Royal IHC said in its latest blog post that they have been working with the Technical University of Delft to develop new CFD (computational fluid dynamics) techniques to simulate different types of dragheads for the trailing suction hopper dredgers (TSHDs).
“This enables us to gain a detailed insight into the processes taking place inside it,” said Bram van Spaendonk, IHC Project Manager R&D.
“As a pioneering company for two-phase models – simulating soil and water – we focused on the influence of geometry, jet location and different soil types. This has led to a greater understanding of flow, pressure and density variations inside a draghead.”
“We evaluated the flow patterns of several excavating dragheads. This provided detailed information about the behavior of the flows and pressures inside a draghead and highlighted the optimum geometry, as well as how to minimize the flow resistance.”
Using CFD simulations, different jet water nozzle positions were evaluated. This was to determine the optimal placement in order to deliver high production rates and the most homogenos mixture in the draghead.
“In addition, modelling conducted in settings based on medium fine and fine sands, demonstrated that the jets penetrate deepest in medium fine soils. Visualizing the mixture flow allows us to optimize a draghead for a specific type of soil, resulting in optimal production levels,” added Bram van Spaendonk.
“With regards to maintenance, we are able to accurately identify spots within the draghead that will be most prone to wear. Using the CFD insights, the geometry of a draghead can be optimized or locally reinforced with wear resistant material.”
Innovating new concepts
To prove that CFD is an effective design tool, IHC used it to develop the new Mighty Dragon draghead for clay – a notoriously difficult soil type to excavate.
The subsequent smooth shape, combined with optimum jet nozzle locations, results in a draghead design that is optimized for dredging clay without blockage. There are no recirculation zones, which equates to less wear and a lower flow resistance.
Following promising laboratory tests, the first Mighty Dragon model was tested on a TSHD in operational conditions. It was able to dredge clay with a stiffness of 75kPa, without clogging, which could not be done before. It also demonstrated a better performance in silt and sand.
“Following on from this success, IHC is looking into other ways CFD can be used to further optimize and develop new designs. For us, CFD is becoming a crucial tool for researching and creating innovative dredging components and systems,” concluded Bram van Spaendonk.