Mechanical Characteristics And The Control Measurement For The Vertical Vortex

The vertical vortex frequently occurs in the spillway tunnel intake, which is aserious damage to the safety of flood discharge, so it must be avoided in the engineeringpractice. In this paper, the research is aimed to avoid the vertical vortex phenomenon onXiluodu hydraulic project via the study on experiment investigation, theory analysis andengineering application.The experiment study was carried out on the huge hydraulic model of Xiluoduproject. The vortex shape evolution was observed under different submergence depthswith different intake types, different intake boundaries and different flow discharges.The form characteristics and hydraulic effects were analyzed, and the formation andevolution of vertical vortex were studied theoretically. The flow field velocitydistribution was measured by the Particle Tracking Velocimetry (PTV) technology infront of spillway tunnel intake. The development of surface velocity distribution wasobtained with different submergence depths and the changing of velocity circulationwas calculated with different submergence depths.Surface velocity distribution and critical submergence depth are two importantaffects to vertical vortex, which have been studied theoretically in this paper. Since allthe related velocity formulas have disadvantage, a new formula of surface velocitydistribution was proposed based on the Navier-Stokes Equations and the experimentresults, whose advantage has been confirmed by comparing with former formulas. Theproposed formula is applied to engineering practice via the "method of images", whichcan consider the effect of boundary. The vortex theory was developed from free vortexto bounded vortex within boundary, and it is more easily to apply the research theory tothe engineering practice. Moreover, the experiment results certified the precision ofproposed formula and the applicability of "method of images".Based on the theory of "Critical Spherical Sink Surface (CSSS)", the mechanismabout formation and evolution of vertical vortex was analyzed theoretically. A criterionof critical submergence depth was proposed which is modified by the model experimentresults. Meanwhile, the optimizing research was put forward on spillway tunnel intake,and an optimal type was proposed, which should be more helpful to anti-vortex inengineering practice. The purpose of experiment investigation and theoretical research in this paper is toavoid or reduce the vertical vortex phenomenon in engineering practice. Therefore, thecommon anti-vortex measurements were systematic generalized, and the relatedmechanism was discussed. The theoretical analyses were mainly focused on surfacevelocity distribution and critical submergence depth, so as to give suggestions to theengineering practice.