基于DEM法的贯流式水轮机内部鱼类损伤机理

Investigation on mechanism of damage to fish caused by tubular turbine based on DEM

借助压力试验探究了不同压强下有无鳞鱼的损伤情况,得出压力损伤阈值后结合离散元素法(DEM)计算灯泡贯流式水轮机内鱼体受不同损伤的概率.研究结果表明:当正压低于0.4 MPa时试验鱼均无损伤;当压力降低到-20 kPa时试验鱼出现损伤,选取-20 kPa作为压力损伤的数值模拟阈值.相同水头下,导叶开度越大,鱼体受伤概率越大;相同导叶开度下,随着水头增加,鱼体在转轮区域受压力、压力梯度和剪切损伤的概率逐渐增加,受撞击的概率逐渐减小,并且前三者增加的幅度要比撞击损伤概率减小的幅度更大.叶片撞击与负压是导致鱼体损伤的主要因素,最高损伤概率分别为18.92%和18.01%;压力梯度及剪切力是次要因素,最高概率仅为5.43%和0.0352%.

The damage to scaled and unscaled fish at different pressures was investigated by pressure tests.The pressure damage threshold was combined with the discrete element method to further calculate the probability of different damage to fish inside a bulb tubular turbine.The results show that the test fish aren't injured when the positive pressure is lower than 0.4 MPa.When the pressure is reduced to-20 kPa,the fish are injured,and-20 kPa is selected as the numerical simulation threshold of pressure injury.Under the same head,the larger the opening of the guide vane,the greater the probability of fish injury.Under the same opening,as the head increases,the probability of fish injury being subjected to pressure,pressure gradient and shear injury in the runner area gradually increases,and the probability of impact gradually decreases.The increase of the first three is greater than the decrease of the latter.Blade impact and negative pressure are the main factors causing damage to the fish,with the highest probability of damage being 18.92%and 18.01%.Pressure gradient and shear are the secondary factors,with the highest probability being only 5.43%and 0.0352%.