Numerical and Experimental Investigation of Flow in Fish Tanks for Small-Scale Aquaponic Systems

Abstract

Aquaponic systems combine recirculating aquaculture (growing of fish) with hydroponics (growing of plants in water). The fish in the recirculating aquaculture systems provide nutrients for the plants and the plants remove excess nutrients from the water, making these systems more efficient than traditional farming methods in terms of nutrient utilization. Small, recirculating aquaponic systems may provide a more sustainable and cost-effective alternative for securing food supply in both developing and developed nations. Recirculating aquaculture systems tend to be capital-intensive and require significant power to circulate the water in the fish tanks, which helps with the removal of waste and the distribution of oxygen. To reduce capital costs, alternative, culture vessels made from locally available materials were investigated (i.e. square-shaped tanks, and international bulk containers - IBC). These non-standard shaped culture tanks, pose an additional challenge for proper circulation of the water as compared to traditional round tanks. To address the issue of circulation, numerical and experimental data were obtained for rectangular containers. The numerical results were obtained using OpenFoam models of the experimental setup. The experimental data were obtained by measuring flow velocities in an IBC tank using Acoustic Doppler Velocimetry. Currently the experimental data show good repeatability when data are taken for at least five minutes at each position in the tank. The focus of the continuing work is to establish a good agreement between numerical and experimental results. Ultimately the study will contribute to the design of cost-effective recirculating aquaponic fish and plant systems which require lower capital expenditures and achieve energy-efficient circulation of water in the fish culture tanks.