近岸破碎波水体掺气及气泡输运过程研究

Air entrainment and bubble movement processes in breaking waves

为准确探讨破碎波作用下气体如何卷入以及气泡的形成与输运特性,文章结合粒子图像测速技术(particleimage velocimetry, PIV)、高速相机和气泡测量系统,以及基于Navier-Stokes方程的三维数值模型对气泡形成及其运动过程进行研究。研究结果表明:文章建立的数值模型能合理地捕捉到破碎波作用下气体的卷入及其输运过程;波浪的破碎会形成较大的气腔,其破裂过程又将产生大量的气体微团;气泡会增加水体的紊动,造成水体与空气交界面附近形成大量的漩涡以及水体的飞溅;气泡的破裂会消耗大量的水体能量,同时发现较大的紊动动能与气泡的生成有关,且气泡数随平均紊动动能的增加呈线性增长关系。

To investigate how air is entrained and the formation and transport of bubbles under breaking waves,we carry out studies using particle image velocimetry(PIV),high-speed camera,bubble measuring system,and a three-dimensional numerical model based on the Navier-Stokes equations.The results show that the established numerical model can reasonably capture the air entrainment and bubble transport process under the action of breaking wave.A large bubble cavity is formed during wave breaking phase,which in turn produces a large amount of bubble cloud.Bubbles increase the turbulence of water,resulting in the formation of a large number of vortexes and water splash near the interface with the air.The burst of bubbles consumes a large amount of wave energy,and the larger turbulent kinetic energy is related to bubble generation.Moreover,we find that the number of bubbles increases linearly with the increase of average turbulent kinetic energy.