Experimental study on water-entry cavity and trajectory of vehicle with asymmetric nose shape

非对称头型航行器入水空泡形态与弹道特性的实验研究

¹ School of Marine Science and Technology, Northwestern Polytechnical University, Xi'an 710072, China
² Key Laboratory of Unmanned Underwater Vehicle Technology, Northwestern Polytechnical University, Xi'an 710072, China

Received: 31 March 2021

Abstract

Different nose shape can cause a significant influence on the water entry trajectory and cavity. In order to study the evolution characteristics of cavity and trajectory of asymmetric nose in the process of water entry, based on the high-speed photography technology, the low-speed water entry comparative experiments were carried out for three different cut-angle nose types of 35°, 40° and 45° under different water entry angles. Through digital image processing technology, the contour of the water entry cavity and motion attitude information of the vehicle at different times are extracted, and the law of influence of the cut angle and entry angle on the cavity and trajectory is obtained. The experimental results show that: the cut angle side of the asymmetric nose can effectively promote the expansion of the cavity, thus forming the asymmetric water entry cavity; the expansion scale of the cavity is positively related to the initial horizontal expansion speed of the cavity and the area of the section of the head; the water entry trajectory of the asymmetric head will deflect to the cut angle side; the smaller the water entry angle is, the shorter the trajectory leveling time is, and the deeper the leveling depth is However, the change of attitude angle is almost independent of the entry angle.

摘要

头部形状对航行体的入水弹道和空泡形态有着显著的影响，为研究非对称头型在入水过程中空泡和弹道的演变特性，基于高速摄影技术，对带有35°，40°，45°不同切角头型的航行体开展了不同入水角条件下的低速入水对比实验。通过数字图像处理技术提取不同时刻下航行体的入水空泡轮廓以及运动姿态信息，得到了非对称头型航行体切角大小和入水角度对入水空泡和弹道轨迹的影响规律。实验结果表明：非对称头型切角侧能有效促进空泡的扩张从而形成不对称入水空泡；空泡扩张规模与空泡初始水平扩张速度和头型截切的切面区域面积正相关；非对称头型航行体入水弹道会向非切角侧偏转，且头型切角越小弹道偏转幅度越大，姿态角减小也越快；入水角越小，弹道拉平所需要的时间越短，拉平深度也越浅。