A Free Surface Model of a Vertical Slot Fishway to Numerically Predict Velocity and Turbulence Distributions
Andrew F. Barton, Robert J. Keller, and Christos Katopodis
Abstract.—The vertical slot fishway (VSF) is a hydraulic structure used to aid in the passage of fish past barriers to their natural migration. These barriers may consist of such structures as weirs, dams, culverts, and tidal barrages.
This paper presents the detailed flow results of a computational fluid dynamics (CFD) model of the three-dimensional flow within a VSF. The flow is characterized by a free surface with contractions, turbulence, and regions of high velocity and flow separation at the vertical slot jet. Also present within each fishway pool are distinct recirculation regions. The model solves the three dimensional Reynolds-Averaged Navier-Stokes equations, closed with the renormalized group theory (RNG) k-ε turbulence formulation, which incorporates the nonequilibrium wall function. The model also employs the volume of fluid free surface method.
Validated results are presented for depths and velocity components, both internally by the use of sectional planes (including within the vertical slot) and on the free surface of the model. Predictions of turbulence and secondary flow components and distributions are thus developed based on the validations.
A detailed understanding of the flow behavior beyond that readily available by experimentation (physical models and field measurements) has been achieved. An important consequence is the ability to now undertake a CFD methodology that is both efficient and fully predictive for hydraulic analysis of fishways of this genre that will eventually aid in the design process.