Distribution of Pressures on Modified Stepped Spillway by Using Toothed-Steps

Jaafar Maatooq,Ameer Jasim

doi:10.30684/etj.v39i8.1957

Abstract

In the present study a new steeped spillway shape at which “toothed steps” have been adopted instead of traditional steps to enhance the amount and distribution of water pressure along the chute of the stepped spillway. Experiments were conducted under a skimming flow regime, on five physical models of spillway one of which consisted of traditional steps used as a base model. For all investigated models, the chute angle was 45° with fourteen steeps each of 3cm height. Generally, the results show that the new shape models enhance the pressure distribution and reducing the potential for negative pressures along the chute, as well as, reducing the values of positive pressures that usually impact the tread. Specifically, close to the crest, the differences in pressure values being clearly large between the toothed steps modelsand the traditional steps. The new configurations of steps reduce the positive pressures between 116.66% to 1.28 % and the negative pressures were generally close to zero.

Highlights

The traditional stepped chutes and spillways have been studied extensively by many researchers over the world such as (Esery and Horner, 1978; Rajaratnam, 1990; Boes and Minor, 2002; Hazzab and Chafi, 2006; Maatooq, 2006)[1,2,3,4,5]
The pressure in low discharge for Toothed-Steps models is less compared to the traditional model, and the pressure distribution for new models hasan almost constant trend. At this location the new models show a good performance in reducing the fluctuation of pressure through increasing the air presence inflow which creates more cushion effect, this may be attributed to the enhancement of inception point location with toothed models
1) Overall intoothed-steps models the pressure values were enhanced along the chute by reducing the likelihood of negative pressures, as well as reducing the positive pressure, through directing the values to approach zero

Summary

Introduction

The traditional stepped chutes and spillways have been studied extensively by many researchers over the world such as (Esery and Horner, 1978; Rajaratnam, 1990; Boes and Minor, 2002; Hazzab and Chafi, 2006; Maatooq, 2006)[1,2,3,4,5]. The dentate steps have been adopted instead of traditional steps to configure the form of teeth, with spaces between them This model was operated under skimming flow conditions in order to improve the hydraulic aspects by increasing the interlocking surface areas between the mainstream and the lateral spread due to teeth sharp edges. This action leads to increasing the turbulence which creates more eddies to achieve a two-phase flow by which the energy dissipation is increased, besides reducing negative pressure values and excessive dumping forces

Theoretical background

Experimental work

Findings

Result and discussion

Conclusions