摘要:
在具有连续密度跃层的分层流体中,对长径比为7：1的回转体在迎水和背水运动下激发体积效应与尾迹效应内波特性开展了系列实验.结果表明,体积效应激发内波属于一种相对于回转体定常的多模态Lee波结构,而尾迹效应激发主控内波为相对于回转体非定常的拟Lee波结构,这是一类由湍流尾迹中大尺度相干结构作为移动源激发的内波结构,在Lee波与拟Lee波之间存在一个与长径比近似为线性关系的临界转捩Froude数Fr_c,当FrFr_c时拟Lee波为主控内波,而且拟Lee波相关速度Froude数近似为一个常数0.8,其无因次峰-峰幅值随Fr的增大近似线性增大,其中Fr为回转体特征直径Froude数.结果还表明,回转体头部与尾部几何形式并不影响其激发内波临界转捩Froude数Fr_c、拟Lee波相关速度Froude数及其峰-峰幅值变化特性.
Abstract:
Experiments are conducted for the characteristics of both body and wake-generated internal waves due to a revolution body（aspect ratio 7：1） in a stratified fluid with a pycnocline where the revolution body is horizontally towed in forward and backward ways.Results show that the body-generated internal waves are a type of stationary multiple-mode Lee wave structures,and the wake-generated internal waves are a type of non-stationary quasi-Lee structures produced by the large-scale coherent structure in the turbulent wake acting as a moving excitation with respect to the towed revolution body.The transition between Lee and quasi-Lee waves occurs at a critical Froude number Fr_c which is shown to be linearly dependent on the aspect ratios of the revolution bodies where the wave patterns for Fr Fr_c are dominated by Lee waves,whereas the wave patterns for Fr Fr_c are dominated by quasi-Lee waves, Fr is the Froude number for the characteristic diameter of the revolution body.For the quasi-Lee waves,the dimensionless peak-topeak amplitudes linearly increase with Fr and the Froude numbers relative to the correlation velocities remain at a relatively constant value of approximately 0.8 regardless of the aspect ratios.Moreover,the head and the tail shapes of the revolution body have no remarkable influence on the critical Froude number Fr_c,as well as both the Froude numbers relative to the correlation velocities and the dimensionless peak-to-peak amplitudes of the quasi-Lee waves.
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