Learning Forum

[Karthik Remella]

How do you calculate the drag coefficient for an object?

[prajput]

You can calculate drag coefficient rearranging the drag equation. The three dimensional drag coefficient Cd is equal to

D/(0.5*rho*A*V^2)

for 2D problems it is Cd = D/(0.5*rho*L*V^2)

[Karthik Remella]

Thanks @prajput for your reply! Using this equation I am getting a value of 0.38. What does this mean? as in physically?

[prajput]

The drag coefficient is a dimensionless number that engineers use to evaluate the aerodynamic performance of an object in motion for example a flying airplane. It basically quantifies the drag force or resistance of the flow on the object. As mentioned in the previous post, it is proportional to the magnitude of drag force. So a lower drag coefficient indicates the object is subject to a smaller aerodynamic or hydrodynamic drag. 

[Karthik Remella]

So does it mean that having a lower drag coefficient is better?

[Keyur Kanade]

Yes! A low drag coefficient means that you can go faster or consume less fuel. However, higher drag coefficient it can be useful when you want to slow things down, like a parachute for drag races.