Talk:Hydraulic jump

explanation could use some fixing up

The explanation section still needs to be improved. Also, I find the graph impossible to read; I can't tell what the labels on the x and y axis are. The text says there is a circle in the graph. Maybe it means a curve? --Coppertwig 18:56, 5 February 2007 (UTC)

I think if you write out an equation for the sum of kinetic and potential energy before and after the hydraulic jump, you get a cubic equation. I suppose one solution is not physically realizable (e.g. a negative number?) and that the two remaining solutions imply that the water can continue as it's going, or if it's going fast enough it can "jump" to one specific higher level and slower flow, but it can't take on any other values, for example it can't flow neatly at some level in between the lower and higher ones. This explains why there is a sudden jump like that. It would be good to find a textbook that runs through this explanation, reference it and put an explanation like this into the article. Here's a web page; I haven't had time to study it closely yet so I'm not sure if it explains this the way I'd like to see it: I think I get a simpler equation than theirs. I don't worry about viscosity or other complications, and I don't have a quadratic term in my cubic equation. It would be good to be able to reference a textbook with a simple explanation (as simple as a cubic equation can get :-) --Coppertwig 02:21, 7 February 2007 (UTC)

This comment refers to a version of the article from 19 years ago. It no longer seems to apply, as of April 2026. Fiske (talk) 12:12, 1 April 2026 (UTC)

I think there is a mistake in the article

In the section "Analysis of the hydraulic jump on a liquid surface" under subtitle "Height of the jump" i suspect that using Bernoulli's Principle will lead to the correct equation for the jump height.

I solve the equations manually according to the article and the ratio h1/h0 didn't show.

I am studying fluid dynamics using the book by Streeter,Wylie and Bedford and it show that apply the momentum equation and continuty lead to ratio h1/h0 (same as given in wikipedia) and by solving this equations manually the correct ratio h1/h0 is found.

So what i want to stress is that

1) Momentum equation not bernoulli principle lead to h1/h0 2) the ratio h1/h0 is correct in the article (only the method to arrive to it that is wrong) 3) Actually bernoulli equation (energy equation) is used in the book to find the losses in the jump

Thanks ShadySaad 17:26, 29 July 2007 (UTC)

As of March 2026, the Bernoulli equation is not mentioned in the article. Fiske (talk) 13:50, 30 March 2026 (UTC)

Picture 5

I think picture 5 is showing Roll-waves (e.g. http://www.math.ubc.ca/~njb/Research/rollo.htm) and not hydraulic jumps. The flow down spillway chutes is usually supercritical. Does someone knows the slope and discharge in the spillway on this picture?

I agree. The passage on cascades in the article should be revised or removed. Fiske (talk) 12:31, 1 April 2026 (UTC)

Removed cascade discussion. Fiske (talk) 14:08, 4 April 2026 (UTC)

Figure 7 Contains an error

The approach flow to the jump is not laminar. Will the author kindly correct this? Thanks, Steve Burges August 10, 2009 —Preceding unsigned comment added by 128.95.45.186 (talk) 00:16, 11 August 2009 (UTC)

As of March 2026, the figure numbering in the article is inconsistent. The seventh figure refers to an upstream region of laminar flow. It's certainly possible (and reported in literature) for the upstream flow to be laminar. In situations such as a dam, the upstream flow will certainly be turbulent. The figure, and its caption, can certainly be improved. Fiske (talk) 13:53, 30 March 2026 (UTC)

I removed that figure in the course of other edits. A new figure showing a control volume around the jump might be helpful. Fiske (talk) 12:10, 1 April 2026 (UTC)

I replaced that figure with a better one found in Wikimedia. Fiske (talk) 17:13, 2 April 2026 (UTC)

possible addition to "recreational" section

The current section on recreational uses of hydraulic jumps focus on natural phenomena. However, if I am understanding the article properly, man-made water parks use hydraulic jumps in their wave pools/tanks. My only experience is at the original Schlitterbahn in New Braunfels, Texas, which has a circular tank into which a large quantity of water is dumped periodically, generating waves for patrons to enjoy. Is this a hydraulic jump? If so, would someone with more knowledge than me please add it to the article? thank you 165.91.64.202 (talk) 04:27, 2 April 2010 (UTC)RKH

The current version (April 2026) includes a brief section on recreation at the bottom. The section could be expanded. Fiske (talk) 12:16, 1 April 2026 (UTC)

Revised text now includes mention of artificial whitewater parks and a link to the stand-alone article on artificial whitewater. Fiske (talk) 14:09, 4 April 2026 (UTC)

Merger from Hydraulic jumps in rectangular channels

I propose to merge Hydraulic jumps in rectangular channels into here. Since that article is mainly an essay written to satisfy some course requirements. And a hydraulic jump in a rectangular channel is the most basic type of hydraulic jump. -- Crowsnest (talk) 14:12, 11 November 2011 (UTC)

I very much agree. That page is redundant. Fiske (talk) 13:54, 30 March 2026 (UTC)

Basic physics error here

"some energy irreversibly lost through turbulence to heat" is impossible and in violation of basic laws of thermodynamics.

The sentence, in fact, says its not really lost but converted from kinetic energy to heat. Just semantics or poor wording, but should be changed, IMO. — Preceding unsigned comment added by 24.246.168.46 (talk) 03:50, 30 August 2012 (UTC)

Fixed! I am amazed that such a basic mistake stayed on the page for almost 14 years after this comment. Fiske (talk) 12:46, 30 March 2026 (UTC)

Another basic physics error here

The first formula is wrong, the delta needs to be removed. Furthermore, the article can be writtem much more clear. — Preceding unsigned comment added by Arnout.klinkenberg (talk • contribs) 14:05, 4 November 2012 (UTC)

This comment refers to a version of the article many years ago. The current page, as of April 2026, does not have the delta mentioned. Fiske (talk) 12:13, 1 April 2026 (UTC)

Assessment comment

The comment(s) below were originally left at Talk:Hydraulic jump/CommentsTalk:Hydraulic jump/Comments, and are posted here for posterity. Following several discussions in past years, these subpages are now deprecated. The comments may be irrelevant or outdated; if so, please feel free to remove this section.

=Hydraulic_jump&oldid=116005121Version reviewed. This is a fine start for the article. There are different words in engineering and mathematics which could be cleaned up and the maths is very poor. The explanations are a good start but this article needs Diagrams Maths with explanation Relationship to shock waves/tidal bores Rex the first talk | contribs 13:07, 18 March 2007 (UTC)

Last edited at 13:07, 18 March 2007 (UTC). Substituted at 18:34, 29 April 2016 (UTC)

This comment refers to a very old version of the article and does not seem relevant to the current text. Fiske (talk) 12:14, 1 April 2026 (UTC)

Kitchen sink image

The example of water in a kitchen sink was proven last year not to be caused by gravity, see https://www.thechemicalengineer.com/news/circular-hydraulic-jump-not-caused-by-gravity/ --86.12.160.194 (talk) 11:06, 8 April 2019 (UTC)

That's not quite correct. The role of surface tension and the Weber number was documented long before the article mentioned was published. Further, gravity is still operative when surface tension acts. Fiske (talk) 13:57, 30 March 2026 (UTC)

Expand/clarify "Atmospheric hydraulic jumps"

"Hydraulic jumps" are referenced and linked to in the explanation for the Diablo wind, but the only explanation of the atmospheric version is a simple acknowledgement that they can occur, as well as an example (the target of which, oddly, doesn't use this term).

There's also an allusion to their use by Gliders in Hydraulic_jump#Recreational -- but that page doesn't mention hydraulic waves, but Lee wave, which itself mentions hydraulic jumps, but doesn't link here (nor are Lee Waves linked to from here).

Given the complexity of the main discussion, it would be nice if this section was expanded enough for folks jumping in from how it affects winds across mountain tops, perhaps with a nice diagram? (It also isn't clear from why this is a sub-section within "Internal wave hydraulic jumps".)

Cross-linking with Lee Waves would also maybe be a good idea?

MrRedwood (talk) 22:06, 23 June 2019 (UTC)

I agree that some content on hydraulic jumps in stratified flows would be interesting. Fiske (talk) 17:49, 2 April 2026 (UTC)

Added cross-reference to lee waves and to stratified flow. Fiske (talk) 01:46, 4 April 2026 (UTC)

Have also added some discussion of the jump in the lee of the Sierra Nevada and added a link to the Diablo wind article in "See also". Fiske (talk) 14:12, 4 April 2026 (UTC)

Self-promotion of primary literature

Edits in 2018 by @Rajesh cambridge on "The hydraulic jump in a sink" appear to be promoting a paper that was written by the editor. I'm not enough of an expert in this field to appropriately edit the page, but I think this warrants review by someone more knowledgeable. Jevandezande (talk) 15:38, 21 November 2022 (UTC)

The 2018 paper has since been challenged in other publications. I suggest that this material be deleted, as it may not be ready to be included in an encyclopedia. Fiske (talk) 15:35, 30 March 2026 (UTC)

I have removed this passage, given that: a) it appears to be a conflict-of-interest addition; and b) the substance of the claim is disputed. Fiske (talk) 01:43, 4 April 2026 (UTC)

Image of rafting is not the best illustration of hydraulic jump

The current image of people in a green raft does not illustrate the hydraulic jump phenomenon very well. I suggest using an image more easily recognized, without a boat, such as a dam's spillway. Fiske (talk) 01:54, 30 March 2026 (UTC)

I have moved the kitchen sink image to replace the rafting photo because the kitchen sink is an everyday process that clearly shows the phenomenon. The rafting photo is now in the recreation section where it fits much better. Fiske (talk) 01:29, 31 March 2026 (UTC)