推移质动床模型中模型沙运动比较研究

Comparison study on sand characteristics in bed load mobile model experiment

模型沙的选择是推移质动床模型试验中一项关键技术,直接影响推移质运动的相似性和河道冲淤趋势与量级的判断。整理以往的研究成果,结合概化动床模型试验,从起动条件、输沙强度和沙波形态三个方面对比精煤和天然沙这两种典型模型沙的运动特性。研究表明,精煤为代表的轻质沙与天然沙在起动条件和输移强度方面基本类似,都能模拟天然河道中的推移质起动和输移现象,但是在较大水流强度时形成沙波形态后,在波高、波长等几何形态上存在明显差异,对床面阻力的准确模拟有一定影响。因此,遇超过沙波临界条件的较大水流强度时,宜采用天然沙作为动床模型沙模拟推移质运动。该研究成果可为推移质动床模型选沙和设计提供参考依据。

Selection of model sediments is a key program for mobile model design,which influences the simulation of bed load transport and the tendency of fluvial process,and further influences its quantity of silt or erosion. Light model sediment,such as coal and plastic,and nature sediment are common used in mobile modeling according to the incipient similarity rules. This paper compares model sediment motion characteristics of light model sediment and nature sand from incipience motion,transportation and sand wave morphology based on former research results and simplified flume model experiment. The result indicates that both coal and nature sands show better similarity on incipience motion and transportation. However,the bed morphology is much different and it affects the simulation accuracy of the resistant of river bed sand after wave emerged in stronger flow condition. This study shows that nature model sediment is suitable for bed load mobile model in supercritical flow and will be favorable to select model sand and mobile model design.