Hydraulics Lab Southampton

374 ANIMAL EINSTEINS
Some of you may remember that in 2021 a BBC team was in our lab to do a small piece on our research on beaver dams. The fill programme is now available on dailymotion, our lab appears from 07:00 onwards

Chris Packham's Animal Einsteins episode 3 - video Dailymotion Chris Packham's Animal Einsteins episode 3: Finding somewhere to keep safe is one of the biggest challenges an animal faces. But some animals don’t have to find a safe place - they build one. In this episode, Chris reveals some of the best building animals in the world - a group that is incredibly...

373 WORK ON HEAT ENGINES
The work on the theory of the Newcomen Engine which we are doing in cooperation with Dr Brano Meres from the Althandel Civic Society was finally rewarded

Power Industries Division awards Gerald Muller and Branislav Meres for the 2023 Edwin Walker Prize The Power Industries Division have awarded Gerald Muller and Branislav Meres the 2023 Edwin Walker Prize for their paper on "Assessment of the Newcomen engine’s development potential as heat engine for low temperature waste heat”.

372 THE HYDRAULIC JUMP - WHY DOES IT BECOME STABLE FOR Fr = 4.5?
as you know, we are doing research on theoretical as well as on experimental hydraulics. Recently, we introduced a new concept into the classic momentum-balance analysis in hydraulic engineering: the use of the moments of the forces acting on a control volume to determine stability limits of breaking waves. This technique now allowed to investigate and explain the transition from an unsteady , oscillating hydraulic jump to a stable jump:
https://www.tandfonline.com/doi/full/10.1080/00221686.2025.2468952?src=exp-la
The paper is open access.

Theoretical model for the onset condition of a steady hydraulic jump A hydraulic jump constitutes a transition from supercritical to subcritical flow. At the jump a roller forms, the water level suddenly increases, the flow velocity reduces, and power is dissipated....

371 ARTICLE IN THE "GUARDIAN"
In today's edition of the Guardian, there is an article about waterwheels to which I had contributed.

How climate-friendly waterwheels are coming around again From the Himalayas and Nepal to Northern Ireland, sustainable source of energy seems to be back in vogue

370 1001 VIEWS
The article I published on simple theoretical models for the speed of propagation, and the breaking condition for a solitary wave has reached 1001 views only about 1 1/2 years after publication. For the IAHR Journal, this is quite a good number..

368 LINEAR WAVE THEORY
That’s the theory most widely used to describe water waves. It gives a sinusoidal shape of the wave, results in the orbital particle motion and we can determine the wave length L and speed vc from given parameters., i.e. wave period T, water depth d and height H.

However, for the average person the maths behind LWT is fairly complex, Laplace-equation, boundary conditions, differential equations etc. So the question was, can we use simple hydraulic principles such as momentum and continuity to analyse water waves? And surprisingly, the answer is “yes”.

From observations of e.g. foam specks on the surface of the ocean, we can see that the foam (or the fluid particles) move a bit forward with the crest, and a bit backwards with the trough. This is shown nicely in a video with a buoy https://lsintspl3.wgbh.org/en-us/lesson/buac20-int-waterwavemotion/1 and, in a more abstract way, in the first picture. This means, that the particle remains on average at the same place. Since it also moves up and down, it performs a 2D-motion. It rotates about an average position in x and y, Assuming that its velocity is constant, this path of motion must be a circle. From this conclusion, we can easily see that the surface profile must be sinusoidal, second picture.

Now we can progress to the momentum balance. Here we assume that the particle velocity has a maximum at the wave crest and reduces linearly – since we know the (a) the effect of the wave reduces with depth and (b) that the particle velocity ab the bed must be zero. We can then draw write the momentum balance, third picture.

With a further assumption for deep water, namely that the wave amplitude ‘a’ is very small compared with the water depth d, i.e. a

367 FOREST FIRE PREVENTION
There's once again a big discussion in Europe about forest fires / wild fires and what can be done about them. The discussion of course revolves around fire fighting, firemen, helicopters and aircraft etc. No one seems to be aware of the discussion in the US about the role of beaver dams in preventing, blocking or delaying fires and providing safe havens for animals. Seems very few people read "Scientific American" or "National Geographic". Here's a recent article from Scientific American with a nice photo at the beginning

Beaver Dams Help Wildfire-Ravaged Ecosystems Recover Long after Flames Subside Dams mop up debris that would otherwise kill fish and other downstream wildlife, new observations suggest

367 THE MAY NEWSLETTER
has finally arrived, with an editorial on education in hydraulic engineering

366 THE NEW NEWSLETTER
has finally arrived, with an editorial about .. oysters. Sorry about the long delay, and I hope that this year we will be publishing on a more regular basis

365 BEAVER DAM IN ALASKA
The picture shows an aerial view of a beaver dam in Alaska. A closer look indicates more interesting details. The beavers built a dam to raise the water level upstream. They then added a canal to a lower ground area, which they flooded to create a pond. Here they could build their lodge. So, with a comparatively short canal they created a rather large pond. This of course raises some questions regarding the cognitive abilities of our beavers. They must have realised that (a) the ground beside the river is lower than the increased water level in the river after dam construction, and (b) that the lower ground is surrounded by higher ground so that it retains the water and does not drain towards the river downstream.

Quite clever, really. This reminded me that MIT’s mascot is a beaver. However, I think they are too busy developing robots, AI etc so that they do not seem to look at what their mascots are doing. Well, here at least we are ahead…

Picture: University of Alaska

364 NEW PAPER "Two simple theoretical models for teaching wave mechanics in coastal engineering"

This is a short paper describing very simple models for the speed of propagation of a solitary wave and an I think rather novel approach for wave breaking. I intended the work for teaching, to avoid having to use either very complex maths or - more likely - simply the results of complex maths only, which does not support the understanding of the underlying principles. the paper is open access and available here:
https://doi.org/10.1080/00221686.2023.2235811