In this paper,the effect of geometries of tube open end on the shock,compression and expansion wavespropagating in the tube was investigated numerically and experimentally.One of them is a conventional straightshock tube with an open end.The other has a divergent tail tube at the exit.Applying a divergent tail tube(flaretube)to an open end shock tube,the period of one-cycle process could be shortened and the pressure behind theexpansion wave produced at the exit of the shock tube could be lowered much more below the atmosphericpressure than that produced in the straight tube.The results suggested that the intake air into the engine wassignificantly increased by applying a flare tube instead of a straight tube. In this paper, the effect of geometries of tube open end on the shock, compression and expansion wavespropagating in the tube was investigated numerically and experimentally. One of them is a conventional straightshock tube with an open end. The other has a divergent tail tube at the exit. Applying a divergent tail tube (flaretube) to an open end shock tube, the period of one-cycle process could be shortened and the pressure behind theexpansion wave produced at the exit of the shock tube could be lowered much more below the atmosphericpressure than that produced in the straight tube. The results suggested that the intake air into the engine wassignificantly increased by applying a flare tube instead of a straight tube.