摘要
自振空化射流冲蚀模式是射流作业的最直观特征,但其演化机制尚不完全清晰,限制了模式的主动调控及射流高效应用。首先基于自振空化射流冲蚀试验,探明冲蚀模式随空化数和靶距的演变规律,通过高速摄像手段获取不同冲蚀模式下空泡云瞬时形态特征,采用正交模态分解得到空泡溃灭的统计规律;在此基础上,基于瞬态大涡模拟的计算流体动力学仿真方法,获得典型冲蚀模态下流体动力学特性,深入探究并揭示冲蚀模式形成机制。研究结果表明,不同空化数下随靶距变化,射流冲蚀特征呈现出3种典型冲蚀模式A、B、C,其中冲蚀模式A由冲蚀环1和较大冲蚀环2组成,冲蚀模式B仅包含冲蚀环1,冲蚀模式C主要由冲蚀环1及较小冲蚀环3组成;三种冲蚀模式中,均存在冲蚀环1,其能量最强,为主环,而不同冲蚀模式之间的转换方式与空化数有关。三种冲蚀模式形成机制如下:靶距较短时,冲蚀模式A中冲蚀环1由空化射流剪切生成的主空泡云溃灭空蚀而成,冲蚀环2由壁面涡环产生的次生空泡云溃灭造成;靶距较长时,冲蚀模式B仅包含冲蚀环1,该冲蚀模式下射流空蚀能力较强;特定空化数及靶距下,冲蚀模式C中冲蚀环1及冲蚀环3,分别由空化射流的主云团与次云团交替脱落后,依次撞击靶物产生。
The erosion pattern of self-excited cavitating waterjet is the most intuitive characteristic of operation.However,its evolution mechanism is not yet clear,which limits the active control of the pattern and the efficient application of waterjet.Firstly,erosion experiments of self-excited cavitating waterjet were carried out to elucidate the evolution of erosion pattern as cavitation number and standoff distance changed.The instantaneous morphological characteristics of the cavitation cloud under different erosion patterns were obtained by visualization experiments based on a high-speed camera.The statistical regularity of bubble collapse was obtained by orthogonal modal decomposition.Meanwhile,combined with the computational fluid dynamics simulation method based on transient large eddy simulation,the fluid dynamic characteristics under typical erosion patterns were obtained to explore and clarify the erosion patterns’formation mechanism.The research results show that under different cavitation numbers,with the increase of standoff distance,three representative erosion patterns,A,B and C,appear,in which erosion pattern A is composed of erosion ring 1 and larger erosion ring 2,erosion pattern B contains only erosion ring 1,erosion pattern C mainly comprises erosion ring 1 and smaller erosion ring 3.Ring 1 as the primary ring occurs in all the patterns,which possesses the highest erosive power.The transfer mode between different erosion pattern is related to cavitation number.The formation mechanisms of three erosion patterns are as follows:when the standoff distance is short,ring 1 of pattern A is eroded by the collapsing of the cavitation cloud that appears in the waterjet’s shear layer,and ring 2 is caused by the secondary cavitation cloud incepted in vortex ring near the wall.When the standoff distance is large,erosion pattern B contains only ring 1,mainly caused by the collapse of the primary cavitation cloud in the waterjet’s shear layer.Under a specific cavitation number and standoff distance,rings 1 and 3 in erosion pattern C are generated by the alternating shedding and colliding of the cavitating waterjet’s primary and secondary cavitation clouds.
作者
蔡腾飞
潘岩
王啸林
马飞
祝启恒
韩健
CAI Tengfei;PAN Yan;WANG Xiaolin;MA Fei;ZHU Qiheng;HAN Jian(School of Mechanical Engineering,University of Science and Technology Beijing,Beijing 100083;Shunde Innovation School,University of Science and Technology Beijing,Foshan 528399)
出处
《机械工程学报》
EI
CAS
CSCD
北大核心
2024年第6期378-385,共8页
Journal of Mechanical Engineering
基金
国家重点研发计划(2021YFB3401502)
中央高校基本科研业务费(FRF-TP-22-032A1)
佛山市科创基金(BK22BE020)资助项目。
关键词
自振射流
空化射流
冲蚀模式
空泡云
流体动力学
self-excited waterjet
cavitating waterjet
erosion pattern
cavitation cloud
fluid dynamics
