Hopper Loading: What Happens Beneath the Surface

Hopper loading in the sunset

Above is a typical view from the bridge of a trailing suction hopper dredge. I had to visit this dredge, because the operator had problems loading the hopper. As the valuable cargo of sand is always covered beneath a layer of water, they had no idea what the problem exactly was. Although the waterline was dangerously high, the delivered pile of sand on the quay was relatively small. After a couple of dredge cycles, measuring the loading curve and sounding the surface of the sand beneath the water layer, it dawned to me, there were in fact two problems. One, the dredged sediment was much heavier than the hopper density would allow. Two, the distribution in the hopper was not very efficient and on the return trip home, most of the sediment was washed out again. The first problem took some time to convince the owner, but finally the argument came through. The last problem was very difficult to imagine for them and as I had no proof or calculations to show them, they could not visualize the faulty loading process. Luckily, they accepted the proposed modifications and could make some profit again.

Ever since that incident, we were looking for some way to model the hopper loading more credibly with better visual reporting. Simultaneously, this could also improve our design and layout of our hopper dredgers. One of the best models we could use, were those by Van Rhee1, or by Miedema and Vlasblom2. As we have close contact with the Delft University of Technology, we asked them for a graduation project to improve these calculations. Eventually, Ben Sloof applied for the assignment and proposed a very interesting approach to solve this mystery.

Whereas the existing models rely on analytical models with at most a few well defined areas, Ben indicated, that there was also the possibility to address this with a regular CFD solver. He would have to modify the various components to work with particles in the fluid, but he was convinced he could pull it off. As this implies a lot of coding and knowledge of fluid dynamics, this was a tall order and certainly took some time. Now, he is almost ready to graduate. As this is a very interesting topic for everyone, he will take part in the Young CEDA pitch talks3 at the CEDA Dredging Days. His presentation on a ‘Re-engineered model to optimize the settling of material in the hopper’ will certainly be interesting to attend.

Concentration and Velocity

References

  1. Van Rhee hopper loading model
  2. Miedema & Vlasblom
  3. Young CEDA pitch talks

See also

Damen Standard TSHD

Damen MAD

Countdown to the CEDA Dredging Days 2017

Audience at CEDA Dredging Days 2015 (Credit: CEDA 2015)

One week from now, the CEDA Dredging Days 2017 will be held in Rotterdam1. This is THE event for the dredging industry to share the latest developments on a technical level. So far I’ve attended every single Dredging Days since 1993. None of them have been a disappointment. There is always something new to discover. Either a presentation with a novel development, or new people to meet or old acquaintances that share a new story on the latest work.

As this is the place to be for discoveries in dredging, I will start of my first serious posts with this event. It is for you to discover whether my personal interests will be exciting enough to read. I do hope you will be fascinated enough, that I may serve you as your personal reporter on site.

There are a lot of exciting items on the program and I can’t cover them all, but most interesting to me are:

  1. Technical visit to the Prinses Beatrix Lock expansion project2
  2. The presentation of the Checklist for Successful Dredging Management3
  3. Presentation Klaas Slager, A novel approach to determine dredge pump NPSHr in field conditions
  4. Presentation Ewout van Duursen, New approach of a double walled pump house
  5. Young CEDA Pitch Talk by Ben Sloof, CFD in hopper loading calculations
  6. Damen Booth at the Dredging Exhibition4

Each of them have a personal interest to me, one way or the other. As there is a lot to discuss about these items, I will cover them in their own posts over the course of the next weeks. Maybe interspersed with reports of noteworthy events as they happen.

So, I hope to see you on the CEDA Dredging Days, I will be at the Damen booth #15 on the Dredging Exhibition. Or you can come back and read my reports here.

Receiving a visitor at the Dredging Exhibition 2015 (Credit: CEDA 2015)

References

  1. CEDA Dredging Days 2017
  2. Technical visit
  3. Checklist for Successful Dredging Management
  4. Damen Booth at the Dredging Exhibition

See also

Discover Familiar Grounds in Dredging

Panorama of 17th century Utrecht by Joost Droochsloot
Utrecht, Joost Cornelisz Droochsloot, via Wikimedia Commons

Did you ever visit your home town? How many of you have been living in the same place, without even going to the local attractions that are advertised to lure tourists to your own city? I know I didn’t. I was brought up in a beautiful medieval city and never went into the city center to gaze at all the beautiful things that are there. Years later, I visited my city during a conference and we had a guided tour there in our program. That afternoon I discovered my own hometown again.
As our local expert in the dredging division, I took my colleagues on tours through the wonderful world of dredging. Most of them already well seasoned in dredging engineering, but sometimes unaware of hidden treasures of special knowledge that make dredges really work or how elegant some dredging solutions are executed. Helping them discover those details really helped them relate to the particular problem they were working on.
There are several ways to guide people through the intricacies of geophysics, fluid dynamics, and material sciences that are all part of dredging knowledge. I have been giving internal courses, writing academic papers, lectures. But also a lot of knowledge transfer happens in working groups, committees and at the coffee machine. I know even have a dredging experience center at my disposal to demonstrate those special phenomena hands on.

Overview of the Damen Dredging Experience
Overview of the Damen Dredging Experience

As our company expanded and we were also cooperating more with other divisions, the number of people that can be reached by these roads is limited. I started a journal of my discoveries through dredging, but this was not working well enough. Hence we were contemplating extending my reach by using the internet. So, my employer persuaded me to share my personal professional experiences with a wider audience. Both accessible to my colleagues and our customers alike.
Cue this website. This will be a platform to show you parts of dredging knowledge that you might be familiar with, but will be interesting to be discovered in a new perspective. You will find here explanations on geophysics, fluid dynamics and material sciences. But also hidden features of common dredging equipment. And some perspective on historical episodes, current events and future trends. Maybe even some personal touches or my own opinion.
I hope you will enjoy my stories and share them with anybody who has the same passion for dredging like you and me.

Kind regards,
Mark Winkelman

Mark Winkelman with VAMOS MV
Mark Winkelman posing with ¡VAMOS! Mining Vehicle