一种塑料模型沙运动特性试验

对一种复合塑料模型沙的水下休止角、群体沉速、起动流速等运动特性进行了试验研究:使模型沙在静水中自然落淤成丘,通过几何关系可得水下休止角;将沙样按粒径分组进行单颗粒沉速试验,统计平均后再按质量加权得到模型沙群体沉速;在玻璃水槽中对5种水深下的泥沙起动流速进行了测量及经验公式验证。试验结果表明:该模型沙水下休止角为28.4°,较传统塑料沙、水下休止角范围大,具有较好的水下成形特性;对于该模型沙,其单颗粒沉速用W.W.Rubey公式计算精度较高,但群体沉速用中值粒径进行经验计算则精度不够,合理的代表粒径有待进一步研究;起动流速比传统塑料沙大,这与水下休止角试验是相符的,通过调整沙莫夫系数K,沙莫夫公式可较好地表述个别起动和少量起动的情况,大量起动时则不够精确。

Experiment of motion characteristics of a kind of plastic model sediment

An experimental study was performed on the submarine repose angle,group settling velocity,and incipient velocity of a kind of compound plastic model sediment.The submarine repose angle can be determined from the geometric relationship of the cone formed by the model sediment accumulating naturally in static water.The sediment sample was divided into different groups according to diameter to perform the single particle settling experiment.Then,the arithmetic average settling velocity of each group was calculated and the group settling velocity was obtained with the weighted average of all groups.The incipient velocities under five kinds of water depth were measured in a glass flume and were verified by experienced formulas.Experimental results show that the submarine repose angle was 28.4°,larger than the value of traditional plastic sediment,which manifests outstanding underwater shaping ability;the W.W.Rubbey formula is acceptable for calculating single particle settling velocity,but it is not accurate enough to calculate the group settling velocity using formulas with the median particle diameter,meaning that the proper representative diameter needs further research;the incipient velocities measured are larger than the traditionally used ones,corresponding to the submarine repose angle experiment;and Shamov's formula can properly formulate the states of individual initiation and a small amount initiation by adjusting the coefficient K,while it is not accurate enough for the state of a large amount of initiation.