Quasi-3D Solver of Meandering River Flows by CIP-Soroban Scheme in Cylindrical Coordinates with Support of Boundary Fitted Coordinate Method

Abstract

A new numerical solver is developed for the quasi-3D flow model to simulate meandering river flows. This solver can investigate the flows in an arbitrary curved river channel, by means of the adaptive CIP-Soroban (CIP-S) scheme in a cylindrical coordinate system with support of a boundary fitted coordinate (BFC) system. Time development of water velocity in an advection phase is computed by the orthogonal curvilinear coordinate system without any transformation of the governing equations, whereas a non-advection phase such as the continuity equation is solved by the BFC method, so that the mass conservation is fully satisfied and the water level is accurately calculated. From the verification of this solver on the meandering virtual river flows compared with the original BFC method, it is shown that the proposed solver accurately predicts the main flow profile in the regularly curved section of the flows, and that the horizontal velocity vectors both at the free-surface and at the bottom are reasonably predicted with the effect of the secondary currents in the curved section of the virtual river with some tributary streams.