Three-dimensional mode coupling around a conical seamount in an ocean waveguide is studied. It is shown that strong mode coupling occurs at the edge of a conical seamount for the incident normal modes with significant...Three-dimensional mode coupling around a conical seamount in an ocean waveguide is studied. It is shown that strong mode coupling occurs at the edge of a conical seamount for the incident normal modes with significant amplitudes below the top of the seamount. Therefore, mode coupling is critical for the investigation of the acoustic field around a seamount. In addition, we suggest the use of random discretization for representing smoothly varying bathymetry. For the use of uniform discretization, when the horizontal step size is greater than half of the wavelength, artificial diffraction lobes appear due to coherent backscatter. However, by using the random discretization scheme instead, such artificial diffraction lobes are diffused, resulting in a faster convergence rate.展开更多
A spectral coupled-mode solution of the three-dimensional （319） acoustic field generated by a point source in the presence o[ an axisymmetric seamount is developed. Based on the same theoretical foundation as the fo...A spectral coupled-mode solution of the three-dimensional （319） acoustic field generated by a point source in the presence o[ an axisymmetric seamount is developed. Based on the same theoretical foundation as the for- mulation presented by Taroudakis [3. Comput. Acoust. 4 （1996） 101], the present approach combines a spectral decomposition in azimuth with a coupled-mode theory for two-way range-dependent propagation. However, the earlier formulations are severely limited in terms of frequency, size and geometry o[ the seamount, the seabed composition, and the distance between the source and the seamount, and are there/ore severely limited in regard to realistic seamount problems. Without changing the fundamental theoretical foundation, the present approach applies a number of modifications to the formulation, leading to orders of magnitude improvement in numerical efficiency for realistic problems. Therefore, realistic propagation and scattering scenarios can be modeled, including effects of seamount roughness and realistic sedimentary structure.展开更多
A recently developed three-dimensional normal-mode model is adopted to investigate mode coupling around a seamount in a deep water environment. As indicated by the theoretical analysis and verified by the numerical re...A recently developed three-dimensional normal-mode model is adopted to investigate mode coupling around a seamount in a deep water environment. As indicated by the theoretical analysis and verified by the numerical results, strong mode coupling occurs at the edge of a seamount under certain conditions. Therefore, mode coupling is critical for the investigation of the acoustic field in the presence of a seamount. In addition, the issue regarding the number of sectors assuring convergence is also presented. This issue is important in a two-way coupled-mode approach, especially for solving three-dimensional problems, because the computational effort increases dramatically with the number of sectors in representing a varying bathymetry. The theoretical analysis as well as the numerical example in this paper shows that artificial diffraction lobes form in the event that uniform discretization is used with a horizontal step size greater than half of the acoustic wavelength. However, by using random discretization instead, such artificial diffraction lobes are diffused, resulting in a faster convergence rate.展开更多
An efficient, accurate, and numerically stable coupled-mode solution is presented for acoustic propagation in a range-dependent waveguide. This method is numerically stable due to the appropriately normalized range so...An efficient, accurate, and numerically stable coupled-mode solution is presented for acoustic propagation in a range-dependent waveguide. This method is numerically stable due to the appropriately normalized range solutions introduced in the formulation. In addition, by combining a forward marching and a backward marching, this method provides accurate solu- tions for range-dependent propagation problems, especially those characterized by large bottom slope angle and/or high impedance contrast between water and the bottom. Furthermore, this two-way solution also provides high efficiency, which is achieved by applying the single-scatter approximation. Numerical examples are also provided to demonstrate the efficiency, accuracy, and stability of this method.展开更多
文摘Three-dimensional mode coupling around a conical seamount in an ocean waveguide is studied. It is shown that strong mode coupling occurs at the edge of a conical seamount for the incident normal modes with significant amplitudes below the top of the seamount. Therefore, mode coupling is critical for the investigation of the acoustic field around a seamount. In addition, we suggest the use of random discretization for representing smoothly varying bathymetry. For the use of uniform discretization, when the horizontal step size is greater than half of the wavelength, artificial diffraction lobes appear due to coherent backscatter. However, by using the random discretization scheme instead, such artificial diffraction lobes are diffused, resulting in a faster convergence rate.
文摘A spectral coupled-mode solution of the three-dimensional （319） acoustic field generated by a point source in the presence o[ an axisymmetric seamount is developed. Based on the same theoretical foundation as the for- mulation presented by Taroudakis [3. Comput. Acoust. 4 （1996） 101], the present approach combines a spectral decomposition in azimuth with a coupled-mode theory for two-way range-dependent propagation. However, the earlier formulations are severely limited in terms of frequency, size and geometry o[ the seamount, the seabed composition, and the distance between the source and the seamount, and are there/ore severely limited in regard to realistic seamount problems. Without changing the fundamental theoretical foundation, the present approach applies a number of modifications to the formulation, leading to orders of magnitude improvement in numerical efficiency for realistic problems. Therefore, realistic propagation and scattering scenarios can be modeled, including effects of seamount roughness and realistic sedimentary structure.
基金supported by the U.S. Office of Naval Research under Grant No N00014the National Natural Science Foundation of China under Grant No 10734100Research support from Massachusetts Institute of Technology and Woods Hole Oceanographic Institution
文摘A recently developed three-dimensional normal-mode model is adopted to investigate mode coupling around a seamount in a deep water environment. As indicated by the theoretical analysis and verified by the numerical results, strong mode coupling occurs at the edge of a seamount under certain conditions. Therefore, mode coupling is critical for the investigation of the acoustic field in the presence of a seamount. In addition, the issue regarding the number of sectors assuring convergence is also presented. This issue is important in a two-way coupled-mode approach, especially for solving three-dimensional problems, because the computational effort increases dramatically with the number of sectors in representing a varying bathymetry. The theoretical analysis as well as the numerical example in this paper shows that artificial diffraction lobes form in the event that uniform discretization is used with a horizontal step size greater than half of the acoustic wavelength. However, by using random discretization instead, such artificial diffraction lobes are diffused, resulting in a faster convergence rate.
基金supported by the Knowledge Innovation Program of Chinese Academy of Sciences
文摘An efficient, accurate, and numerically stable coupled-mode solution is presented for acoustic propagation in a range-dependent waveguide. This method is numerically stable due to the appropriately normalized range solutions introduced in the formulation. In addition, by combining a forward marching and a backward marching, this method provides accurate solu- tions for range-dependent propagation problems, especially those characterized by large bottom slope angle and/or high impedance contrast between water and the bottom. Furthermore, this two-way solution also provides high efficiency, which is achieved by applying the single-scatter approximation. Numerical examples are also provided to demonstrate the efficiency, accuracy, and stability of this method.
