That thing they were talking about in SD.
How about “vibrational mass flow meter”?
OK, how would this “vibrational” thing talked about in SD be quantified… If it is not Coriolis, then what? I’d like to be in on the ground floor of this innovation.
OK, I believe you that Coriolis meters do not handle bubbles in liquid well. I’m curious, do you know why?
I suppose it has something to do with the pressure difference between the center and outside of the loop (due to centripetal force), causing disruptions in flow (low-density bubbles wouldn’t want to go ‘downwards’ through the first, outward, leg of the loop). In which case, I think that if marbles were being moved by physically pushing them through the tube from the back side (as opposed to being suspended in a liquid moving because of a pressure differential), then a Coriolis meter should work. But I’ll accept that throwing marbles into a pressure-pumped liquid could cause problems.
Chronos, look at the wilkipedia page: it’s pretty clear that there is something rotating; it’s just rotating a short amount in one direction, then rotating back a short amount in the opposite direction. I think calling that “vibration” is a bit misleading, because ‘vibration’ kind of implies uncontrolled, generally non-rotating translation, driven by an initial displacement and then spring-like restoring forces. What’s actually happening is the loop is being actively rotated by a motor; again the thing is that the rotation is just through a small angle before reversing back through the same angle. “Oscillation” would be a better term than “vibration”.
But I think that there is a Coriolis effect going on, and Coriolis is a perfectly cromulent adjective for them.
FWIW, I concur. The rotation about the central pipe is minuscule, but non-zero.
More importantly, if you told me “this pipe vibrates, but when stuff is flowing through it, the vibration twists”, I wouldn’t get why that is. Maybe after some very careful analysis of the forces involved, i would finally figure it out.
But the (non-existent) rotating-pipe version pretty clearly works due to something attributable to the Coriolis effect, and I can kind of intuit it in that context. And I can kind of intuit how the (actual) vibrating-pipe version is similar to the rotating-pipe version, so i don’t mind calling that the Coriolis effect, too.
I agree, intuitively we can say this is caused by the Coriolis force. However, deductively we can explain this with the forces that act on the momentum vector of the water. Both can be said to be “correct”, just that one can be logically deduced and the other intuitively experienced.
“Fractional rotation” here means that the device does not rotate through a complete revolution before it reverses direction. Example, your windshield wipers undergo “fractional rotation.”
Maybe it’s better understood as torsional vibration (cf. linear vibration).
Micro Motion brand meters (what we use) are initially characterized by filling the tubes of the meter completely (no voids) with the process fluid to be measured, and “zeroing” the meter. This gives a baseline density upon which the meter operates from.
From this baseline, a narrow window of acceptable deviation in density, over time, is chosen. Any variance outside of these limits, caused by rapid density changes, E.g. bubbles, is interpreted as noise in the signal. We can set filters to smooth out some noise but, once the signal to noise ratio gets so high, the meter essentially stops functioning.
Hope that helps.
Harmonic flow meter
Sorry I neglected to mention in my last post concerning zeroing the meter… This process is done in a no-flow state.
Video demonstration of how a Coriolis flow meter works, using a large tube with visually obvious torsional vibration and phase shift between the two legs of the oscillating tube.
I think Machine Elf’s video shows behavior predicted by Coriolis effect nicely.
Now getting back to marbles, suppose you pilled a chain (or a frictionless rope) through that device. I posit the behavior would be similar.
Absolutely. I don’t dispute gogogopher’s assertion that a commercially manufactured Coriolis flow meter with strict accuracy specifications has difficulty measuring two-phase flow with acceptable accuracy, but the basic phenomenon would still be in effect: one tube leg has mass moving away from the axis of rotation, the other tube leg has mass moving toward the axis of rotation, and so there’s going to be a phase shift in the torsional vibration of one leg relative to the other.
What if there was a very thin but heavy chain which, at rest, sits in the exact centre of the pipe without touching the inside of the pipe (perhaps because it is suspended in a much less dense fluid that does)? Then I suspect the <whatever> effect would act on the chain independently from the pipe and whatever changes due to the chain moving would not be accurately transmitted to the pipe (and thereafter the sensors). The change in forces might cause the chain to take a different path through the pipe, but would only indirectly affect the pipe.
I suspect that with a multi-phase fluid passing through the pipe, the <whatever> effect acts to change the density configuration of the fluid first instead of accurately transmitting to the external pipe.
The lierature i have claims that a MFM handles bubbles far better than a volumetric meter.
I was doing this in relation to bunkering for ships …which is measured in mass not volume.
Straight off the bat we know volume is susceptible to temperature variations and density.
Also volumetric meters are knkwn to be cheated by cavitation bubbles.
Not to mention constant calaibration as mentioned eksewhere. Because MFM have no moving parts it is a closed system that is far harder to cheat.
But yes…super expensive…of the order of 200k $USD
Pursuant to the discussion way upthread re: residential water meters, mine is an oscillating-piston meter. description and animation can be found here, with many more animations/videos available on YouTube. Pretty simple: one moving part, and all you need is a magnetic pickup to count the number of oscillations of the piston, with each oscillation corresponding to a known quantity of water. The magnetic pickup can move a dial/counter, or it can be used to electronically tally water usage for remote measurement.
First thing I noticed is that the room is stationary, the only motion I see is the apparatus. Our camera frame does not show either the Coriolis force or any of it’s effects. We have to mount our camera on the apparatus so that the apparatus is stationary and the room rocks back and forth. Then the Coriolis force is obvious and it’s effects are clear seen.
In the video, we do not observe it.
This is what I have for my home’s water meter, exact copy, a few of my neighbors as well: {eBay listing} [My apologies for this bad link, no time to figure out problem … please go to eBay and search the term “Sensus iperl 12S3GGXX” … that seems specific enough to get there if there’s one to be found]
… $200 each … not bad compared to brand new impeller types with the reduced lead brass casings.