الفهرس 
chapter 1Only 14 pages are availabe for public view
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Abstract
The aquatic weeds have flourished and spread all over the Egyptian irrigation network. due to the construction of High Dam. The most prevailing type of aquatic weeds is submerged weeds. This type of weeds causes many problems in the irrigation und drainage network. Submerged weeds increuse the 11ow resistance and consequently decrease both the water flow and the hydraulic crticicncy Problems related to hydraulics and sedimentation engineering have previously often been solved by the use of physical models. Physical models arc costly and timeconsuming compared with computational fluid dynamics (CFD) models The present study was carried out to develop a numerical model based on Navier-Stokes Equations to simulate the flow in open channel infested by aquatic weeds. The Navier-Stokes equations were solved, using modified maker and cell method with direct discertization method. The model studied has been the simulation of submerged weeds with their properties as different heights, diameters, density. and elasticity on the roughness of irrigation channels and velocity distributions have been computed using a numerical model The numerical model results showed that the presence of aquatic weeds causes changes in the velocity profiles and the water surface profiles. Also increase the heading up. and reduce the t1ow discharge at the weeds zone. It was concluded that thc cutting of weeds ruther than removing all vegetation will improve the conveyance cfliciency (discharge reduction percentage). which is more economical solution and help in stabilizing the embankment. Also. the height of weeds should not allow exceeding the value equal to half of the upstream water depth. The height of weeds should not allow exceeding the value elJual to half of the upstream water depth. The level of the berm at the heading up uistance (three to lour times the value of upstream water depth measured from the beginning of weeds zone to the