Comparative analysis of flow patterns in aquaculture rectangular tanks with different water inlet characteristics

Abstract

The objective of the work is to improve the design rules of rectangular aquaculture tanks in order to achieve better culture conditions and improve water use efficiency. Particle tracking velocimetry techniques (PTV) are used to evaluate the flow pattern in the tanks. PTV is a non-intrusive experimental method for investigating fluid flows using tracer particles and measuring a full velocity field in a slice of flow. It is useful for analysing the effect of tank geometries and water inlet and outlet emplacements. Different water entry configurations were compared, including single and multiple waterfalls and centred and tangential submerged entries.The appearance of dead volumes is especially important in configurations with a single entry. Configuration with a single waterfall entry shows a zone of intense mixing around the inlet occupying a semicircular area with a radius around 2.5 times the water depth. A centred submerged entry generates a poor mixing of entering and remaining water, promoting the existence of short-circuiting streams. When multiple waterfalls are used, the distance between them is shown to have a strong influence on the uniformity of the velocity field, increasing noticeably when the distance between inlets is reduced from 3.8 to 2.5 times the water depth. The average velocities in configurations with multiple waterfalls are very low outside the entrance area, facilitating the sedimentation of biosolids (faeces and non-ingested feed) on the tank bottom. The horizontal tangential inlet allows the achievement of higher and more uniform velocities in the tank, making it easy to prevent the sedimentation of biosolids.

Classification of flow patterns in rectangular shallow reservoirs

“…Flow detachment and reattachment processes are common in hydraulic engineering; examples are flows over lateral expansions (Abbott andKline 1962, Chu et al 2004), flows over groynes (Uijttewaal et al 2001, Yeo et al 2005, or flows in tanks (Frey et al 1993, Stovin and Saul 1994, Oca et al 2004, involving generally flows with sudden geometric variations.…”

Experimental study of velocity fields in rectangular shallow reservoirs

“…As velocity govems the mechanisms of transport, sedimentation and re-suspension of the inflow, its accurate assessment would allow to predict the preferential sedimentation zones, leading to improved reservoir management. Precise flow-field characterization is also essential for priate design and management of aquaculture tanks (Oca et 2004), since the presence ofdead zones with low water exchange would be detrimental to fish habitats. Furthermore, the flow pattern affects the actual detention time, and consequently the efficiency of shallow ponds, wetlands (Persson 2000) and dredged material containment areas (Thackston et at.…”

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].…”