空气动力学

       要在常规线路上高速运行，对空气动力学提出了许多挑战性的问题，其中包括在隧道和露天压力脉冲的影响和当列车通过车站或经过线路旁的工人时滑流的影响，隧道内的压力脉冲也许是最最难易解决的问题。列车进入隧道产生的压力波沿着隧道孔洞以声波前进，并且从出口洞门反射回来，从而造成压力的巨大变化，而列车必须从中通过。在单孔或双孔隧道中，这就要求行车速度受到限制以免乘客耳朵产生不舒服的感觉。使用通风竖井来减轻压力或采用喇叭式的隧道进口能减少隧道内压力的问题，虽然每种办法都明显地有着实际的局限性。另外，列车高压密封费用高昂而且需要长期的养护费。

       Operation at higher speed on conventional lines poses many challenges in the field of aerodynamics, including the effect of pressure pulses in tunnels and in the open air, and slipstream effects as trains run through stations or pass trackside workers.  Pressure pulses in tunnels probably present the most extreme difficulty.  The pressure waves generated when a train enters a tunnel travel at the speed of sound along the bore and are reflected back from the exit portal, giving rise to significant changes in pressure through which the train must then pass.  In single or double-bore tunnels this can require a speed limit to ensure the aural comfort of passengers. This tunnel problem  can be minimized with air shafts to relieve pressure or flared tunnel entrances, although each obviously has practical limitations.  Pressure-sealing the train is expensive and gives rise to long-term maintenance costs.

       来源：英语笔译实务

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