粗糙度对溢流反弧水力特性及紊流边界层的影响

本文对溢流反弧(R=100cm)不同粗糙度模型水力特性进行了系统的试验观测,探讨了壁面粗糙度对反弧水流流速分布、压强分布及边界层发展的影响。综合分析了流速分布及边界层发展的影响因素,得出了反弧水流边界层外部势流流速不受粗糙度影响的结论,并给出了边界层内流速指数n随粗糙度变化的关系式及反映壁面粗糙度影响的边界层厚度计算式。试验发现粗糙度对离心力压强影响甚微。

Effects of Roughness on Some Hydraulic Characteristics and Turbulent Boundary Layer in the Buckets of Spillway Dams

Through the experiment and researeh upon hydraulic characteristies of series roughness model in bucket of spillway (where R is 100cm), the ruie of the cffcet of wall surface roughness upon vclocity distribution, pressure disiribution and development of boundary layer is disctissed. We have analysed the faetors whieh are retative to velocity distribution completely, and found that wall surface roughness have nothing to do with the vcloeity of potential flow outsidc boundary layer. We proposed the calculation formula of velocity Upw of potential flow on wall surface and veloeity exponential n which is varied with roughness inside boundary layer. The experimental researeh proves that the contrifugal pressure is transitional in buckct, we conelude that the roughness has less influcnee on contrifugal pressure. Based on dimensional analysis, we have studied the effects of all elements upon boundary layer dcvelopment, and presented the rormula of boundary layer thickness which reflets the effcet of wall surface roughness.