Abstract
A current inside the spillway becomes the high-speed flow of the open channel in the pipe. It becomes pulsation flow when a ventilation section can't be secured and when an air velocity becomes bigger than the velocity of the current. It is necessary that pulsation flow isn't made to occur because it becomes the problem of the vibration and the noise in this case.
We thought that a ventilation section was secured in the center of the section, with circling, a current is made to fall, by combining the curve which is vertical to the horizontal curve, referring to the research which has a bending part in the horizontal part about the spillway. It was found out that the tendency of the quantity of entrained air varied in the surface of the water shape in the vertical pipe, and that the surface of the water shape in the vertical pipe could be classified in four by the difference in the hydrological regime of the horizontal curve. It became possible that it was predicted pulsation flow and that it was designed suitably by this. As for the tendency of the quantity of entrained air, it was found out that it became the same with the in-situ measurement as a result of the model test.
