This paper studies the viscid and inviscid fluid resonance in gaps of bottom mounted caissons onthe basis of the plane wave hypothesis and full wave model, The theoretical analysis and the numerical results demonstrat...This paper studies the viscid and inviscid fluid resonance in gaps of bottom mounted caissons onthe basis of the plane wave hypothesis and full wave model, The theoretical analysis and the numerical results demonstrate that the condition for the appearance of fluid resonance in narrow gaps is kh=（2n＋1）π （n=0, 1, 2, 3 ）, rather than kh=nn （n=0, 1, 2, 3, ...）; the transmission peaks in viscid fluid are related to the resonance peaks in the gaps. k and h stand for the wave number and the gap length. The combination of the plane wave hypothesis or the full wave model with the local viscosity model can accurately determine the heights and the locations of the resonance peaks. The upper bound for the appearance of fluid resonance in gaps is 2b/L〈l （2b, grating constant; L, wave length） and the lower bound is h/b〈~ l. The main reason for the phase shift of the resonance peaks is the inductive factors. The number of resonance peaks in the spectrum curve is dependent on the ratio of the gap length to the grating constant. The heights and the positions of the resonance peaks predicted by the present models agree well with the experimental data.展开更多
In the disturbance of unsteady flow field under the sea, the monitoring accuracy and precision of the bottom-mounted acoustic monitoring platform will decrease. In order to reduce the hydrodynamic interference, the pl...In the disturbance of unsteady flow field under the sea, the monitoring accuracy and precision of the bottom-mounted acoustic monitoring platform will decrease. In order to reduce the hydrodynamic interference, the platform wrapped with fairing structure and separated from the retrieval unit is described. The suppression effect evaluation based on the correlation theory of sound pressure and particle velocity for spherical wave in infinite homogeneous medium is proposed and the difference value between them is used to evaluate the hydrodynamic restraining performance of the bottom-mounted platform under far field condition. Through the sea test, it is indicated that the platform with sparse layers fairing structure(there are two layers for the fairing, in which the inside layer is 6-layers sparse metal net, and the outside layer is 1-layer polyester cloth, and then it takes sparse layers for short) has no attenuation in the sound pressure response to the sound source signal, but obvious suppression in the velocity response to the hydrodynamic noise. The effective frequency of the fairing structure is decreased below 10 Hz, and the noise magnitude is reduced by 10 d B. With the comparison of different fairing structures, it is concluded that the tighter fairing structure can enhance the performance of sound transmission and flow restraining.展开更多
为了解决座底式长基线水声跟踪系统的高效校阵问题,结合工程项目实际提出一种智能化分组并行校阵方法。该方法利用水下基阵布阵施工时获得的水声及差分全球定位系统(Differential Global Positioning System,DGPS)测量数据为基准,在校...为了解决座底式长基线水声跟踪系统的高效校阵问题,结合工程项目实际提出一种智能化分组并行校阵方法。该方法利用水下基阵布阵施工时获得的水声及差分全球定位系统(Differential Global Positioning System,DGPS)测量数据为基准,在校阵试验中采用多个水下基阵分组并行校阵的快捷方式,根据自动反馈的测量数据进行校阵误差收敛测量,当满足事先设定的校准误差后,获得水下基阵的精确位置信息,同时完成多个水下基阵的阵型校准。最后,在某水域采用跑船试验的方式进行验证。长基线系统测量的船只航行轨迹与DGPS轨迹重合性好,证明该方法具有智能化程度高、测量精度高、测阵效率及经济性好等优点,具有较高的军事及民用价值。展开更多
基金financially supported by the National Key R&D Program of China(Grant No.2017YFC0405402)
文摘This paper studies the viscid and inviscid fluid resonance in gaps of bottom mounted caissons onthe basis of the plane wave hypothesis and full wave model, The theoretical analysis and the numerical results demonstrate that the condition for the appearance of fluid resonance in narrow gaps is kh=（2n＋1）π （n=0, 1, 2, 3 ）, rather than kh=nn （n=0, 1, 2, 3, ...）; the transmission peaks in viscid fluid are related to the resonance peaks in the gaps. k and h stand for the wave number and the gap length. The combination of the plane wave hypothesis or the full wave model with the local viscosity model can accurately determine the heights and the locations of the resonance peaks. The upper bound for the appearance of fluid resonance in gaps is 2b/L〈l （2b, grating constant; L, wave length） and the lower bound is h/b〈~ l. The main reason for the phase shift of the resonance peaks is the inductive factors. The number of resonance peaks in the spectrum curve is dependent on the ratio of the gap length to the grating constant. The heights and the positions of the resonance peaks predicted by the present models agree well with the experimental data.
基金financially supported by the Natural Science Foundation of Shandong Province(Grant No.ZR2016DQ18)Shandong Provincial Key Technologies of Independent Innovation Project(Grant No.2014GJJS0101)
文摘In the disturbance of unsteady flow field under the sea, the monitoring accuracy and precision of the bottom-mounted acoustic monitoring platform will decrease. In order to reduce the hydrodynamic interference, the platform wrapped with fairing structure and separated from the retrieval unit is described. The suppression effect evaluation based on the correlation theory of sound pressure and particle velocity for spherical wave in infinite homogeneous medium is proposed and the difference value between them is used to evaluate the hydrodynamic restraining performance of the bottom-mounted platform under far field condition. Through the sea test, it is indicated that the platform with sparse layers fairing structure(there are two layers for the fairing, in which the inside layer is 6-layers sparse metal net, and the outside layer is 1-layer polyester cloth, and then it takes sparse layers for short) has no attenuation in the sound pressure response to the sound source signal, but obvious suppression in the velocity response to the hydrodynamic noise. The effective frequency of the fairing structure is decreased below 10 Hz, and the noise magnitude is reduced by 10 d B. With the comparison of different fairing structures, it is concluded that the tighter fairing structure can enhance the performance of sound transmission and flow restraining.
文摘为了解决座底式长基线水声跟踪系统的高效校阵问题,结合工程项目实际提出一种智能化分组并行校阵方法。该方法利用水下基阵布阵施工时获得的水声及差分全球定位系统(Differential Global Positioning System,DGPS)测量数据为基准,在校阵试验中采用多个水下基阵分组并行校阵的快捷方式,根据自动反馈的测量数据进行校阵误差收敛测量,当满足事先设定的校准误差后,获得水下基阵的精确位置信息,同时完成多个水下基阵的阵型校准。最后,在某水域采用跑船试验的方式进行验证。长基线系统测量的船只航行轨迹与DGPS轨迹重合性好,证明该方法具有智能化程度高、测量精度高、测阵效率及经济性好等优点,具有较高的军事及民用价值。
