Crosswind stability

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As a side wind stability the problem of tipping safety is of ground vehicles in strong crosswinds referred. This does not include the driving safety of road vehicles in crosswinds in terms of keeping in lane . Crosswind stability mainly affects vehicles that offer the crosswind a large area of ​​attack from the side and have a relatively narrow track width .

term

In the case of road vehicles, the above Tracking uses other terms such as B. Directional stability. The term is also not used in civil engineering, since wind loads are relevant for the integrity and vibration behavior of a building, but not for its stability in the structural-mechanical sense of resistance to buckling. After all, in aviation, where several axes of movement play a role, the terms crosswind and stability often appear, but not in the context of “crosswind stability” which is too imprecise in the context.

relevance

Crosswind stability is a relevant problem, especially in rail vehicles , where the driver's ability to intervene in terms of driving dynamics is limited and, on the other hand, overturning must be avoided in any case due to the catastrophic consequences. For this reason, corresponding standards and guidelines have existed for several years national and European level, which provide a mathematical proof of stability as a prerequisite for the approval or operability of the vehicle. It should be mentioned here that, contrary to popular belief, crosswinds alone cannot derail a train because the lateral forces are not sufficient. In contrast, the lateral forces contribute significantly to the overturning moment (i.e. the rolling moment around the leeward rail).

The problem of crosswind stability has become more and more important in recent years. The reasons are to be found in the steadily increasing driving speeds and the falling empty weight of the vehicles due to the advancing lightweight construction technology. In the case of rail vehicles, the replacement of heavy locomotives with much lighter railcars or even control cars in high-speed traffic has exacerbated the problem enormously.

When the Shinkansen service was introduced in 1964, the maximum speed was limited in strong cross winds. In Germany, the approval of the ICE 2 was linked to speed restrictions for pushed trains in areas at risk of cross winds.

In hurricane-like weather in Germany, rail traffic was either completely or partially shut down as a precaution (e.g. at storm depths Kyrill or Niklas ), or speed limits were set for certain train categories. When the storm Niklas on March 31, 2015, the local and long-distance traffic in various federal states was completely stopped and the speed for long-distance trains in the north and south was limited to 140 km / h. In such cases, however, the risk arises not only from the vehicle's possibly no longer stable crosswinds, but also from damage to the railway infrastructure (see below).

activities

Apart from constructive measures on the vehicle (e.g. ballasting to increase the vehicle mass and lowering the center of gravity , as for example with the ICE 3 ), crosswind stability can only be increased with a given route by reducing the driving speed or building wind protection walls. The first solution is operationally very problematic, because adapting the speed to the wind requires knowledge of the wind conditions to be expected along the route, which is a non-trivial technical task. In the case of rail vehicles, the possible travel time fluctuations in the timetable must also be taken into account. The second solution is operationally optimal, but associated with enormous costs. Ballasting (in particular the first or last wagon) is therefore still the most common measure to ensure crosswind stability and (or to meet the relevant approval standards). B. also considered for the ICE 4 .

In fact, most of the regulations governing rail transport are characterized by neglecting real current weather conditions. Specifically, it means that the respective vehicle should be able to withstand the wind load that is most unfavorable to be expected for the intended area of ​​use and within a specified period of time. This corresponds to a worst case philosophy or the return period approach used in civil engineering and is recorded in a vehicle and route-specific so-called wind characteristic curve . A change or even interruption of rail traffic due to strong winds is therefore not planned. In extreme wind conditions, the difficult-to-control danger of obstacles on the track systems or damage to the overhead line (e.g. from falling trees) plays an important role. In addition, the wind can hurl objects from the environment or even from oncoming trains against a moving train.

literature

Individual evidence

  1. ↑ See e.g. B .: T. Schütz (Ed.): Hucho - Aerodynamics of the automobile . Springer Vieweg, Wiesbaden 2013.
  2. ↑ See e.g. E.g .: H. plinth, aerodynamics of buildings . Vieweg, Braunschweig 1984.
  3. ↑ See e.g. E.g .: H. Schlichting, Aerodynamik des Flugzeug , Springer, Berlin 2000.
  4. ↑ On the way to solving the ICE problems . In: Eisenbahn-Revue International , issue 10/1998, p. 446 f.
  5. ↑ ICx - a new train for German Railways . In: RTR , issue 1/2012, p. 31.
  6. ↑ The railway infrastructure company or the operator of the respective route section (e.g. in the case of bridges) can, however, introduce additional, also weather-dependent operating restrictions.