The floating harbour transhipper: New-generation transhipment of bulk ore products

Bulk products such as iron ore and coal are usually shipped directly from shore facilities using large bulk carriers. This often involves significant cost due to major dredging operations, long jetties, large storage sheds and the acquisition of large tracts of coastal land. The costs of direct shore to an ocean-going export vessel (OGV) loading often run into billions of dollars – prohibitive for small- to medium-scale mining operations, particularly in remote regions with only distant access to deep water ports. The current industry standard for mitigating these issues is transhipping; the bulk cargo is transported from a smaller shore based facility to the export vessel moored in deep water by a small feeder vessel. Transhipment, while mitigating many of these issues, does introduce other concerns with respect to limiting seastate, environmentally harmful dust and potential spillage during materials transfer. The Australian company Sea Transport Corporation and the Australian Maritime College at the University of Tasmania are developing new technology for bulk ore transhipment: the floating harbour transhipper (FHT). The FHT is essentially a large floating warehouse with an aft well dock to support material transfer operations from the feeder vessel. The major advantages to the mining export industry are in the form of environmental and economic improvements, in some cases completely avoiding expensive dredging while minimising the environmentally invasive onshore infrastructure. In addition, the whole process is enclosed, therefore eliminating grab spillage and dust transport issues common to other transhipping methods. This paper presents an overview of the main hydrodynamic issues currently being investigated: primarily the interaction between multiple floating bodies close to one another in a seaway. The two primary ship-to-ship interactions that are being investigated are the effects experienced by the feeder vessel when it is docking or undocking within the FHT well dock and the interactions between the three vessels when operating in close proximity in an open seaway. A combination of physical scale model experiments and numerical techniques is employed, with a significant portion of the experimental program dedicated to the validation of the numerical simulation codes used to investigate the behaviour of the vessels. ShipMo3D is an object based library developed by DRDC for the purpose of analysing the seakeeping performance of vessels operating in a seaway in either the frequency or time domain. The capabilities of ShipMo3D are applied to this novel application in an attempt to provide realistic simulations of the interaction between the vessels of the FHT system. DualSPHysics, an open source Smoothed Particle Hydrodynamics (SPH) code, is being applied to the domain within the very restricted water environment of the FHT well dock to investigate the fluid flow behaviour and the effect that this has on the feeder vessel when entering/exiting.