CEDA Dredging Days 2021: Sustainable Dredging And Innovation

Promotional banner of the CEDA Dredging Days 2021 (Credit: CEDA)
Promotional banner of the CEDA Dredging Days 2021 (Credit: CEDA)

Tomorrow, another event with a long tradition will start: the CEDA Dredging Days1. Due to the Covid issues, this time, it will be a virtual event, just as a lot of other regular happenings. Hopefully, it will be the last days of this dreadful period. I can’t wait to meet people again in real life. Back at the office, we are slowly starting to get back. But meetings with people far outside the regular circle were difficult. For instance, I was a member of the Technical Paper & Program Committee and the preparation was completely digital.

Home page of your CEDA Dredging Days on the Swapcard platform (Credit: CEDA)
Home page of your CEDA Dredging Days on the Swapcard platform (Credit: CEDA)

Now, the event itself is also digital. Of course, this is still not the real thing. Having a coffee and a chat in the lobby is a much more enjoyable experience than sitting in front of your screen. I have to say that with the Sawpcard platform2 selected by the organising committee, it is much easier to arrange your own program, adapted to your personal interests. Moreover, it will also facilitate meeting people with the same interest. In a sense, this might be an opportunity to approach those. In the real world, people will not get seated next to you when they have the same interest. And certainly don’t have them captioned on their chest.

Pump design workflow (inspired by Suman Sapkota)
Pump design workflow (inspired by Suman Sapkota)

As member of the TPPC, I had the opportunity of a sneak preview of the articles and presentations and I can guarantee there are a lot of interesting sessions. For starters, there are three presentations by my colleagues. Suman Sapkota will have presentation on his research in various novel methods to apply numerical research into the design of dredge pumps3. We are happy to share with you some experiences and insights on the Dredging Days.

Testing the non-radioactive density sensor
Testing the non-radioactive density sensor

Another presentation will be by Frank Bosman4. He has been active in the development of an instrument that will measure the mixture density, without using a radio-active source. This intelligent solution is not only more sustainable, but will also provide easier access to this information. If you don’t know the density, you are very likely to underperform with your dredge. He will present some experiences and data gathered on the performance of this system.

Example of recent electric DOP dredge family

Our last presentation will be by René Sens3. Less technical, but surely an interesting perspective on the future of dredging equipment. Everyone in the dredging community is aware of the necessity to change and adapt to a more sustainable approach of our dredging business. There is an urgency to reach the goals set by the UN to leave the world behind as a better place than we received it. Although usually an increase in size also increases the efficiency of a dredge, the UN goals look beyond that single parameter. With that in mind, small and medium size dredges will be far more interesting than at first sight.

Session 7: Young CEDA ask a CEO (Credit: CEDA)
Session 7: Young CEDA ask a CEO (Credit: CEDA)

There will be a lot more going on and I could produce a long list of other interesting presentations. I think you should also check out: Edwin de Hoog and Joep Goeree, Basel Yousef and Jeroen van Stappen, and if you really want to get academic: Janek Gundlach, Ebi Shahmirzadi and Arno Talmon. You can just add to your own list and see who also joins in in the audience. Other interesting sessions will be the student ‘Flash Talks’5 and the ‘Young CEDA ask a CEO’ session6 with Peter Berdovski and Kees van de Graaf. And I am very curious what the other working groups and commissions of CEDA have to present about their work.

Thursday evening is the big get together of the dredging community; meet you there! (Credit: CEDA)
Dredging Days as a they used to be: personal interaction (Credit: CEDA)

References

  1. CEDA Dredging Days 2021, CEDA
  2. CEDA Dredging Days 2021, Outsourced Events
  3. Session 5: Latest in dredging equipment and technology
  4. Session 2: Developments in modelling and measuring hydraulic transport, CEDA
  5. Session 8: Young CEDA Flash Talks
  6. Session 7: Young CEDA ask a CEO

See also

Dellewal Terschelling: Stunning Example Ancient Building With Nature

Panorama of the port of West Terschelling and constructed mudflat
Panorama of the port of West Terschelling and constructed mudflat

For most of us, the summer holiday is already long gone. So for me also. Still there is an observation I made that I want to share with you. We have been sailing on the Waddenzee1 this summer. Sailing, anchoring, mudflat hiking2, counting seals and other animals. One of the highlights was a visit to the island of Terschelling. A lot has changed since I was there last time with our boat. It must have been at least 30 years ago. At that time, we had to moor against the quay wall wherever one could find a spot. Now, there is a modern marine in the back of the port, specially made for yachts. Although stacking the boats next to each other is still the standard.

Port of West Terschelling and the new marina
Port of West Terschelling and the new marina

The new marina is more or less in the same area where we used to moor. From there you have an excellent view on a mudflat, that has been there been for ages3. When I was young, I couldn’t understand what its purpose was. Only that old fashioned Dutch flat bottomed boats were still allowed to anchor and stand dry. For us kids, it was an excellent place to muck about with our little dinghy and get dirty walking on the mudflat. We just enjoyed it was there. I still don’t know the exact name of the mudflat. I’ve seen it called ‘Dellewal’, although that seems to be just the quay side over there. Other names that I found on charts are ‘Oostelijk Ras’ and just ‘De Plaat’. Enjoying a nice sundowner and contemplating life and dredging in particular, I suddenly saw the purpose of the area: it works like a ‘Spuikom’4. I really don’t know how to translate this in English. So, let me explain what it is intended for.

Explanation on the working principle of a ‘Spuikom’
Explanation on the working principle of a ‘Spuikom’

Basically it is a part of the mudflat that is located at the south of Terschelling. About 85 ha in surface area, it is separated from the Waddenzee by a low dam. Just high enough to the high water level in the neap tides. The dam has an opening at the back of the harbour, near the marina. I Noticed that the water outside the marina was rushing by and the water inside was practically standing still. I figured out that the rushing tide was used to flush the old port. The huge surface area stores a lot of water that has to pass the quay in the port. Effectively increasing the flow velocity there and reducing sedimentation. This certainly helps in maintaining a navigable depth for marine traffic. Moreover, as each tide the area is filled from all around the dam and mostly emptied through the port, there is a resulting nett transport out of the port.

Hjulström diagram for particle transport in streams (Credit: Wikipedia)
Hjulström diagram for particle transport in streams (Credit: Wikipedia)

Voila, that is why the old islanders build those dams! Any other person would be satisfied with this plausible answer. Have pity on me, I can’t stop solving the riddles of the sands. Wouldn’t this be easier with a dredge? Apparently, near Terschelling, there is a sedimentation rate of 0.5 to 1 mm per year5, or about 600 m³ annually. With the dam, this has to be kept out of the port with the volume behind the dam. The average increase in flow is about 0.5 knots. According to the Hjuström diagram6, this will transport particles smaller than 10 mm out of the harbour. The stored volume has a potential energy as in a power dam of about 6.25 GJ. This is released twice each tide, resulting in a delivered power of 280 kW. Combined, this results in a specific transport power consumption of 4000 kW/m³/h. No contractor in his right mind will ever use a machine with such a performance. BUT: the energy is free and working flawlessly for at least 200 years. I still have to see a machine doing that. OK. We can step up the analysis even further. Drawing the 280kW continuously from the tide is eventually slowing down the rotation of the Earth. Just for those worried: each year, one day will be in the order of 10-19 seconds longer…

The moon decelerating earth’s rotation by tugging on the tides (Credit: NASA)
The moon decelerating earth’s rotation by tugging on the tides (Credit: NASA)

References

  1. Wadden Sea, Wikipedia
  2. Mudflat hiking, Wikipedia
  3. Landschapsvisie Baai Dellewal Terschelling, Feddes Olthof
  4. Spuikom, Wikipedia (Dutch))
  5. Slibsedimentatie in de kwelders van de Waddenzee, Arcadis
  6. Hjulström curve, Wikipedia

See also

Graduation Of Wim Kleermaker: Measuring And Predicting Wear In Impellers

Wim Kleermaker during the practical phase of his graduation in dredging
Wim Kleermaker during the practical phase of his graduation in dredging

Yesterday, Wim Kleermaker graduated at the TU Delft on a research project he conducted on our slurry test circuit at Damen Dredging Equipment. Specifically, he was investigating the wear behaviour in our dredge pumps. The noteworthy aspect of this project, was that Wim was supervised by our colleague Suman Sapkota. As long time readers in the audience might remember Suman was my own pupil some years ago1.

Example of a worn impeller at the Damen Dredging Experience
Example of a worn impeller at the Damen Dredging Experience

Wear is a very common process in the dredging industry and one of the main cost factors in a project2. It is beneficial to know the amount of wear to expect in a certain condition and be able to predict the budget to reserve for this nuisance. This is only possible when we as a manufacturer will be able to predict the wear rate and pattern can provide the information to the operator for his estimates. We do have historical data that will allow us to provide a ball park figure, but a more analytical approach might assist us in particular unusual cases. Furthermore, it will also provide us insight in the impact of certain design decisions for the wear performance of a certain pump design. For Wim’s graduation, he had to approach this academically: come up with a simulation model and verify this with measurements.

Damen dredge pump slurry test circuit on the outfitting quay in Nijkerk
Damen dredge pump slurry test circuit on the outfitting quay in Nijkerk

The measurements were done in our slurry pump test circuit. This circuit has been highlighted a couple of posts back3. For Wim’s experiments, he used an impeller under a certain operating condition and mixture properties. Before and after a representative period, the condition of the impeller was measured and the difference is a measure of the wear experienced.

CFD result for the wear experiments
CFD result for the wear experiments

Wear (or scientifically: erosion) is related to the impact of the particles on the material surface. In order to know the kinetic energy of the particles, the flow field has to be known. As the flow fleild cannot be measured directly at the test circuit, we have to resort to Computation Fluid Dynamics. We already know of Suman’s graduation, to look for patterns in the flow lines, but Wim has extended the procedure to also quantitively estimate the related erosion.

Comparing CFD results (l) with measured erosion (r)
Comparing CFD results (l) with measured erosion (r)

Although there is only a limited amount of data available, comparing the results of the CFD estimation and the measured erosion are looking promising. This is certainly a workflow that will provide us the unique tools for engineering better pumps and assisting customers in their specific projects.
Although Wim will not join our ranks in the dredging community and pursue a different career in another interesting industry, we are sure he will be constructive and dedicated colleague at Marin.

Another master and student fighting evil forces (Credit: Star Wars)
Another master and student fighting evil forces (Credit: Star Wars)

References

  1. Graduation Suman Sapkota: Where wear parts were worn down, Discover Dredging
  2. Wear parts, Discover Dredging
  3. Student Interviews On Their Projects With Our Dredge Pump Slurry Test Circuit In Damen Nieuws, Discover Dredging

See also