CFD helps to deliver bow thruster tunnel innovation
Sophisticated software applications are advancing our research and development techniques, and transforming the way we tackle design challenges.
This was evident in Royal IHC’s approach to creating innovative wing-shaped bow thruster tunnels for hopper dredgers SCHELDT RIVER and MINERVA.
A longstanding challenge
Cylindrical bow thruster tunnels – accommodating a circular propeller – commonly suffer a reduction in performance in ‘slow-forward’ conditions. For regular vessels, this is rarely an issue, since they only use bow thrusters for manoeuvring in harbours.
But trailing suction hopper dredgers use bow thrusters more often, and the reduction in power is a widely recognised issue across the dredging sector.
Acknowledging this, we started a research project to study the problem and asked a student to explore potential solutions.
Analysing the problem
Computational fluid dynamics (CFD) software was utilised to model the hull of a vessel with a bow thruster tunnel. The results enabled us to see the flows and understand the net side force generated.
From academic literature, we identified a hypothesis about alternative shapes for bow thruster tunnel openings. One suggestion was that a wing-shaped design could improve the hydrodynamic pressure around the tunnel opening and reduce the negative effects of the flows when the vessel has slow-forward speed.
CFD simulations were made and the results were compared to traditional round-shaped openings. The calculations overwhelmingly supported the wing-shaped opening, and this design was implemented in the SCHELDT RIVER and MINERVA.
Realising the potential
When these vessels underwent sea trials, we were able to test our conclusions. The data showed that a wing shape opening provides enhanced performance and results in a larger net side force generated by the bow thrusters in slow-forward conditions. Compared to a similar vessel, the SCHELDT RIVER showed significantly larger vessel rotation with the bow thrusters while the vessel was sailing.
This is a great example of how CFD is helping us to develop innovative solutions. What we achieved with it in just one year, would have been much tougher with traditional model testing.
Therefore, we could easily see model tests replaced by CFD when it comes to answering complex hydrodynamic questions and developing the innovations of the future.
Erik van der Blom
Innovation manager vessels
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