MODELLING AND SIMULATION
Flow field around a football travelling at 20m/s (the speed of a cross that you can head). This looks like a relatively simple problem but it requires millions of degrees of freedom and advanced models, in this case large eddy simulations (LES), in order to obtain relatively accurate values of drag and lift. The solution shown in this figure takes days to compute on a desktop computer just to simulate half a second of flight
ever, thanks to the development of electric vehicles, which provide a much quieter ride, compared to traditional vehicles. The field of aeroacoustics is also
increasingly relevant in other industries, including machining and tooling where manufacturers want to reduce noise created by large cooling fans, for example. Fine said: ‘This is a key and unique application area where we have the domain knowledge and understanding to solve these issues, not just simulate them, but also predict corrections and geo- spatial modifications that can solve any number of problems.’ The fields of plasma science and
electrochemistry have both expanded significantly in recent years, according to Fontes, who explained: ‘Here, we find problems involving CFD, electromagnetic fields, chemical, and electrochemical reactions, but also the usual conjugate heat transfer problems (coupled heat transfer in solids and fluids with CFD in the fluids) that emerge in all processes where heat is required or generated.’ Biomedical applications such as heart pumps and other medical implants are also ‘an interesting area of application,’ according to Fontes, who added: ‘Medtech is a fascinating new area for CFD. If we look at the traditional fields where simulation and modelling is often used, they are simple systems, compared to biological systems. Now, thanks to advances in CFD technology, we can deal with increasingly complex biological systems.’ Comsol Multiphysics was recently
used to simulate the HeartMate 3 left ventricular assist device (LVAD) from Abbott Laboratories. In patients with a poorly functioning left ventricle, an LVAD pump is responsible for circulating oxygen-rich blood through the body. CFD
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and electromagnetics modelling helped the Abbott team design a powerful, efficient and hemocompatible pump with pulsatile flow, which more closely mimics a functioning heart. Freddy Hansen, a physicist at Abbott
Laboratories, said: ‘It is easy to enter your own mathematical expressions in Comsol, in particular as you can type in an equation anywhere you can enter a number, and for us this greatly simplifies comparing different designs for their hemocompatibility. To do this, we enter custom algebraic and differential equations and solve these alongside the
”Thanks to advances in CFD technology, we can deal with increasingly complex biological systems”
CFD. We find that the relatively large gaps that we have in the HeartMate 3 between its rotor and the surrounding walls – gaps that are only possible with a magnetically levitated rotor – offer the design that is the most gentle on the blood.’ Such work could revolutionise the field of medicine, as Fontes concluded: ‘Medicine today is very much trial and error but, using CFD, we could analyse a model and then create treatments that are not only cheaper, but adapted to an individual’s symptoms and physical characteristics.’ Environmental technology is another
growing CFD field ‘involving processes such as carbon sequestration and processes related to the hydrogen society,’ according to Fontes. ‘CFD and fluid-structure interaction of wind turbines
has been a popular application for at least 10 years, but also the design around the wind turbines becomes interesting. For example, acoustics, water flow for offshore farms, and airflow around wind farms presents many interesting CFD and multiphysics problems involving, for example, fluid-structure interaction.’
Smokin’ CFD The Barcelona Supercomputing Center (BSC) is currently working on the Estimate project, a European initiative from the Clean Sky Joint Undertaking. Researchers are developing advanced CFD software to help the design of the new generation of efficient and sustainable Ultra High Bypass Ratio engines, with a focus on soot emissions.
When at full power conditions,
soot emissions tend to be low but, at intermediate conditions, particulate formation can be significant. Estimate uses a multidisciplinary approach to predict soot formation from chemistry oxidation to particle formation, based on high-fidelity simulations validated with reference experiments. The project will shed light onto the influence of the combustion model and the treatment of turbulence chemistry interactions on the prediction capabilities of the soot models, in terms of soot volume fraction, soot volume density and particle size distributions. The team is currently developing these models, and is addressing a range of challenges in its work. Oriol Lehmkuhl, large-scale computational fluid dynamics group leader at BSC, said: ‘We do not have a good model to predict combustion and turbulence together with soot formation and evolution. We have challenges on the chemical, modelling and computational
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