A method and system for calculating the intensity of forward scattering of the seabed based on the ray theory

Abstract

This invention belongs to the field of underwater acoustics technology and discloses a method and system for calculating the intensity of forward scattering from the seabed based on ray theory. This invention constructs a two-dimensional ray tracing model based on... N The ×2D method generates a three-dimensional seabed scattering region. The azimuth step size is adaptively adjusted according to the horizontal distance of the scattering point. Based on the calculated total propagation time, the isochronous scattering region is meshed using triangulation. An anomalous triangular scattering surface element is removed by setting a maximum side length threshold, and the continuous scattering surface is discretized into a set of triangular scattering surface elements. The effective scattering region area is calculated by numerical integration, and the seabed forward scattering intensity at different grazing angles is obtained according to the sonar equations. This invention utilizes... N The ×2D method generates a three-dimensional seabed scattering region, realizing three-dimensional seabed forward scattering modeling. While ensuring calculation accuracy, it significantly reduces the amount of computation, providing a new technical approach for accurate and efficient calculation of seabed forward scattering intensity at different grazing angles in complex marine environments.

Description

Technical Field

[0001] This invention belongs to the field of underwater acoustics technology, and in particular relates to a method and system for calculating the intensity of forward scattering from the seabed based on ray theory. Background Technology

[0002] Seabed acoustic scattering primarily originates from seabed interface roughness, sediment internal inhomogeneities, air bubbles, and shell fragments. Depending on the sonar system's transceiver configuration, seabed acoustic scattering can generally be categorized into two main types: forward scattering and backscattering.

[0003] Forward scattering from the seabed refers to the physical process by which sound energy propagates forward to the receiver after interacting with the seabed, specifically the scattering effect when the sound source and receiver are located in the same vertical plane. Compared to backscattering from the seabed, forward scattering is fundamental to reverberation prediction in multi-base sonar systems, and accurately calculating its scattering intensity is crucial for improving the accuracy of reverberation prediction.

[0004] Current methods for calculating seabed forward scattering intensity do not adequately consider the influence of sound velocity profiles. Since forward scattering is more sensitive to the sound propagation path and the spatial location of the scattering point, neglecting the sound velocity profile will lead to calculation errors. Accurately tracing the sound propagation path and obtaining scattered sound ray information has become a key challenge in calculating forward scattering intensity. Ray theory, with its clear physical meaning under these conditions, is an important tool for solving sound propagation path tracing in complex environments. Therefore, there is an urgent need to design a method and system for calculating seabed forward scattering intensity based on ray theory.

[0005] Based on the above analysis, the problems and shortcomings of the existing technology are as follows: (1) Existing methods for calculating forward scattering intensity on the seabed are mostly based on the assumption of constant sound speed, which do not fully consider the influence of sound speed profile on sound ray path in actual marine environment, resulting in inaccurate location of scattering area.

[0006] (2) Traditional three-dimensional ray tracing methods involve large computational loads and are difficult to achieve efficient solutions while ensuring computational accuracy, which limits their application in the calculation of large-scale seabed scattering intensity.

[0007] (3) Existing methods for calculating the effective scattering area mostly use analytical approximation or regular grid division, which are poorly adaptable to complex isochronous scattering regions and are difficult to accurately describe the scattering region formed by the superposition of multiple paths. Summary of the Invention

[0008] To overcome the problems existing in related technologies, such as the failure of current methods for calculating seabed forward scattering intensity to fully consider the influence of sound velocity profiles, the large computational burden of three-dimensional ray tracing, and the poor adaptability of effective scattering region area calculations to irregular scattering regions, this invention discloses a method and system for calculating seabed forward scattering intensity based on ray theory, used to calculate seabed forward scattering intensity at different grazing angles. This invention addresses the aforementioned shortcomings by proposing a method for calculating seabed forward scattering intensity based on ray theory. The method extends the two-dimensional ray tracing results to three-dimensional space, determines the boundary of the isochronous scattering region by distance-time interpolation, and uses triangulation to achieve accurate discretization of the three-dimensional seabed scattering region. While ensuring the accuracy of the calculation of the forward scattering intensity of the seabed, it significantly reduces the amount of computation.

[0009] The technical solution is as follows: a method for calculating seabed forward scattering intensity based on ray theory, including the following steps: S1. Construct a two-dimensional ray tracing model. Based on the sound velocity profile, establish the ray path equation in cylindrical coordinates. Use Snell's law to constrain the ray propagation direction. Calculate the cumulative reflection loss through the seabed reflection coefficient to obtain the sound ray path from the sound source to the seabed and from the seabed to the receiver. Record the grazing angle, arc length, and propagation loss of the seabed scattering points. Construct an interpolation model for the scattering points obtained by tracing the sound ray from the sound source and an interpolation model for the scattering points obtained by tracing the sound ray from the receiver using acoustic reciprocity. Analyze and refine the interpolation of the seabed scattering points generated by sound source tracing. S2, based on N The ×2D method generates a three-dimensional seabed scattering region. N The ×2D method extends the two-dimensional ray tracing results of the sound ray path at the sound source to three-dimensional space by rotating the azimuth angle. The azimuth angle step size is adaptively adjusted according to the horizontal distance of the scattering point to obtain the three-dimensional spatial coordinates of the seabed scattering point. The interpolation model constructed by the receiver tracing the sound ray is used to match the sound ray parameters from the scattering point to the receiver and calculate the total propagation time. S3. Based on the calculated total propagation time, the isochronous scattering region is divided into grids using the triangular partitioning method. An abnormal triangular scattering surface element is removed by setting a maximum side length threshold, and the continuous scattering surface is discretized into a set of triangular scattering surface elements. S4. Using the triangular scattering surface element set, the effective scattering area is calculated by numerical integration, and the forward scattering intensity of the seabed at different grazing angles is obtained according to the sonar equation.

[0010] In step S1, an interpolation model for the scattered points obtained by tracing sound rays from the sound source and an interpolation model for the scattered points obtained by tracing sound rays from the receiver using acoustic reciprocity are constructed. The seabed scattered points generated by sound source tracing are interpolated and encrypted, including: setting the emission angle and angle interval, tracing sound rays from the sound source to the seabed, and tracing sound rays from the receiver to the seabed using acoustic reciprocity, and recording the corresponding sound ray parameters.

[0011] Furthermore, the seabed scattering points under different sound source tracing paths are analyzed according to their emission angles. Sort and remove duplicates by emission angle For each independent variable, construct the following set of spline interpolation functions, with the following expressions: ; ; ; ; ; In the formula, The horizontal distance from the sound source to the point of scattering off the seabed. The propagation time from the sound source to the point of scattering on the seabed. Let be the arc length from the sound source to the point of scattering off the seabed. The incident grazing angle, The cumulative reflection coefficient at the transmitting end; To launch angle The horizontal distance obtained for the independent variable spline interpolation function, To launch angle The propagation time from the sound source to the seabed scattering point is obtained as the independent variable. spline interpolation function, To launch angle The arc length from the sound source to the seabed scattering point is obtained as the independent variable. spline interpolation function, To launch angle The incident grazing angle obtained as the independent variable spline interpolation function, To launch angle The cumulative reflection coefficient of the transmitter obtained as the independent variable spline interpolation function; within the emission angle range Inner step length Uniform interpolation encryption is used to obtain the scattering point parameters corresponding to each sampling angle through the above interpolation function group, and generate a list of scattering points from the sound source to the seabed.

[0012] Furthermore, for the seabed scattering points tracked from the receiver along different paths, the horizontal distance is calculated. For each independent variable, construct separate sets of interpolation functions: ; ; ; ; In the formula, The horizontal distance from the scattering point to the receiver. The propagation time from the receiver to the scattering point on the seabed. Let be the arc length from the point of scattering off the seabed to the receiver. The grazing angle is the scattering angle. The cumulative reflection coefficient at the receiving end. For horizontal distance The propagation time from the receiver to the seabed scattering point is obtained as the independent variable. spline interpolation function, For horizontal distance The arc length from the seabed scattering point to the receiver, obtained as the independent variable. spline interpolation function, For horizontal distance The scattering grazing angle obtained as the independent variable spline interpolation function, For horizontal distance The cumulative reflection coefficient of the receiver obtained as the independent variable The spline interpolation function.

[0013] In step S2, the three-dimensional spatial coordinates of the seabed scattering point are obtained, including: depth The harmonic parameters remain constant during rotation, and the azimuth step size is... An adaptive strategy is adopted, based on the horizontal distance of the scattering point. Adaptive adjustment, the expression is: ; In the formula, For the target arc length resolution, and Limited to a preset range Within this range, avoid excessively dense near-range scattering points or excessively sparse far-range scattering points, and prevent excessively large or small azimuth step sizes in extreme cases.

[0014] Furthermore, by constructing a set of receiver interpolation functions, the horizontal distance from the seabed scattering point to the receiver is considered. Interpolation is used to obtain the acoustic parameters of the receiving end; horizontal distance Scattering points outside the valid interpolation range are marked as invalid and discarded; the source-tracking ray parameters of each valid scattering point are matched with the receiver-tracking ray parameters to form a complete seabed scattering ray from the sound source through the seabed scattering point to the receiver; the total propagation time of each valid scattering point is calculated. : ; In the formula, The propagation time from the sound source to the point of scattering on the seabed. This represents the propagation time from the seabed scattering point to the receiver.

[0015] In step S3, the meshing of the isochronous scattering region using triangulation includes: using triangulation to mesh the discrete scattering points on the horizontal plane. The continuous scattering surface is discretized into a set of triangular scattering surface elements by performing mesh generation on the above. Given sound source pulse length Let the start time of the time window be... Based on total transmission time Grouping the effective scattering points will satisfy The scattering points are included in this window, forming the isochronous scattering region at that moment; for the effective set of scattering points within each time window, on the horizontal plane... Perform triangulation on the top; the area of ​​each triangle Calculated using the outer product: ; In the formula, These are the horizontal coordinates of the three vertices of the triangle; Set the maximum side length threshold Remove any side with a length exceeding A triangle; The effective scattering region area of ​​this time window for: ; In the formula, The threshold for the maximum side length within this time window. The index of the valid triangular scattering surface elements retained after filtering. For the first The area of ​​each triangular scattering surface element.

[0016] In step S4, the forward scattering intensity of the seabed is numerically integrated using a triangular scattering element set to obtain the forward scattering intensity of the seabed at different grazing angles. The calculation formula is as follows: ; In the formula, The forward scattering intensity at the seabed. The incident grazing angle, The grazing angle is the scattering angle. It is the azimuth angle. To receive signal strength, At the source level, This refers to the propagation loss from the sound source to the scattering point on the seabed. This represents the propagation loss from the seabed scattering point to the receiver. The effective scattering area is denoted by .

[0017] Another objective of this invention is to provide a system for calculating seabed forward scattering intensity based on ray theory. This system implements the aforementioned method for calculating seabed forward scattering intensity based on ray theory. The system includes: The two-dimensional ray tracing module establishes the ray path equation in cylindrical coordinates based on the sound velocity profile, uses Snell's law to constrain the ray propagation direction, calculates the cumulative reflection loss through the seabed reflection coefficient, obtains the sound ray path from the sound source to the seabed and from the seabed to the receiver, and records the grazing angle, arc length and propagation loss of the seabed scattering points. It constructs an interpolation model for the scattering points obtained by tracing the sound ray from the sound source and an interpolation model for the scattering points obtained by tracing the sound ray from the receiver using acoustic reciprocity, and performs interpolation densification on the seabed scattering points generated by sound source tracing. The three-dimensional scattering region generation module is based on N The ×2D method generates a three-dimensional seabed scattering region. N The ×2D method extends the two-dimensional sound ray tracing results at the sound source to three-dimensional space through azimuth rotation, with an azimuth step size of [missing information]. The three-dimensional spatial coordinates of the seabed scattering point are obtained by adaptively adjusting the horizontal distance of the scattering point, and the ray parameters from the scattering point to the receiver are matched by an interpolation model constructed by tracking the sound rays through the receiver, and the total propagation time is calculated. The effective scattering area calculation module uses triangulation to divide the isochronous scattering area into a grid based on the total propagation time calculated. It sets a maximum side length threshold to remove abnormal triangular scattering elements and discretizes the continuous scattering surface into a set of triangular scattering elements. The scattering intensity calculation module uses the triangular scattering surface element set to calculate the effective scattering area by numerical integration, and obtains the seabed forward scattering intensity at different grazing angles according to the sonar equation.

[0018] Furthermore, the seabed forward scattering intensity calculation system based on ray theory is mounted on a computer-readable storage medium, which stores a computer program. When the computer program is executed by a processor, it can realize the functions of the seabed forward scattering intensity calculation system based on ray theory.

[0019] Combining all the above technical solutions, the beneficial effects of this invention are as follows: This invention constructs a two-dimensional ray tracing model based on sound velocity profiles to trace sound rays from both the sound source and receiver to the seabed, obtaining the sound ray path and seabed scattering point parameters. The scattering points obtained from the sound source tracing are then interpolated and refined according to the emission angle, and an interpolation model at the receiver with horizontal distance as the independent variable is constructed. N The ×2D method extends the two-dimensional ray tracing results at the sound source to three-dimensional space, with the azimuth step size adaptively adjusted according to the horizontal distance of the scattering point. An interpolation model at the receiver matches the acoustic ray parameters from each scattering point on the seabed to the receiver, forming a complete seabed scattering ray. The discrete scattering points are divided into triangular scattering elements using triangular partitioning, and abnormal triangular scattering elements are removed by setting a maximum side length threshold. The effective scattering area is calculated by numerical integration of the triangular scattering elements. Based on the sonar equations, the forward scattering intensity of the seabed at different grazing angles is obtained. This invention... N The ×2D method generates a three-dimensional seabed scattering region, realizing three-dimensional seabed forward scattering modeling. While ensuring calculation accuracy, it significantly reduces the amount of computation, providing a new technical approach for accurate and efficient calculation of seabed forward scattering intensity at different grazing angles in complex marine environments.

[0020] This invention achieves efficient and accurate calculation of seabed forward scattering intensity, which can significantly reduce computational costs compared with existing three-dimensional numerical methods. It can provide key technical support for scenarios such as multi-base sonar target detection performance prediction, seabed reverberation prediction and suppression, underwater sound field modeling and marine environment analysis, and has important application value.

[0021] To address the shortcomings of existing methods for calculating seabed forward scattering intensity, which generally assume a constant seawater sound velocity and neglect the effect of sound ray bending, a new technical solution based on ray theory is proposed, filling the technical gap in calculating seabed forward scattering intensity considering the influence of seawater sound velocity profiles. Achieving accurate and efficient calculation of seabed forward scattering intensity while fully considering the influence of seawater sound velocity profiles is a key technical challenge in the field of underwater acoustics. Existing methods neglect sound ray bending, leading to inaccurate positioning of the scattering region, making it difficult to balance calculation accuracy and efficiency, and making it difficult to accurately obtain the area of ​​the effective scattering region. This invention overcomes these challenges, achieving for the first time accurate and efficient calculation of seabed forward scattering intensity considering the influence of seawater sound velocity profiles. Attached Figure Description

[0022] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with the disclosure of this invention and, together with the description, serve to explain the principles of this disclosure; Figure 1 This is a flowchart of the seabed forward scattering intensity calculation method based on ray theory provided in the embodiments of the present invention; Figure 2The total propagation time provided in this embodiment of the invention is when the sound source depth is 25m and the receiver depth is 2801m. A schematic diagram of the effective scattering region corresponding to 3.144s; Figure 3 The hydrophone is located at a depth of 2201m, a frequency of 4kHz, and an incident angle of [missing information]. =54.5°, azimuth angle Results under the condition of 0°; Figure 4 The hydrophone is located at a depth of 2601m, a frequency of 4kHz, and an incident angle of [missing information]. =51.7°, azimuth angle Results under the condition of 0°; Figure 5 The hydrophone is located at a depth of 2801m, a frequency of 4kHz, and an incident angle of [missing information]. =50.2°, azimuth angle Results under the condition of 0°; Figure 6 The hydrophone is located at a depth of 3101m, a frequency of 4kHz, and an incident angle of [missing information]. =47.7°, azimuth angle Results under the condition of 0°; Figure 7 The hydrophone is located at a depth of 2201m, a frequency of 4kHz, and an incident angle of [missing information]. =54.5°, scattering angle Results under the condition of 54.4°; Figure 8 The hydrophone is located at a depth of 2601m, a frequency of 4kHz, and an incident angle of [missing information]. =51.7°, scattering angle Results under the condition of 51.6°; Figure 9 The hydrophone is located at a depth of 2801m, a frequency of 4kHz, and an incident angle of [missing information]. =50.2°, scattering angle Results under the condition of 50.1°; Figure 10 The hydrophone is located at a depth of 3101m, a frequency of 4kHz, and an incident angle of [missing information]. =47.7°, scattering angle Results under the condition of 47.8°. Detailed Implementation

[0023] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of the present invention. However, the present invention can be practiced in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0024] The innovation of this invention lies in: the interpolation encryption method for seabed scattering points and the interpolation matching model at the receiver end with horizontal distance as the independent variable; N The ×2D method is applied to the construction of a three-dimensional forward scattering region on the seabed, and combined with an interpolation matching model to achieve efficient acquisition of ray parameters at scattering points; a method for calculating the scattering region area is based on triangulation and combined with a maximum side length threshold to remove spurious surface elements. N The ×2D method extends two-dimensional ray tracing results to three-dimensional space, tracing sound rays from the sound source and receiver to the seabed, constructing an interpolation model to match the complete sound ray parameters of the scattering point, and using triangulation to accurately discretize the effective scattering region, achieving accurate and efficient calculation of seabed forward scattering intensity while fully considering the influence of sound velocity profile.

[0025] Example 1: A method for calculating seabed forward scattering intensity based on ray theory, establishing a two-dimensional ray tracing model, and employing... The method generates a three-dimensional seabed scattering region and calculates the effective scattering region area based on triangular scattering surface elements, thus achieving accurate and efficient calculation of seabed forward scattering intensity considering the influence of sound velocity profile. like Figure 1 As shown, the specific steps include: S1. Construct a two-dimensional ray tracing model. Based on the sound velocity profile, establish the ray path equation in cylindrical coordinates. Use Snell's law to constrain the ray propagation direction. Calculate the cumulative reflection loss through the seabed reflection coefficient to obtain the sound ray path from the sound source to the seabed and from the seabed to the receiver. Record the grazing angle, arc length, and propagation loss of the seabed scattering points. Construct an interpolation model for the scattering points obtained by tracing the sound ray from the sound source and an interpolation model for the scattering points obtained by tracing the sound ray from the receiver using acoustic reciprocity. Analyze and refine the interpolation of the seabed scattering points generated by sound source tracing. S2, based on N The ×2D method generates a three-dimensional seabed scattering region. N The ×2D method extends the two-dimensional ray tracing results of the sound ray path at the sound source to three-dimensional space by rotating the azimuth angle. The azimuth angle step size is adaptively adjusted according to the horizontal distance of the scattering point to obtain the three-dimensional spatial coordinates of the seabed scattering point. The interpolation model constructed by the receiver tracing the sound ray is used to match the sound ray parameters from the scattering point to the receiver and calculate the total propagation time. S3. Based on the calculated total propagation time, the isochronous scattering region is divided into grids using the triangular partitioning method. An abnormal triangular scattering surface element is removed by setting a maximum side length threshold, and the continuous scattering surface is discretized into a set of triangular scattering surface elements. S4. Using the triangular scattering surface element set, the effective scattering area is calculated by numerical integration, and the forward scattering intensity of the seabed at different grazing angles is obtained according to the sonar equation.

[0026] For example, in step S1, the emission angle and angle interval are set, the sound ray is traced from the sound source to the seabed, and the sound ray is traced from the receiver to the seabed using acoustic reciprocity, and the corresponding sound ray parameters are recorded.

[0027] This invention innovatively proposes to track the seabed scattering points under different paths of the sound source according to the emission angle. Sort and remove duplicates by emission angle For each independent variable, construct the following sets of spline interpolation functions: ; ; ; ; ; In the formula, The horizontal distance from the sound source to the point of scattering off the seabed. The propagation time from the sound source to the point of scattering on the seabed. Let be the arc length from the sound source to the point of scattering off the seabed. The incident grazing angle, The cumulative reflection coefficient at the transmitting end; To launch angle The horizontal distance obtained for the independent variable spline interpolation function, To launch angle The propagation time from the sound source to the seabed scattering point is obtained as the independent variable. spline interpolation function, To launch angle The arc length from the sound source to the seabed scattering point is obtained as the independent variable. spline interpolation function, To launch angle The incident grazing angle obtained as the independent variable spline interpolation function, To launch angle The cumulative reflection coefficient of the transmitter obtained as the independent variable spline interpolation function; within the emission angle range Inner step length Uniform interpolation encryption is used to obtain the scattering point parameters corresponding to each sampling angle through the above interpolation function group, and generate a list of scattering points from the sound source to the seabed for use in subsequent steps.

[0028] This invention innovatively proposes to track seabed scattering points along different paths from the receiver, using horizontal distance... For each independent variable, construct separate sets of interpolation functions: ; ; ; ; In the formula, The horizontal distance from the scattering point to the receiver. The propagation time from the receiver to the scattering point on the seabed. Let be the arc length from the point of scattering off the seabed to the receiver. The grazing angle is the scattering angle. The cumulative reflection coefficient at the receiving end. For horizontal distance The propagation time from the receiver to the seabed scattering point is obtained as the independent variable. spline interpolation function, For horizontal distance The arc length from the seabed scattering point to the receiver, obtained as the independent variable. spline interpolation function, For horizontal distance The scattering grazing angle obtained as the independent variable spline interpolation function, For horizontal distance The cumulative reflection coefficient of the receiver obtained as the independent variable The spline interpolation function. For example, in step S2, the depth... The harmonic parameters remain constant during rotation. This invention innovatively proposes an azimuth step size... An adaptive strategy is adopted, based on the horizontal distance of the scattering point. Adaptive adjustment: ; In the formula, For the target arc length resolution, and Limited to a preset range Within this range, avoid excessively dense near-range scattering points or excessively sparse far-range scattering points, and prevent excessively large or small azimuth step sizes in extreme cases.

[0029] Using the receiver interpolation function set constructed in S1, the horizontal distance from the seabed scattering point to the receiver is calculated. Interpolation is used to obtain the acoustic parameters at the receiving end. Horizontal distance Scattering points outside the valid interpolation range are marked as invalid and discarded. The source-tracing ray parameters for each valid scattering point are matched with the receiver-tracing ray parameters to form a complete seabed scattering ray from the sound source through the seabed scattering point to the receiver. The total propagation time for each valid scattering point is calculated. : ; In the formula, The propagation time from the sound source to the point of scattering on the seabed. This represents the propagation time from the seabed scattering point to the receiver.

[0030] For example, in step S3, the discrete scattering points are analyzed on the horizontal plane using a triangulation method. The continuous scattering surface is discretized into a set of triangular scattering surface elements by meshing.

[0031] Given sound source pulse length Let the start time of the time window be... Based on total transmission time Grouping the effective scattering points will satisfy The scattering points are included in this window, forming the isochronous scattering region at that moment. For the effective set of scattering points within each time window, on the horizontal plane... Perform triangulation on top. The area of ​​each triangle... Calculated using the outer product: ; In the formula, These are the horizontal coordinates of the three vertices of the triangle. To avoid creating false large triangles in sparse scattering regions, a maximum side length threshold is set. Remove any side with a length exceeding The invention innovatively proposes that the effective scattering region area of ​​this time window is a triangle. for: ; In the formula, The threshold for the maximum side length within this time window. The index of the valid triangular scattering surface elements retained after filtering. For the first The area of ​​each triangular scattering surface element.

[0032] In step S4, the forward scattering intensity of the seabed is numerically integrated using the triangular scattering element to obtain the forward scattering intensity of the seabed at different grazing angles. The calculation formula is as follows: ; In the formula, The forward scattering intensity at the seabed. The incident grazing angle, The grazing angle is the scattering angle. It is the azimuth angle. To receive signal strength, At the source level, This refers to the propagation loss from the sound source to the scattering point on the seabed. This represents the propagation loss from the seabed scattering point to the receiver. The effective scattering area is denoted by .

[0033] As can be seen from the above embodiments, the present invention adopts... N The ×2D method extends two-dimensional ray tracing results to three-dimensional space, effectively reducing the computational complexity of three-dimensional ray tracing while maintaining computational accuracy, and significantly improving computational efficiency compared to the full three-dimensional ray tracing method.

[0034] This invention fully considers the influence of sound velocity profile on the sound ray propagation path, and obtains parameters such as grazing angle and arc length of each scattering point through ray tracing, which can accurately describe the sound propagation characteristics in complex marine environments and improve the accuracy of seabed forward scattering intensity calculation.

[0035] This invention proposes a distance-time interpolation matching method between the sound source and the receiver, which can accurately determine the boundary of the isochronous scattering region, effectively solve the problem of multipath sound ray matching, and achieve accurate separation of scattering contributions from different path types.

[0036] This invention uses triangulation to divide the scattering region into grids, which can adapt to irregularly shaped isochronous scattering regions. It effectively removes abnormal grids through a side length threshold filtering mechanism, thereby improving the accuracy and robustness of scattering area calculation.

[0037] This invention can be applied to fields such as seabed reverberation prediction, detection of buried targets on the seabed, and fine structure analysis of the seabed sound field, providing technical support for the reverberation background assessment and target acoustic detectability analysis of active sonar systems.

[0038] Example 2: A system for calculating seabed forward scattering intensity based on ray theory, the system comprising: The two-dimensional ray tracing module is used to construct a two-dimensional ray tracing model. Based on the sound velocity profile, it establishes the ray path equation in cylindrical coordinates, uses Snell's law to constrain the ray propagation direction, calculates the cumulative reflection loss through the seabed reflection coefficient, obtains the sound ray path from the sound source to the seabed and from the seabed to the receiver, and records the grazing angle, arc length and propagation loss of the seabed scattering points. It constructs an interpolation model for the scattering points obtained by tracing the sound ray from the sound source and an interpolation model for the scattering points obtained by tracing the sound ray from the receiver using acoustic reciprocity, and performs interpolation densification on the seabed scattering points generated by sound source tracing. A three-dimensional scattering region generation module is used for... N The ×2D method generates a three-dimensional seabed scattering region. The method extends the two-dimensional ray tracing results of the sound ray path at the sound source in step S1 to three-dimensional space by rotating the azimuth angle. The azimuth angle step size is adaptively adjusted according to the horizontal distance of the scattering point to obtain the three-dimensional spatial coordinates of the seabed scattering point. The interpolation model constructed by the receiver tracing the sound ray is used to match the sound ray parameters from the scattering point to the receiver and calculate the total propagation time. The effective scattering area calculation module is used to divide the isochronous scattering area into a grid based on the total propagation time calculated, using the triangulation method, setting a maximum side length threshold to remove abnormal triangular scattering elements, discretizing the continuous scattering surface into a set of triangular scattering elements, and numerically calculating the effective scattering area. The scattering intensity calculation module is used to calculate the forward scattering intensity of the seabed at different grazing angles.

[0039] Example 3, as another embodiment of the present invention, involves establishing a two-dimensional ray tracing model based on sound velocity profiles to trace sound rays from the sound source and receiver to the seabed and constructing an interpolation model; based on The method generates a three-dimensional scattering region; then, triangulation is used to calculate the effective scattering region area; finally, the sonar equation is used to calculate the forward scattering intensity of the seabed.

[0040] The experimental parameters were set as follows: the water depth in the experimental area was 3221m, the sound source frequency was 4kHz, the sound source was located at a depth of 25m, and there were 4 receivers located at depths of 2201m, 2601m, 2801m, and 3101m respectively. The horizontal distance between the sound source and the receivers was 3km.

[0041] The method for calculating seabed forward scattering intensity based on ray theory provided in this embodiment of the invention specifically includes the following steps: Step 1: Construct a two-dimensional ray tracing model. The model obtains the ray paths from the sound source to the seabed and from the seabed to the receiver through numerical solution, and records the grazing angle, arc length and propagation loss of the scattering point on the seabed. In cylindrical coordinate system Now, assuming the speed of sound depends only on depth. sound speed profile The ray path equation is obtained through spline interpolation from measured depth-velocity data. ; ; ; ; In the formula, Horizontal distance For depth, Let the arc length be along the ray. This is a sound speed profile. and These are the horizontal and vertical components of the slowness vector; The formula for calculating the propagation time along a ray is: ; In the formula, This represents the propagation time of the sound wave along the ray.

[0042] The ray path satisfies Snell's law: ; In the formula, The initial glancing angle at the sound source. Let be the speed of sound at the sound source. For the ray at depth The glancing angle at that location.

[0043] The formula for calculating the glancing angle of the seabed scattering point is: ; In the formula, Let be the grazing angle at the point of scattering from the sound source on the seabed. When calculating the ray from the sound source to the point of scattering from the seabed... For the incident grazing angle Conversely, when calculating the rays from the seabed scattering point to the receiver, For scattering glancing angle .

[0044] The formula for calculating the cumulative arc length is: ; In the formula, For the arc length of the ray, The number of integration steps, For the first The position of the ray in the step.

[0045] The seabed reflection coefficient is calculated using the Rayleigh reflection model. ; In the formula, For the acoustic impedance of seawater, For seabed acoustic impedance, For density, The angle of attack in seawater. The angle of refraction in the ocean is determined by Snell's law: ; The formula for calculating the cumulative reflectance coefficient is: ; In the formula, The cumulative reflection coefficient along the ray path, The number of reflections, For the first The reflection coefficient of secondary reflection.

[0046] The formula for calculating propagation loss is: ; In the formula, The terms represent propagation losses: the first term is the geometric spread loss, the second term is the reflection loss, and the third term is the seawater absorption loss. This refers to the seawater absorption coefficient. Since it is related to the frequency of the sound wave, it can be calculated using Thorp's formula: ; In the formula, Frequency, in kHz.

[0047] The emission angle and angle interval are set, and sound rays are emitted from the sound source and receiver. The intersection of each sound ray with the seabed is tracked, and the corresponding sound ray parameters are recorded. During the sound ray tracking process, each time the sound ray encounters a seabed reflection, it is marked as "B", and each time it encounters a sea surface reflection, it is marked as "S". These are pieced together in the order of reflection to form a path type identifier. The seabed scattering points are grouped and matched according to the path type. For example, when calculating the scattering contribution of path B, the scattering points of path B from the sound source to the seabed need to be matched with the scattering points of path B from the receiver to the seabed to obtain the complete seabed scattered sound ray.

[0048] Tracking sound sources along different paths and analyzing seabed scattering points by emission angle Sort and remove duplicates by emission angle For each independent variable, construct the following sets of spline interpolation functions: ; ; ; ; ; In the formula, The horizontal distance from the sound source to the point of scattering off the seabed. The propagation time from the sound source to the point of scattering on the seabed. Let be the arc length from the sound source to the point of scattering off the seabed. The incident grazing angle, This represents the cumulative reflection coefficient at the transmitting end.

[0049] Within the launch angle range Inner step length Uniform interpolation encryption is used to obtain the scattering point parameters corresponding to each sampling angle through the above interpolation function group, and generate a list of scattering points from the sound source to the seabed for use in subsequent steps.

[0050] Utilizing the reciprocity of acoustics, the receiver emits sound rays in the opposite direction, tracing them to the seabed and establishing a horizontal distance. The interpolation model is for the independent variable. For sequences along different paths, separate sets of interpolation functions are constructed: ; ; ; ; In the formula, The horizontal distance from the scattering point to the receiver. The propagation time from the receiver to the scattering point on the seabed. Let be the arc length from the point of scattering off the seabed to the receiver. The grazing angle is the scattering angle. This represents the cumulative reflection coefficient at the receiver.

[0051] Step 2, based on N The ×2D method generates a three-dimensional seabed scattering region, which extends the two-dimensional ray tracing results to three-dimensional space by azimuth rotation. The horizontal distance of each seabed scattering point obtained from the two-dimensional ray tracing is taken. Azimuth angle around the vertical axis of the sound source Rotate to generate 3D coordinates: ; ; depth Harmonic parameters remain constant during rotation. Azimuth step size. An adaptive strategy is adopted, based on the horizontal distance of the scattering point. Adaptive adjustment: ; In the formula, For the target arc length resolution, and Limited to a preset range Within this range, avoid excessively dense near-range scattering points or excessively sparse far-range scattering points, and prevent excessively large or small azimuth step sizes in extreme cases.

[0052] For each 3D scattering point generated by the rotation, calculate its horizontal distance to the receiver. The calculation formula is as follows: ; In the formula, The horizontal coordinates of the scattering point represents the horizontal coordinates of the receiver.

[0053] Further calculate the azimuth angle at each scattering point. This is used in subsequent scattering intensity calculations to characterize the degree of deviation between the incident and scattering directions. Azimuth angle The angle between the incident direction vector and the scattering direction vector is determined by the following formula: ; In the formula, The horizontal coordinates of the scattering point (i.e., the incident direction vector, since the sound source is located at the origin of the coordinate system). This represents the scattering direction vector component from the scattering point to the receiver. =0° corresponds to the forward scattering of sound rays on the horizontal plane. =180° corresponds to backscattering.

[0054] Using the receiver interpolation function set constructed in step 1, the horizontal distance from the seabed scattering point to the receiver is determined. Interpolation is used to obtain the acoustic parameters at the receiving end. Horizontal distance Scattering points outside the valid interpolation range are marked as invalid and discarded. The source-tracing ray parameters for each valid scattering point are matched with the receiver-tracing ray parameters to form a complete seabed scattering ray from the sound source through the seabed scattering point to the receiver. The total propagation time for each valid scattering point is calculated. :

[0055] In the formula, The propagation time from the sound source to the point of scattering on the seabed. This represents the propagation time from the seabed scattering point to the receiver.

[0056] Step 3: Use the triangulation method to analyze the discrete scattering points on the horizontal plane. The continuous scattering surface is discretized into a set of triangular scattering surface elements by meshing.

[0057] Given sound source pulse length Let the start time of the time window be... Based on total transmission time Grouping the effective scattering points will satisfy The scattering points are included in this window, forming the isochronous scattering region at that moment. For the effective set of scattering points within each time window, the horizontal coordinates are... Duplicate scattering points are deduplicated and merged. The resulting set of scattering points is then triangulated on a horizontal plane, and the area of ​​each triangle is calculated. Calculated using the outer product: ; In the formula, These are the horizontal coordinates of the three vertices of the triangle. To avoid creating false large triangles in sparse scattering regions, a maximum side length threshold is set. Remove any side with a length exceeding The triangle. The area of ​​the effective scattering region for this time window is: ; Figure 2 The total propagation time provided in this embodiment of the invention is when the sound source depth is 25m and the receiver depth is 2801m. The effective scattering region diagram corresponding to 3.144s.

[0058] Step 4: Use the triangular scattering surface element to numerically integrate the forward scattering intensity of the seabed to obtain the forward scattering intensity of the seabed at different grazing angles.

[0059] Received signal strength The voltage signal was obtained by short-time Fourier transform and narrowband power spectrum estimation from the measured hydrophone output signal. The time-domain voltage signal output by the hydrophone is denoted as... Based on the sound source emission time and sound propagation delay, in Intercepting time Nearby short-time signal segment This indicates that the short signal segment is considered to be stationary. After applying a window function, a Discrete Fourier Transform is performed to obtain the signal's spectrum. At the center frequency The power spectrum is averaged over a 1 / 3 octave bandwidth to obtain the narrowband average power spectral density: ; In the formula, For the center frequency, Sampling rate, This represents the number of sampling points for the short-time signal segment. and These are the lower limit frequencies of 1 / 3 octave bandwidth. and upper limit frequency The corresponding frequency point number.

[0060] Received signal strength The sound pressure level is calculated from the narrowband average power spectral density after hydrophone sensitivity correction: ; In the formula, This refers to the receiving sensitivity of the hydrophone.

[0061] Finally, the forward scattering intensity from the seabed is calculated based on the sonar equations: ; In the formula, The forward scattering intensity at the seabed. The incident grazing angle, The grazing angle is the scattering angle. It is the azimuth angle. To receive signal strength, At the source level, This refers to the propagation loss from the sound source to the scattering point on the seabed. This represents the propagation loss from the seabed scattering point to the receiver. The effective scattering area is denoted by .

[0062] The scattering angle provided in the embodiments of the present invention Relationship with forward scattering intensity from the seabed Figure 3 The hydrophone is located at a depth of 2201m, a frequency of 4kHz, and an incident angle of [missing information]. =54.5°, azimuth angle Results under the condition of 0° Figure 4 The hydrophone is located at a depth of 2601m, a frequency of 4kHz, and an incident angle of [missing information]. =51.7°, azimuth angle Results under the condition of 0° Figure 5 The hydrophone is located at a depth of 2801m, a frequency of 4kHz, and an incident angle of [missing information]. =50.2°, azimuth angle Results under the condition of 0° Figure 6 The hydrophone is located at a depth of 3101m, a frequency of 4kHz, and an incident angle of [missing information]. =47.7°, azimuth angle Results under the condition of 0°.

[0063] The azimuth angle provided in the embodiments of the present invention Relationship with forward scattering intensity from the seabed Figure 7 The hydrophone is located at a depth of 2201m, a frequency of 4kHz, and an incident angle of [missing information]. =54.5°, scattering angle The result under the condition of 54.4° Figure 8 The hydrophone is located at a depth of 2601m, a frequency of 4kHz, and an incident angle of [missing information]. =51.7°, scattering angle The result under the condition of 51.6° Figure 9 The hydrophone is located at a depth of 2801m, a frequency of 4kHz, and an incident angle of [missing information]. =50.2°, scattering angle The result under the condition of 50.1° Figure 10 The hydrophone is located at a depth of 3101m, a frequency of 4kHz, and an incident angle of [missing information]. =47.7°, scattering angle Results under the condition of 47.8°.

[0064] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications, equivalent substitutions and improvements made by those skilled in the art within the scope of the technology disclosed in the present invention and within the spirit and principles of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for calculating the intensity of forward scattering from the seabed based on ray theory, characterized in that, The method includes the following steps: S1. Construct a two-dimensional ray tracing model. Based on the sound velocity profile, establish the ray path equation in cylindrical coordinates. Use Snell's law to constrain the ray propagation direction. Calculate the cumulative reflection loss through the seabed reflection coefficient to obtain the sound ray path from the sound source to the seabed and from the seabed to the receiver. Record the grazing angle, arc length, and propagation loss of the seabed scattering points. Construct an interpolation model for the scattering points obtained by tracing the sound ray from the sound source and an interpolation model for the scattering points obtained by tracing the sound ray from the receiver using acoustic reciprocity. Analyze and refine the interpolation of the seabed scattering points generated by sound source tracing. S2, based on N The ×2D method generates a three-dimensional seabed scattering region. N The ×2D method extends the two-dimensional ray tracing results of the sound ray path at the sound source to three-dimensional space by rotating the azimuth angle. The azimuth angle step size is adaptively adjusted according to the horizontal distance of the scattering point to obtain the three-dimensional spatial coordinates of the seabed scattering point. The interpolation model constructed by the receiver tracing the sound ray is used to match the sound ray parameters from the scattering point to the receiver and calculate the total propagation time. S3. Based on the calculated total propagation time, the isochronous scattering region is divided into grids using the triangular partitioning method. An abnormal triangular scattering surface element is removed by setting a maximum side length threshold, and the continuous scattering surface is discretized into a set of triangular scattering surface elements. S4. Using the triangular scattering surface element set, the effective scattering area is calculated by numerical integration, and the forward scattering intensity of the seabed at different grazing angles is obtained according to the sonar equation.

2. The method for calculating seabed forward scattering intensity based on ray theory according to claim 1, characterized in that, In step S1, an interpolation model for the scattered points obtained by tracing sound rays from the sound source and an interpolation model for the scattered points obtained by tracing sound rays from the receiver using acoustic reciprocity are constructed. The seabed scattered points generated by sound source tracing are interpolated and encrypted, including: setting the emission angle and angle interval, tracing sound rays from the sound source to the seabed, and tracing sound rays from the receiver to the seabed using acoustic reciprocity, and recording the corresponding sound ray parameters.

3. The method for calculating seabed forward scattering intensity based on ray theory according to claim 2, characterized in that, Tracking sound sources along different paths and analyzing seabed scattering points by emission angle Sort and remove duplicates by emission angle For each independent variable, construct the following set of spline interpolation functions, with the following expressions: ； ； ； ； ； In the formula, The horizontal distance from the sound source to the point of scattering off the seabed. The propagation time from the sound source to the point of scattering on the seabed. Let be the arc length from the sound source to the point of scattering off the seabed. The incident grazing angle, The cumulative reflection coefficient at the transmitting end; To launch angle The horizontal distance obtained for the independent variable spline interpolation function, To launch angle The propagation time from the sound source to the seabed scattering point is obtained as the independent variable. spline interpolation function, To launch angle The arc length from the sound source to the seabed scattering point is obtained as the independent variable. spline interpolation function, To launch angle The incident grazing angle obtained as the independent variable spline interpolation function, To launch angle The cumulative reflection coefficient of the transmitter obtained as the independent variable spline interpolation function; Within the launch angle range Inner step length Uniform interpolation encryption is used to obtain the scattering point parameters corresponding to each sampling angle through the above interpolation function group, and generate a list of scattering points from the sound source to the seabed.

4. The method for calculating seabed forward scattering intensity based on ray theory according to claim 2, characterized in that, For tracking seabed scattering points along different paths from the receiver, with horizontal distance For each independent variable, construct separate sets of interpolation functions: ； ； ； ； In the formula, The horizontal distance from the scattering point to the receiver. The propagation time from the receiver to the scattering point on the seabed. Let be the arc length from the point of scattering off the seabed to the receiver. The grazing angle is the scattering angle. The cumulative reflection coefficient at the receiving end. For horizontal distance The propagation time from the receiver to the seabed scattering point is obtained as the independent variable. spline interpolation function, For horizontal distance The arc length from the seabed scattering point to the receiver, obtained as the independent variable. spline interpolation function, For horizontal distance The scattering grazing angle obtained as the independent variable spline interpolation function, For horizontal distance The cumulative reflection coefficient of the receiver obtained as the independent variable The spline interpolation function.

5. The method for calculating seabed forward scattering intensity based on ray theory according to claim 1, characterized in that, In step S2, the three-dimensional spatial coordinates of the seabed scattering point are obtained, including: depth The harmonic parameters remain constant during rotation, and the azimuth step size is... An adaptive strategy is adopted, based on the horizontal distance of the scattering point. Adaptive adjustment, the expression is: ； In the formula, For the target arc length resolution, and Limited to a preset range Within this range, avoid excessively dense near-range scattering points or excessively sparse far-range scattering points, and prevent excessively large or small azimuth step sizes in extreme cases.

6. The method for calculating seabed forward scattering intensity based on ray theory according to claim 5, characterized in that, By constructing a set of receiver interpolation functions, the horizontal distance from the seabed scattering point to the receiver is used. Interpolation is used to obtain the acoustic parameters of the receiving end; horizontal distance Scattering points that are outside the valid range of interpolation are marked as invalid and discarded; The source-tracking ray parameters of each effective scattering point are matched with the receiver-tracking ray parameters to form a complete seabed scattering ray from the sound source through the seabed scattering point to the receiver. Calculate the total propagation time for each effective scattering point. : ； In the formula, The propagation time from the sound source to the point of scattering on the seabed. This represents the propagation time from the seabed scattering point to the receiver.

7. The method for calculating seabed forward scattering intensity based on ray theory according to claim 1, characterized in that, In step S3, the meshing of the isochronous scattering region using triangulation includes: using triangulation to mesh the discrete scattering points on the horizontal plane. The continuous scattering surface is discretized into a set of triangular scattering surface elements by performing mesh generation on the above. Given the pulse length of the sound source Let the start time of the time window be... Based on total transmission time Grouping the effective scattering points will satisfy The scattering points are included in this window, forming the isochronous scattering region at that moment; for the effective set of scattering points within each time window, on the horizontal plane... Perform triangulation on the top; the area of ​​each triangle Calculated using the outer product: ； In the formula, These are the horizontal coordinates of the three vertices of the triangle; Set the maximum side length threshold Remove any side with a length exceeding A triangle; The effective scattering region area of ​​this time window for: ； In the formula, The threshold for the maximum side length within this time window. The index of the valid triangular scattering surface elements retained after filtering. For the first The area of ​​each triangular scattering surface element.

8. The method for calculating seabed forward scattering intensity based on ray theory according to claim 1, characterized in that, In step S4, the forward scattering intensity of the seabed is numerically integrated using a triangular scattering element set to obtain the forward scattering intensity of the seabed at different grazing angles. The calculation formula is as follows: ； In the formula, The forward scattering intensity at the seabed. The incident grazing angle, The grazing angle is the scattering angle. It is the azimuth angle. To receive signal strength, At the source level, This refers to the propagation loss from the sound source to the scattering point on the seabed. This represents the propagation loss from the seabed scattering point to the receiver. The effective scattering area is denoted by .

9. A system for calculating the intensity of forward scattering from the seabed based on ray theory, characterized in that, The system implements the method for calculating seabed forward scattering intensity based on ray theory as described in any one of claims 1-8, and the system includes: The two-dimensional ray tracing module establishes the ray path equation in cylindrical coordinates based on the sound velocity profile, uses Snell's law to constrain the ray propagation direction, calculates the cumulative reflection loss through the seabed reflection coefficient, obtains the sound ray path from the sound source to the seabed and from the seabed to the receiver, and records the grazing angle, arc length and propagation loss of the seabed scattering points. It constructs an interpolation model for the scattering points obtained by tracing the sound ray from the sound source and an interpolation model for the scattering points obtained by tracing the sound ray from the receiver using acoustic reciprocity, and performs interpolation densification on the seabed scattering points generated by sound source tracing. The three-dimensional scattering region generation module is based on N The ×2D method generates a three-dimensional seabed scattering region. N The ×2D method extends the two-dimensional ray tracing results of the sound ray path at the sound source to three-dimensional space by rotating the azimuth angle. The azimuth angle step size is adaptively adjusted according to the horizontal distance of the scattering point to obtain the three-dimensional spatial coordinates of the seabed scattering point. The interpolation model constructed by the receiver tracing the sound ray is used to match the sound ray parameters from the scattering point to the receiver and calculate the total propagation time. The effective scattering area calculation module uses triangulation to divide the isochronous scattering area into a grid based on the total propagation time calculated. It sets a maximum side length threshold to remove abnormal triangular scattering elements and discretizes the continuous scattering surface into a set of triangular scattering elements. The scattering intensity calculation module uses the triangular scattering surface element set to calculate the effective scattering area by numerical integration, and obtains the seabed forward scattering intensity at different grazing angles according to the sonar equation.

10. The seabed forward scattering intensity calculation system based on ray theory according to claim 9, characterized in that, The seabed forward scattering intensity calculation system based on ray theory is mounted on a computer-readable storage medium, which stores a computer program. When the computer program is executed by a processor, it can realize the functions of the seabed forward scattering intensity calculation system based on ray theory.

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