Flow in Tubes

A B C

3. Where is the pressure highest?

Fluid Flow

1. Where is the flow in kg/sec largest?

A, B, C? If the flow is the largest and the same in more than one place hold up more than one card. Same everywhere. Think of water instead of air. If more water entered A than B, where would the extra water go?

Bernoulli tells us the pressure is LOWEST where the flow

is fastest, in section B.

2. Where is the flow in fastest (m/s)? A, B, C? More than one place? B. If we have the same fluid passing through a smaller tube, it must flow faster.

Fluid Flow

Continuing the train of thought ….

Which way will the bottle move?

A. Toward the flow

B. Away from the flow

C. The bottle won’t move unless the flow points directly at it.

The pressure is lowest where the flow is fastest.

Low Pressure

High Pressure

constgyvP 2

21

Bernoulli:

Should keep in mind that this really applies to an incompressible fluid flowing smoothly in streamlines without friction.

Air is compressible, the flow in our demos includes friction, and there would be turbulence.

Yet qualitatively Bernoulli gives us the right answers even in these experiments.

Let’s look at one more.

Electronic Scale

Electronic Scale

Force will

A. Increase

B.Decrease

C.Stay the same

Vertical momentum of a chunk of air changes from mv to 0 if y positive down.

Vertical momentum of a chunk of air changes from mv to -mv if y positive down.

Very similar to the Australian and New Zealand ice rugby players. Not a Bernoulli equation problem!

Force of flowing fluid