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難道，今天介紹的無葉片風(fēng)機(jī)與卡門渦街有關(guān)？  
When a cylindrical structure such as a fireplace, stands in the way of a course of fluid such as wind, a phenomenon called Von Karman vortex street occurs. The fluid forms a cyclic pattern of swirling spiral motion that hits the structure and makes it oscillate at the sides. It has an aerodynamic explanation deciphered by the physicist Theodore von Karman in 1911. Since then, engineering takes into consideration these vortices and makes available prevention methods to prevent the infrastructures’ robustness from being compromised. Now the Spanish start-up Vortex Bladeless has decided to put a new spin on the approach and exploit this phenomenon to generate wind power. To this end, it has created Vortex, a wind turbine with no blades that oscillates from one side to another according to the wind to capture the kinetic energy. This is how it works “These eddies are a problem that usually engineers try to avoid at all costs because buildings could collapse,” explains David Suriol co-founder Vortex Bladeless. The manager explains that his case is just the opposite: “We deliberately look for it and optimize it”. To do this, the company has created a structure whose geometry is coupled to the oscillation frequency of swirls and compels them to replicate orderly around it. The turbine contains a coil and magnets system integrated on a mechanism which in addition to generating electricity makes that the structure is “tuned” to the right frequency to optimally swing to the rhythm of swirls. At first sight, the device appears as a vertical cone-shaped cylinder made of glass fiber, which makes it both lightweight as rigid. Current prototypes reach six meters tall, although the company is planning taller versions. In 2015 they will launch a 12.5 meters model and within three years, one higher than 100 meters. “The greater the height, the greater the performance is,” explains Suriol. “By working with no blades, the design eliminates many of the traditional mobile and mechanical parts of the turbine, which will significantly reduce wind energy manufacturing and operating costs,” says the co-founder. He expects to achieve 53% reduction in costs of the building process compared to a normal wind turbine. Furthermore, “downsizing and the absence of blades will also facilitate transport and maintenance work,” says the responsible. The materials used for its construction have also less impact on the carbon footprint, “because since no gear systems are present, Vortex does not need oil,” he adds. Benefits In addition to reducing costs, this technology has other beneficial features compared to other models. Suriol explains that Vortex can generate energy along a wide range of wind speeds, “higher than that of conventional wind turbines.” Specifically, the device boots from a wind speed of one meter per second, “l(fā)ess than that required by a traditional turbine” he explains. The multi-blade turbines start operating from three meters per second. The cylindrical shape of the structure also eliminates the need to orient the wind turbine in the direction of the wind stream, as needs be done by the wind turbines with blades, though, at the same conditions, the energy produced by Vortex would be about 30% lower than that generated by a traditional wind turbine. Furthermore, its design also makes Vortex less invasive in natural landscape and the absence of blades makes it less dangerous to birds. Neither makes it noise, reducing their environmental impact even further. Towards piezoelectric In the medium and long term, Bladeless Vortex researchers are working on an alternative to electromagnetic induction in order to generate electricity from Vortex oscillations. This alternative would be based on piezoelectricity. This phenomenon, discovered in 1880 by the brothers Pierre and Jacques Curie, occurs in some crystals such as quartz, which lack a center of symmetry. When compressed, their mass is polarized and generates an electrical potential. Since its discovery, piezoelectricity (of Greek piezein, “wring or squeeze”) has served for many purposes, from the design of submarine sonar and mechanism of lighters and watches through the pickups that amplify the acoustic signal of guitars. Piezoelectricity has also been used for energy harvesting applications, but not for generating large amounts of energy. As for Vortex, by including piezoelectric materials in the interior of the cylinder, the oscillations of the wind would deform components, thus producing electricity. “Right now the piezoelectric materials existing today are not powerful enough to be profitable, tons would be needed,” explains Suriol. However, there are different research groups working on new materials based on plastics and ceramics, more powerful and with lighter weight “that would indeed be interesting to Vortex” he concludes.
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