The Race is On

The America’s Cup (AC) race and the competitive sailing events leading up to it feature some of the most advanced sailing yachts on the water. The event is a digital engineering bonanza with engineering and simulation software playing a significant role in designing these vessels and also impact their performance.

Simulation, modeling and other technologies can be used to model and simulate the race and assist with designs competitors use. With effective simulation and modeling, designs may be tested and tried, with iterations, to arrive at a competitive design. This is particularly important, because teams are only allowed to build a single hull under current class rules.

The majority of the teams involved in the 37th America’s Cup have close partnerships with simulation software providers. INEOS Britannia uses Cadence Fidelity Fine Marine’s CFD software to model the hydrodynamics behavior of its boat, including lift and drag predictions, cavitation and ventilation. Luna Rossa Prada Pirelli works with ESTECO, leveraging its modeFRONTIER software to optimize simulation workflows.

Emirates Team New Zealand (ETNZ) has taken this a step further, establishing its own design subsidiary, Design Works, to apply its experience to designing commercial marine projects. The group includes several dozen designers and engineers across disciplines such as naval architecture, composite engineering, mechanical design, fluid dynamics, simulation development, optimization, mechatronics, software engineering, machine learning and AI.

Julien Chaussée is the technical manager for simulation and design support at Altair, which is the official computational science and artificial intelligence (AI) partner for the New York Yacht Club American Magic team. The team uses Altair’s CFD, structural analysis, data analytics and high-performance computing (HPC) technology to accelerate and simplify design processes.

Chaussée says that at the lowest level, one of the key benefits of simulation is being able to measure, visualize and understand aspects of the physical world that are not easily visible.

“Structural analysis [finite element analysis (FEA)] allows us to visualize stresses in a structure and understand how it breaks,” says Chaussée. “Computational fluid dynamics (CFD) allows us to understand the behavior of a fluid around any object, like a sailboat. It enables engineers to understand why a particular component breaks or why a given design performs better than another. And getting these insights is often faster than testing them in the real world.”

Chaussée explains that sailboats move in two different mediums at the same time: air and water. More importantly, air is propelling the yacht forward but also slowing it down. Because of this, designing an AC yacht is an extremely multiphysics problem, even more so than designing an aircraft or a car. It is hard to decouple all these aspects. So, the level of simulation required becomes complex very quickly.

“At the heart of any sailboat design office, you will usually find a velocity prediction program (VPP), a program that allows designers to assess the behavior of the yacht at a wide range of speeds, wind velocities and angles, and with different trimming of sails or weight distribution. From this data, engineers can determine at every point of sail (wind speed, angle, sail trim and yacht attitude), how to balance all the forces on the yacht to extract the most power possible and/or find the fastest route around a course,” Chaussée explains.

He adds that AC teams use very complex dynamic VPPs with a full 6 degrees of freedom motion. They include every aspect from weight and inertia to aero and hydrodynamic effects, flexing of the structure, sail shape and the controls the sailors have access to on the yacht.

“These complex tools tend to use low to midfidelity simulation tools for structural and CFD aspects, so they can run quickly (sometimes pretty much ‘live’ just like a simulator),” Chaussée explains. “But the low-fidelity methods are calibrated and bolstered by much higher fidelity solutions such as AcuSolve (CFD) and Optistruct or Radioss (structures).”

Applied Data Using Digital Tools

A key component of simulation and modeling is garnering sufficient data to carry out applications using such tools as CFD.

Ed Fontes is the vice president of development at COMSOL on America’s Cup and Simulation. Fontes emphasizes that to simulate the race itself, you need a great deal of data.

“This means that you also need to run a considerable amount of CFD simulations,” says Fontes. “To do this, you would probably use surrogate models trained on CFD simulation results and on the gathered data. During the race, lightning fast surrogate models can be used and incorporated into digital twins to compute, for example, optimum upwind performance given the real-time wind direction and speed and communicate this to the skipper. In the past, simulations of how a vessel performs under different conditions were validated with tank tests and wind tunnel tests during the design and optimization stages. Surrogate models trained using CFD simulations can now also use data from the race and, in this way, capture the real conditions during the race.”

Fontes says that after the race, the newly gathered data can be used to improve the vessel design, such as the design of the foils. One interesting approach to this process, he notes, is to couple CFD and structural mechanics, so-called fluid–structure interaction (FSI).

“These types of simulations account for the structural deformation of, for example, sails and foils due to the forces exerted by the wind and water flow around the boat,” says Fontes. “The deformation of these components also changes the path of the air and water around the boat, so the simulation would involve a two-way coupling, also called a multiphysics coupling. This interplay between different physics phenomena is important to understand in order to optimize the design of key components.”

Design Performance Using Multiple Tools

Using such tools as CFD and FEA is helpful when accommodating the dynamic loads and the applicable dynamics in a marine environment.

“One of the opportunities of the new digital era is a holistic exploration design incorporating hydrodynamic analysis in actual sea conditions, FEA and FSI,” says Dmitry Ponkratov, marine director for Siemens Digital Industries Software. “These components were previously disconnected. For example, the optimum hull form from a hydrodynamics point of view could not be the optimum form from a structural point of view. Combining these components in one design exploration space now gives naval architects a unique opportunity to push the optimization boundaries to their maximum. That’s why races like the America’s Cup become not only sailing competitions but technology competitions and we as an industry learn a lot from these events.”

Israr Kabir is the director for emerging technologies at the American Society of Mechanical Engineers (ASME). He notes that racing yachts must withstand tremendous dynamic loads from ocean waves and the forces generated by their powerful rigs (masts, sails, rigging, etc.).

“FEA empowers engineers to virtually test the boat’s structure under extreme conditions to identify potential weaknesses and optimize material distribution for optimal strength-to-weight ratio,” he says. “As in automotive racing, a lighter vehicle (or vessel) is faster, so FEA is also instrumental in achieving the ideal balance between lightweighting and structural integrity.”

Kabir adds that there are other niche simulation tools specifically used in racing yacht applications, including VPP. VPPs combine hydrodynamic and aerodynamic models to predict a boat’s performance in various wind and wave conditions. This modeling allows engineers to optimize boat designs for specific racecourses and weather scenarios.

Nick Goodall is the general manager, Ansys Business, LEAP Australia, Ansys Elite Channel Partner. Goodall says that multiphysics simulation has been a big focus in the 2021 and 2024 campaigns.

“Simulations have moved on from isolated assessment of the yacht’s aerodynamics or hydrodynamics to now focus on the combined effects of trim and sail deformation to confirm how the vessel will perform under specific sailing conditions,” says Goodall. “On the structural side, simulations are also critical for the yacht’s carbon composite components to make sure they are as light as possible and strong enough to withstand significant loads while sailing.”

Goodall adds that multiphysics simulation with Ansys is central to the ongoing structural and aerodynamic optimization that occurs continually at Emirates Team New Zealand (ETNZ). “With the evolution towards foiling craft, these yachts now fly at over 50 knots on a thin hydrofoil (daggerboard) elevating them out of the water,” he says. (You can read more about Ansys and ETNZ here.)

“As such, the most significant design and engineering challenges have moved from our previous concerns with minimizing the wave-induced drag on the hull, to focusing on the need to design structures that can handle the massive forces generated by the high apparent wind speed over the sails and to balance the overall design performance for both speed and controllability across a range of sailing conditions,” Goodall says.

“Through these countless simulations, we can accurately predict the performance of these incredible sailing machines, which gives us the basis to further optimize and develop our racing yacht continually throughout the [AC],” says Steve Collie, aerodynamics coordinator for ETNZ. “I fully expect to still be running simulations even in the last few days during racing in October, right down to the last race,” Collie says. “We’re continually trying to extract extra performance from all of our equipment and use simulation to get that extra edge.”

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