Design criteria for rotating flow cells in rectangular aquaculture tanks

Abstract

This work analyzes the simplest inlet and outlet configurations that create homogeneous rotating flow cells in rectangular aquaculture tanks, in order to combine the advantages of rectangular and circular tanks. All the configurations analyzed had a single jet discharge per rotating flow cell, with the drain placed in the center of each rotating flow cell. Length/width ratios (L/W) of 0.95, 1.43 and 1.91 were tested. In addition, the effect of placing oblique baffles in the walls to redirect the water currents was assessed. Experiments were conducted in a laboratory-scale tank with a Reynolds number of approximately 6000. Particle tracking velocimetry techniques were used to characterize the flow pattern in a horizontal cross-section at the midpoint of the water depth. A tank resistance coefficient (C t) was defined in order to characterize the resistance offered by each tank configuration to the circulation of water. Results indicated that when L/W was increased from 0.95 to 1.43, the main vortex that was formed occupied most of the rotating cell area and did not create significant dead volumes in the tank. A L/W ratio of 1.91 dramatically reduced flow uniformity and hardly increased C t values. The presence of baffles contributed to high velocities in the area around the center drains and decreased C t values by 30-35%. Higher velocities are critical to the self-cleaning properties of the tank. The calculation of a C t value makes it easier to obtain the desired average velocities in the tank by adjusting the water exchange rate and the water jet discharge velocity.

Changes to flow and turbulence caused by different concentrations of fish in a circular tank

“…Hydrodynamic conditions within various designs of aquaculture tanks and cages have been measured or simulated in order to both optimize and characterize various designs; however, fish were generally not present during these tests (Jeong, Chung, Kim, Choi, & Bae, 2004;Labatut, Ebeling, Bhaskaran, & Timmons, 2007;Oca & Masaló, 2007, 2013Timmons, Summerfelt, & Vinci, 1998;Zhao et al, 2013). Other studies have shown that fish can have an effect on hydrodynamic conditions in both tanks and cages.…”

Use of Suspended Plastic Conduit Arrays during Brown Trout and Rainbow Trout Rearing in Circular Tanks

“…Placing these types of structures in hatchery tanks can be problematic because they may trap food and feces, increase disease risk, or interfere with the hydraulic self‐cleaning that is inherent to circular tanks (Tvinnereim and Skybakmoen ; Baynes and Howell ; Timmons et al. ; Tuckey and Smith ; Oca and Masalo , ; Krebs et al. ).…”

Effluents from Fish Farming Ponds: A View from the Perspective of Its Main Components

“…Oca and Masaló [15] evaluated the width-to-length ratio in the formation of dead volumes. Evaluations using particle tracking velocity (PTV) techniques indicate that a single water inlet in a rectangular tank provides more areas with dead volumes [16].…”