# Talk:Rossby number

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Changed inertial to acceleration because the Coriolis force is the only force in the Navier Stokes equations that can be called inertial. It is inertial because it can be eliminated as a force by a coordinate transformation to a nonrotating system with origin at the earth's center. The acceleration component of the Navier stokes equations is really the sum of all the other forces (both inertial and noninertial, i.e. a piece of the pressure gradient force that is not balanced by coriolis being the most important) that arise in the fluid.

Also removed fictitious as a description of the Coriolis force. The force is no more fictitious than the force of gravity. You can eliminate gravity by boosting to a freely falling frame, does that make it fictitious? No way. Coriolis force is felt and observed in a coordinate system tangent to the earth's surface rotating with the earth and thus is quite real. Calling the force fictitious makes it seem like there are frames of reference that are more "true" than others.

For people that are interested in this enough to read the discussion section, you should realize that a large Rossby number doesn't always mean you can neglect rotation (only very near the equator where models do in fact do that) but it always means you must include the acceleration term in the flow model. That is the annoying part since the acceleration is a sum of frictional stresses (sometimes neglected) and a piece of the pressure gradient force.

--Dba5 21:26, 16 August 2006 (UTC)dba

## WikiProject class rating

This article was automatically assessed because at least one WikiProject had rated the article as stub, and the rating on other projects was brought up to Stub class. BetacommandBot 10:03, 10 November 2007 (UTC)

## Coriolis force and bathtubs

It's been fairly conclusively shown that the Coriolis effect is completely negligible in the case of water draining from a bathtub, except under the most tightly controlled of circumstances. Similarly, while tornados do tend to rotate counterclockwise in the north and clockwise in the south, this is not directly attributable to the Coriolis effect. Any claims to the contrary would need to be sourced quite carefully. I've therefore reverted to an earlier version which does not include the discussion of these effects.

The mention of Einstein's hypothesis regarding van Baer's law is interesting, and it might be possible to add it back in, although I'm a little uncomfortable doing so myself unless I can find a clickable source.

J. Langton (talk) 14:14, 18 November 2013 (UTC)

## Centrifugal force?

This article mentions centrifugal force in a few places. I fail to see the relevance of this. Can anyone explain? Martin Hogbin (talk) 12:55, 27 August 2015 (UTC)

Also this, 'A dimensionless number relating the ratio of inertial to Coriolis forces for a given flow of a rotating fluid'. I can see what they are getting at but it is wrong as written because the Coriolis force is an inertial force. 'A dimensionless number relating the ratio of other inertial forces to Coriolis forces for a given flow of a rotating fluid' might be OK. Martin Hogbin (talk) 13:00, 27 August 2015 (UTC)