涌波的基本性质

Basic characters about bore

分析了溃坝波和涌潮等波动的基本特征。水流穿越涌波时,水流流量、动量虽保持守恒,但机械能大量损耗,因此通常所用的SaintVenant方程并不能描述涌波附近的流动。从微观角度看,考虑铅垂流速分量及水平速度不均匀性所引起的色、耗散效应后,涌波波后将产生衰减的高频波,波陡大为增加,因此表面失稳,进而形成漩滚。分析说明,Froude数也是色、耗散效应的比值,决定了涌波的局部形态。数值计算结果与试验值极为接近。由于天然河道形态复杂,进行涌波数值计算时,需对控制方程的源项进行处理,方能对涌波有深入的了解。

The basic characteristics of bore and dambreak wave are analyzed. Although the flux mass and momentum of flow remain conservational when a flow goes through a bore, there is certain loss of mechanical energy, so SaintVenant equations cannot be used to describe the flow near the bore. Microcosmically, if dissipation and dispersion are taken into account, which are caused by component of vertical velocity and nonuniformity of horizontal velocity, the attenuated high frequency wave occurs in the back of bore, and wave steepness increases rapidly, causing water surface unstable, and then forming roller. The analysis shows that Froude number is the ratio of dispersion to dissipation, which controls the local shape of bore, and the results are close to the experimental data. Because of the complexity of configuration of river, the source item of controlling equations should be handled when numerical simulation executed, in order to further understand the characterstics of bore.