On the circulating tank newly bult at the National Research Institute of Fisheries Engineering

Here the authors present the design philosophy, the outline and the principal performance of the advanced circulating tank constructed for the purpose of conducting studies on fisheries engineering at the Fishing Boat and Instrument Division of the National Research Institute of Fisheries Engineering. The circulating tank is a vertical type one with the following main dimensions of the tank are 24.5m in length and the working section is 8.0m in length, 2.8m in breadth, 1.4m in draft. The water quantity is 280ton and the maximum velocity is 3.0/s. The newly developed devices are set up to introduce higher hydrodynamic performance and to try model experiment under high level condition. As the most reasonable device of the driving method to ensure laminar and uniform flow, the two impellers driving system is installed and it is capable of inducing higher effect of diffuser by introducing such a system. The MVR-type surface flow accelerator is the machine completely to make the near free surface flow uniformly during transition from low speed to high region. The air bubble extractor is set at the upper side after the working section, and it is designed for providing good quality flow without air bubbles at high speed as well as low speed. The water quantity adjustment machine has been developed with the purpose of setting the optimum condition under given velocity and by using this apparatus it is possible to reduce the free surface undulations and to promise the reproducible same experiment condition. Computer system is applied automatically to drive the circulating tank, to control equipments and to analyze the measured data. Discussions are made about the results of the measurements of velocity distributions, velocity fluctuations and the free surface undulations in the working section. A new estimation method on the steady wave height and the mean inclination is proposed and the undecided questions on these hydrodynamical characteristic are shown