The flow pattern is very complex in the plunge pool with multi-submerged jets plunging into it. Around each jet, there are a lot of back-flow swirls near the water surface and cross rod eddies close to the bottom; besides, vertical-axis eddies may appear between two jets. To research the hydraulic characteristics and occurring mechanics and whether the vertical axis eddies can reach the bed, experiments, theories and numerical simulation are applied in this paper. The results show that the vertical axis eddies near the plunge pool bed are caused by the interaction of the 3-D violent turbulent and boundary conditions; the vertical-axis eddies are often random and unsteady. They can not reach the bed, and will gradually disappear with the formation of the cross rod eddy, however, their potential damage need to be further studied.
