Venturi Metter - Conceptual Question

[FutureEnginr]

I am working on a lab, and *think* I understand what is going on, but looking for a double check of my logic from someone more experience than I am.

In short its a multi-piezometric tube venturi meter, with 1 throat near the begining, a couple of expansions, and a control valve near the end. We took measurements at the various tubes, and I am trying to summarize the data qualitatively.

The 9 piezometric tubes on the pipe are setup as follows: (points A - H)

A) 26mm diameter pipe (13mm in front of the constriction, 25mm long)
B) 16mm throat (16 mm long as well)
C) 26mm pipe that comes after a gradually increasing pipe diameter
D) 51mm pipe that comes after a sharper increasing pipe diameter (totall diffuser = 89mm)
E) A control valve in the 55mm pipe
F) A straight 51 mm pipe section
G) A continued straight 51 mm pipe
H) The end of the meter (still 51 mm diameter pipe, total pipe length = 130 mm)

Here is my understanding is regarding the data we took
(sorry about the formatting, but hopefully you can understand my notes):

(flows) Q (l/s) A(mm) B(mm) C(mm) D(mm) E(mm) F(mm) G(mm) H(mm) I(mm)
flow 1 .18 370mm 332mm 360mm 356mm 360mm 318mm 324mm 322mm 222mm
flow 2 .24 330mm 274mm 320mm 316mm 324mm 254mm 262mm 260mm 160mm
flow 3 .28 370mm 284mm 350mm 346mm 354mm 260mm 272mm 270mm 168mm

Here is what I think happens as water flows through the meter...

'A' p builds due to upcoming constriction
'B' v increases, p drops as water is 'sucked' along
'C' p returns to almost state 'A' (losses occur)
'D' slight drop in p as area increases slightly
'E' p builds in front of valve obstruction
'F' p drops a little after passing valve
'G' p continues to drop as near opening
'H' p still dropping
'I' at end, p as close to 0 as possible (within this system).

Am I on the right track?

Thanks.

 

[Carid]

Sounds pretty reasonable.

I am not any sort of expert in this matter, but did you try to compare the average pressures you found to the radius, cross-sectional area, or volume of the various pipe-sections to detect any relationship?

 

[nlightner]

As a scientist, it is always important to double check your understanding and data interpretations. From the information provided, it seems like you have a good understanding of the setup and the data collected. Your notes on the changes in pressure at each point are correct, and it is clear that the venturi meter is causing a drop in pressure as the water flows through it. However, it is important to also consider other factors such as the velocity of the water and the changes in pipe diameter. It would be helpful to also include these factors in your analysis to get a more complete understanding of what is happening in the system. Additionally, it would be helpful to compare your data to theoretical calculations or previous studies on similar venturi meters to validate your findings. Overall, it seems like you have a good grasp on the concept and your analysis is on the right track. Keep up the good work!