CFD Supports Greener Shipping

Environmental concerns are influencing a greater need for renewable and sustainable energy across the world with specialist technologies being at the forefront of new designs and solutions. As maritime industries begin to tackle climate change issues, ports and shipping companies are looking for carbon-free alternatives by testing potential solutions for vessels. The requirement to make a move toward greener shipping is imminent. As companies start to concentrate their efforts in developing efficient solutions for improving performance and reducing emissions, Cape Horn Engineering is applying its skills and expertise to support and contribute to the design of these advancements.

CFD (computational fluid dynamics) technology has become a crucial support for naval architects, yacht designers and design engineers to optimize designs for critical elements such as weight saving, performance predictions, reducing emissions and design optimization.

Using Specialist CFD Technology

Cape Horn Engineering’s expertise is used to optimize the design of racing yachts, sailing yachts, power boats, superyachts, commercial ships and renewable energy structures for clients around the world. It has been at the core of simulation-based America’s Cup and Ocean Racing design campaigns for over 15 years, always pushing the boundaries. Similarly, it has vast experience in ship hydrodynamics, having been involved in yacht and ship design using CFD for the last two decades. It specializes in high-fidelity RANS-based simulation techniques where accurate forces and moments are obtained for the given shape candidates and operating conditions. For all simulations, Cape Horn Engineering use one of the best commercial software packages available, Star-ccm+ from Siemens PLM, and has access to a large high-performance computing cluster on the cloud.

Its CFD methods cover a large variety of flow behaviors and includes free-surface flow, viscous flow, full-scale performance prediction, fluid-structure-interaction and dynamic behavior.

Wind Propulsion Technology

To address the problem of global commercial shipping, the introduction of WPT (wind propulsion technology) has been evaluated. According to some recent studies, wind-assisted ship propulsion using rigid wings, sails, kites, Magnus rotors or other novel devices on some specific vessel types such as bulk carriers and tankers has the potential of fuel savings and emission reductions around 10 to 30 percent. The IMO has recently acknowledged wind propulsion as one of the solutions for the shipping industry to meet decarbonization targets.

Cape Horn Engineering is supporting Windship Technology Ltd. in a solid wing power concept that is being developed by a consortium of key players in the global shipping industry that could revolutionize the way tomorrow’s vessels carry goods across the world’s oceans. The patented U.K. designed Windship rig system is a powerful fuel and emission saving wind system that will help the shipping industry move closer toward achieving reduction in emissions.

Cape Horn Engineering is running a CFD program to further improve the design of the solid wings. One focus is to provide a clearer, unbiased and more detailed analysis of the new technologies available. This allows interested parties to be confident in the investment of greener technology. The analytical evidence provided will give businesses a clearer understanding of the potential savings that can be realized with the implementation of the green propulsion systems.

Without significant mitigating action, it is projected that the global shipping industry could account for almost a fifth of carbon emissions by 2050. In order for the shipping industry to adopt these new technologies, accurate analysis of the potential savings and the results must be presented to all stakeholders involved. Improved simulation techniques are needed to optimize design and routing. Several factors need to be accounted for, including the aerodynamics of the thrust-producing devices, the vessel hydrodynamics, propellers and engine types, and the optimal routing.

CFD Simulations

Cape Horn Engineering ran an extensive CFD program to further improve the design of the solid wings. A multitude of wing assembly shape configurations were analyzed in varying wind conditions. In total, almost 1,000 high-fidelity CFD simulations were performed and analyzed. The simulations were used to set up force models needed to describe the vessel’s hydrodynamic and aerodynamic behavior. Operating conditions for the WPT devices are apparent wind angle and speed, wind shear and wind gradient (variation of wind speed and direction with height above the water surface), and angle of attack of the wings and its flaps.

A 2 digit percentage improvement in the aerodynamic performance of the wing assembly was obtained. Some selected simulation points were compared and validated with the wind tunnel testing, as well as with previous CFD analysis provided by Lloyd’s Register. Experts from the Wolfson Unit (University of Southampton) were also involved in the analysis of the CFD results. Extreme wind load cases were delivered to structural experts for assuring optimum weight and safety of the structures.

Further CFD design optimization in 2020 will take the Windship concept into consideration as a whole, including the ship hydrodynamics, engine and propulsion, aerodynamics, and optimal routing. The operating conditions for the vessel will include the advance speed and the drift, heel and rudder angles. Furthermore, windage on superstructures and the added resistance due to sea state will be modeled and taken into account.

When it comes to building a new ship, the design must be optimized to fit the wings on deck efficiently from both an operational and performance perspective. The design of hull features such as skegs or bilge keels might be required to balance the transversal instability induced by the installation of the WPT. Having a CFD model comprising both the hydrodynamic and aerodynamic artifacts of the design will allow highly targeted design optimizations.

Currently, wind propulsion systems and ship design are considered as two entities, hence, they are designed independently. It is reasonable to believe that they should be designed as a whole from the earliest stage, due to the dependency of each aspect on the other. The optimization process and predicted potential performance will determine the optimal operational points resulting in the lowest required engine power, fuel consumption and total emissions. The aim of the project is to facilitate the uptake of WPTs and enable the implementation of these technologies in the shortest time frame possible.

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