Numerical Analysis of Hydraulic Performance of negative surge on Earth Dam Discharge

A negative surge is an unsteady flow characterised by a decrease in water depth. Negative surgescan occur downstream of a control structure when the discharge is reduced. They also occurupstream of a control structure that is opened rapidly or The failure time is very low. For astationary observer the negative surge appears to be a gentle lowering of the free surface. The Hecrasmodel based on the linearized implicit finite-difference model which based on the De St. Venantequations. The various implicit methods of finite differences that have been developed, thePreissmann-type schemes. When the surge occurs, the De St. Venant differential equations are notvalid in the neighborhood of the surge. In this case was used software Fortran 90 and write code tosolve The Explicit McCormack model. According to This paper provides the Parametric Modelsmethods and numerical model such as MacCormack Explicit scheme and Preissmann Implicitscheme using Hec-Ras to simulate dam break furthermore it used to predict breach outflowhydrographs .Unsteady flow modeling is often used in dam breach analysis due to the need toobtain more detailed or accurate results. The breach parameters will directly and substantiallyaffect the estimate of the flows. Due to this illustrate the failure time is very low, as a result thenegative surge occurs, However De St. Venant differential equations are not valid in theneighborhood of the surge. In order to evaluate the effective of negative wave on the outflowhydrograph. according to this, the outflow computed by the simplified model with The explicitmethod of characteristics MacCormack.

کلیدواژه ها:

Explicit ، supercritical ، subcritical ، Negative surges ، Preissmann ، peak breach discharge ، De St. Venant