Computational modeling and analysis of low flow through large culverts for fish passage.

摘要

A culvert is a hydraulic structure used to channel water and is commonly used for runoff to pass underneath a road, railway, or embankment. As flow volume increases at these culverts, the streams actively degrade in order to accommodate higher flows and may interrupt natural fish migration. Fish and aquatic organism passage through culverts is an important component of road and stream crossing design. As a result wildlife issues are gaining more importance on government agendas. The most common physical characteristics that create barriers to fish passage are excessive outlet drops, high water velocity within the culvert, turbulence within the culvert, accumulation of sediment and debris and inadequate water depth within the culvert. Major hydraulic criteria influencing fish passage are: flow rates during fish migration periods, fish species, roughness, and the length and slope of the culvert. Additional complexity in flow development is caused by the presence of corrugations that are used for strength; as a result, Computational Fluid Dynamics (CFD) is used as an analysis tool for resolving the flow parameters through the culvert. To analyze the flow field through the culvert, physical modeling is the best approach and therefore experiments are generally conducted by reducing the scale of the setup. However, it requires a considerably long time and is very costly. An alternate way to analyze the flow field is to perform simulations under experimental conditions.;The objective of this study is to develop a three-dimensional single-phase simulation model using Commercial CFD software STAR-CCM+ for the flow development through culverts for fish passage and validating these results with the experimental data obtained from TFHRC (Turner Fairbank Highway Research Center). Other tasks include identifying the flow regions through the culvert with suitable conditions and parameters for fish passage and improving the design criteria and methodology for the same. To use the models to perform analysis to assess flow regions for fish passage under a variety of flow conditions. In order to more accurately evaluate the ability of fish to traverse culverts, it is desirable to look at the changes in the local average velocity of the flow adjacent to the culvert wall under low flow conditions. The computational model is based on the three-dimensional transient RANS k-epsilon turbulence model with wall function treatment. A modeling approach that uses a short section of culvert geometry and assumes fully developed flow conditions has been developed and results have been verified against experimental data.