3-D FLOW SIMULATION OF AN ICE-HARBOR FISHWAY

Fishways are hydraulic structures that enable fish to overcome obstructions to their spawning and other migrations. This paper presents a 3-D Volume of Fluid method (VOF) applied for the flow in an Ice-Harbor fishway. In the 3-D VOF, 3-D incompressible continuity equation and Navier-Stokes (N-S) equations are solved incorporated with a convective equation of VOF function. The donor-cell scheme is employed to discretize the convective terms of N-S equations and the donor-accepter scheme characterizing the VOF is applied for discretization of the equation of VOF function. As for other spatial differencing terms, the second order central difference approximation is used. A successive-over-relaxation (SOR) method is used for advancing the pressure and velocities in time throughout the computational cells. The fishway used is a model of the fishway installed at Akaishi second Headwork in Akaishi River, Aomori, Japan. Field observation of flow structure was also conducted to obtain the data for validation of numerical results. The numerical model was able to reproduce the rapid flow over a notch and through an orifice. Circulating flow behind the non-submerged part of the baffle was also reproduced well. For further quantitative evaluation, modeling efficiency (EF) was introduced. The EF value made clear the longitudinal velocity component was reproduced better than transversal and vertical velocity components.