基于水流黏滞性的模型沙选择

Model sand selection based on water flow viscosity

对于研究泥沙问题的全沙动床模型试验,模型沙的设计是整个模型试验的关键。当原型泥沙粒径过小,不考虑模型与原型的温度差异时,按比尺计算得到的天然模型沙粒径太小,通常不易获得。因此在满足悬移相似条件下,通过控制试验水温,根据不同温度及不同水黏滞系数ν,得到合理的颗粒粒径从而优化模型选沙。在原温和变温两种条件下分别计算所选泥沙的沉速和沉速比尺,表明改变温度所选的模型沙粒径是合理的,用较大粒径天然沙模拟原型较细沙,既满足沉速相似也满足悬移相似要求。试验验证结果表明模型沙选择满足设计要求,模型设计合理。

For the studies of the total-load movable-bed model tests, the design of the model sand has become a keyto the whole model testing. As the prototype sediment particle size is much sm all, ignoring the temperaturedifferences between the model sand and the prototype sand, it is difficult to get the suitable natural model sand ifthe particle size of the natural sand calculated by the model scales is too small. So by controlling the flowtemperature for the model experiments, under the conditions of different temperatures and different water flowviscosities, the reasonable sediment particle size can be got, so as to select optimized model sand in conditionssatisfying suspension similarity. The sediment settling velocities and sediment settling scales have been simulatedunder the conditions of original and variable temperatures. And the model testing analysis results show that thechoice of the model sand particle size in variable temperature conditions is available, and that the natural coarsesand used for simulation of the prototype finer sand not only meets the similarity requirements of the settlingvelocities, but the suspension similarity as w ell. The results of model testing validation indicate that the model sandselection has met the requirements of design and that the model design is reasonable.