Characteristics of Flow Field in Annulus Space between Train and Tunnel

The characteristics of flow fields in annuluses between moving and static walls formed in train running through a tunnel is the important content of tunnel aerodynamics and also one of the main bases to study and solve the problem of the piston wind in tunnels.According to the pipe turbulence theory,the annulus flow is viewed as the combination of two kinds of flow,namely the Poiseuille turbulence in rough areas caused by the annulus pressure gradient and the Couette turbulence caused by drag forces on train surfaces.On the basis of the pipe turbulence theory in rough areas and taking advantage of the mirror and relative movement principles,the essential relationship of the Couette turbulence is established through flow transformation;by the property of time-averaged turbulence and the method of coordinate transformation,the law of annulus combination flow is deduced:the velocity distribution relationship and characteristic velocity location relationship of annulus flow are put forward,the wall friction velocity closely related to wall shear stresses is determined.The research provides the main baseis for solving the problem of tunnel piston wind.