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Gemma Church investigates how simulation and modelling is changing to meet the needs of the aerospace industry

 

Credit: Dassault Systèmes

Aerospace is transforming to meet the current innovation and sustainability mandates, and today’s simulation tools are helping engineers design the aircraft of tomorrow. But in an industry entrenched in regulation and with notoriously long lead times, digital change has not always been easy to realise.

'Historically, simulation tools have lagged behind the market requirement, often playing catch up to address new trends and technologies,' according to Paul Lethbridge, director of product marketing at SimScale. 

But this is no longer the case, according to Lethbridge, who added: 'Modern agile software development methods and the shift away from on-premises applications to ‘always releasing’ cloud-based simulation tools have significantly compressed this lag time.'

However, aerospace companies still face a number of challenges in both the tools and processes used in the industry. Information silos and vendor lock-in make information sharing difficult, next-generation vehicles and advancing electrification increase design complexity, and decarbonisation targets are putting engineers under mounting pressure.

Now, couple these challenges with geopolitical pressure to innovate faster and cheaper and you might wonder how the aerospace industry ever manages to get any new design ideas off the ground. 

Roel Van De Velde, vice president for aerospace at Esteco, explained: 'A twenty-year wait time for the next-generation fighter that’s massively over budget will no longer be accepted. Governments are expecting a significant increase in the use of modern digital engineering tools, so that they can buy with confidence and protect their freedom and democracies.'

This is where simulation and modelling can help, as Van De Velde added: 'Solving these problems may seem daunting at first, but a big step in the right direction would be to use domain-specific simulation tools that can be integrated and automated in a modern, all-encompassing framework for multidisciplinary design optimisation and simulation process data management (SPDM). 

'This will allow you to easily conduct trade studies and find the optimal design by collaborating, not only internally between different departments, but also externally between prime and supplier, or prime and customer for example.'

Digital twins are increasingly used to connect the dots, providing engineers with a way to use simulation and modelling across the design and development lifecycle. 

Aziz Tahiri, vice president of global aerospace and defence for Hexagon’s Manufacturing Intelligence division, said: 'We are seeing exciting new developments in the use of digital twins in the industry, which marry the virtual and the real to optimise design. They are virtual representations of physical entities that can be tested, prototyped and iterated at very low running costs and with high degrees of accuracy.'

Software vendors are also helping to further break down these developmental silos, with many pushing for interoperability. 

Altair, for example, open-sourced a powerful matrix-based computational engine called OpenMatrix, which supports tool-independent standards, including Functional Mock-up Interface, and ensures its tools natively support and integrate with open-source languages, such as Modelica and Python. 

'The goal here is to have better and more open interactions within the community and drive innovation faster together,' according to Blaise Cole, senior technical account manager at Altair, who added: 'The idea of having a single source of truth, or the ability to track a model/product from conception to production to in-service lifecycle, is proving to be a very large enterprise-wide challenge that many aerospace firms are focusing on.'

Hexagon is also focused on open innovation, as Tahiri explained: 'We offer solutions across design, quality inspection and production; our design tools are not ‘locked’ – an engineer can use our tools in combination with other solutions, but we can also be that partner that supports across the full workflow.'

Hexagon’s recently-launched Nexus platform, for example, 'is designed to enable more dynamic collaboration across teams so that aerospace manufacturers can streamline their processes from design to production,' Tahiri added.

These are just two examples – interoperability appears to be a watchword for software vendors working in the aerospace industry. 

But it’s not just design processes that need to be connected across the development lifecycle. Aerodynamic simulations are increasingly required to cover the entire flight envelope and this requires a rethink of establishing simulation methods. 

One example are computational fluid dynamics (CFD) simulations. Swen Noelting, SIMULIA aerospace industry process director at Dassault Systèmes, explained: 'CFD has been used in the aerospace industry for several decades to characterise the aerodynamic behaviour, helping to dramatically reduce drag and improve the overall aerodynamic performance of modern aircraft.’

However, traditional CFD tools cannot accurately capture the aerodynamic behaviour. 'These configurations still require months-long wind tunnel and flight tests. There is a strong demand to expand CFD capabilities to accurately capture the aerodynamic behaviour in the entire flight envelope,' Noelting added.

To achieve this, SIMULIA PowerFLOW CFD technology is gaining acceptance in the aerospace industry, according to Noelting, 'because of its ability to simulate regions of turbulent and separated flow accurately, which is required to capture aircraft behaviour at the edges of the flight envelope.'

Structural simulations are seeing similar changes, according to Noelting. 'Aerospace customers demand a complete and fully integrated process to ensure the structural integrity of an aircraft. This includes the calculation of internal loads of the entire aircraft based on aerodynamic databases, weights and inertia calculations, which are continuously updated as the aircraft design evolves, as well as detailed simulations of the strength, stiffness and durability at the component level.'

The aerospace industry is also using simulation to help develop next-generation aircraft and systems, including advanced propulsion systems, novel aircraft architectures and urban air mobility (UAM) solutions with the corresponding development of electric vertical take-off and landing (eVTOL) vehicles.

But UAM solutions and eVTOL vehicles are presenting new challenges for aerospace engineers, as Noelting explained: 'This segment faces numerous challenging problems – ensuring the safety of the novel aircraft designs, reducing noise to acceptable levels for surrounding communities, improving battery technology and safely integrating them into the aircraft structure, developing electric drives, and ensuring connectivity to enable autonomous operation in crowded urban airspaces.'

This is where a multiphysics approach can help. Yamaha Motor, for example, recently used Hexagon’s MSC Nastran to lead the design and development of unmanned helicopters for residential areas, incorporating acoustic fluid–structure  co-simulation practices into their workflows. 

By combining MSC Nastran with Hexagon’s Cradle CFD fluid dynamics and Actran acoustic simulation software, these multiphysics solutions provided 'new opportunities to innovate by ensuring that Yamaha Motor had the comprehensive suite of digital tools required to develop a range of business scenarios for unmanned helicopters and investigate those scenarios using an upstream to downstream design process,' according to Tahiri.

Changing climates

While modifications to traditional aircraft are continuing to push today’s development lifecycles and simulation tools; sustainability is also affecting the aerospace industry.

'As we’re seeing globally, the aviation industry has a huge amount of pressure to move quickly towards a cleaner, more reliable, and affordable future – all in a bid to help tackle climate change,' Mariano Morales, EMEA senior manager of technical account management, A&D and industrial equipment at Ansys, explained.

Of course, cleaner air travel is a multifaceted problem with an array of solutions under investigation. 

Hydrogen, for example, is being considered as an energy source for medium- to long-haul flights, which account for 90 per cent of air traffic CO2 emissions. 'But using hydrogen as a primary source of energy requires a rethink of deep storage infrastructures,' according to Morales.

Morales explained: 'Hydrogen burns ten times faster than jet fuel, takes up four times the volume of jet fuel, and gets much hotter than a standard jet engine today. These challenges require simulations of advanced materials, storage systems, coatings and cooling systems. Structural and fluid flow simulations must also be run to understand how to store the liquid hydrogen and metre its flow into the system.'

This has sparked research into simulating complex, chemical reaction systems with ammonia, including the vaporisation of liquid ammonia inside heat exchange tubes, heat transfer, and the combustion of ammonia and hydrogen in the air.

Morales added: 'The goal is to use ammonia as a main hydrogen carrier by inducing chemical catalysis to leverage ammonia’s hydrogen components while only releasing safe emissions into the air. In addition to the sustainability of ammonia, it is naturally liquid at high altitudes, easier to handle than hydrogen and does not require additional storage.'

Lightweighting is another key area of investigation to reduce the amount of fuel used by aircraft. With fuel currently representing 50 per cent of an aircraft’s operating costs, the financial and environmental costs cannot be ignored.

Progress is being made both in terms of both the structure and materials used. Tahiri explained: 'Modelling and simulation, combined with artificial intelligence, is helping to optimise the design of the structure to reduce overengineering and the accompanying detrimental effects to performance and cost.'

Tahiri added: 'Lightweighting in both the battery and the aircraft itself can be achieved through a variety of innovations, many of which are already mature; additive manufacturing and optimised composite design can help reduce weight, while innovations in battery efficiency through more optimised and innovative thermal design and management can extend the lifetime between charges.'

For example, thermal and mechanical engineers at Safran Aircraft Engines recently used Ansys’ simulation solutions for advanced engine developments, including sophisticated structural designs, such as an open unducted fan, upgraded composite material to combat higher temperatures and hybrid electrification to lower emissions. 

The solution’s high-fidelity solver features, such as fluid–structure interaction capabilities and faster solve times will allow Safran Aircraft Engines to 'slash development time with a significant reduction in simulation workflow compared to the company’s previous FEA tools,' according to Morales.

Lightweighting is also affecting parametric design exploration and the topology/topological optimisation for structural and thermal (FEA) codes. Lethbridge explained: 'Until about 5 to 10 years ago, access to these simulation capabilities was the domain of simulation experts working on simplified models with limited real-world applications.

'The continued push for lighter, stronger parts has forced the evolution of simulation techniques, seeing dramatic enhancements in solver speed utilising high core count CPUs, and GPUs for solver operations, in addition to the ability to parallelise parametric design studies,' Lethbridge added.

SimScale, for example, provides access to up to 96 core machine instances, and allows users to run a virtually unlimited number of parallel simulations enabling them to explore their design space in considerable detail very efficiently. 

As a result, parametric space exploration has advanced, solver speed has increased and the organic complex shapes resulting from topological optimisation can now be realised through additive manufacturing methods. 

These improvements have come about thanks to collaboration, according to Lethbridge, who added: 'Simulation tool workflows have been progressively simplified, either as a result of strategic partnerships between vendors, in-house development or even mergers/acquisitions of the component solution providers.

'The end result is far more streamlined workflows that eliminate the need to jump in/out of tools from multiple vendors and require less scripting/API, meaning that these solutions are easier to deploy, maintain, are generally lower in cost, and are more accessible to designers and engineers.'

Tomorrow’s simulation and modelling tools will increasingly rely on artificial intelligence (AI) and machine learning (ML) to continue to drive such innovations forward. Cole explained: 'We will continue to see more simulations being used more often and earlier in the design cycle and using all the data generated by those simulations to build and train AI/ML models so future decisions can be made quicker.'

Morales added: 'There is an increased demand for AI and ML to reduce preparation time, increase the robustness of solutions and make decisions on behalf of the user based on the objective of a given analysis.' 

Going forward, the aerospace industry will continue to evolve with technologies, processes and people continuing to collaborate and converge, Cole concluded: 'At the end of the day, we are going to see a convergence of simulation, high performance computing and data. These are three topics that seem discrete now, but in 20 years every mechanical engineering student will use these in their everyday work.’

Credit: Vadim Sadovski/Shutterstock

21 January 2022