Pressure transients generated when high-speed trains pass in a tunnel

An analysis is made of the pressure transients generated when two high-spee d trains meet in a tunnel. Safe operation at speeds exceeding about 300 km/ h usually demands that the hydraulic blockage produced by a train should be small. The problem can then be formulated in terms of the scattering of th e potential flow near field of each train by the moving surface of the othe r train, and this permits the derivation of closed form representations of the unsteady pressure in the special case of 'snub nosed' trains in a tunne l of semicircular cross-section. This solution is used to devise a general procedure for calculating pressure transients generated by trains of arbitr ary nose profiles in tunnels of arbitrary cross-sectional shape in terms of a knowledge of the local incompressible potential flow produced by each tr ain travelling separately in the tunnel. Numerical results indicate that at train Mach numbers exceeding 0.25 the amplitudes of the pressure transient s generated by meeting trains will typically exceed about 25 per cent of th e amplitude of the compression wave produced when a train enters or leaves the tunnel.