磁致伸缩仪超声空化流的数值研究

夏冬生，孙昌国，于彦，张会臣

(大连海事大学机械工程系，辽宁大连116026)

摘要：基于CFD方法采用“Singhal完全空化模型”及动网格技术对磁致伸缩仪超声空化流进行数值计算。结果表明，变幅杆高频振动引起试样表面附近局部流场发生空化，且在试样表面形成脉冲压力；压力与空泡体积组分在试样表面近似呈环形分布，并随试样振动，二者周期性变化。试样表面中心区域空泡经两次振荡后溃灭产生强烈脉冲压力，峰值可达5 MPa；脉冲压力在试样表面按间隔环形区域分布，且随试样振动在相邻环形区域交替出现。随超声波在空化流场中传播声压快速衰减；压力只在距变幅杆端面约20 mm内波动明显，振幅从25 μm增大到30 μm时试件中心区域脉冲压力增大；振幅增大到35 μm时空化效果增强，试件中心区域所受脉冲压力作用减弱。

关键词：空化；超声空化流；高频振动；脉冲压力

中图分类号:TV131.3文献标志码：A

基金项目：国家自然科学

收稿日期：2014-08-07修改稿收到日期：2014-10-23

Numerical study on magnetostriction-induced cavitation flow

XIADong-sheng,SUNChang-guo,YUYan,ZHANGHui-chen(Department of Mechanical Engineering, Dalian Maritime University, Dalian 116026, China)

Abstract:The magnetostriction-induced ultrasonic cavitation flow was numerically simulated by using the “Singhal full cavitation model” and the dynamic mesh technique. The computational results show that cavitation occurs at the local flow field proximate to the specimen and the specimen is subjected to the impact of impulse pressure caused by high frequency vibration of the specimen. The pressure and vapor volume fraction (VVF) are annularly distributed around the center of the specimen, and vary periodically along with the vibration. Bubbles usually collapse after twice oscillations in the center region of specimen, which results in intense impulse pressure that can reach about 5MPa. The impulse pressure forms in the interval annular zones and alternately occurs in the adjacent annular zones along with the vibration cycle. Acoustic pressure quickly attenuates as the ultrasonic wave propagates in the ultrasonic cavitation flow field. The considerable fluctuation of pressure occurs only within a distance of 20 mm to the end of ultrasonic solid horn. The impulse pressure is promoted in the central region of specimen as the vibration amplitude is increased from 25μm to 30μm. When the vibration amplitude is further increased to 35μm, the effect of cavitation is further enhanced, but the impulse pressure is weakened in the central region of specimen.

Key words:cavitation; ultrasonic cavitation flow; high frequency vibration; impulse pressure

当局部压力降至足够低时低压区液体可气化、溶解在液体中的气体析出，产生空泡。空泡从初生、发展、塌陷直至溃灭的整个过程称为空化。空化不仅使流体机械零部件表面产生空蚀破坏，降低机械的工作效率，甚至会导致设备无法正常工作[1-2]。空蚀机理为当空泡在固体表面附近溃灭时，产生高速微射流或(与)冲击波[3-4]，作用于固体表面形成显著的冲击压力，表面材料因受冲击压力频繁作用发生疲劳破坏。……