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Transonic Wing Section Design and Optimization

The design of optimized profiles for a high performance/speed transport aircraft is indeed a complex task. This complexity derives from the fact that the wing sections have to cope with different requirements which are often in competition with each other. Typically the designer might want to minimize the wave drag at high cruise speed, while being obliged to maintain an adequate thickness, in order to grant a lighter structural weight and enough room to accommodate the landing gear, systems and most importantly, the fuel. Another requirement, quite a common one, is the minimization of the sections pitching moment, which turns into a lower trim drag in cruise. However, such a wing sections will most probably feature bad stall characteristics (nose stall) and a too low pitching moment profile, i.e. a low camber airfoil, might not possess enough lift reserve at Mach dive for a 1.5 g pull-up manoeuvre (requirement set forth by the FAR). These first considerations may already convey an idea of the complexity involved in designing one single wing profile. An advanced transonic wing is usually lofted on three or more.

Indeed, consultants or specialized consultancy groups typically require for the development of one new wing section around twelve weeks, and please note, just for one single section of the wing. The cost that a customer must expect for this kind of service usually amounts to several tens thousand euros. Sometimes the customer is asked to provide an airfoil that somehow can suit to the new project, as a basis for a initiating the optimization procedure.

Evolution Designs, thanks to its expertise and methodology, can dramatically reduce the development time and the corresponding cost and yet provide highly optimized wing sections, created via an evolutionary process, which doesn’t requires any database to set-off and provides solutions tailored on their specific design points.

Airfoil design for high performance gliders

Evolutions Designs provides consultancy to develop wing sections suitable to high performance sailplanes. Here we talk about low speed airfoils. Yet they have to feature the finest aerodynamics characteristics in order to achieve the highest Cl/Cd ratios for inter-thermal flight and the least climb index for minimum sink rate during the climb. In other words, a multi-objective optimization problem! Moreover, EDGAR can regard the deflection of a trailing edge flap as an additional gene of the chromosome, in order to find the optimal deflection for that one design at each design point. The example shows one solution generated for an 18 mt. span glider, designed to provide high climb performance at 90 km and high L/D ratios at 150 km/h and 170 km/h. Let Evolution Designs helping you to select the correct trade-off solution, while keeping an eye to other important aerodynamic features, such as the max lift coefficient and the airfoil stall characteristics.

Airfoil design for very-light aviation

It is a fact that the development of a wing section was so far a lengthy and not exactly a cheap process. This is why the majority of those who are enthusiastic in aeronautics and willing to bring to live and then to the market an ultra-light aircraft usually take refuge, using an airfoil picked up from the literature.

This was not the case though for the new and very appealing project Shark. At the beginning they considered to adopt a MS-313 for their wing. Then they decided to give ED the chance to develop profiles optimized for fast cross-country flight. ED provided two wing sections optimized for 20% and 80% wingspan positions respectively. The results were very satisfactory indeed as this chart shows.

If you’re thinking to design and produce a new very-light aircraft and you need wing section tailored on your wing and flight regime, ED would be proud offering its consultancy and providing you with affordable, quick and remarkably good solutions.

Flap Design

How would one should design and position a flap for a given wing section? If the design of a wing section is a complicated matter, the design of its flap it’s not any easier. Two lifting systems, two vortices, coexist interacting with each other. Their interaction can very well be such to lead to a flow separation on both the elements already at a moderate angle of attack.  What should then the optimum contour of a Fawler or of a hinged flap look like in order to maximize the lift coefficient for landing? Would that shape depend on its wing section geometric characteristics because of that mutual interaction? Or does it rather depend on the deflection and positioning of the flap with respect to the wing, or both?

One way to find an answer would be to run an extensive series of experiments or numerical simulations to map the locus of maximum lift coefficient for a certain number of contours at a few different deflections. This would be clearly a lengthy and expensive way to proceed. Moreover, as large as the number of selected flap contours can be, it will always have to be for obvious practical reasons a very limited one.

Another way to get away with the problem of designing a flap is in our view to apply a powerful search tool like a genetic algorithm. That’s why at Evolution Designs very convenient parameterizations were ideated to allow the automatic generation of fowler or hinged flap systems and thereafter they were implemented within the main frame of the same evolutionary algorithm used for the wing section design and optimization.

To get things a bit more complicated a designer could need to consider the chord of the flap as a further variable of the search problem. In fact, the shorter the flap the larger the gain of  volume for fuel storage and the lighter the flap system. Just the right kind of problem to be faced with EDGAR HL.

The design of a new wing section is not completed without the design of its flap. Let ED take care of that and provide you with solutions that maximize the lift at landing, the aerodynamic efficiency at take-off and the fuel volume of your new aircraft.

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