Page 469 - Practical Design Ships and Floating Structures

444

7 CLOSURE
In an unusual procedure, dictated by short delivery time, a dredger design was verified by computations
rather than model tests. Thus the aims of the yard, viz. to obtain reasonable inflow for the propeller and
wake information for the propeller design, were achieved. In a very short period of time, calculation
results were made available so that a technical assessment was possible. This manner of hull
examination proved to be so fast that, while realizing the critical delivery time, a design alternative
could be investigated. Full scale trials with the vessel constructed according to the chosen design later
revealed a satisfactory performance in all critical aspects.

Meanwhile, similar computational analyses have been carried out with success for twin-screw dredgers
as well. Flow simulation for these hulls, which are based on the twin-gondola concept, is a challenge
for the numerical analysts, because of the complex geometry, and hence complex flow phenomena.
The next step will be to include the effects of restricted water depth.
References

Hoekstra, M. (1 999). Numerical simulation of ship stem flows with a space-marching Navier-Stokes
method. PhD thesis, Delft University of Technology, the Netherlands.

Hoekstra, M. and Eqa, L. (1998). PAFWASSOS: an efficient method for ship stem flow calculation. In
proceedings of 3rd Osaka Colloquium on Ship Viscous Flows, Osaka, Japan.

Valkhof, H.H., Hoekstra, M. & Andersen, J.E. (1998). Model tests and CFD in hull form optimization.
Transactions SNAME.