JEC COMPOSITES MAGAZINE - Issue #73 - June 2012 - 56

design
for designers. When designing a particular component, the choices are often only limited by the development budget or the designer’s creative imagination. Classical “by-the-book” approaches to structural design do not work for high-performance, lightweight concepts. Prescriptive rules are often too inflexible, especially for advanced composite elements. In addition, it is necessary today to give due attention to the recycling properties of composite materials, besides their strength aspects (see Figures 3 and 4).

Fig. 1: Exhaust gas. CFD simulation of smoke dispersion

be accounted for during the initial design stages. The simulation tools to support low-noise design are currently being expanded to also include underwater noise, an aspect that receives growing attention in the megayacht industry.

Fig. 3: Stern of a megayacht. Original design (left) and modified design for reduced slamming impact (right); slamming pressures were reduced by almost 30%

Increasing design freedom
Several projects illustrate how advanced simulation-based design methods increase design freedom for shipyards and owners. The lightweight design of the record-breaking trimaran “Earthrace” was only made possible by using sophisticated CFD simulation for the load and subsequent finite-element analyses of the composite hull structure. ln another pioneering project, the solar catamaran “Tûranor PlanetSolar”, the obtainable speed in waves – a crucial parameter for the first circumnavigation of the world by a solar-powered vessel – was predicted as early as the conceptual design stage. Another example is the largest megayacht of its time, which sets new standards in terms of size and speed. ln all these cases, highly innovative designs were implemented based on high-performance simulation of both hydrodynamic and structural behaviour (see Figure 2). Composite materials are increasingly used in high-performance vessels, including megayachts. It is the combination of low weight, high strength and mouldability that makes these materials attractive

Fig. 4: Composites. Structural analyses of the trimaran “LAMU III”

Achieving better designs in less time
Using CFD simulation to develop the hull lines of high-performance yachts has been standard procedure for years. Formal optimisation, however, is a relatively new field of application. CFD simulation may improve the required power (and associated weight). Alternatively, the gain in efficiency may be used to increase the speed of the boat at the given installed power. Optimisation requires considerable computer resources due to the complex flow patterns and the enormous number of design alternatives to be investigated. However, in our experience, the effort is justified by the good results obtained, and CFD simulation is quickly becoming a standard tool in high-performance yacht design (see Figure 5). Simulations are similarly useful when designing propellers, waterjets, rudders and other appendages. On fast ships especially, these components are frequently affected by cavitation issues. Unfortunately, problems often remain undetected until the ship undergoes sea trials or has been in operation for some time. Even then, simulation can guide efficient troubleshooting and redesigning, but avoiding cavitation-related problems in

Fig. 2: “Tûranor Planetsolar”. The obtainable speed in waves was predicted during the conceptual design stage

56 jec composites magazine / No73 June 2012

JEC COMPOSITES MAGAZINE - Issue #73 - June 2012

Table of Contents for the Digital Edition of JEC COMPOSITES MAGAZINE - Issue #73 - June 2012