Talk:Secondary flow

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Lateral variations in current speed in river bends

Observations consistently show that current speeds in river bends are higher on the outside of the bend (concave bank) than on the inside of the bend (convex bank). (Also see "Point Bar") — Preceding unsigned comment added by 74.240.32.69 (talk) 05:53, 22 July 2012 (UTC)[reply]

What source are using to support your claim? In the absence of a reliabled published source Wikipedia regards statements like this as original research. The article does nominate a quotation and its source to support its statements on this matter. Edward J. Hickin, at Note 1, is quoted as writing In the absence of secondary flow, bend flow seeks to conserve angular momentum so that it tends to conform to that of a free vortex with high velocity at the smaller radius of the inner bank and lower velocity at the outer bank where radial acceleration is lower. Dolphin (t) 07:50, 22 July 2012 (UTC)[reply]

Bernoulli's principle

The article refers to Bernoulli's principle several times in relation to pressure difference in different parts of a vortex, but that only applies to points on the same streamline, which isn't the case in any of the examples used. I don't know whether the pressure differences mentioned actually exist in some of these cases or has been inferred from Bernoulli's principle, so I'm not sure whether just the references to Bernoulli's principle or the whole statements should be removed. 188.164.31.97 (talk) 12:30, 2 August 2016 (UTC)[reply]

It is true that Bernoulli's principle can be applied, with great accuracy, to all points on a streamline. It can also be applied with the same accuracy to all points on all streamlines in any region of irrotational flow. A free vortex is an example of irrotational flow and therefore the same Bernoulli constant applies along all streamlines that make up the vortex. Dolphin (t) 20:51, 2 August 2016 (UTC)[reply]

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Circular flow within a bowl or cup

Article says, "At any elevation within the water the pressure is a little greater near the perimeter of the bowl or cup where the water is a little deeper, than near the center. The water pressure is a little greater where the water speed is a little slower, and the pressure is a little less where the speed is faster". These two sentences contradict each other. The water pressure can't be both greater and less near the perimeter, where the speed is faster. Philgoetz (talk) 01:01, 8 May 2019 (UTC)[reply]

Hi Phil. I think the error in your reading of these sentences is that you are thinking the fastest water speed is at the perimeter. At the perimeter, the water speed is slowest, and the speed increases as we get closer to the center of the bowl or cup. This speed profile is called free vortex flow; think of the wind speed in a cyclone (hurricane, typhoon, etc) where the wind speed is catastrophically high near the centre (eye) of the cyclone, but decreasing as we move away from the centre. Dolphin (t) 05:47, 8 May 2019 (UTC)[reply]