عنوان مقاله [English]
Formation of Vortices is one of the serious problems in dam operation. In the present work, to study the vortex and its effects on orifice spillways of Karun III dam in southwestern Iran, partial (with only one orifice) physical models were constructed. Regarding to the special conditions in orifice spillways (changing discharge by changing the reservoir elevation) this study showed that when a decrease in reservoir elevation occurs, first strong vortices take place and after reaching a maximum value the strength of these vortices decreases. This research also showed that, by increase in vortex strength, the discharge coefficient may reduce down to 10 percent. Measuring the critical submerged depth showed that among theoretical methods, Gordon and Knauss have better results.