Amgad Elansary

The control of stresses and liquid pressure surges in pipes is an important problem in the design of hydraulic pipe networks. The method of characteristics has been used to solve the transient stresses and pressures in liquid-filled piping systems. The friction force is included in the equations of motion for the fluid and the pipe wall. The maximum pressure and maximum stress at any point along the length of the pipe are evaluated for the entire simulation time. A nonlinear search technique has been developed using the simplex method. The optimal valve closure is sought, that will minimize the maximum pressure and/or stresses. A continuous optimal valve closure policy is specified using spline functions. Numerical examples are presented showing the reduction of the dynamic pressure and the dynamic stress from linear valve closure to optimal valve closure for a simple pipeline and a complex pipeline. Also, a method for choosing the shortest time of closure which will keep the stresses below specified allowable stresses is presented.

The control of axial stresses and liquid pressure surges in pipes is an important problem in the design of hydraulic pipe networks. The method of characteristics has been used to solve the transient stresses and pressures in liquid-filled piping systems. Friction is included in the equation of motion. The HZim pressure and maximum stress at any point along the length of the pipe are evaluated for the entire simulation tine. A nonlinear search technique has been developed using the simplex method. The optimal valve closure is sought, that will minimize the maximum pressure and/or stresses. A continuous optimal valve closure policy is specified using spline functions. Numerical examples are presented showing the reduction of the dynamic stress and the dynamic pressure from linear valve closure to optimal valve closure.

A numerical method to calculate the load-settlement of an axially loaded pile is presented. The method is based on an iterative scheme that tests the global equilibrium conditions and the load transfer (t-z) equations. The scheme is both accurate and computationally very economical.

A mathematical model to simulate overland and channel flow using the finite element technique was adapted and applied to a small semi-arid rangeland watershed (2,035 acres) in the USDA Walnut Gulch experimental watershed in the Southwestern United States. The Holtan equation was used to estimate precipitation excess, and with the precipitation excess as input, the finite-element technique was used to route overland and channel flow. The program was structured with sufficient flexibility so that effect of land use changes either gradual or sudden, on runoff hydrograph could be estimated. Abstraction losses in the stream channel are accounted for. The simulation model predictions are compared with field data for several storms and the comparisons are satisfactory; however, improvements could be made with additional data on antecedent moisture content and better estimates of abstraction losses. Based on these comparisons, it is felt that the model can be used to estimate runoff hydrographs from ungaged watersheds in semi-arid regions.

A mathematical model to stimulate overland and channel flow using the finite element technique was adapted and applied to a small semiarid rangeland watershed (2035 acres) in the USDA Walnut Gulch experimental watershed in the southwestern United States. The Holtan equation was used to estimate precipitation excess, and with the precipitation excess as input, the finite-element technique was used to route overland and channel flow. The program was structured with sufficient flexibility so that the effect of land use changes, either gradual or sudden, on the runoff hydrograph could be estimated. Abstraction losses in the stream channel are accounted for. The simulation model predictions are compared with field data for several storms, and the comparisons are satisfactory; however, improvements could be made with additional data on antecedent moisture content and better estimates of abstraction losses. Based on these comparisons, it is felt that the model can be used to estimate runoff hydrographs from ungaged watersheds in semiarid regions.