Tesis doctoral de Ingrid Masaló Llora
The purpose of this work is to characterise the hydrodynamics of the most commonly used aquaculture tanks and to define design criteria that will improve self-cleaning properties and optimise the use of space and water. The dissertation is submitted as a compilation of individual articles. Two of the articles focus on the hydrodynamic characteristics of various tank geometries with different water inlet designs. The remaining articles examine the turbulence required for sedimentation and resuspension of biosolids generated in aquaculture tanks. The turbulence values obtained are compared with the turbulence generated by fish swimming activity in aquaculture tanks. hydrodynamic characteristics were studied in the laboratory by applying particle-tracking velocimetry techniques to scale models. the turbulence generated by fish swimming activity was studied using acoustic velocimetry techniques and quantified using the root mean square (rms) of velocities. Finally, the turbulence needed to resuspend biosolids was determined using an oscillating grid adapted to the specific characteristics of the aquaculture biosolids (high organic content and high cohesiveness); rms was also used to quantify the turbulence needed to resuspend biosolids. analysis of the hydrodynamic characteristics of scale models revealed that the flow pattern is strongly affected by the water inlet design. The flow pattern was homogeneous in configurations in which water flowed along the tank from the upper to the lower end, and dead zones and bypass currents were frequently observed. Flow velocities were low. The homogeneous flow pattern and higher water velocities were observed when water was injected tangentially to create a rotating flow pattern. Rotating flow cells produced a circular flow pattern in rectangular tanks. We defined a tank resistance coefficient (ct), which was found to be suitable for evaluating both circular and rectangular tanks with rotating flow patterns. The coefficient was used to assess the effect of baffles and various length/width cell ratios. We found that baffles increased the water velocity at the outlets, which is important in the removal of biosolids and for producing self-cleaning properties. acoustic velocimetry was used to study fish swimming activity. We found that the turbulence generated by swimming activity increases with density and that the photoperiod has a strong effect on the swimming activity of sea bass. finally, an oscillating grid was used to determine the turbulence needed to resuspend biosolids and the turbulence needed to keep them in the water column; these experiments illustrated the effect of consolidation time on the turbulence required for resuspension. hysteresis was observed when turbulence was reduced to evaluate sedimentation following resuspension, and different levels of turbulence were required for resuspension in different tanks (with different densities and fish sizes).
Datos académicos de la tesis doctoral «Hidrodynamic characterisation of aquaculture tanks and design criteria for improving self-cleaning properters«
- Título de la tesis: Hidrodynamic characterisation of aquaculture tanks and design criteria for improving self-cleaning properters
- Autor: Ingrid Masaló Llora
- Universidad: Politécnica de catalunya
- Fecha de lectura de la tesis: 10/09/2008
Dirección y tribunal
- Director de la tesis
- Joan Oca Baradad
- Tribunal
- Presidente del tribunal: raúl Piedrahita
- francesc Piferrer circuns (vocal)
- franz Peters (vocal)
- daniel Crespo artiaga (vocal)