This paper presents an application of linear and nonlinear analyses to the turning ability of a towing system consisting of a tug and a barge. The influence of several parameters is examined on the turning performance of the towing system. Longer towline, larger tug and tow point nearer to the bow of the barge increase the turning diameter. Tow point on the tug closer to its centre of gravity decreases the turning diameter significantly.

This paper proposes a numerical model for course stability of a towed ship coupled to tow ship through towline using both nonlinear and linear approaches. Captive model tests were conducted at the towing tank to obtain hydrodynamic derivatives of both tow and towed ships. Effects of unstable towed ship (2B) and stable towed ship (2Bs), towline, tow points and rudder autopilot parameters at tow ship were treated in the numerical analysis. The simulation results demonstrated better course stability of 2Bs compared to 2B. A longer towline and shifting the tow point towards the bow both for 2B and 2Bs made the towing system more course stable, which is indicated through attenuation in slewing motion. Lateral motion of the tow ship increased gradually with shifting the tow point forward of the ship’s centre of gravity. This degrades the course stability of the towing system. The rudder action enforced by the autopilot improved the course stability. In general, the increase of the tow ship’s dimension was still insufficient to improve the course stability of the ship towing system.

The paper presents a two-stage approach for ship design optimisation under uncertainties related to stochastic parameters that cannot be controlled by the designer. The designer decision is partitioned into two sets: the first contains variables that have to be decided before the onset of any uncertain condition, while the second involves variables that may be decided once the random events have occurred. The first-stage variables are selected so that the sum of the first-stage cost and the expectation of the second-stage cost is minimised. The problem is solved as a two-nested-loop minimisation problem, which combines robustness of the first-stage decision with flexibility of the second-stage decision. The approach is applied to the conceptual optimisation of a bulk carrier.

Ships feature superstructures and components with steps, recesses and styling surfaces that lead to flow separation. A favourable air flow becomes a design criterion, particularly for mega-yachts and cruise ferries. For instance, exhaust gases should be kept from passengers and crew. This paper shows how Computer Aided Design (CAD) and Computational Fluid Dynamics (CFD) can be coupled for aerodynamic design. An example of a mega-yacht is studied. Systematic refinements were undertaken to clarify the levels of detail necessary for resolving geometry and fluid domain. Subsequently, the funnel was optimised in order to improve emissions.

Large Eddy Simulation is employed for the investigation of the wake instability of a submarine propeller in open water conditions. The time-resolved velocity and pressure fields are computed in the near wake where the instability occurs. The study focuses in particular on the analysis of complete time series of the flow velocity at the probes in the wake. The results are compared with Laser Doppler Velocimetry measurements.

The paper introduces a technique by which the hull girder shear forces and bending moments can be minimised, based on the equality of the moments of higher order of the weight and buoyancy forces. Cargo hold weights determined on the basis of these equalities can be shown to result to minimum bending moments and shear forces. The proposal is illustrated in the simplified case of a barge and a 24000 tdw bulk carrier.

The present paper provides a brief introduction to the holistic approach to ship design, defines the generic ship design optimization problem and demonstrates its solution by use of advanced optimization techniques. A set of software tools for the parametric design and evaluation of ROPAX vessels has been developed and linked to a multi-objective optimization software, to form an integrated ship-design methodology, facilitating the design space exploration and selection of optimal designs in a rational and efficient way, Zaraphonitis et al. (2007). The present paper focuses on the optimization of design of conventional ROPAX vessels. For an application to high-speed, twin hull vessels, see Skoupas et al. (2009).

This paper describes the background of the seakeeping code GL RANKINE. The code determines motions and loads of ships in seaways. The zero-order (steady) potential due to steady ship motion is completely considered. The seakeeping contributions are considered up to first order, i.e. for the contributions depending linearly on wave amplitude. Results are validated for a modern container ship.