Question

Fluid flows over a smooth cylinder. The diameter of the cylinder is D and the length normal to the flow direction is L. The drag coefficient is defined as: The drag coefficient is essentially constant with a value of 1.1 in the range of Reynolds numbers of 103 to 105. In this range, at a velocity of 2 m/s the drag force is 3 N. When the velocity is doubled to 4 m/s the drag force is:

Answer 1

Step-by-step explanation:

Given

Coefficient of drag
`C_d=1.1`

Reynolds number
`Re.no.=103 to 105`

velocity
`v=2 m/s`

`F_d=3 N`

if velocity if 2v i.e.
`4 m/s`

`F_d=(1)/(2)C_d\rho A v^2----1`

keeping other factors as constant

`F'_d=(1)/(2)C_d\rho A (2v)^2----2`

dividing 1 and 2

`(F_d)/(F'_d)=(v^2)/(2v^2)`

`F'_d=4F_d`

`F'_d=4* 3=12 N`