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MODELLING AND SIMULATION g


keeping those things balanced, in terms of the design process, was one of the things we did throughout.’ Yu believes that, when it comes to designing a new product and trying to optimise for aerodynamics, the foundation and key first step is simulation. ‘It’s really cost- and time-prohibitive to go and make 1,000 prototypes,’ he said. ‘Whereas, in simulation, you can really explore the boundaries of that envelope to figure out which design to use. When we have a road race like the Tour de France, there are many stages where aero is the biggest factor to overcome, but there are a lot of stages that are basically hill climbs and a sense that you’re fighting gravity, and in those cases, minimising weight up to the minimum allowed in the rules is a big deal. Having the tools to be able to optimise the system to have minimum weight for the aero and structural targets we’ve set is super critical.’ The team utilised the Hyperworks’ CFD


capability using CFD solver AcuSolve for the fluids optimisation, and Optistruct to optimise the structural and carbon ply by ply analysis to ensure that there is no excess material anywhere in the frame. Yu continued: ‘When we started transitioning into using powerful tools like the Altair Hyperworks suite, we were able to realise a lot of those small changes that maybe you can’t physically measure individually, if you stack them up in simulation and then build a prototype, you’re able to then measure a really large gain in the tunnel. By using the Hyperworks tools and the CFD analysis, on this frame, especially in terms of the amount of prototypes, we’re able to put through the simulation in the time block that we had to design this thing, I feel is at least a two- to four-fold increase in what we had before, in terms of the number of prototypes that we’re able to run virtually.’


Virtual wind testing Returning to the wind tunnel testing debate, Altair also has available for customers a virtual wind tunnel tool under


Specialised Bicycle Components utilised Altair’s HyperWorks simulation tools in the development of a new bike for the 2015 Tour de France


“It’s really cost- and time- prohibitive to go and make 1,000 prototypes. Whereas in simulation you can really explore the boundaries of that envelope”


the Hyperworks umbrella. VWT is a vertical solution providing an efficient environment for external aerodynamic studies. With its automated and streamlined workflow based on the company’s CFD solver AcuSolve, the virtual wind tunnel performs simulations of flow around objects, delivering transient or steady state solutions. With a focus on drag and lift prediction


of vehicles in the automotive sector, other uses include aerodynamics of buildings, motor bikes and bicycles, as Montreal- based cycle manufacturer Argon 18 discovered. Argon 18 partnered with the ÉTS


Research Chair on engineering of processing, materials and structures for additive manufacturing to make a track bike for Lasse Norman Hansen, a Danish cyclist competing at the 2016 Rio Olympic Games. The aim was to develop a bike that was stiffer, highly integrated and more aerodynamic, providing greater efficiency. Martin Faubert, research and


The peloton project helped to gain a greater understanding of the aerodynamic interactions between cyclists in a large racing group


28 Scientific Computing World August/September 2018


development manager at Argon 18, explained: ‘Our main goal is to enhance the performance of the rider by providing the best bike possible. Improving the structural design and aerodynamic performance by using Altair HyperWorks’ greatly streamlined our product


development process.’ A key aspect of the project was the


development of a new aluminium stem to be used by Hansen, and the company used OptiStruct for structural analysis, AcuSolve for CFD, and VWT.


Drag reduction Finite element analysis (FEA) was employed to understand the structure of the design, and then to improve and optimise it. CFD analyses and virtual wind tunnel simulation helped to improve the aerodynamics. Several iterations between the FEA and


CFD processes followed, trying different configurations of the components, making the blade wider, thinner, and taking it far from the wheel, bringing it closer, while keeping a close watch on the CFD and FEA data.


The design improvements resulted in a significant reduction (six per cent) of the aerodynamic drag (CdA), a critical parameter in making faster bikes. The linear stress analysis was conducted using Altair OptiStruct for validation of the stem body and clamp design. The stress analysis demonstrated a


greater stiffness, about nine per cent, than the typical carbon fibres stem. It also identified several dimensions to be adjusted in order to preserve the integrity of the parts, such as the thickness of the tubular section and the handlebar clamping section. To ensure its reliability, a fatigue test was performed on the final design, which showed no significant loss of rigidity or cracking, as well as good correlation with the stress analysis. The stiffness proved to be greater than the fibre-reinforced composite bracket.


@scwmagazine | www.scientific-computing.com


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