摘要:
对于三维空间等深水中,无旋性自由表面周期性规则前进重力波传递在均匀流中的波流场,依质量守恒取—波长的流体质点的运动位移的波长平均高程,所得其标注参数恰为其在原静止水中的位置下,完全以Lagrange方式的参数控制式,解出此波流场至第三阶的全Lagrange形式解且得到检验验证;其中波流交互作用效应存在于Lagrange流速势中,使得波流场中的压力不受均匀流的影响.而Euler形式解所无法描述的流场特性,包括大于前进波周期的流体质点的运动周期,与其受前进波引起的质量传输速度、它们间的关系,及流体质点对其运动周期平均的高程与成因等,都说明是随流体质点所在的高程向下做指数函数样递减;而流体质点的三维空间螺旋曲线式的运动轨迹与烟线,其随均匀流的流向流速而变化的情况,例如其在均匀流于前进波波向有同向的流速分量时,是受流体质点恰在波谷断面处时的流速大小而变的形式,与其在均匀流于前进波波向有反向的流速分量时,则受流体质点恰在波峰断面处时的流速大小而变的形式,有很大不同的倒反形式甚至以封闭曲线形式呈现.最后,说明波流场变成稳定性运动流场时的特性,并证实其在无流时退化成纯前进波的情况.
Abstract:
A third-order Lagrangian solutions is found directly by the full Lagrangian parametric governing equations,with the parameters of identifying each water particle which is obtained in mass conservation from taking the wavelength-averaged level of the vertical displacement of water particles along the direction of the wave propagation and is just the position of particle in the original still water, for the irrotational free surface progressive gravity waves propagating on uniform current in the three dimension.It is found that the effect of wave-current interaction is occurred in Lagrangian velocity potential,so that the pressure is not affected by the uniform current in the wave-current field.The drift velocity,Lagrangian mean level of particle and its motion period longer than the wave period which are exponentially decreasing with the depth of particle＇s level and the pathlines of particle and the streakline are then all presented, these are to be excluded in Eulerian solution.Furthermore,the forms of the helical pathlines of particles varying with the direction and speed of the uniform current are appeared to be turned from the wave velocity and current velocity component in co-direction to in anti-direction,even become into a closed orbit.The special case when the wave-current field is at the steady motion is also interpreted its consequential charateristics.The present solution can be reduced to that of the pure progressive waves as no current exists.
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