Analytical Models for Optimal Design of a Trapezoidal Composite Channel Cross-Section

Abstract In this paper, several analytical models are presented for the optimal design of a trapezoidal composite channel cross-section. The objective function is cost per unit length channel, which includes excavation and lining costs. To define system, variables including depth, width, side slopes, freeboard, roughness coefficients were used. constraints include Manning’s equation, flow velocity, Froude number, water surface width. Simultaneous Perturbation Stochastic Approximation (SPSA) algorithm was used to solve optimization problem. results in three parts; first part, values different discharges. second relationship between discharges form conceptual mathematical functions. Finally, third changes as graph based on discharge variations. Results indicate that increases with increasing left slope, equivalent coefficient, freeboard.