Hydraulics Lab Southampton

28/07/2026

378 BEAVER DAMS AND FOREST FIRES
In my Department, we just had a discussion about the large forest fires near Almeria / Spain, and Paris / France, reported in the news. It again occurred to me that the role of beavers, beaver dams and the wetlands they create regarding water retention and wildfire resilience seems to be largely overlooked in Europe. In the US and Canada on the other hand this is a topic which reached the popular science journals like National Geographic and the Scientific American as well as the news channels, e.g. CBC, have a look at these links

https://lnkd.in/ejpS46Yj

National Geographic
https://lnkd.in/erjtTpSQ

Scientific American
https://lnkd.in/eZKCWT7V

or the US Forest service
https://lnkd.in/eT_hhEgD

Seems to me that in Europe we can still do a lot of wildfire prevention rather than just look at fire management and fighting and wondering why this happens.
The picture shows the effect of beaver wetlands (courtesy of Emily Fairfax)

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27/07/2026

377 Shallow water wave speed of propagation and particle velocity:

well, this is for those who are also teaching wave mechanics. In my epxerience, and especially in introductory courses, we use the formulas from linear wave theory and especially the approximations for deep and shallow water without really thinking about how these formulas were derived. To make things easier, I am trying to develop these approximations from basic hydraulic concepts, e.g. momentum balance, which makes it easier to understand why the parameters are in this or that formula, how they interact and where these formulas actually come from. Since in our waves only energy travels, i also introduced an energy balance rather than a momentum balance for the analysis.

Anyway, here's a short 2.3 page long determination of the shallow water wave speed and the hor. particle velocity. feedback is welcome..

22/07/2026

376 SOLAR CHIMNEY GDP
In this year's 4th year Group Design Project (GDP) the students developed and designed a solar chimney power plant which also uses wind to generate power. The idea was that
1. Wind at the top of the tower ( 200 m above ground) is quite strong adn induces suction / upward air flow at the tower's top
2. Wind is strongest during winter, when the sun's intensity is lowest. Also, wind also blows at night.
3. Combining wind and solar in one installation can increase power output / cost/effectiveness.
The project confirmed and quantified it, including wind power generation wold nearly triple the annual power output with very small strucctural modifications necessary.
The students have to produce a project video as part of the module submuissions, so here it is...
I shoudl addd that we applied for a patent for the solution with the gate, his again demnstrates the quality of our student projects

21/07/2026

375 GROUND EFFECT
Soe of you may have heard about the groud effect: when an aircraft is close to the ground, wings and ground interact to create additional uplift. Here's a good demonstration of the ground effect with sail planes at the Red Bull Flugtag
https://www.facebook.com/reel/1031639745899155
you can see how the aircraft first drop down until the ground effect kicks in.. the record holder was clearly designed by aerodynamicists who knew what they wer doing, the negative winglets reinforce the effect..

20/04/2025

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: 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...

02/04/2025

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

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”.

28/03/2025

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.

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....

18/01/2025

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

From the Himalayas and Nepal to Northern Ireland, sustainable source of energy seems to be back in vogue

15/01/2025

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..

14/07/2024

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