Optimization of the number of stairs in stairwells using physical models

 Recent advances in dam technology, created extensive equipment for construction of great dam’s reservoirs and canals. These advances are involved in development of design and construction methods, especially for systems that can discharge enough overflows. Chute and Spillways for passing more flows over a hydraulic Structure will be designed in such ways that don’t have any negative effect on structure. In water flow over spillway it is necessary some energy be dissipated using by following methods: 1- Decreasing the flow velocity in the plunging pool.

2- Stilling basin in downstream. 3- Step spillways.                                 

In the present study 54 step spillways make of ple. Glass, 5 discharges (10, 20, 30, 40 and 50 l/s/m) and 3 slopes, 30º, 26/56º and 21/8º degree (totally 275 experiments were conducted). Finding of the present study are as follows: 1- Performed modeling observations revealed that the relative energy dissipation along with spillway will be decreased with increasing discharge. 2- It is shown that energy dissipation is increase with increasing step numbers, but energy dissipation will be stopped in a certain number of steps. 3- According to presented study, optimal number of steps base on different values of yc/h and Froude Number is determined for the maximum energy dissipation. It is shown that optimal number of steps is affected by slope of spillway. Increasing spillway slope causes more energy dissipation.