The exit pipe axis and the valve ports are misaligned and therefore a swirling motion in the exit pipe is expected. However, the streamline visualization shown in Fig. 6 illustrates that the main stream from the valve ports hit the top of the exhaust port walls and flows foremost relatively straight towards the exit pipe. In the R valve port, the conical jet follows the valve stem towards the top wall, where the jet is deflected into the exit pipe. The annular jets cause inherently fluid entrainment, which drains fluid from the ports into the exit pipe. Thereby, a low static pressure zone is generated in the R valve port surrounding the annular jet (see Fig. 7), which stretches upwards to the lower region of the exit pipe. Further, Fig. 7 shows that the static pressure in the R valve port is lower than in the L valve port. Nevertheless, due to the
blockage of the flow from the L valve port, the flow is redirected around the high momentum flow from the R valve port and streams towards the low pressure region, which is illustrated in Fig. 6. This change of flowing direction induces the helical motion in the exhaust pipe. Fig. 6 shows that the strong helical motion is initiated beneath the stream rising out of the R valve port. Inspecting Fig. 6 showing streamlines initiated separately in the individual ports, it can be observed that streamlines emitted in the L valve port propagate even into the R valve port. The lower static pressure in the R valve port induces the higher flow velocities in the R valve port.