What Is the Reason for Tapering the Tube of Rotameter?

i know boss..i am just an instkid....

GA for good grace and sense of humor.

The taper keeps the ball from falling out the bottom of the tube.

Or,what Tornado said.

I don't think it has any glass tube, tapered or not...

Arhs-rotameter

It is a variable area flow instrument, it is the taper of the tube that makes the area vary proportional to the bob's position.

What does Bob's position have to do with anything? Is he in the picture in post #3?

A rotameter is also called as Venturimeter. Now what's this venturi.....hope, you are mechanical / civil engineer you would have studied it in Fluid Mechanics. Else, just google.

A differential pressure is created across the venturi and this will be the factor of flow rate across the flow meter. A non linear graduated scale and placed adjacent to the glass / acrylic tube rotameter in accordance to the flow rate generated across this venturi w.r.t., a standard reference flow meter or a practical method of calibration like flow through pipes.

Dear Mr.instman,

The Float weight and the kinetic energy of the moving fluid finds an equal force equilibrium and the float is standstill. For higher flow, the velocity will be more and hence kinetic energy is also more and push the float. If there is no taper, the float will be pushed to the top of the meter. The taper provides additional area for the flow of fluid.

The ascending taper will reduce the velocity and hence the kinetic energy of the fluid will reduce and strike a balance with the float's weight.

The taper provides additional flow area, where as the float has a constant area and the fluid column below the float provides the buyoncy.

DHAYANANDHAN.S