RIASSUNTO
ABSTRACT
In this paper, a three-dimensional numerical model was established by using computational fluid dynamics to explore the improvement of hydrodynamic conditions and the flow field characteristics in a rectangular tank with arc angle. Design parameters of inlet system such as the jet angle and the number of inlet holes (the total inlet area remains constant) were studied on the velocity distribution uniformity in the aquaculture tank. The results indicate that the velocity distribution uniformity in the tank is the best when the jet angle is 0° the number of inlet holes has little effect on velocity distribution of tank when the total inlet area remains constant.
INTRODUCTION
Industrial aquaculture is a modern, high-density, intensive breeding model. Through the physical filtration and biological filtration of aquaculture wastewater, aquaculture water is recycled under the condition of ensuring water quality (Zhao, 2017). The design of tanks in aquaculture systems is an essential issue in order to achieve optimal conditions for fish and realize the reuse of water, reduce environmental pollution (Timmons, Summerfelt and Vinci, 1998; Watten, Honeyfield and Schwartz, 2000; Ross, Watten, Krise and DiLauro, 1995). The flow field characteristics in the aquaculture tank will have an important impact on the feeding and growth of the aquaculture object. The unideal hydrodynamic condition of aquaculture tank is one of the main problems that plagued the development of recirculating aquaculture industry. The main means of solving this problem are experimental research and numerical calculations. With the advancement of computer technology, the advantages of numerical simulation technology are becoming more and more obvious. In recirculating aquaculture, numerical simulation techniques are applied to study flow field characteristics, waste collection and elimination, biofilters, etc. (Jayen, 2003; Michael and Ewen, 2004; Wei, 2013; Liu, Liu and Yu, 2017). The flow field characteristics in the tank directly determine the suitability of the aquaculture system, the welfare of the aquaculture object, and the waste discharge efficiency of the tank. Davidson J et al. conducted an experimental study on water inlet structure and showed that adjusting water inlet structure would affect the flow field characteristics in the tank (Davidson and Summerfelt, 2004); Benoit D discovered that the jet angle is an important parameter affecting the tangential velocity and radial velocity in the tank (Benoit, 2007); Liu Yao et al. pointed out that the CFD numerical results are important for revealing the optimization of RAS internal fluid dynamics and its parameters (Liu, Liu, Lei, Guang and Huang, 2017). The rectangular tank with arc angle is one of the structure type of the culture tank commonly used in aquaculture farms, but there are few research on the flow field characteristics in a rectangular tank with arc angle. At present, most of the study focused on circular and rectangular tanks. In this paper, the flow field characteristics in a rectangular tank with arc angle is selected as the research goal, a three-dimensional numerical model was established by using computational fluid dynamics, design parameters of inlet system such as the jet angle and the number of inlet holes (the total inlet areas remain unchanged) were studied on the velocity distribution uniformity in the aquaculture tank, in order to understand the characteristics of the velocity distribution in the rectangular tank with arc angle and to provide rationalization suggestions for construction and production of aquaculture industry.