卵砾石河道摩阻流速计算方法探讨

通过水槽试验,采用6种方法:对数流速分布回归法、外延雷诺应力分布法、三维紊动能法、垂向紊动能法、韩其为经验公式法和拖曳力系数法,计算了卵砾石河床的摩阻流速。以韩其为计算摩阻流速的经验公式为标准,分析了各种方法中参数取值对计算结果的影响及其在不同水力和床面条件下各种方法的适用性。提出了2种可行的计算途径:光滑床面条件下各方法计算摩阻流速所得结果最大均方差为2.15,其中对数流速分布回归法较准确,三维紊动能法计算值普遍偏小;相对粗糙床面条件下各方法计算摩阻流速的结果均方差最大达到8.84,其中对数流速分布回归法和三维紊动能法较准确。

Calculation methods of shear velocity in open gravel channel

Based on a series of flume experiments,6 methods,i.e.the logarithmic velocity distribution regression method,the extensible Reynolds stress distribution method,the 3-D turbulence kinetic energy method,the vertical turbulence kinetic energy method,Han's empirical formula,and the drag coefficient method were adopted for calculation of the shear velocity of gravel river bed.Based on Han's empirical formula for shear velocity calculation,the influences of parameter values of different methods on the calculated result as well as the applicability of each method under different hydraulic and river bed conditions were analyzed.The result showed that the maximum mean square error of the shear velocity calculated by the above methods was 2.15 under the condition of smooth river bed,while the value was up to 8.84 under the condition of rough river bed.As a result,the logarithmic velocity distribution regression method is much suitable for smooth river bed because of its high accuracy,while the result of the 3-D turbulence kinetic method is relatively small under the same condition.Meanwhile the logarithmic velocity distribution regression method and the 3-D turbulence kinetic energy method are both suitable for rough river bed as compared with other methods.