IADC Young Author Award for 1DH Hopper Loading Model of Jordy Boone

Jordy Boone receives the IADC Young Author Award at the CEDA Dredging Days

OK, one last time we will revisit the CEDA Dredging Days. There was so much to see and experience, that there could be some more posts about them. However, daily life already demands more of my focus and there are fun facts to tell about them also. The conclusion of this series is about a well-deserved IADC award to Jordy Boone. Both, because he did write a terrific article and we will read more about it in the Terra et Aqua journal soon enough.

So, why was his article and presentation so special? Hopper loading is one of the key process components in the production cycle of a trailing suction hopper dredge. And therefore there is a lot of interest in this subject. Countless articles and numerous experiments have been performed on this topic, resulting in a lot of different hopper models. Traditionally a literature review starts with Camp (1936). And there are a lot of models that build on that approach. Camp and the derived models are similar to the Lagrangian approach, where they follow the trajectory of a single particle.

Basics and relations of Camp and derived models

A whole different approach is to follow Euler and fix the frame of reference. The contents of the system has to be modelled as a continuum. Ground breaking work has been done by van Rhee. He modelled the hopper in a 2D environment and based a more comprehensive 1DV model on that. Others have followed up and so does Jordy Boone.

Van Rhee and similar ‘Euler’ models

Other approaches don’t take any physics in their modelling, but consider the hopper as a process block in a control system. At the moment they are only useful for monitoring and controlling an existing system, they don’t have a predictive value, yet.

Control system models

In this overview, we can see, that the 1DH Boone model is part of the Euler family. Normally solving multi-dimensional 2D and 3D Euler problems tend to be slow. Van Rhee already pointed this out and part of his PhD. thesis was the presentation of a more comprehensive 1DV model. Basically a column cross-section through the hopper. Mixture would be deposited on the bed and water flows up and out of the system. Where that model does lack the influence of the density current, Boone literally upended this simplification by using horizontal strata in the hopper. Here, the mixture section can incorporate the horizontal density current conditions. This will give correct mass and momentum equations. Vertical exchange processes are than calculated by closure relations.

Comparison van Rhee and Boone

On top of the cake, Boone also verified his approach in laboratory experiments and prototype measurements. As his manuscript is also well written and accessible, he rightfully received the IADC Young Authors Award. Keep up the good work Jordy, we hope to see more interesting work from you.

Jordy Boone presenting his 1DH model at the CEDA Dredging Days

References

Camp T. R. (1936). ”A study of the rational design of settling tanks.” Sewage Works Journal 8(5), pp, 742-758

Miedema, S.A., Vlasblom, W. (1996). ”Theory of Hopper Sedimentation”. 29th Annual Texas A&M Dredging Seminar, New Orleans: WEDA

Van Rhee, C. (2002). ”On the sedimentation process in a Trailing Suction Hopper Dredger”. PhD thesis, TU Delft, the Netherlands

Braaksma, J., Klaassens, J. B., Babuska R., de Keizer, C.(2007). ”A computationally efficient model for predicting overflow mixture density in a hopper dredger”. Terra et Aqua, 106, pp. 16-25

Spearman, J. (2013) ”TASS Software – User Guide for TASS version 4.0”. HR Wallingford

Jensen, J.H., Saremi, S.(2014). ”Overflow concentration and sedimentation in hoppers” J. Waterw., Port, Coast. Ocean Eng., ASCE, 40

Konijn, B.J. (2016). ”Numerical simulation methods for dense-phase dredging flows”. PhD thesis, Universiteit Twente, the Netherlands

J. Boone, J, de Nijs, M.A.J., (2017) “1DH Modeling of Transport and Sedimentation Inside a Hopper of a Trailing Suction Dredger” CEDA Dredging Days 2017
Note: Not available online yet. Depending on publication by CEDA.

See also

Hopper Loading: What Happens Beneath the Surface

Overview of hopper loading models by Ben Sloof
Nice report with an overview of the various hopper loading models

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