Field test study on the dynamic characteristics of sewage collection in circular recirculating water aquaculture tank

Abstract

To investigate the dynamic characteristics of sewage collection in circular circulating water aquaculture tank, this paper systematically studies the influence of flow rate Q of the jet pipe, the layout distance ratio d/r (d is the distance between the midpoint of the axis and the nearest tank wall, and r is the radius of the circular aquaculture tank), the layout angle θ, the structure of the jet pipe, etc. In the field tests, a high-definition camera was used to record the distribution of sewage in the aquaculture tank, and the distribution of the flow field in the aquaculture tank was measured by an Acoustic Doppler Current Profiler, and the distance between the sewage and the center of the tank was quantified. Meanwhile, the sewage collection effect of the aquaculture tank was evaluated by comparing the maximum distance between the sewage and the center of the tank under different working conditions. The evaluation results indicated that the formation of an effective horizontal circulation in the circular aquaculture tank is the primary condition for sewage accumulation to the center of the tank, and different flow rate of the jet pipe, the layout distance ratio d/r, the layout angle θ, and the structure of the jet pipe all affect the sewage collection effect in the tank. In the horizontal single-tube single-hole jet pipe structure mode, the best sewage collection result was obtained at the layout angle θ of 0°, the layout distance ratio of 1/4, and the layout flow rate Q of 7 L/s (hydraulic retention time is 70 minutes); when the layout flow rate Q was less than 7 L/s, the sewage gathered near the wall of the circular aquaculture tank, and the degree of feed dispersion was relatively high. In the vertical single-tube porous jet pipe structure mode, better sewage collection effect was obtained when the layout flow Q was adjusted to 7 ~ 9 L/s, the layout angle θ was set to 45°, and the layout distance ratio d/r was set to 1/4. The sewage collection performance of the aquaculture tank under the vertical single-tube porous jet pipe layout mode was obviously better than that of the horizontal single-tube single-hole jet pipe mode. Without major changes to the original structure, the research results directly and effectively guide the actual production and application to reduce the flow rate and energy consumption and improve the circular circulating water aquaculture tank of the Qinghai Lake Nude Carp Rescue Center.