稳定分层流数值模拟方法及圆球绕流特征研究

  目的  旨在研究分层流中潜艇加减速对尾迹特征特性的影响规律，为潜艇尾迹隐身提供理论依据。  方法  应用CFD技术，首先验证该技术模拟潜艇运动对自由面兴波的准确性，再基于自由面兴波与其辐聚辐散场、内波速度场进行分析，对实尺度潜艇进行加减速航行模拟。通过对自由面速度场求散度，深入研究潜艇加、减速对自由面及跃层的影响。  结果  研究表明：潜艇进行非定常运动时，尾流场横波、散波分布规律较匀速运动截然不同，其兴波夹角增减约10%~25%，且兴波峰值位置明显前置与后置，结合波高及速度散度场得到潜艇加、减速造成自由表面辐聚辐散效应的差异。  结论  当潜深和分层模式等相同，潜艇减速时，可降低尾流场扰动、兴波高度及其粗糙度，加速状态可显著增加潜艇近场扰动与被探测概率。

On the numerical methods of the stable stratified flows and wake characteristics around a sphere

  Objectives  This paper seeks to grasp the influence of a submarine's acceleration and deceleration on its wake spectrum characteristics in stratified flow, and provide a theoretical basis for submarine stealth.  Methods  The accuracy of CFD technology in simulating the motion of the submerged body making waves on the free surface is first verified, and then analyses are made of the wave-making on the free surface, its convergence and divergence field, and internal wave velocity field under the acceleration and deceleration of a real-scale submarine. By calculating the divergence of the velocity field of the free surface, the influence of submarine acceleration and deceleration on the free surface and jump layer is determined in depth.  Results  The results show that when the submarine is in unsteady motion, the shear wave and scattered wave distribution of the wake field are completely different from those under uniform motion. Combining the wave height and velocity divergence field, the acceleration and deceleration of the submarine causes the free surface convergence and divergence effect.  Conclusions  When the submarine depth and stratification mode are the same, the wake field disturbance, wave height and roughness can be reduced when the submarine decelerates, and the acceleration state can significantly increase the probability of near-field disturbances leading to the detection of the submarine.