Coriolis Force or Coriolis Effect? 

One common example given to illustrate the Coriolis force is that of a ball propelled through the air a long distance in a straight line from the North Pole towards a target on the equator.  By the time the ball arrives at the equator, it will not land at its apparent target, because the earth will have rotated sufficiently underneath the moving ball so that it will land some distance away from the perceived target on the equator.  From the perspective of the person standing where the ball is “thrown,” the ball will appear to have curved.

In this case, there is no force acting to push the ball in a curved direction.  Instead, its motion will appear to be curved from the perspective of the ball-thrower because the frame of reference is moving underneath the ball.  This is why the Coriolis “force” is more appropriately called the Coriolis effect.  It refers to the apparent effect on the motion of an object passing over a rotating frame of reference when viewed from the perspective of the point of origin of that moving object.

Coriolis or “Inertial Mass” Flowmeters?

Instead of having a rotating frame of reference, Coriolis flowmeters work on the principle that the inertia created by fluid flowing through an oscillating tube causes the tube to twist in proportion to mass flowrate.  It seems pretty clear that what causes Coriolis tubes to twist is the inertia of the fluid flowing through them.   Furthermore, it is not clear what is added by labeling this inertial force a “Coriolis” force.

It may be that the example of the earth’s rotation, or that involving a ball thrown from the center of a merry-go-round, are useful analogies to help people grasp how Coriolis flowmeters work.  This does not make them scientifically correct, and in fact they may be misleading.  At the very least, Coriolis theory could use another look. It would be useful to understand what in addition to the effects of inertia makes them work.  While there is probably little hope that the name of the flowmeter will be changed, there appears to be an explanation gap here that needs to be filled.

We encourage you to comment! Please enter your comments below, which are emailed to Flow Research. After review, they will be posted back to this page. Thank you for your participation.

Thank you!

Flow Research, Inc.

27 Water Street

Wakefield, MA 01880

(781) 245-3200

(781) 224-7552 (fax)

info@flowresearch.com

www.flowresearch.com