明渠减速流下床面摩阻流速研究

Friction velocity in decelerating open channel flow

针对明渠非均匀流,采用立面二维数值试验的方法,并将雷诺应力垂线分布计算结果延伸至床面,以此计算减速流情况下床面摩阻流速,得到了不同壅水下床面摩阻流速的计算结果.研究表明:在壅水情况下,当流量和底坡相同时,壅水段摩阻流速随水深的增加而逐渐减小;在相同水深和底坡下,摩阻流速随流量的增加而增大;在相同流量和水深下,摩阻流速随底坡的增大而增大.为满足工程中计算的需要,根据数值试验结果拟合得到了明渠水流壅水情况下床面摩阻流速的实用计算式.

Vertical two-dimension numerical simulations were carried out to investigate the shear ve-locity under decelerating non-uniform flow conditions .For estimation of the shear velocity under dif-ferent backwater conditions ,the Reynolds shear stress predicted by the numerical model was extended to the bed surface .Results show that in a backwater condition ,the friction velocity decreases with the increase of water depth when flow rate and bottom slope are fixed ;the friction velocity increases with the increase of flow rate when the water depth and bottom slope are kept constant ;the friction veloci-ty increases with the increase of bottom slope when the same flow rate and water depth are fixed .To meet the needs of practical engineering calculations ,based on the numerical results ,a convenient cal-culation formula for friction velocity was proposed .