Author(s): Gorazd Novak, Dusan Zagar, Matjaz Cetina, Martin Bombac
Keywords: DualSPHysics; Vertical slot fishway; 3D simulation; CFD;
Abstract: Correct predictions of flow through fishways are important for both designing and determining their suitability for diverse fish species. We present simulations with Dual SPHysics v4.2 code in a vertical slot fishway (VSF) previously investigated with extensive field measurements, a physical model and a validated two-dimensional depth-averaged numerical model PCFLOW2D. Field measurements of water surface elevation and flow velocity components were performed during steady flow with Q = 1.0 m3/s discharge, average depth h = 1.3 m and head difference Δh = 0.05 m between adjacent pools. An inlet section, 9 pools, and an outlet section were simulated, amounting to dimensions of 39.5 x 2.2 x 1.5 m. A periodic boundary condition was used to simulate a subcritical free-surface flow. The following execution parameters of DualSPHysics were employed: initial inter-particle distance of 0.02 m (amounting to about 15 million particles), simple precision, Verlet algorithm, artificial viscosity alpha value of 0.01, zero viscosity factor with boundary, no delta-SPH, no shifting. Time of simulation was set to 30 s to allow flow conditions to become steady. Simulations were performed on a PC with a single Nvidia GTX 1080 graphics card. Discharge and water depth were calculated correctly in the observed pool in the middle of the fishway and in both adjacent pools. The longitudinal water surface drops Δh between the pools were slightly underestimated, and the tailwater elevation was slightly overestimated. Despite certain discrepancies, the measured and the calculated velocity profiles were in relatively good agreement. DualSPHysics proved to be a fast and satisfactory accurate tool for 3D modeling of flow conditions in VSF.