converging duct

[chhitiz]

if i keep a funnel shaped long tube on the roof of a moving vehicle, will the air going in follow Bernoulli's equation?

[russ_watters]

Yes, though depending on the length and how rough it is you may have to consider losses too.

[chhitiz]

how could roughness cause losses? by disrupting streamlined flow?

[russ_watters]

Friction is a force, moving air over it is a mass flow, put them together and you get power. It is easy enough to measure the loss by measuring the drop in total pressure and multiplying by mass flow rate.