High speed
on the flow field generated under high-speed trains.
It is too early to say how the
aerodynamics of a train could be modified to reduce the effects of cross winds, pressure waves and the slipstream from a passing train, which, as Dillmann points out, can be strong enough to pluck people off a station platform. The new facility is still being optimised to develop the calculation tools needed to produce solid results. As Mr Sigfried Loose, the DLR’s specialist in vehicle aerodynamics, says the technical limit for commercial high- speed trains is 400-440km/h, because a disproportionate amount of energy is needed to achieve only a small increase in speed beyond 440km/h. Even so, to reach 440km/h safely and at an affordable operating cost means building light trains and modifying their shape. For this, Loose says information on the aerodynamic flows round the underside of a train in particular is vital to design the train of the future, and none of the test facilities elsewhere can give a realistic picture of this due to inadequate simulation techniques. This is one of the reasons why the Göttingen facility was built. “Generally our main goal at the moment is to develop measurement techniques for aerodynamic drag, slipstream, flying ballast and
“At speeds of 300km/h the
front section of a double-deck train can start to lift, making it prone to tilting in strong side winds, despite the fact that the train may weigh several
hundred tonnes. Prof Andreas Dillmann
aerodynamic characteristics as a whole,” Loose says, explaining that data is still being collected for comparison with results from standard wind tunnels and observations of trains in service. Loose predicts that many of the findings from the new facility will be incorporated in the Technical Specifications for Interoperability (TSI) when they are revised in five years time. In the meantime, the current phase of the NGT project is due for completion at the end of this year. Aside from the aerodynamic issues associated with the NGT project, many other aspects are being covered by this inter-disciplinary programme. Other objectives include improving passenger comfort by reducing vibration, climate control, noise, and cabin pressure, as well as finding ways to speed up boarding and alighting, and developing
an efficient baggage handling system. It is also hoped that the cost of
producing new high-speed trains can be considerably reduced by using modular designs and system integration, as well as finding ways to reduce life-cycle costs. In addition the DLR is looking at related areas such as track design and automatic train control, and it also sees significant potential for improving development and approval procedures. It will be interesting to see how long it will take for a next-generation high- speed train to come into operation, and where the limits really lie. IRJ
42
IRJ July 2013
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