Study On Several Hydraulic Problems Of Vertical Slot Fishways

The vertical slot fishway was one type of the most widespread adoptions all over the world. The designing work involved many hydraulic problems. In this paper numerical simulation methods and hydraulic model tests were used to systematically study several hydraulic problems of the vertical slot fishway. The main research results were as follows:1. In the range of 0.8-2.0m/s, the average velocity of the vertical slot section had no obvious effect on the flow field of the general pool. The results indicated that the hydraulic characteristics of the general pool lay on its layout and size, so the reasonable layout of the general pool gotten in the condition of a special velocity had good universalities.2. The layout of the vertical slot fishway with with streamline heads was presented and studied in this paper. The study results indicated that if the streamline head was used on baffles, the main flow region would in the middle parts of the general pool and its velocities attenuated well along the way. For the recirculation region, its influence domain was about 80% of general pool plane and its velocity magnitudes were very small. So the layout could be applied to practical engineerings.3. The hydraulic characteristics of the resting pool were systematically studied and it was found that the main flow traveled along one sidewall and one large scale recirculation region occurred, so the corresponding optimization measures were presented. If the deflection angle of the upstream vertical slot was designed to be in the range of 23°-26° or a baffle is added on the left sidewall, above bad flow patterns would disappear.4. The hydraulics of the turning pool and the forking pool were systematically studied in the paper and their unique characteristics were revealed. It is indicated that bad flow patterns easily occurred in the turning pool and the forking pool. To slove these problems, setting baffles on sidewalls were presentd and the flow patterns were optimized.5. A unique layout of the entrance part of the vertical slot fishway was presented, which effectively sloved the hydraulic problem of adapting the large amplitude of water level. By making use of obstruction functions from baffles, different inlets could achieve the effect of automatic switchover in entrance parts which automatically adapted to the change of downstream water level. The advantages involved that no gates was set, the operations were simple, and it is good for improving the efficiency of gathering fishes.6. A layout of the exit part of the vertical slot fishway with overflow sections was presented in this paper, which solved the problem of seting two or more outlets to adapting the amplitude of upstream water level.7. The idea of luring fishes by jets was presentd, and the layouts of one jet and two jes were respectively studied in the paper. It was found that if a jet and a series of small jets were respectively set on the upstream and downstream of the fishway entrance, luring fish flow field would form in the downstream river and the velocity magnitude of the recirculation region would be very small. On the other hand, If two adjacent jets were set in the upstream of the fishway entrance, the velocity magnitude was designed to be 2-3 times of the average velocity of the vertical slot section, and the angles are respectively 90°-120° and 30°, the flow field in the regions of the fishway entrance and its downstream would be suitable for the fish back behavior and swimming into fishway entrance parts, so the adjacent jets are good for increasing luring fish efficiency.