自由面对潜艇尾流场流动特性影响研究

潜艇周围绕流场流动特性会影响潜艇的机动性能, 特别是近水面航行时, 自由面的存在会增大潜艇尾流场的复杂程度.为探究潜艇在近水面航行时自由液面对潜艇尾流场流动特性的影响机理,借助大型水下三维粒子图像测速技术开展潜艇尾流场流动特性研究.首先通过美国泰勒水池标准模型实验结果对试验方法准确性进行验证; 随后,用验证后的模型试验方法对潜艇尾流场进行测量,得到不同潜深工况、不同速度下的桨盘面轴向速度以及脉动速度,同时辅以数值模拟对试验无法测得的兴波波系及中纵剖面速度场加以补充,从兴波角度阐述了自由面对潜艇尾流场流动特性影响机理. 研究结果表明:潜艇在近水面航行时, 随着Fr增大,桨盘面处轴向速度云图中上方等值线整体趋于扁平化, 较4D潜深工况,1.5D潜深工况出现局部脉动速度极大值, 且脉动速度结构整体下移; 自由面存在时,艇体与自由面间流场速度明显增大, 特别在桨盘面区域, 流场速度明显提升.随着Fr增大, 桨盘面处的自由液面高度逐渐降低,这就导致了桨盘面位置出现更大的流体速度, 即造成了桨盘面伴流场挤压现象. 

RESEARCH ON THE INFLUENCE OF FREE SURFACE ON THE FLOW CHARACTERISTICS OF SUBMARINE WAKE 1)

The flow characteristics around the submarine will affect the maneuverability of the submarine, especially when the submarine is near the water surface, the existence of the free surface will increase the complexity of the wake field of the submarine. In order to explore the influence mechanism of free surface on the flow characteristics of submarine wake when the submarine near the free surface, the research on the flow characteristics of submarine wake is carried out with the help of large-scale underwater three-dimensional particle image velocimetry technology. Firstly, the accuracy of the test method in this study is verified by the standard model experiment of DTMB in USA; Then, the wake field of the submarine is measured by the model test, and the axial velocity and pulsating velocity of the propeller disk under different submergence depths and different speeds are obtained. At the same time, the wave and the velocity field of the longitudinal section which can not be measured by the model test are supplemented by numerical simulation, and the influence mechanism of the free surface on the flow characteristics of the wake field is expounded from the wave point of view. The results show that: When the submarine near the water surface, with the increase of Fr, the upper isopleth of the axial velocity at the propeller disk tends to be flattened; and compared with the 4D submergence depths, the local maximum value of pulsating velocity appears in the 1.5D submergence depths, and the structure of pulsating velocity moves down as a whole. When the free surface exists, the velocity of flow field between the hull and the free surface increases obviously, especially in the area of the propeller disk. With the increase of Fr, the height of the free surface of the propeller disk decreases gradually, which leads to a larger fluid velocity and the squeeze phenomenon of wake field on propeller disk.