Experiments are carried out to study the characteristics of active bubbles entrained by breaking waves as these propagate over an abruptly topographical change or a submerged breakwater. Underwater sounds generated by...Experiments are carried out to study the characteristics of active bubbles entrained by breaking waves as these propagate over an abruptly topographical change or a submerged breakwater. Underwater sounds generated by the entrained air bubbles are detected by a hydrophone connected to a charge amplifier and a data acquisition system. The size distribution of the bubbles is then determined inversely from the received sound frequencies. The sound signals are converted from time domain to time-frequency domain by applying Gabor transform. The number of bubbles with different sizes are counted from the signal peaks in the time-frequency domain. The characteristics of the bubbles are in terms of bubble size spectra, which account for the variation in bubble probability density related to the bubble radius r. The experimental data demonstrate that the bubble probability density function shows a - 2.39 power-law sealing with radius for r 〉 0. 8 mm, and a- 1.11 power law for r 〈0.8 mm.展开更多
This paper presents an improved Nearest Neighboring Particle Searching （NNPS） technique for numerical modeling of water waves with the Smoothed Particle Hydrodynamics （SPH） method. The proposed technique differs f...This paper presents an improved Nearest Neighboring Particle Searching （NNPS） technique for numerical modeling of water waves with the Smoothed Particle Hydrodynamics （SPH） method. The proposed technique differs from others by introducing the concept of Inner and Outer Particle Searching （lOPS） and shifting most of advanced CPU operations into simple addition operations. The IOPS method is shown to significantly improve the computational efficiency and reduce the CPU time especially for large number of particles, based on comparisons with other two NNPS methods. This method is implemented in a 2DV numerical wave flume conducted by the SPH method. Three test cases are examined, including generations and propagations of dam-breaking induced waves, solitary wave and irregular wave. Calculated results are in good agreements with experimental data and theoretical solutions with fairly satisfactory CPU time-consuming. The wave motions observed in physical facilities are successfully reproduced by the SPH numerical wave flume, revealing its robust capability of modeling realistic wave propagation and substantial potential for a wide variety of hydrodynamic problems.展开更多
文摘Experiments are carried out to study the characteristics of active bubbles entrained by breaking waves as these propagate over an abruptly topographical change or a submerged breakwater. Underwater sounds generated by the entrained air bubbles are detected by a hydrophone connected to a charge amplifier and a data acquisition system. The size distribution of the bubbles is then determined inversely from the received sound frequencies. The sound signals are converted from time domain to time-frequency domain by applying Gabor transform. The number of bubbles with different sizes are counted from the signal peaks in the time-frequency domain. The characteristics of the bubbles are in terms of bubble size spectra, which account for the variation in bubble probability density related to the bubble radius r. The experimental data demonstrate that the bubble probability density function shows a - 2.39 power-law sealing with radius for r 〉 0. 8 mm, and a- 1.11 power law for r 〈0.8 mm.
基金Project supported by the Program for New Century Excellent Talents in University of China (Grant No. NCET-07-0255)the Special Fund of State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering,Hohai University (Grant No. 2009585812)
文摘This paper presents an improved Nearest Neighboring Particle Searching （NNPS） technique for numerical modeling of water waves with the Smoothed Particle Hydrodynamics （SPH） method. The proposed technique differs from others by introducing the concept of Inner and Outer Particle Searching （lOPS） and shifting most of advanced CPU operations into simple addition operations. The IOPS method is shown to significantly improve the computational efficiency and reduce the CPU time especially for large number of particles, based on comparisons with other two NNPS methods. This method is implemented in a 2DV numerical wave flume conducted by the SPH method. Three test cases are examined, including generations and propagations of dam-breaking induced waves, solitary wave and irregular wave. Calculated results are in good agreements with experimental data and theoretical solutions with fairly satisfactory CPU time-consuming. The wave motions observed in physical facilities are successfully reproduced by the SPH numerical wave flume, revealing its robust capability of modeling realistic wave propagation and substantial potential for a wide variety of hydrodynamic problems.
