Modelling Spillage in Rotating Cutter Suction Heads

Modelling Spillage in Rotating Cutter Suction Heads: A combined Finite Volume and Discrete Element Model

Nieuwboer, B.J. (TU Delft Offshore and Dredging Engineering)

van Rhee, C. (promotor)
Keetels, G.H. (copromotor)

Delft University of Technology

2022-10-26

Due to an increased demand for transport, ships become larger, needing a larger navigable depth. For these reasons a waterway needs to be dredged and a Cutter Suction Dredger is a vessel suitable for this operation.

A Cutter Suction Dredger is a floating vessel which removes sand, clay or soft rock from sea or river beds. It has a cutter head with pickpoints attached to it. By rotating and swinging, the pickpoints are pushed into the soil, disintegrating it. The soil enters the cutter head where it is mixed with water. From inside the cutter head it is hydraulically transported to the vessel via the suction mouth and pipe. The rotational speed of the cutter head can be varied by the vessel operator. When increasing the rotational velocity and swing speed, more production can be obtained. However, this leads to an outflow of water and dredged material near the ring, spilling the soil.

When the Cutter Suction Dredger is employed for cutting sand, the sand particles are easily kept in suspension due to the rotating motion before it is sucked up. A cutter suction dredger is also used for cutting rock, leading to large pieces, which are more influenced by gravity and the centrifugal force. Due to these forces, the pieces are thrown out of the cutter head more easily than smaller sand particles. The pieces of rock which are thrown out of the cutter are considered spilled. This spillage is unfavourable since this material has to be dredged a second time or is left on the sea floor. When the material is left on the sea floor, a larger layer of soil needs to be dredged for creating the same navigable depth.

To reduce spillage, the processes contributing to spillage should be quantified in order to design a better cutter head or working method. This dissertation contributes to this goal by presenting a validated model for simulating the spillage of rock particles inside a rotating cutter head. Such a model can be used to quantify different processes and test new cutter head designs…

Dredging
Cutter Suction Dredger
Discrete Element Method
Computational Fluid Dynamics
Dynamic Mesh
OpenFOAM

https://doi.org/10.4233/uuid:ec0356e9-c264-4d1d-91b3-0a16ef13a348

978-94-6458-611-4

Institutional Repository

doctoral thesis

© 2022 B.J. Nieuwboer