is the Coriolis Effect a mathematical principle?

Factual Questions
21

Beg to differ… What YOU say is just wrong. In an effort to explain, I offer a few cites:
http://videos.emersonprocess.com/detail/video/4579439030001/theory-of-coriolis?autoStart=true&page=1&q=micro motion
and Siemens FC430 Coriolis Meter - How it Works - YouTube
(sorry if there is any redundancy from previous links). Follow the suggested videos from there for even more info.
Any cite you may provide that these meters are not in fact, based upon the Coriolis effect, is eagerly anticipated.

You must live in an affluent water district. A Coriolis meter is a very expensive (emphasis on VERY) option for a municipal water supplier. FYI: “drive by” meter reading is not Coriolis dependent… Any type of flow meter can be remote enabled.

Why not mention Coriolis? (See above reply to Chronos).
BTW: A train of marbles would not work in a Coriolis meter… Gas entrainment (around the void between the marbles) in the flow stream would wreak havoc, (as it would in most other types of meters).

No, it is not a gimmick. It sounds no more “brainier” than other descriptors, such as Delta differential pressure, Magnetic flux differential, K-factor harmonics, etc, etc, etc.

With the exception of your statement: “This set-up is impractical for the typical home water meter” which seems to be in conflict with your previous statement that your water meter IS of the Coriolis design (as suspect as that may be)… I have no concept of what it is that you are trying to put forth in the balance of your post.

I am not a Physicist, nor am I an Engineer or Mathematician, yet I can grasp the Coriolis flow meter concept, even though it is different from the traditional Earth rotation/atmospheric perspective that most seem to adhere to as the gold standard of legitimacy. However: I encourage any or all of you to contact the Engineers at Micro Motion (Emerson), Endress Hauser, Siemens, et al, and express your concerns that they don’t understand what they are doing, and that the concept of a Coriolis flowmeter is a mere misnomer, sic gimmick.

If you would be so kind, please report back here with resulting cites, not opinions.

22

The “twist” IS dependent on the flow rate/density… However, twist is not measured directly.

Flow is measured as a relationship to the difference between a null harmonic shift generated by the drive coils at zero (in a no flow condition) as compared to the phase shift experienced during a flow… Detected by a pick up head (receiver). Density is derived by comparing said flow to the frequency differential compared to the previously mentioned no flow (zero) condition.

Hope this helps.

23

For what it is worth, when watchwolf49 made that statement, I never imagined he was talking about his home water meter. I was imagining that he worked at some engineering site with lots of vats and pipes and stuff, and the “here” he was referring to was his workplace.

24

OK, let’s make this simple. Is there, or is there not, something rotating in your device? And I mean actual rotation, not just “vibration that simulates rotation”, whatever that is. If there is not, then it is not based on the Coriolis effect.

25

I imagine (although I can’t find much online about the history of the device) that it got its name from a fully-rotating meter like the one illustrated here, and kept it even when it was converted to the vibrating type.

26

Apparently there is a type of Coriolis mass flow meter with continuously rotating tubes.. This definitely looks like the Coriolis effect to me.

The vibrating pipe design seems to use the same exact principle, so I think it’s fair to say it is using the Coriolis effect that happens during each period of rotation.

27

Chronos– look at the Wikipedia article. Yes, there is real rotation. I believe the ‘vibration’ is essentially rotation that is changing direction very quickly (millisecond clockwise, millisecond counter-clockwise, repeat). Pretty clever.

Are you talking about difficulties with pumping marbles in general, or something specific to a Coriolis meter? Because I can’t see why, assuming the marbles (or BBs or sand/mud slurry or whatever) are indeed flowing, a Coriolis meter wouldn’t work.

And in fact, I’m not sure why anyone would want a mass flow meter specifically (instead of a volumetric flow meter) unless what’s flowing has significantly varying density (e.g. slurry).

28

From that article:

So I don’t think there are actual production examples of the continuously-rotating design, it’s just there to illustrate how the operating principle relates to the Coriolis effect.

I imagine that a fully rotating design would need some more complex seals at the ends of the rotating bit and be more failure-prone.

29

On the other hand, the wobbling design seems to introduce a new level of complexity with regard to angular acceleration. So the original Coriolis’ formula wouldn’t really work.

30

It can work “instantaneously” :slight_smile: . I figure it reduces to “there is some fluid-momentum-dependent torque on the pipe that affects the phase of vibration” and then the calibrate the fuck out of it to characterize the instrument. The real “engineering” bit is eliminating the sources of noise and error.

31

I’m at a loss, though, to see how this complicated design could be any better at measuring a flowing liquid than a simple turbine or water wheel.

32

I can’t say it’s obvious to me either, but presumably there are some fluids that are valuable and volatile enough to make it worthwhile, or else these companies would stop making these.

I can see how some fluids might corrode any moving parts at all. Also the fact that it measures mass flow instead of volume flow might be useful for compressible fluids, or to compensate for temperature changes.

33

No actual moving parts. No seals to leak. Nothing impeding the flow.

For measuring things in many process operations mass flow is what matters. We don’t really care how many cubic feet of carbon & oxygen go into our reactor to create CO2. But we sure care that we get the mass ratio correct so we have 1 mole of C to 1 mole of O2.

34

It would be nice if you could provide a credible cite that they are. These two are advertising copy and can hardly be expected to explain why these meters are based on the Coriolis force. The first only says it is … and the second gave a 10 second explanation. [more on this below]

Just a small hick rural town, I thought they were fairly common for home water meters. Check your own, are you sure that’s an impeller meter? Maybe not, we just completely replaced our water treatment plant, so maybe there was money left over to buy these cheap-o iPerls.

I apologize for not linking to the animations I was implicitly referencing, these are found on the Wikipedia article “Mass flow meter”. So what I’m saying it that the principle of operation is simpler to describe using the top two animation, a pipe rotating. The same principles are in effect for the vibrating system in the bottom two animations, except for two instants per cycle when the system is stationary. It every other instant, the motion is identical to that of the rotating system.

The rest of that post of mine talks about how energy is imparted and withdrawn from the water, and the amount of energy depends on the mass of the water, with everything else the same.

Just a comment about the Coriolis force, and I’m referring to the second video in GoGoGophers post I’m quoting. In the first case, the camera is stationary to the environment, it has no motion. We observe the marble’s motion as having constant velocity and can correctly say there are no forces acting on it as it rolls across the spinning plate. In the second case our camera is in rotational motion, and what the camera captures is the sum of the motions of it and the marble. The marble appears to have an acceleration to the right as though a force was acting on it. However, we know there are no forces acting on the marble, and we know we’re observing the sum of the forces, therefore what we are observing is the force acting on the camera.

The Coriolis force cannot be observed from stationary frame of reference, yet mass flow meters work just fine … the explanation of how they work must not include forces that are not observed.

35

It must be possible to explain how they work without referring to inertial forces, but that doesn’t mean that it is wrong to switch to the rotating frame and use the inertial forces in your description.

Another example of such a device that “relies on inertial forces” is a centrifugal governor. Its operation can be described in the non-rotating frame in terms of forces exerted by the arms on the weights and gravity, but it is more simply described in the rotating frame in terms of gravity and the centrifugal force. Neither description is wrong, but one is more convenient than the other.

36

The net effect of a turbine is dependent on the mass flow, though, as the impulse depends on the momentum. And it could be essentially free-flowing; only supported by two rods of the same (inert) material; and with a contained magnet which could be sensed from the exterior of the pipe.
On the other hand, a bending pipe would experience a lot of stress forces, and probably give or crack in a short time.

37

I agree 100% … we can explain what we observe without referring to inertial forces … the problem is we cannot explain this in an inertial frame of reference with the Coriolis force, it just doesn’t even appear.

Whatever description must conserve energy, and this is best demonstrated in the inertial frame.

38

I don’t understand your point.
The Coriolis force appears very clearly in the rotating frame of reference. As the fluid moves ‘outward’ through the pipe, it is pushed sideways into the pipe, requiring the pipe to exert an opposing force (in the direction of rotation); this happens in opposite when the fluid moves ‘inward’. The sideways push is the Coriolis force.

I’m not sure what you’re trying to say about conservation of energy; the energy to twist the loop against the spring forces of the pipe comes from whatever power source rotates the loop.

39

Bolding mine

I agree the Coriolis force appears in a rotating frame of reference, and it appears exclusively in that frame. Therefore, any effect this causes can only be observed in a rotating frame of reference. Here’s where the mischief comes in as far as I’m concerned, if we say this is caused by the Coriolis force, then we also say it cannot be observed to work in an inertial frame of reference.

So the question is how to explain what we observe when Coriolis force isn’t there?

40

This. To me, a layman, interested in epistemology of physics.

Don’t post-GR scientists come up on this type of question all the time? And not get all bent out of shape (although the “bending” going on here and in this very query is of the essence)?