Fishway Hydraulics Study Based On Fish Swimming Behavior

Mounting researches and practices show that fishway hydraulics is an interdisciplinary subject.The compatibility between the fish swimming features and the hydraulic characteristics in the fishway is the key to ensure that the fishway is effective.In this paper,we used grass carp fingerlings of 5～15cm body length to study the fish swimming motion features under the uniform flow field,and the fish swimming behaviors under the characteristic flow field.This study provides an important reference for the hydraulic design of fishways.The main contents of this paper are as follows:1.The swimming ability index of juvenile grass carp is tested.In the self-made test chamber,this study measures the induction speed index and burst swimming speed index of juvenile grass carp in a uniform flow field.A quantitative relationship is obtained between juvenile grass carp burst swimming speed and body length,as well as that between the burst swimming speed and the critical swimming speed.2.This dissertation studies the response of juvenile grass carps’ swimming behavior to flow velocity changes.Incremental flow method is used to analyze how rapid flow rate changes affect juvenile grass carps’ swimming behavior.According to the changes in test fishes’swimming status,a method to classify fish swimming behaviors under increasing flow velocity is proposed.The critical values of flow velocity in the main flow zone and the high velocity flow zone in the fishway pool room are estimated for grass carp juveniles.3.The study carried out experiments in which fish swims upstream though the fishway model in particular flow fields.In order to create different flow hydraulics in the fishway pool,three kinds of lead angle fishways were built.The fluent software is used to simulate the flow fields in fishway pool,and ADV to measure the flow fields inside the fishway model.The video analysis software is used to capture the trajectories of fish swimming.Thereupon,fish swimming trajectories and characteristic flow hydraulics in fishway pool are combined.4.The study also analyzes the relationship between key hydraulic factors and juvenile grass carp anadromous behaviors.Though analyzing the fish trajectories in different designed flow fields,this study innovatively reveals how hydraulic factors such as flow velocity,turbulent energy,and flow resistance,affects the anadromous swimming behavior of juvenile grass carps.The results can provide the preferred hydraulic ranges for fishway design.