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Simulation software simplifies stress

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Design engineers are increasingly turning to simulation software to ensure they make the best choices. Tom Wilkie reports

It is a commonplace of modern industrial society that products are getting ‘smarter’ – and therefore more complex. Whether it be the eponymous smartphone or an oil drilling rig, many more functions and capabilities are being built-in – often, in the consumer market, more than the customer can actually make use of.

But before complexity and ‘smartness’ can be built-in, they need to be designed-in; and this is posing multiple challenges for the providers of computer-aided engineering (CAE) software. Where once individual aspects of physics could be evaluated sequentially – electronics and then structural mechanics for a phone; structural mechanics and fluid dynamics for an off-shore oil rig – now the demand is for multi-physics packages to do it all at once. And the people worrying about the antenna design of a smartphone need to talk to the people designing the case, yet they come from two different disciplines – can the software allow mechanical engineers and electronic engineers to talk together effectively, even if they are on different continents?

This trend to more complex, smarter products is a key driver for the software developers, according to Barry Christenson, director of product management at Ansys, which specialises in engineering simulation software. Products have electronics in them that they never had before, he remarked, citing the example of oil drill-bits. These sometimes go down two miles and it would be impracticable to use wires to communicate with the drill-bit, so they are equipped with an electronics package that sends a sonogram back to the surface for interpretation. ‘Twenty years ago you would not have thought of electronics in a drill bit,’ he said.

The point about such complex systems, he went on, is that they do not fail individually; they fail as a system. Thus it is no longer possible to optimise a system by optimising the individual components – the system has to be evaluated, and optimised, as a whole: ‘This creates complexity, and is one of the challenges that software developers must face and overcome.’

A second driver for innovation and development in CAE software is that engineering designers want their products to be more robust and to work over a wider range of conditions. Partly, this is because in today’s age of publicity, the failure of one consumer product will not result in just one disgruntled customer but will be tweeted or otherwise disseminated on social media, much more widely than before. Thus, he said, engineers will want to evaluate lots of different designs but it will be impracticable to build as many physically as they want to evaluate. The only solution is simulation, in his view. But, Christenson continued, simulation is nowadays being used not just to validate or troubleshoot a single design but to study hundreds of designs to make sure they are robust.

Complexity needs collaboration

Growth in demand was evident across all areas, he said, although there was particularly strong interest in simulating larger models, requiring access to more powerful computing power such as high-performance computing (HPC). ‘You can evaluate designs very quickly on a large cluster or network,’ he said.

Complex designs necessitate large design teams, with mixes of different scientific and engineering disciplines. One further aspect of modern engineering simulation software, according to Christenson, is that it should facilitate communication between these different people who may not be in the same office together or may not even be in the same country. Added to that, companies want to expand their in-house engineering resources by getting more people to use simulation software and take decisions which means that the creators of the software, such as Ansys, have to make it easier to use and more accessible. The key direction is to make it more ‘automatable’ so that people can customise their own workflows rather than making it ‘automatic’, which may be too restrictive.

For Esteco, the Italian-based company specialising in research and development of engineering software, an aircraft design project by Alenia Aermacchi exemplifies the benefits of a multiphyics, many-design evaluation. This study was performed in the framework of the Clean Sky Joint Technology Initiative, whose objective was to develop a new generation aircraft that generated less noise, particularly on take-off and landing, and had better fuel efficiency. One way to achieve this is to alter the profile of the wing, making it thinner – but there are counterbalancing drivers such as maintaining the structural integrity (and therefore safety) of the wing while reducing its weight, which would point to a thicker design. Any solution had to comply with the Top Level Aircraft Requirements (TLAR).

The problem is one of simulation and optimisation while dealing with the structural mechanics of the wing design and the fluid dynamics (CFD) of the airflow over it. Esteco’s design automation process, employing its ‘modeFrontier’ software, enabled 20,000 design profiles of the 2D wing shape to be evaluated, while taking account of aerodynamic and structural analysis via Alenia in-house software. After the optimal 2D profile had been selected, CFD computations were validated against a parametric Catia 3D wing-body. According to Enrica Marentino, CFD Specialist at Alenia Aermacchi, the process helped the design team to achieve a 2.5 per cent enhancement of aerodynamic performance at the same time as obtaining a four per cent reduction in the weight of the wing. ‘The optimised configurations, while still matching TLAR, determined substantial advantages compared to the initial wing profiles,’ she concluded.

Optimising train design

Energy consumption is equally a concern for modern railways and, just as in aero-engineering, can be accomplished by optimising the aerodynamic shape of the train. But there are conflicting constraints: the best models for drag do not have a good stability against crosswinds. In addition, trying to accommodate a lot of passengers also conflicts with optimal aerodynamic shape.

In an ideal world, form and function may 
go faultlessly hand in hand, but in the real world of trade-offs in engineering design, elegance and functionality do not always do so.

These were some of the challenges faced by Bombardier, the Canadian transport engineering company, in the development of Zefiro train, intended to be the world’s most economical and eco-friendly very high speed train, which can reach speeds of 380 km/hr. Bombardier used Esteco’s modeFrontier not only to integrate the various CAE tools that it was using but also to drive the geometry modification and simulation process, and to provide the necessary graphical tools for the statistical interpretation of results.

Bombardier’s engineers considered some 60 different design parameters in their models, including the train’s outer shell, the cab, behaviour in the event of a crash, and ergonomic constraints.

In the end, the company brought the aerodynamic resistance down by 20 per cent, thereby reducing energy consumption by about 10 per cent.