Exploring flow discharge strategies of a mixed-cell raceway (MCR) using 2-D computational fluid dynamics (CFD)

Abstract

Computational fluid dynamics (CFD) is a numerical analysis tool used to simulate fluid-flow characteristics around or within physical boundaries, such as aquaculture tanks. CFD allows predicting performance of tanks under virtually unlimited operating conditions and configurations, and it has the advantage of being more flexible and cost-effective than physical testing. A two-dimensional (2-D) simulation of a mixed-cell raceway (MCR) was performed using CFD to explore basic hydrodynamics of an MCR and optimize flow discharge strategies to improve solids removal. Accuracy of the simulations was validated against previously obtained field data in a large-scale MCR. The CFD simulation was conducted using the RNG k–ɛ turbulence model in a segregated solution scheme using a 17,000-cell triangular grid of the x–y plane of the MCR. Simulations were conducted for three different bottom-drainage conditions. Results of the vector and contour plots revealed good agreement between the CFD simulations and the field data in describing fluid-flow characteristics of the raceway. However, given the constraints of a two-dimensional model, accurate prediction of velocity magnitudes required the calibration of the inlet velocity with field-measured data. Upon calibration, the simulation produced good agreement between the observed and predicted data. As opposed to three-dimensional CFD simulations, two-dimensional models are simple to implement and can be run in a mainstream, basic computer. Due to its flexibility and cost-effective characteristics, aquaculture research facilities can use 2-D CFD as a rapid proof-of-concept tool, for the design, testing, development, or optimization of aquaculture tanks and other reactor systems.