drop weight cquals the drag force ; air buoyancy förce can be neglected. Approx ans: (a) Vw~ 0.3 m/s ; (b) Fw/Fa-4 ; (c) D21) I = 1.6

Answer 1