分层流体中潜艇模型螺旋桨作用对内波特性影响实验研究

Experimental investigation of propeller effect from a submarine model on internal waves in a stratified fluid

在具有连续密跃层的分层流体中,采用多通道电导率阵列技术和循环拖曳技术,对长径比为8和带有5叶左旋桨的自推进Suboff潜艇模型在3种拖曳速度(Fr=0.7、2.1和4.2)下,伴随不同强度的螺旋桨效应Jnd生成的内波特性进行了实验研究。结果表明,在水平波形结构中,螺旋桨效应激发的内波为一类内层V字型波,由对称结构和非对称结构组成。在低速(Fr=0.7和2.1)时,存在一个螺旋桨效应的临界点;当Jnd小于临界值时,主控内波是定常的,其激发源为艇体和螺旋桨的组合体积效应;当Jnd大于临界值时,主控内波是非定常的,其激发源为螺旋桨的尾迹效应;转捩前后的无因次内波峰-峰幅值均随Jnd增大而线性增大;内层V字型波的出现时间和波形张角随Jnd增大而逐渐提前和变大。在高速(Fr=4.2)时,主控内波是非定常的;在自航点前,主控激发源为艇体的尾迹效应,螺旋桨对其有衰减作用,无因次内波峰-峰幅值随Jnd增大而线性减小,内层V字型波也逐渐减弱,衰减作用在自航点达到最大;在自航点后,主控激发源为螺旋桨的尾迹效应,无因次内波峰-峰幅值随Jnd增大而线性增大,内层V字型波也逐渐增强。

Experiments are conducted for internal waves excited by different propeller effects Jnd under the circumstances that the self-propelled Suboff model with an aspect ratio of 8 and 5 lefe rotative blades is towed horizontally at three different velocities（Fr=0.7, 2.1, 4.2） in the stratified fluid with a pycnocline. The wave characteristics are analyzed by means of multi-channel conductivity probe arrays technology. Observation shows that the propeller-generated wave is a kind of inner V shaped wave on the horizontal plane, composed of symmetrical structure and asymmetrical structure. Results show that there exists a critical point of propeller effect at low towed speeds（Fr=0.7, 2.1）; the dominant wave is stationary with respect to the body before the critical point indicating that the excitation source is the combined volume effect of body and propeller; the dominant wave is nonstationary after the critical point, indicating that the excitation source is the wake effect induced by the propeller;dimensionless peak-to-peak amplitudes increase with increasing Jnd linearly; the inner V shaped wave gradually becomes larger in angle and come ahead of time with increasing Jnd. Furthermore, the internal wave is nonstationary at high towed speed（Fr=4.2）;the excitation source is the wake effect of body prior to the self-propulsion point; dimensionless peak-to-peak amplitudes decrease with increasing Jnd linearly and the inner V shaped wave weakens due to the propeller effect; after that, the excitation source is the wake effect of propeller; dimensionless peak-to-peak amplitudes increase with increasing Jnd linearly and the inner V shaped wave strengthens gradually.