The force-coupling method (FCM) developed by Maxey and Patel (2001) was modified and applied to trace the trajectories of spherical bubbles with solid-like and slip surfaces. Careful comparison was made to the experim...The force-coupling method (FCM) developed by Maxey and Patel (2001) was modified and applied to trace the trajectories of spherical bubbles with solid-like and slip surfaces. Careful comparison was made to the experimental results of Takemura et al. (2000, 2002a, 2002b). First, the result obtained by use of the original version of the FCM was compared to the experimental results. It was found that the original FCM was not feasible for tracing spherical bubble trajectories. Then, a correction was made to the FCM calculation of the bubble velocity by renormalization in terms of the bubble Reynolds number, which could very well trace the trajectory of the bubble with a solid-like, no-slip surface, but not that of a bubble with a slip surface. Finally, a substantial correction was made to the monopole term of the FCM, which could trace the trajectory of a bubble with a solid-like or slip surface very well even for the Reynolds number up to 20.展开更多
声空化实验中经常观察到由许多空化气泡组成的各种泡群结构.本文利用气泡群及群内任一气泡的Rayleigh-Plesset方程并结合van der Waals型过程方程,研究了不同类型气泡组成的混合泡群中的气泡半径、泡内温度和群内压力脉冲变化规律,得到...声空化实验中经常观察到由许多空化气泡组成的各种泡群结构.本文利用气泡群及群内任一气泡的Rayleigh-Plesset方程并结合van der Waals型过程方程,研究了不同类型气泡组成的混合泡群中的气泡半径、泡内温度和群内压力脉冲变化规律,得到以下结果:相同尺寸相同气体气泡和相同尺寸不同气体气泡组成的两种泡群中气泡所含的不同气体对泡内温度有较明显的影响,但对气泡半径变化和群内压力脉冲峰值的影响较小;不同尺寸相同气体气泡和不同尺寸不同气体气泡组成的两种混合泡群中,随着大气泡数的增多,大小气泡内温度开始快速下降,之后大泡内温度逐渐趋近于纯大气泡组成泡群的泡内温度,小泡内温度逐渐趋近于许多大泡辐射作用下的单一小气泡泡内温度;气泡崩溃时产生的压力脉冲峰值,先急剧减小到拐点,之后平稳增加并逐渐趋近于纯氩气大气泡和纯氦气大气泡组成泡群内的压力脉冲峰值;群内大气泡数占比对泡群空化特性有重要影响,只有大气泡数占比达到一定值后泡群中才能出现不同尺寸气泡同时崩溃的现象.展开更多
Based on the theory of compressible fluid, a three-dimension boundary element method is utilized to research the motion of bubble. The far-field noise radiation during the growth and contraction is calculated by the K...Based on the theory of compressible fluid, a three-dimension boundary element method is utilized to research the motion of bubble. The far-field noise radiation during the growth and contraction is calculated by the Kirchhoff formula and the Ffowcs Williams-Hawkings （FW-H） formula with a fixed radiation surface being arranged at the near-field of bubble as a new acoustic source. The results show that the amplitude of the sound pressure induced by non-spherical bubble is lower than that of spherical bubble in the contraction phase. The retardance effect is more obvious when the observer is farther away from the bubble. In the anaphase of contraction, the observer with the maximum amplitude of sound pressure moves up with the obvious jet. Larger buoyance parameters will generate lower sound pressure amplitudes in the anaphase, while larger intensive parameters will cause higher sound pressure amplitudes in the whole procedure of bubble motion.展开更多
文摘The force-coupling method (FCM) developed by Maxey and Patel (2001) was modified and applied to trace the trajectories of spherical bubbles with solid-like and slip surfaces. Careful comparison was made to the experimental results of Takemura et al. (2000, 2002a, 2002b). First, the result obtained by use of the original version of the FCM was compared to the experimental results. It was found that the original FCM was not feasible for tracing spherical bubble trajectories. Then, a correction was made to the FCM calculation of the bubble velocity by renormalization in terms of the bubble Reynolds number, which could very well trace the trajectory of the bubble with a solid-like, no-slip surface, but not that of a bubble with a slip surface. Finally, a substantial correction was made to the monopole term of the FCM, which could trace the trajectory of a bubble with a solid-like or slip surface very well even for the Reynolds number up to 20.
文摘声空化实验中经常观察到由许多空化气泡组成的各种泡群结构.本文利用气泡群及群内任一气泡的Rayleigh-Plesset方程并结合van der Waals型过程方程,研究了不同类型气泡组成的混合泡群中的气泡半径、泡内温度和群内压力脉冲变化规律,得到以下结果:相同尺寸相同气体气泡和相同尺寸不同气体气泡组成的两种泡群中气泡所含的不同气体对泡内温度有较明显的影响,但对气泡半径变化和群内压力脉冲峰值的影响较小;不同尺寸相同气体气泡和不同尺寸不同气体气泡组成的两种混合泡群中,随着大气泡数的增多,大小气泡内温度开始快速下降,之后大泡内温度逐渐趋近于纯大气泡组成泡群的泡内温度,小泡内温度逐渐趋近于许多大泡辐射作用下的单一小气泡泡内温度;气泡崩溃时产生的压力脉冲峰值,先急剧减小到拐点,之后平稳增加并逐渐趋近于纯氩气大气泡和纯氦气大气泡组成泡群内的压力脉冲峰值;群内大气泡数占比对泡群空化特性有重要影响,只有大气泡数占比达到一定值后泡群中才能出现不同尺寸气泡同时崩溃的现象.
基金supported by the Key Program of the National Natural Science Foundation of China(No.50939002)the National Defense Basic Scientific Research Program of China(No.613157)the Excellent Young Science Foundation of the National Natural Science Foundation of China(No.51222904)
文摘Based on the theory of compressible fluid, a three-dimension boundary element method is utilized to research the motion of bubble. The far-field noise radiation during the growth and contraction is calculated by the Kirchhoff formula and the Ffowcs Williams-Hawkings （FW-H） formula with a fixed radiation surface being arranged at the near-field of bubble as a new acoustic source. The results show that the amplitude of the sound pressure induced by non-spherical bubble is lower than that of spherical bubble in the contraction phase. The retardance effect is more obvious when the observer is farther away from the bubble. In the anaphase of contraction, the observer with the maximum amplitude of sound pressure moves up with the obvious jet. Larger buoyance parameters will generate lower sound pressure amplitudes in the anaphase, while larger intensive parameters will cause higher sound pressure amplitudes in the whole procedure of bubble motion.
