密度分层流体中不同长径比拖曳潜体激发内波特性实验
摘要
Experiments are conducted for the kinematic and dynamic characteristics of the internal waves excited by horizontally towed bodies with three aspect ratios in a stratified fluid with a pycnocline. Based on the dynamic measurements of the density perturbation generated by towed bodies, it is shown that the body-generated waves are a type of stationary Lee wave structures with multi-modes; moreover the wake-generated waves are a type of non-stationary quasi-Lee wave structures with respect to the towed bodies, where the quasi-Lee waves are shown to be produced by the large-scale coherent structure in turbulent wakes acting as a moving excitation. Results show that the transition between the Lee and quasi-Lee waves occurs at a critical Froude number <italic>Fr</italic><sub>c</sub> which is shown to be linearly dependent of the aspect ratio, and the Froude numbers with respect to the correlation velocities of the quasi-Lee waves remain at relatively constant value of approximately 0.8 regardless of the aspect ratios. Results further show that there exists a Froude number <italic>Fr</italic><sub>p</sub> which is linearly dependent of the aspect ratio. The wave patterns for <italic>Fr</italic><<italic>Fr</italic><sub>p</sub> are dominated by Lee waves and the dimensionless peak-to-peak amplitudes for such waves increase with <italic>Fr</italic>. Though the wave patterns for <italic>Fr</italic><sub>p</sub><<italic>Fr</italic><<italic>Fr</italic><sub>c</sub> are also dominated by Lee waves, the dimensionless peak-to-peak amplitudes for such waves decrease with <italic>Fr</italic> and the influence of quasi-Lee waves gradually increases; the wave patterns for <italic>Fr</italic>><italic>Fr</italic><sub>c</sub> are dominated by quasi-Lee waves and the dimensionless peak-to-peak amplitudes for such waves linearly increase with <italic>Fr</italic> regardless of the aspect ratios, where <italic>Fr</italic> is the Froude number for the characteristic diameter of the s