Method for calculating medium-high-frequency underwater radiation noise of ship in limited water area

Abstract

The invention relates to a method for calculating medium-high-frequency underwater radiation noise of a ship in a limited water area. The method comprises the following steps of: 1, establishing a ship underwater radiation noise finite element-statistical energy hybrid model and a statistical energy calculation model; 2, calculating the radiation sound pressure of a target point; 3, calculating the contribution of each subsystem to the sound pressure of the target point; 4, establishing a sound ray analysis and calculation model; 5, determining an excitation source in the sound ray analysis and calculation model; and 6, calculating to obtain the radiation sound pressure of the target point of the limited water area. The ship limited water area radiation noise is calculated by comprehensively applying multiple existing noise calculation methods, operation is easy, physical significance is clear, and the method can be applied to calculation of limited water area underwater radiation noise of ships, ocean platforms and other complex structures.

Description

Technical Field

[0001] The present invention relates to the technical field of vibration reduction and noise reduction for ships and vessels, and in particular to a method for calculating mid-high frequency underwater radiated noise of ships in a limited water area. Background Art

[0002] For the numerical calculation of underwater radiated noise of ships, the finite element method or the finite element-boundary element hybrid method is generally used at low frequencies, the finite element-statistical energy hybrid calculation method is used in the mid-frequency range, and the statistical energy method is used at high frequencies.

[0003] However, in the statistical energy model, the external acoustic radiation water area is usually simulated by semi-infinite fluid elements (semi-infinite fluid) to calculate the radiated sound pressure value. This method does not consider the influence of the water area boundary conditions and is difficult to apply to a limited water area environment, such as a port water area environment.

[0004] Many scholars have carried out theoretical research on the acoustic propagation characteristics in a shallow water environment, which has a relatively wide calculation frequency domain. However, most of them take a simple point source as the research object and cannot be applied to complex models, such as the acoustic radiation calculation of ships.

[0005] The ray analysis method (Ray analysis) is applicable to the acoustic radiation calculation of complex models, can take into account the influence of boundary conditions, and has a relatively wide calculation frequency. However, the sound source in the ray analysis method is generally also an ideal simple sound source, such as a point source, which limits the application scope of the ray analysis method.

[0006] In the existing technology, the numerical calculation method of mid-high frequency underwater radiated noise of ships does not consider the influence of water area boundary conditions and is difficult to apply to a limited water area environment.

[0007] Therefore, we propose a method for calculating mid-high frequency underwater radiated noise of ships in a limited water area. Summary of the Invention

[0008] The applicant of the present invention aims at the above-mentioned disadvantages in the existing production technology and provides a method for calculating mid-high frequency underwater radiated noise of ships in a limited water area, that is, using the acoustic ray method to correct the calculation results obtained by the mid-frequency finite element-statistical energy hybrid method and the high-frequency statistical energy method to obtain the underwater radiated noise of the target point in the limited water area considering the influence of boundary conditions, and solving the numerical calculation problem of mid-high frequency underwater radiated noise of ships in a limited water area.

[0009] The technical solution adopted by the present invention is as follows:

[0010] A method for calculating mid-high frequency underwater radiated noise of ships in a limited water area, including:

[0011] The first step: establishing a finite element-statistical energy hybrid model and a statistical energy calculation model for underwater radiated noise of ships;

[0012] Step 2: Calculate the radiated sound pressure of the target point;

[0013] Step 3: Calculate the contribution of each subsystem to the sound pressure at the target point;

[0014] Step 4: Establish a ray analysis calculation model;

[0015] Step 5: Determine the excitation source in the ray analysis calculation model;

[0016] Step 6: Calculate the radiated sound pressure of the target point in a limited water area.

[0017] It is further characterized in that:

[0018] In the first step, a finite element - statistical energy hybrid calculation model is adopted in the mid - frequency region; a statistical energy calculation model is adopted in the high - frequency region.

[0019] In the second step, the radiated sound pressure of the target point is composed of the calculation results of the mid - frequency finite element - statistical energy calculation model and the high - frequency statistical energy calculation model, including mid - frequency and high - frequency parts, without considering the boundary conditions of the limited water area.

[0020] In the third step, the contribution of each subsystem to the sound pressure at the target point is expressed by the energy input of the subsystem to the target point, and the subsystem with the largest total energy input to the sound pressure at the target point is determined as the subsystem with the largest sound pressure contribution.

[0021] In the fourth step, the ray analysis calculation model includes models of the water surface, the outer surface of the ship's hull below the water surface, the bottom of the water, and the outer surface of obstacles within the range.

[0022] An air impedance boundary condition is set on the water surface, an acoustic impedance boundary condition corresponding to the hull plate is set on the outer surface of the ship's hull, an acoustic impedance boundary condition corresponding to the bottom water medium is set on the bottom of the water, and an acoustic impedance boundary condition corresponding to the medium is set on the outer surface of the obstacle.

[0023] In the fifth step, the excitation source is represented by a point source, and the position of the excitation source is determined by the subsystem with the largest sound pressure contribution in the third step.

[0024] The position of the excitation source is in the direction perpendicular to the geometric centroid of the subsystem with the largest sound pressure contribution and the subsystem. The direction of the excitation source is parallel to this perpendicular direction and points to the outer surface of the ship's hull; the position of the excitation source is outside the hull surface, and the distance from the subsystem with the largest sound pressure contribution is d, where d = min{0.1D, 0.5m}, and D is the distance from the target point to the subsystem with the largest sound pressure contribution; the magnitude of the excitation source adopts the calculation result in the second step.

[0025] The beneficial effects of the present invention are as follows:

[0026] The present invention realizes the calculation of the radiated noise of a ship in a limited water area by comprehensively applying a variety of existing noise calculation methods. It is simple to operate and has clear physical meanings, and can be applied to the calculation of the underwater radiated noise of complex structures such as ships and offshore platforms in a limited water area. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic flow chart of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0028] The following combines the drawings to illustrate the detailed implementation manners of the present invention.

[0029] As Figure 1 shown, a method for calculating the mid-high frequency underwater radiated noise of a ship in a limited water area includes the following steps:

[0030] The first step: Establish a finite element-statistical energy hybrid model and a statistical energy calculation model for the underwater radiated noise of the ship;

[0031] The second step: Calculate the radiated sound pressure at the target point;

[0032] The third step: Calculate the contribution of each subsystem to the sound pressure at the target point;

[0033] The fourth step: Establish a ray analysis calculation model;

[0034] The fifth step: Determine the excitation source in the ray analysis calculation model;

[0035] The sixth step: Calculate the radiated sound pressure at the target point in the limited water area.

[0036] In the first step, a finite element-statistical energy hybrid calculation model is adopted in the mid-frequency region; a statistical energy calculation model is adopted in the high-frequency region. The calculation water area is simulated by a semi-infinite domain fluid element, and the semi-infinite domain fluid element is set at the target point to calculate the radiated sound pressure value at the target point.

[0037] In the second step, the radiated sound pressure at the target point is composed of the calculation results of the mid-frequency finite element-statistical energy calculation model and the high-frequency statistical energy calculation model, including the mid-frequency and high-frequency parts. At this time, the calculation results obtained do not consider the limited water area boundary conditions.

[0038] In the third step, the contribution of each subsystem to the sound pressure at the target point is expressed by the energy input of the subsystem to the target point, and the subsystem with the largest total energy input to the sound pressure at the target point is determined as the subsystem with the largest sound pressure contribution.

[0039] In the fourth step, the ray analysis calculation model should include the water surface, the outer surface of the ship below the water surface, the water bottom and the outer surface models of the obstacles within the range.

[0040] An air impedance boundary condition is set on the water surface, an acoustic impedance boundary condition corresponding to the hull plate is set on the outer surface of the hull, an acoustic impedance boundary condition corresponding to the bottom water medium is set at the bottom, and an acoustic impedance boundary condition corresponding to the medium is set on the outer surface of the obstacle.

[0041] In the fifth step, the excitation source is represented by a point source, and the position of the excitation source is determined by the subsystem with the largest contribution to the sound pressure in the third step. The position of the excitation source is in the direction perpendicular to the geometric centroid of the subsystem with the largest contribution to the sound pressure. The direction of the excitation source is parallel to this perpendicular direction and points to the outer surface of the hull. The position of the excitation source is outside the hull surface, and the distance from the subsystem with the largest contribution to the sound pressure is d, where d = min{0.1D, 0.5m}, and D is the distance from the target point to the subsystem with the largest contribution to the sound pressure. The magnitude of the excitation source adopts the calculation result in the second step.

[0042] The calculation of the radiated noise of a ship in a finite water area is realized by comprehensively applying a variety of existing noise calculation methods. The operation of the present invention is simple and its physical meaning is clear, and it can be applied to the calculation of the underwater radiated noise of complex structures such as ships and offshore platforms in a finite water area.

[0043] The above description is an explanation of the present invention, not a limitation of the invention. For the scope defined by the present invention, refer to the claims. Any form of modification can be made within the protection scope of the present invention.

Claims

1. A method for calculating the medium and high frequency underwater radiated noise of a ship in a limited water area, characterized in that, Including: The first step: establishing a finite element - statistical energy hybrid model and a statistical energy calculation model for underwater radiated noise of ships; The second step: calculating the radiated sound pressure at the target point; The third step: calculating the contribution of each subsystem to the sound pressure at the target point; The fourth step: establishing a ray analysis calculation model; The fifth step: determining the excitation source in the ray analysis calculation model; The sixth step: calculating the radiated sound pressure at the target point in a limited water area.

2. The calculation method of medium and high frequency underwater radiated noise of ships in limited waters according to claim 1, wherein: In the first step, a finite element - statistical energy hybrid calculation model is adopted in the mid - frequency range, and a statistical energy calculation model is adopted in the high - frequency range.

3. A method for calculating the medium and high frequency underwater radiated noise of a ship in a limited water area according to claim 1, characterized in that: In the second step, the radiated sound pressure at the target point is composed of the calculation results of the mid - frequency finite element - statistical energy calculation model and the high - frequency statistical energy calculation model, which includes mid - frequency and high - frequency parts, without considering the boundary conditions of the limited water area.

4. The high-frequency underwater radiated noise calculation method for ships in limited waters according to claim 1, wherein: In the third step, the contribution of each subsystem to the sound pressure at the target point is expressed by the energy input of the subsystem to the target point, and the subsystem with the largest total - level energy input to the sound pressure at the target point is determined as the subsystem with the largest contribution to the sound pressure.

5. A method for calculating the medium and high frequency underwater radiated noise of a ship in a limited water area according to claim 1, characterized in that: In the fourth step, the ray analysis calculation model includes models of the water surface, the outer surface of the ship below the water surface, the seabed, and the outer surface of obstacles within the range.

6. A method for calculating the medium and high frequency underwater radiated noise of a ship in a limited water area as described in claim 5, characterized in that: An air impedance boundary condition is set on the water surface, an acoustic impedance boundary condition corresponding to the hull plate is set on the outer surface of the ship, an acoustic impedance boundary condition corresponding to the seabed medium is set on the seabed, and an acoustic impedance boundary condition corresponding to the medium is set on the outer surface of the obstacle.

7. A method for calculating the medium and high frequency underwater radiated noise of a ship in a limited water area as claimed in claim 1, characterized in that: In the fifth step, the excitation source is represented by a point source, and the position of the excitation source is determined by the subsystem with the largest contribution to the sound pressure in the third step.

8. A method for calculating the medium and high frequency underwater radiated noise of a ship in a limited water area according to claim 7, characterized in that: The position of the excitation source is in the centroid of the geometry of the subsystem with the largest contribution to the sound pressure and in the perpendicular direction of this subsystem. The direction of the excitation source is parallel to this perpendicular direction and points to the outer surface of the ship. The position of the excitation source is outside the hull surface, and the distance from the subsystem with the largest contribution to the sound pressure is d, where d = min{0.1D, 0.5m}, and D is the distance from the target point to the subsystem with the largest contribution to the sound pressure. The magnitude of the excitation source adopts the calculation result in the second step.

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