# is the Coriolis Effect a mathematical principle? **URL:** \ **Category:** Factual Questions\ **Created:** [March 9, 2016, 10:55am UTC](https://boards.straightdope.com/t/is-the-coriolis-effect-a-mathematical-principle/748391 "2016-03-09T10:55:28Z")\ **Posts on this page:** 20\ **Page:** 3
**Author:** ![Ignotus](https://avatars.discourse-cdn.com/v4/letter/i/ecc23a/32.png) [@Ignotus](https://boards.straightdope.com/u/Ignotus)\ **Post date:** [March 11, 2016, 9:09pm UTC](https://boards.straightdope.com/t/is-the-coriolis-effect-a-mathematical-principle/748391/41 "2016-03-11T21:09:34Z")
> [@Leo\_Bloom](#): > > 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)? You think of the old idea of a perfectly stiff rod, which could transfer messages faster than light, simply by twisting it? (It’s more special relativity, by the way). ---
**Author:** ![Andy\_L](https://avatars.discourse-cdn.com/v4/letter/a/c67d28/32.png) [@Andy\_L](https://boards.straightdope.com/u/Andy_L)\ **Post date:** [March 11, 2016, 9:17pm UTC](https://boards.straightdope.com/t/is-the-coriolis-effect-a-mathematical-principle/748391/42 "2016-03-11T21:17:54Z")
> [@watchwolf49](#): > > 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? For the continuously rotating Coriolis mass flow meter, I’d say the twist we observe in the tubes is explained in the inertial frame as “the water is trying to flow straight, but the tubes are rotating, exerting a force on the water, so the water exerts an equal and opposite force that twists the tubes a bit” (in the rotating frame, of course, the answer is “There’s this Coriolis force that affects things moving towards or away from this special axis, so when the water moves that way the Coriolis force twists the water (and thus the tubes)”). ---
**Author:** ![LSLGuy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lslguy/32/5813_2.png) [@LSLGuy](https://boards.straightdope.com/u/LSLGuy)\ **Post date:** [March 11, 2016, 10:45pm UTC](https://boards.straightdope.com/t/is-the-coriolis-effect-a-mathematical-principle/748391/43 "2016-03-11T22:45:38Z")
> [@Andy\_L](#): > > For the continuously rotating Coriolis mass flow meter, I’d say the twist we observe in the tubes is explained in the inertial frame as “the water is trying to flow straight, but the tubes are rotating, exerting a force on the water, so the water exerts an equal and opposite force that twists the tubes a bit” (in the rotating frame, of course, the answer is “There’s this Coriolis force that affects things moving towards or away from this special axis, so when the water moves that way the Coriolis force twists the water (and thus the tubes)”). Exactly. ---
**Author:** ![ZurBob](https://avatars.discourse-cdn.com/v4/letter/z/71e660/32.png) [@ZurBob](https://boards.straightdope.com/u/ZurBob)\ **Post date:** [March 12, 2016, 5:58pm UTC](https://boards.straightdope.com/t/is-the-coriolis-effect-a-mathematical-principle/748391/44 "2016-03-12T17:58:10Z")
> [@Quercus](#): > > **Chronos** – > > snip\> > > 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). The technical difficulty of pumping a train of marbles is not the point, it’s understood we’re talking hypotheticals in this case. As I stated, Coriolis meters don’t handle gas entrainment (the void between the marbles) very well. In other words: Bubbles. Typically in process flows, these problematic bubbles are of the gaseous form, caused by pump cavitation, leaky seals, flashing of liquid to vapor in the pipes, etc. There is nothing to prevent a bubble from being composed of a liquid, E.g. water condensing out in a natural gas line. The point is, Coriolis meters don’t handle two phase measurement very well, and a train of marbles is a good example of a flow comprised of two phases… The marbles, and the medium they are being pumped in (be it air, water, argon, or acetone). In other words: Coriolis meters don’t play well with large aggregate slurries. Make the aggregate composition fine enough, say as in a magnesium hydroxide suspension in water, where the particle size is 20 microns, and they do just fine, because it “sees” but one component, acting in a homogeneous manner, at one density. They do flow, mass (and mass flow :rolleyes:) exceptionally well, but we often use them simply for flow, reasons being: They are dead nuts accurate, precise, and reliable. No moving parts. No impinging flow restrictions. No routine calibration (there is no calibration necessary, they come from the factory pre-calibrated) and they either work perfectly or they don’t work at all. Compared to all the other types of flowmeters we have to contend with; requiring constant calibration and otherwise constant fiddling with to keep them operational, Coriolis meters are a dream… Expensive, but worth it IMHO. ---
**Author:** ![ZurBob](https://avatars.discourse-cdn.com/v4/letter/z/71e660/32.png) [@ZurBob](https://boards.straightdope.com/u/ZurBob)\ **Post date:** [March 12, 2016, 6:32pm UTC](https://boards.straightdope.com/t/is-the-coriolis-effect-a-mathematical-principle/748391/45 "2016-03-12T18:32:43Z")
> [@LSLGuy](#): > > snip\> > 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. Exactly. In the old days, to get the stoichiometry in our reactors just so, required waiting on the lab …(tic-toc:eek:) then the calculations for the next charge were done based on their density analysis with fingers crossed that we didn’t loose the reaction (or worse). Now, our Coriolis meters do it all, instantaneously. ---
**Author:** ![ZurBob](https://avatars.discourse-cdn.com/v4/letter/z/71e660/32.png) [@ZurBob](https://boards.straightdope.com/u/ZurBob)\ **Post date:** [March 12, 2016, 7:18pm UTC](https://boards.straightdope.com/t/is-the-coriolis-effect-a-mathematical-principle/748391/46 "2016-03-12T19:18:11Z")
> [@watchwolf49](#): > > 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. Understood. I feel your pain as it relates to someone citing advertisements… I’ve been where you are now, and I reacted as you have. It was the best I could do, given the limited time that I’m willing to devote to this. However, the cites I provided weren’t THAT awful, I thought they were mildly instructive… Especially compared to the cites offered to the contrary (none). > [@watchwolf49](#): > > 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](http://sensus.com/products/iperl-north-america/). I too, live in a hick town, but you thought wrong. Coriolis meters do not live in residential water supplies, irrespective of one’s geographical location. Sorry. ---
**Author:** ![ZurBob](https://avatars.discourse-cdn.com/v4/letter/z/71e660/32.png) [@ZurBob](https://boards.straightdope.com/u/ZurBob)\ **Post date:** [March 12, 2016, 8:15pm UTC](https://boards.straightdope.com/t/is-the-coriolis-effect-a-mathematical-principle/748391/47 "2016-03-12T20:15:20Z")
To conclude my rant postings… It doesn’t bode well for my position that Coriolis meters are actually based upon the Coriolis effect, but… Many of you have convinced yourselves that there was/is some kind of Coriolis meter that has spinning, twirling, or otherwise… some kind of 360 degree rotating flowtubes in the CONVENTUIAL sense… This is not the case, nor was it ever, at least for the past 42 years. The rotating animations viewed online are merely an attempt to get one to perceive how the torsional flux in an oscillating tube (with flow going through it) relate to the Coriolis effect. Sorry if your perception of this “effect” doesn’t fit your limited definition of what is correct, but the fact is… It works. Maybe there is something going on here that you simply don’t understand. Fancy that! ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [March 12, 2016, 9:32pm UTC](https://boards.straightdope.com/t/is-the-coriolis-effect-a-mathematical-principle/748391/48 "2016-03-12T21:32:40Z")
Oh, I’m sure these devices exist, and work, and have all of the nice properties others are describing. I’m just saying that, whatever the principle is that they’re based on, it can’t be the Coriolis effect if there’s nothing rotating. ---
**Author:** ![watchwolf49](https://avatars.discourse-cdn.com/v4/letter/w/e9c0ed/32.png) [@watchwolf49](https://boards.straightdope.com/u/watchwolf49)\ **Post date:** [March 12, 2016, 10:34pm UTC](https://boards.straightdope.com/t/is-the-coriolis-effect-a-mathematical-principle/748391/49 "2016-03-12T22:34:20Z")
> [@Chronos](#): > > Oh, I’m sure these devices exist, and work, and have all of the nice properties others are describing. I’m just saying that, whatever the principle is that they’re based on, it can’t be the Coriolis effect if there’s nothing rotating. Specifically, we ourselves are not rotating … the principle involved has to based on something else. ---
**Author:** ![Blue\_Blistering\_Barnacle](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/blue_blistering_barnacle/32/3386_2.png) [@Blue\_Blistering\_Barnacle](https://boards.straightdope.com/u/Blue_Blistering_Barnacle)\ **Post date:** [March 12, 2016, 11:26pm UTC](https://boards.straightdope.com/t/is-the-coriolis-effect-a-mathematical-principle/748391/50 "2016-03-12T23:26:45Z")
If fictional centrifugal forces can manifest with fractional rotations, why can’t fictional Coriolis forces also manifest with fractional rotations? ---
**Author:** ![Trinopus](https://avatars.discourse-cdn.com/v4/letter/t/2bfe46/32.png) [@Trinopus](https://boards.straightdope.com/u/Trinopus)\ **Post date:** [March 13, 2016, 2:01am UTC](https://boards.straightdope.com/t/is-the-coriolis-effect-a-mathematical-principle/748391/51 "2016-03-13T02:01:41Z")
What is a “fractional rotation?” The rate of rotation can be very small – one revolution per year – or it can be quite high – a million revolutions per second. It’s a measurement of angular change. “Fractional rotation” doesn’t have any meaning. There is no Google cite for it. Both centrifugal and coriolis force will appear with any non-zero rate of rotation (although, in practice, it might be too small to detect. If you run eastward, you will weigh slightly less than if you run westward…but good luck observing that difference in real practice.) ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [March 13, 2016, 2:04am UTC](https://boards.straightdope.com/t/is-the-coriolis-effect-a-mathematical-principle/748391/52 "2016-03-13T02:04:41Z")
A fractional rotation is a rotation by an amount less than 2pi radians. Though I’m not clear that the devices even do that. ---
**Author:** ![leahcim](https://avatars.discourse-cdn.com/v4/letter/l/b4bc9f/32.png) [@leahcim](https://boards.straightdope.com/u/leahcim)\ **Post date:** [March 13, 2016, 2:20am UTC](https://boards.straightdope.com/t/is-the-coriolis-effect-a-mathematical-principle/748391/53 "2016-03-13T02:20:24Z")
> [@Chronos](#): > > A fractional rotation is a rotation by an amount less than 2pi radians. Though I’m not clear that the devices even do that. Clearly we are meant to model the vibrations as a small rotation in one direction, followed by a small rotation in the other over and over again, and imagine the Coriolis forces as switching between those that would be experienced by an apparatus rotating in one direction followed by those for the other direction. ---
**Author:** ![watchwolf49](https://avatars.discourse-cdn.com/v4/letter/w/e9c0ed/32.png) [@watchwolf49](https://boards.straightdope.com/u/watchwolf49)\ **Post date:** [March 13, 2016, 4:26am UTC](https://boards.straightdope.com/t/is-the-coriolis-effect-a-mathematical-principle/748391/54 "2016-03-13T04:26:27Z")
> [@Blue\_Blistering\_Barnacle](#): > > If fictional centrifugal forces can manifest with fractional rotations, why can’t fictional Coriolis forces also manifest with fractional rotations? I can’t tell you how glad I am that you brought up the centrifugal force. Let us consider the average centrifuge, As it spins, the centrifugal force is directed outward, providing the more massive particles with greater acceleration in the direction of the force than the less massive particles. So when the lab tech pulls out the sample, it’s graduated based on mass. He’s happy, and doesn’t care one bit the that mass was graduated the exact opposite of what Newton’s 2nd Law predicts. With our mass flow meters, the Coriolis force is of the right magnitude, who cares if it’s pointed the wrong direction, we still have an accurate mass measurement. In a centrifuge, the apparatus is applying a centripetal force due to the electromagnetic forces holding the apparatus in it’s solid state (very strong btw). This force is pointed inward provides the more massive particles _less_ acceleration than the less massive particles. Similarly, in our mass flow meter, it is the apparatus that is providing the force to accelerate the water. We know the amount of force, we measure the acceleration and quickly calculate mass. Unnecessary details … perhaps … but what is it we’ve been fighting since 1974? ---
**Author:** ![watchwolf49](https://avatars.discourse-cdn.com/v4/letter/w/e9c0ed/32.png) [@watchwolf49](https://boards.straightdope.com/u/watchwolf49)\ **Post date:** [March 13, 2016, 4:32am UTC](https://boards.straightdope.com/t/is-the-coriolis-effect-a-mathematical-principle/748391/55 "2016-03-13T04:32:17Z")
> [@leahcim](#): > > Clearly we are meant to model the vibrations as a small rotation in one direction, followed by a small rotation in the other over and over again, and imagine the Coriolis forces as switching between those that would be experienced by an apparatus rotating in one direction followed by those for the other direction. It’s a rotation with an oscillating torque. The inlet and outlet pipes define our axis of rotation. ---
**Author:** ![ZurBob](https://avatars.discourse-cdn.com/v4/letter/z/71e660/32.png) [@ZurBob](https://boards.straightdope.com/u/ZurBob)\ **Post date:** [March 13, 2016, 7:34pm UTC](https://boards.straightdope.com/t/is-the-coriolis-effect-a-mathematical-principle/748391/56 "2016-03-13T19:34:30Z")
It’s good to see this conversation has maintained legs, despite early (and continued) foot stomping. This is a very difficult concept to visualize. Apologies to the OP because this thread was, to some degree, hijacked. Hope your presentation went well. ---
**Author:** ![ZurBob](https://avatars.discourse-cdn.com/v4/letter/z/71e660/32.png) [@ZurBob](https://boards.straightdope.com/u/ZurBob)\ **Post date:** [March 13, 2016, 8:23pm UTC](https://boards.straightdope.com/t/is-the-coriolis-effect-a-mathematical-principle/748391/57 "2016-03-13T20:23:58Z")
Sort of like envisioning a single point on an automobile tire rotating in two dimensions… Graphically, it would be depicted as a sine wave… No 360 degree rotation there. But combine that sine with a third dimensional perspective, and viola! 360 degree rotation. Similarly, envision the tubes in a Coriolis meter that are excited by the drive coils. Keep in mind: They do not oscillate in a PLANAR fashion, they oscillate in an ARC at rest… (TWO dimensional at zero flow). Combine this with the torsional twist in a FLOW condition (the third dimension over time) and you have 360 degrees of physical rotation relative to the pick up head. Or so as it has been explained to me by factory reps… Anyone have anything more believable? ---
**Author:** ![Andy\_L](https://avatars.discourse-cdn.com/v4/letter/a/c67d28/32.png) [@Andy\_L](https://boards.straightdope.com/u/Andy_L)\ **Post date:** [March 13, 2016, 9:22pm UTC](https://boards.straightdope.com/t/is-the-coriolis-effect-a-mathematical-principle/748391/58 "2016-03-13T21:22:26Z")
> [@watchwolf49](#): > > I can’t tell you how glad I am that you brought up the centrifugal force. Let us consider the average centrifuge, As it spins, the centrifugal force is directed outward, providing the more massive particles with greater acceleration in the direction of the force than the less massive particles. So when the lab tech pulls out the sample, it’s graduated based on mass. He’s happy, and doesn’t care one bit the that mass was graduated the exact opposite of what Newton’s 2nd Law predicts. Mass settles out in the same way in an ordinary gravitational field as it does in a centrifuge - with the denser material at the bottom; it just takes longer in ordinary gravity. Newton’s laws still work; it’s just that less dense material experiences more fluid resistance (less density means more mass per unit surface area), so the less dense material falls more slowly, whether in ordinary gravity or in a centrifuge. At least that’s how I think it works - it’s just like dropping a handful of feathers and sand in an atmosphere; the sand will hit the ground first, separating from the feathers it was originally mixed with. ---
**Author:** ![EastUmpqua](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/eastumpqua/32/6025_2.png) [@EastUmpqua](https://boards.straightdope.com/u/EastUmpqua)\ **Post date:** [March 13, 2016, 9:54pm UTC](https://boards.straightdope.com/t/is-the-coriolis-effect-a-mathematical-principle/748391/59 "2016-03-13T21:54:08Z")
> [@Chronos](#): > > Oh, I’m sure these devices exist, and work, and have all of the nice properties others are describing. I’m just saying that, whatever the principle is that they’re based on, it can’t be the Coriolis effect if there’s nothing rotating. In Atmospheric Science, the Coriolis force is used to compensate for a rotating spherical reference frame. It’s a cool name for an interesting flow meter, but it could have a more accurate name. ---
**Author:** ![ZurBob](https://avatars.discourse-cdn.com/v4/letter/z/71e660/32.png) [@ZurBob](https://boards.straightdope.com/u/ZurBob)\ **Post date:** [March 13, 2016, 10:56pm UTC](https://boards.straightdope.com/t/is-the-coriolis-effect-a-mathematical-principle/748391/60 "2016-03-13T22:56:03Z")
> [@EastUmpqua](#): > > In Atmospheric Science, the Coriolis force is used to compensate for a rotating spherical reference frame. It’s a cool name for an interesting flow meter, but it could have a more accurate name. Such as? [Previous page](https://boards.straightdope.com/t/is-the-coriolis-effect-a-mathematical-principle/748391.md?page=2) [Next page](https://boards.straightdope.com/t/is-the-coriolis-effect-a-mathematical-principle/748391.md?page=4)