Panagiotis D. Scarlatos

Breach erosion of earthfill dams (BEED) model

A computer model has been developed for simulation of breach erosion of earthfill dams (BEED). The model incorporates the processes of surface erosion and slope sloughing to simulate breach enlargement. Depletion of reservoir water is approximated by a volume continuity equation while broad-crested weir hydraulics is utilized to describe flow over and through the breach. Due to the implicit form of these equations, an iterative solution is proposed with convergence achieved within only a few iterations. The BEED model is written in both FORTRAN 77 and BASIC computer languages. Testing of the model using historical data of the failures of Teton and Huaccoto dams showed that timing, shape, and magnitude of the predicted outflow hydrograph were adequately simulated by this model. The same is true for the dimensions of the terminal breach. A sensitivity analysis indicated that internal friction angle and the relation for surface erosion were the major factors affecting the model results.

Long-wave transmission through porous breakwaters

Abstract An analytical model for the study of wave transmission through porous breakwaters is developed. The analysis is based on the principles of harmonic treatment of linearized long-wave equations. Wave motion within the porous structure is simulated both by Darcy and Dupuit-Forchheimer types of flow. The model includes the effects of damping due to bottom friction, and provides a more realistic presentation of the breakwater characteristics. A comparison with other existing theories and experimental data shows satisfactory agreement.

An improved Lewis-Milne equation for the advance phase of border irrigation

SummaryThe Lewis-Milne (LM) equation has been widely applied for design of border irrigation systems. This equation is based on the concept of mass conservation while the momentum balance is replaced by the assumption of a constant surface water depth. Although this constant water depth depends on the inflow rate, slope and roughness of the infiltrating surface, no explicit relation has been derived for its estimation. Assuming negligible border slope, the present study theoretically treats the constant depth in the LM equation by utilizing the simple dam-break wave solution along with boundary layer theory. The wave front is analyzed separately from the rest of the advancing water by considering both friction and infiltration effects on the momentum balance. The resulting equations in their general form are too complicated for closed-form solutions. Solutions are therefore given for specialized cases and the mean depth of flow is presented as a function of the initial water depth at the inlet, the surface roughness and the rate of infiltration. The solution is calibrated and tested using experimental data.

Errors Due to Linearization in Tidal Propagation

Propagation of tidal disturbance is simulated using the St. Venant system of equations which is a partial differential, nonlinear system of hyperbolic type and can be solved by means of numerical methods. However, certain assumptions can reduce the system into the linearized form of Telegrapher’s equation, so that a closed-form solution is feasible. This linearization suppresses the tidal distortion induced by water shallowness, convectional velocities and bottom friction. Another source of error is the semi-empirical calibration of the linearized harmonic parameters.

Effects of Permeable Breakwater on Shallow Wave Propagation

Wave propagation is considerably affected by the existance of permeable breakwaters. The energy of the incident wave is partially reflected, partially transmitted and partially dissipated within the structure. The reflection-transmission properties of a breakwater depend both on wave dynamics and on the physical and geometrical characteristics of the structure. In this paper an analytical model is presented for simulation of shallow wave propagation through a pervious breakwater. The analysis is based on the principles of continuity and momentum balance. The wave is considered as linearized and frictional. Water motion within the structure is described by both Darcy and Dupuit-Forcheimer theories. The breakwater is assumed of rectangular shape and homogeneous. Comparison of the model with other theories and experimental data showed satisfactory agreement.