Roohollah Ehsani - Islamic Azad University,University-ayatollah Amoli Branch,Department of Civilengineering, Amol, Iran
Hoda Hedayati - MSc Students, Water engineering department, Sari Agricultural Sciences and Natural Resources University, Water resource Engineer, Khazar ab Consulting Engineers
Amir Fooladi - Geotechnical Engineer, Khazar ab Consulting Engineers

In general the coefficient of discharge for various types of weirs (such as a broadcrested weir, sharp crested circular-crested weir) can be found from a standard formula. The rigid body weirs have a constant shape under all overflow conditions; therefore the relationship between the dam height and discharge over the weir thatcan be found. In the case of inflatable dams, this relationship is more complex than rigid body dams. Despite the increasing interest for rubber dams, little information is available on their hydraulic performances. Also once the rubber dam is in the safestate, the hydraulic operation is as same as rigid body dams, but because of the flexible operation of these dams, there are many effective parameter of the coefficientof discharge for rubber dams. In rubber dams, the discharge coefficient is flounced by a number of factors, such as the ratio of overflow head to height of dam, dams shape,surface tension force, viscosity, slope of upstream channel, surface roughness, fin , the pressure under nappe, downstream apron interference and submergence. In this studythe effect of these parameters for rubber dam’s coefficient of discharge was determined from the experimental data and the result of physical model was analyzed. The experiments have been done for the several roughnesses of rubber dam’s body and for several canal slopes on upstream. By doing physical model on the weir of rubber dam, interesting results have been achieved.

Rubber Dam, Fin, Roughness, Nappe, Submergence