An instrument popular in the beverage industry is the target
flowmeter in Fig. A small flat disk is mounted
in the center of the pipe, supported by a strong but thin rod.
(a) Explain how the flowmeter works. (b) If the bending
moment M of the rod is measured at the wall, derive a formula
for the estimated velocity of the flow. (c) List a few
advantages and disadvantages of such an instrument.
(a)
Target flowmeters measures the flow, particularly measuring the amount of the force exerted by the fluid on the suspended target in the path of the flow stream.
The working principle of the target flowmeter is very familiar that the force exerted on the suspended target is proportional to the pressure drop across it.
When the fluid flows in the meter pipe and as it hits the target which is suspended in its path, the transmitter attached to the target (based on the calibration in accordance to the Bernoulli’s equation) shows the force it’s experiencing.
(b)
Provided that the bending moment on the wall is measured due to striking of fluid on the suspended target is M.
Consider the rod which is connecting the transmitter with the suspended target of length l. Now write the expression for the force experienced by the target suspended in fluid flow and multiply both side by length of the rod l.
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