分层流体中自航和拖曳模型生成内波特性实验

Experiments on the characteristics of internal waves generated by self-propelled and towed models in a stratified fluid

在强密度跃层分层流体中,采用沿分层流水槽中纵剖面对称布置电导率探头阵列方法,对全附体潜艇模型在匀速自航和拖曳运动下生成内波时空特性进行了系列实验。结果表明:在两种运动方式下,在体积效应和尾迹效应内波之间均存在一个临界Froude数Fr_(c),其中拖曳方式下Fr_(c)≈3.40,而匀速自航方式下Fr_(c)≈2.9,小于拖曳方式下的临界值。当Fr<Fr_(c)时,内波相关速度等于物体运动速度,正对称的体积效应内波为主控内波,而且匀速自航方式下产生的体积效应内波最大峰-峰幅值H_(m)比拖曳情况大,表明推进器效应也会产生体积效应,并与艇体的体积效应形成正叠加;当Fr>Fr_(c)时,内波相关速度均小于物体运动速度,非对称的尾迹效应内波为主控内波,在拖曳方式下其相关速度Froude数Fr_(iw)在0.7~1.4范围内变化,内波最大峰-峰幅值随Fr增大而增大;在匀速自航方式下Fr_(iw)变化范围为0.4~1.5,内波无因次最大峰-峰幅值不随Fr增大而增大,而在0.04~0.07范围内变化。

Experiments were conducted for the time-space characteristics of internal waves generated by self-propelled and towed models located below the strong pycnocline of a stratified fluid.By means of realtime measurement of conductivity probe arrays arranged symmetrically in transverse sections of the stratified fluid tank,it is shown that the transition between the body-generated waves and wake-generated internal waves is related to the critical Froude number Fr_(c),where Fr_(c)=3.40 for the towing case and Fr_(c)=2.95 for the self-propelling case,smaller than the towing case.For Fr<Fr_(c),the internal wave correlation velocities are equal to the towed or self-propelled speeds of the models,and the internal waves are dominated by symmetric body-generated waves,and the maximum peak-peak amplitudes for such internal waves generated by the self-propelled model are bigger than those generated by the towed model,showing that the behavior of the propeller can also produce the body-forced effect.For Fr>Fr_(c),the internal wave correlation velocities are noticeably lower than the translating speeds of the models and the internal waves are dominated by asymmetric wake-generated waves.For the towing case,the Froude numbers associated with the correlation velocities Fr_(iw) for wake-generated internal waves vary within the range from 0.7 to 1.4,the maximum peak-peak amplitudes linearly increase with Fr.For the self-propelling case,the Fr_(iw) varies within the range from 0.4 to 1.5,the dimensionless maximum peak-peak amplitudes do not increase with Fr while varying within the range of 0.04~0.07.