A system and method for testing direct radiation components of flow noise from a sea pipe

Abstract

The application discloses a kind of direct radiation component test systems of sea pipe orifice flow noise, including test bench, test pipeline and underwater acoustic sensor, the test bench includes three-dimensional support structure, floating raft shock isolation seat and sea pump;The bottom of the three-dimensional support structure is fixed to the bottom of lake, the top of the three-dimensional support structure is provided with floating raft shock isolation seat, and the floating raft shock isolation seat is located on the water surface;The sea pump is installed on the floating raft shock isolation seat;The outlet of the test pipeline is connected with the inlet of the sea pump, and the water inlet of the test pipeline is the sea inlet;The underwater acoustic sensor is installed at the measuring point in front of the sea inlet.The application also discloses a kind of direct radiation component test methods of sea pipe orifice flow noise.The beneficial effects of the application are that the test method for separating the direct radiation component of sea pipe orifice flow noise can exclude the vibration sound radiation interference of the first sound channel and the second sound channel, and the direct radiation energy of sea inlet flow noise is separated through later data processing.

Description

Technical Field

[0001] This invention relates to the field of marine machinery noise control, specifically to a system and method for testing the direct radiation component of flow noise at a sea outlet. Background Technology

[0002] From the perspective of acoustic energy transmission path, the radiated noise of the sea passage system includes three components: first, the vibration transmission of the first acoustic channel generates sound radiation underwater; second, the vibration transmission of the second acoustic channel pipeline generates sound radiation underwater; and third, the fluid medium inside the second acoustic channel pipeline mainly transmits the pump flow noise, which directly generates sound radiation at the sea passage.

[0003] With the application of floating rafts and flexible support chocks, the noise problem caused by vibration in the first and second acoustic channels has been largely resolved. However, the problem of flow noise radiation in the second acoustic channel has become increasingly prominent. To strengthen the control of flow noise in the sea passage system, it is first necessary to effectively evaluate the radiated noise control effect of the flow noise control measures. The prerequisite for this is the effective separation of the direct radiated component of the flow noise at the sea passage.

[0004] The shipbuilding industry has conducted extensive experimental research on radiated noise from sea passage systems. Currently, research on the direct radiated component of noise from separated pipe outlets falls into two categories: one is onshore bench testing, which involves installing a sea passage pump outlet on shore and conducting radiated noise tests in lake water; the other is conducting radiated noise tests by submerging large sections of the ship into large reservoirs. However, these two research methods each have their own problems.

[0005] The problem with shore-based test bench research is that, due to the limitations of the natural lake water depth distribution pattern, the lake water near the shore test bench is relatively shallow, requiring the configuration of very long test pipelines to reach deep water areas in order to meet the boundary conditions of the radiated sound field at the estuary. The large pipeline length results in a large attenuation of pipeline flow noise, causing the radiated noise level obtained from the estuary test to be significantly lower than that of the actual ship radiated noise level, with the characteristic line spectrum being more than 20 dB lower, and some test benches even failing to measure the characteristic line spectrum noise data present in the actual ship.

[0006] The problem with large-section testing is that, due to the large contact area between the large sections and the water, the vibration radiation area of ​​the sections is also large. Even with vibration isolation by floating rafts, the vibration of the first and second acoustic channels of the sea passage system is transmitted to the sections, significantly increasing the radiation area and the proportion of vibration sound radiation in the total radiated noise energy. In contrast, the proportion of direct radiation energy of flow noise decreases and is difficult to separate. This is why current section tests have not successfully separated the direct radiation noise of flow noise from the sea passage system nozzles. In addition, section tests are large in scale and costly. If the direct radiation of flow noise cannot be successfully separated, the modification of the test platform will be very difficult and costly. Summary of the Invention

[0007] The purpose of this invention is to provide a system and method for testing the direct radiation component of flow noise at a sea outlet, addressing the shortcomings of existing technologies.

[0008] The technical solution adopted in this invention is: a test system for the direct radiation component of flow noise at a sea outlet, comprising a test bench, test pipeline, and underwater acoustic sensors.

[0009] The test bench includes a three-dimensional support structure, a floating raft isolation seat, and a sea-penetrating pump; the bottom of the three-dimensional support structure is fixed to the bottom of the lake, and the top of the three-dimensional support structure is equipped with a floating raft isolation seat, which is located on the water surface; the sea-penetrating pump is installed on the floating raft isolation seat.

[0010] The outlet of the test pipeline is connected to the inlet of the sea-crossing pump, and the inlet of the test pipeline is the sea outlet.

[0011] The underwater acoustic sensor is installed at the measuring point directly in front of the estuary;

[0012] A diversion pipe is reserved at the bottom of the lake.

[0013] According to the above scheme, the three-dimensional support structure includes a three-dimensional bracket and an installation platform, with the installation platform located on top of the three-dimensional bracket. The three-dimensional bracket is generally a trapezoidal structure with a wider bottom and a wider top. It includes uprights, crossbars, and reinforcing bars. The lower end of the uprights is fixed to the bottom of the lake, and the upper ends of two adjacent uprights are connected by crossbars. The middle parts of two adjacent uprights are connected by several inclined reinforcing bars.

[0014] According to the above scheme, the uprights, crossbars, and reinforcing bars are all cylindrical components.

[0015] The present invention also provides a method for obtaining the direct radiation component of the flow noise at the sea outlet based on the test system described above, the method comprising the following steps:

[0016] Step 1: Design the test bench as shown above;

[0017] Step 2: Select a lake with a water depth of more than 10m, and set up the test platform as described above, so that the installation platform is higher than the lake surface;

[0018] Step 3: Fabricate a test pipeline according to the actual ship's pipeline length and diameter. Connect the outlet of the test pipeline to the inlet of the sea-crossing pump, and the inlet of the test pipeline to the sea-crossing outlet; reserve a guide pipe at the bottom of the lake.

[0019] Step 4: Set up radiated noise measurement points at the estuary and install underwater acoustic sensors at the measurement point locations;

[0020] Step 5: Start the estuary pump. The pump set is started at various speeds. Under each speed condition, the sound pressure level of the radiated noise at the estuary is measured when the guide pipe is not connected. Lp1 And the underwater radiated noise sound pressure level at the pipe inlet when connecting the guide pipe to the sea mouth. L p2 The direct radiation component of the flow noise was calculated using the principle of acoustic energy superposition. L p-fluid .

[0021] According to the above plan, in step five, L p-fluid The calculation formula is:

[0022] .

[0023] According to the above scheme, in step three, the guide pipe is located in front of the estuary, and the two axes are parallel; the diameter of the guide pipe is not less than the diameter of the test pipeline.

[0024] According to the above plan, in step three, the total water depth at the estuary... H Not less than 10m.

[0025] According to the above scheme, in step four, the radiated noise measurement points at the sea outlet are arranged on the axis outside the critical distance of the sea outlet, and the distance between the measurement points and the sea outlet is... r The following relationship must be satisfied:

[0026] a 2 / λ <r<2d / 3 ,

[0027] in, This is the critical distance; The diameter of the estuary is in meters (m). λ is the wavelength of the sound wave, in meters; d is the distance between the geometric center of the estuary and the water surface, in meters.

[0028] According to the above scheme, in step four, the distance between the geometric center of the estuary and the water surface... d Satisfy 5 a < d <0.5 H ,in H The total water depth at the estuary is in meters (m). The diameter of the estuary is in meters (m).

[0029] According to the above scheme, in step four, the length of the guide tube is greater than 10. r ; r Let be the distance between the measuring point and the estuary, in meters (m).

[0030] The beneficial effects of this invention are as follows: The test method for separating the direct radiation component of the flow noise at the sea outlet proposed in this invention can eliminate the vibration and sound radiation interference of the first and second sound channels. Through subsequent data processing, the direct radiation energy of the flow noise at the sea outlet can be separated, and the test results are accurate, providing technical support for the effective evaluation of the acoustic effects of flow noise control measures in sea outlet systems. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the test bench in this invention.

[0032] Figure 2 This is a diagram showing the critical distance for the arrangement of radiated noise measurement points in the Tonghaikou area in this invention.

[0033] Figure 3 This is a diagram showing the upper limit of the distance for the arrangement of radiation noise measurement points in the Tonghaikou area in this invention.

[0034] Figure 4 Schematic diagram of the principle for separating the direct radiation component of the noise from the estuary.

[0035] Figure 5 This is a diagram illustrating the calculation of the separation of the direct radiation component of flow noise in this invention. Detailed Implementation

[0036] To better understand the present invention, it will be further described below with reference to the accompanying drawings and specific embodiments.

[0037] like Figure 1 The system shown is a test system for the direct radiation component of flow noise at a sea outlet, including a test bench, a test pipeline 5, and a hydroacoustic sensor.

[0038] The test bench includes a three-dimensional support structure, a floating raft isolation seat 2, and a sea-penetrating pump 1; the bottom of the three-dimensional support structure is fixed to the bottom of the lake, and the top of the three-dimensional support structure is provided with the floating raft isolation seat 2, which is located on the water surface; the sea-penetrating pump 1 is installed on the floating raft isolation seat 2.

[0039] The outlet of the test pipeline 5 is connected to the inlet of the sea-crossing pump 1, and the inlet of the test pipeline 5 is the sea-crossing inlet 5.1;

[0040] The underwater acoustic sensor is installed at the measuring point directly in front of the 5.1 estuary.

[0041] A guide pipe 6 is reserved at the bottom of the lake, and the estuary 5.1 can be connected to the guide pipe 6 via a rubber hose.

[0042] A method for obtaining the direct radiation component of flow noise at a sea passage pipe, the method comprising the following steps:

[0043] Step 1: Design the test bench as shown above.

[0044] Step 2: Select a lake with a water depth of more than 10m, and set up the test platform as described above, so that the installation platform 3 is higher than the lake surface.

[0045] In this invention, the test bench is erected in a lake and includes a three-dimensional support structure, a floating raft isolation seat 2, and a sea-penetrating pump 1. The bottom of the three-dimensional support structure is fixed to the bottom of the lake, and the top of the three-dimensional support structure is provided with the floating raft isolation seat 2, which is located on the water surface. The sea-penetrating pump 1 is installed on the floating raft isolation seat 2.

[0046] Preferably, the three-dimensional support structure includes a three-dimensional bracket 3 and an installation platform 4. The installation platform 4 is set on the top of the three-dimensional bracket 3 and is higher than the lake surface. The floating raft isolation seat 2 is mounted on the installation platform 4 via a base.

[0047] In this invention, the mounting platform 4 provides a mounting base for the floating raft vibration isolation seat 2.

[0048] Preferably, the three-dimensional support 3 has a trapezoidal structure with a larger bottom and a larger top, and includes uprights 3.1, crossbars 3.2 and reinforcing bars 3.3. The lower end of the uprights 3.1 is fixed to the bottom of the lake, and the upper ends of two adjacent uprights 3.1 are connected by crossbars 3.2; the middle parts of two adjacent uprights 3.1 are connected by several inclined reinforcing bars 3.3.

[0049] Preferably, the upright 3.1, the crossbar 3.2, and the reinforcing bar 3.3 are all cylindrical components; such cylindrical components and the floating raft vibration isolation seat 2 can reduce interference in the first acoustic channel.

[0050] In this embodiment, the lake bottom is not planar. To adapt to the lake bottom, some of the uprights 3.2 are shorter. After the three-dimensional support 3 is erected, the top of it is horizontal so as to set up the installation platform 4.

[0051] In this invention, considering the distance between the estuary and the lake embankment, and while maintaining the same test pipeline length as the actual vessel, the estuary pump 1 must be installed on the lake surface. Therefore, a vibration isolation scheme for the estuary pump based on a cylindrical three-dimensional support structure is proposed. This scheme utilizes the raft vibration isolation to attenuate the vibration transmission of the first acoustic channel of the estuary pump. Under the premise of ensuring support stiffness, the cylindrical three-dimensional support structure is further used to reduce the vibration radiation area, thereby minimizing the vibration radiation of the first acoustic channel.

[0052] Step 3: Fabricate test pipe 5 and drainage pipe 7 according to the actual ship's pipe length and diameter configuration. Connect both pipes to the sea-crossing pump 1 (specifically, the outlet of test pipe 5 is connected to the inlet of sea-crossing pump 1, and the inlet of drainage pipe 7 is connected to the outlet of sea-crossing pump 1). The inlet of test pipe 5 is the sea-crossing inlet 5.1. A guide pipe 6 is pre-installed on the lake bottom, located in front of the sea-crossing inlet 5.1, with their axes parallel. The diameter of guide pipe 6 is not less than the diameter of test pipe 5. See Appendix for details. Figure 4 .

[0053] In this embodiment, the distance between the sea outlet of test pipeline 5 and the water surface is... d It is about 2m long. The diversion pipe 6 is about 4m in front of the 5.1 estuary. The length of the diversion pipe 6 is about 4m.

[0054] Preferably, the total water depth at point 5.1 of the estuary is... H Not less than 10m.

[0055] In this invention, the length of the test pipeline 5 is consistent with that of the inlet pipeline of the actual ship to avoid excessive or insufficient attenuation of convective noise due to excessively long or short pipelines, which would result in significant differences between the radiated noise test results and those of the actual ship. Considering the water depth conditions, the sea inlet 5.1 of the test bench needs to be located in a deep water area far from the lake dike; the total water depth at the sea inlet 5.1 location... H The depth exceeds 10m, which satisfies the boundary conditions of the radiated sound field and avoids significant differences between the acoustic impedance conditions of the pipe flow noise radiation and those of the actual ship.

[0056] Step 4: Set up measurement point 8 for the radiated noise at the estuary and install underwater acoustic sensors at the measurement point locations. Specifically, the radiated noise measurement point at the estuary is arranged on an axis outside the critical distance from the estuary, and the distance between measurement point 8 and the estuary 5.1 is... r The following relationship must be satisfied: a 2 / λ <r<2d / 3 ;

[0057] in, This is the critical distance; The diameter of the estuary is 5.1 meters, in meters (m). The wavelength of the sound wave is in meters (m). d Let be the distance, in meters, from the geometric center of the 5.1 estuary to the water surface.

[0058] Preferably, the distance between the geometric center of the estuary 5.1 and the water surface is... d Satisfy 5 a < d <0.5 H ,in H The total water depth at location 5.1 of the estuary is in meters.

[0059] Preferably, the length of the guide tube 6 is greater than 10. r .

[0060] In this invention, the following issues must be addressed in the arrangement of measurement points: first, to avoid the near-field radiated sound field at the estuary to prevent large fluctuations in test data caused by drastic changes in the near-field sound field distribution; and second, to eliminate interference from sound reflections from the water surface and lake embankment.

[0061] The spatial distribution of the radiated sound field at Tonghaikou is quite complex. Taking the geometric center of Tonghaikou 5.1 as the starting point, at the critical distance (the critical distance is...) , The diameter of the estuary is in meters (m). Within the range of sound wave wavelength (m), i.e., the acoustic near field, the radiated noise sound pressure varies with distance. r Dramatic changes prevent acoustic testing; beyond the critical distance, the radiated noise sound pressure level increases with distance. 20log(r) The noise decays regularly, exhibiting a radiated sound field similar to that of a monopole sound source. Therefore, this invention arranges the radiated noise measurement points at the estuary on an axis outside the critical distance from the estuary, as detailed in the appendix. Figure 2 As shown, this also facilitates the later conversion of the source level data of the radiated noise in Tonghaikou according to the distance.

[0062] Although measuring points are required to be placed beyond a critical distance, there is an upper limit to the distance between the measuring points and the estuary to eliminate interference from sound reflections from the water surface and lakebed. This value is closely related to the distance from the estuary to the water surface. Typically, the distance between the estuary and the water surface is determined... d First, the impact of hydrodynamics must be considered. Whether it's the outlet or the inlet, if the inflow and outflow at the estuary significantly affect the water surface shape, it will severely impact the acoustic field boundary conditions of the noise radiation from the estuary flow, causing unnecessary interference to acoustic testing. Therefore, referring to common practices in the field of hydrodynamics, the geometric center of the estuary 5.1 is located at a depth greater than 5 times the diameter of the estuary at the water surface.

[0063] Because the water surface is a soft boundary, sound reflection from the water surface is total internal reflection, resulting in a 180° phase difference. Simplifying the 5.1 estuary as a monopole sound source, the sound reflection from the water surface can be equivalent to the effect of a mirror sound source with a 180° phase difference. Furthermore, the sound intensity of this mirror sound source is the same as that of the estuary monopole sound source. (See appendix for details.) Figure 3 As shown. The distance between the radiated noise measuring point and the estuary 5.1 is... r <2d / 3 At that time, the distance from the measuring point to the mirror sound source l> r Therefore, the sound pressure level generated by the Tonghaikou monopole sound source at the measuring point is higher than that of the mirror sound source. 20log(l / r) > 10dBAt this point, the influence of the mirror sound source on the measuring point can be ignored; if the distance from the measuring point to the sea outlet... r>2d / 3 ,So 20log(l / r) < 10dB At this point, the influence of the mirror sound source on the measuring point can be considered non-negligible. Therefore, this invention will... 2d / 3 The distance between the measuring point and the estuary 5.1 r The upper limit.

[0064] Once the locations of the radiated noise measurement points are determined, as long as the distance from the 5.1 estuary to the water surface is less than 0.5 times the total water depth, then according to... 20log(r) According to the attenuation law, the sound pressure level generated by the Tonghaikou monopole sound source at the measuring point is more than 10 dB higher than that of the sound reflection from the lake bottom. At this point, the influence of the sound reflection from the lake bottom can also be ignored.

[0065] In summary, the underwater positioning and radiated noise measurement point layout parameters for the estuary are shown in the table below. Following this layout can ensure accurate measurement of radiated noise at the estuary.

[0066] Table 1. Parameters for underwater positioning and radiated noise measurement point layout at Tonghaikou

[0067]

[0068] In this embodiment, an 8106-type underwater acoustic (radiated noise) sensor is arranged 1m directly in front of the axis of the test pipeline's outlet to the sea. For underwater acoustic testing at a maximum frequency of 1000Hz in the test pipeline, the critical distance is 0.02m. The outlet to the sea is 2m from the water surface, corresponding to an upper limit of 1.3m for the measurement point arrangement distance. This embodiment uses a measurement point arrangement distance of 1m (i.e., the distance between the measurement point and the outlet to the sea is 1m), which meets the measurement point arrangement requirements of this invention and can avoid near-field radiated sound field interference, sound reflection interference from the water surface and lake bottom.

[0069] Step 5: Start the sea-connecting pump 1. The pump set is started under various speed conditions. Under each speed condition, the sound pressure level of the radiated noise at the sea outlet 5.1 without the guide pipe 6 connected is measured. L p1 (Unit: dB), and the underwater radiated noise sound pressure level at the estuary of the Tonghaikou 5.1 when connected to the guide pipe 6 via a rubber hose. L p2 (Unit: dB) The direct radiation component of the flow noise was calculated using the principle of acoustic energy superposition. L p-fluid (Unit: dB) L p-fluid The calculation formula is as follows: ,

[0070] Furthermore, the energy proportion of the radiated noise component at the estuary under various operating conditions can be calculated, including the proportion of flow noise radiated energy.β The calculation formula is:

[0071] ;

[0072] Vibration radiation energy ratio α The calculation formula is:

[0073] .

[0074] Specifically, this embodiment uses a test pipeline with the same length as the actual ship's pipeline, connected to the inlet of the sea-crossing pump 1; a guide pipe 6 is reserved on the lakebed below the sea-crossing outlet 5.1; the sea-crossing outlet 5.1 extends directly into the water without an acoustic baffle, as detailed in the appendix. Figure 4 As shown, this minimizes pipeline vibration and radiated noise.

[0075] The test bench is used for underwater radiated noise testing in the following two states:

[0076] (1) Tonghaikou 5.1 is not connected to the diversion pipe 6.

[0077] Although the test bench design can minimize the vibration-induced sound radiation of the first and second sound channels, it cannot completely eliminate it. Therefore, with the inlet 5.1 disconnected from the guide pipe 6, the radiated noise measured at the measuring point still contains vibration-induced noise components from the first and second sound channels. With the inlet 5.1 disconnected from the guide pipe 6, the underwater radiated noise sound pressure level at the pipe opening is recorded as follows: L p1 .

[0078] (2) Tonghaikou 5.1 is connected to the diversion pipe 6 via a rubber hose.

[0079] A non-pressure-bearing rubber hose is used to connect the lake bottom guide pipe 6 to the sea outlet 5.1 of the test pipeline 5. The distance between the end of the lake bottom guide pipe 6 and the measuring point 8 is sufficiently large (≥ After connecting the guide pipe 6, the sound pressure level generated by the flow noise radiation at the measuring point from the pipe opening of the guide pipe 6 is essentially negligible. With the guide pipe 6 connected at the sea outlet 5.1, the underwater radiated noise measured at the measuring point only includes the vibration radiated noise components of the first and second sound channels. The underwater radiated noise sound pressure level at the pipe opening in this case is denoted as... L p2 .

[0080] Based on the test results of the two states mentioned above, the direct radiation component of the estuary flow noise can be calculated using the principle of acoustic energy superposition. L p-fluid For the size details, please refer to the following formula and appendix. Figure 5 .

[0081] .

[0082] Furthermore, the energy proportion of the radiated noise component at the estuary under each operating condition can be calculated.

[0083] In this embodiment, the relevant test parameters and energy percentages are shown in the table below.

[0084] Table 2. Energy of vibration radiation and direct flow noise radiation in radiated noise at the estuary.

[0085]

[0086] The above description is merely a preferred embodiment of the present invention, but the present invention should not be limited to the content disclosed in this embodiment and the accompanying drawings. All equivalents or modifications made without departing from the principles disclosed in the present invention fall within the protection scope of the present invention.

Claims

1. A system for testing the direct radiation component of flow noise at a sea outlet, characterized in that, Includes test bench, test pipelines, and underwater acoustic sensors. The test bench includes a three-dimensional support structure, a floating raft isolation seat, and a sea-penetrating pump; the bottom of the three-dimensional support structure is fixed to the bottom of the lake, and the top of the three-dimensional support structure is equipped with a floating raft isolation seat, which is located on the water surface; the sea-penetrating pump is installed on the floating raft isolation seat. The outlet of the test pipeline is connected to the inlet of the sea-crossing pump, and the inlet of the test pipeline is the sea outlet. The underwater acoustic sensor is installed at the measuring point directly in front of the estuary; A diversion pipe is reserved at the bottom of the lake.

2. The direct radiation component testing system for sea passage pipe flow noise as described in claim 1, characterized in that, The three-dimensional support structure includes a three-dimensional bracket and an installation platform, with the installation platform located on top of the three-dimensional bracket. The three-dimensional bracket is generally trapezoidal in shape, wider at the bottom and narrower at the top. It includes uprights, crossbars, and reinforcing bars. The lower ends of the uprights are fixed to the bottom of the lake, and the upper ends of two adjacent uprights are connected by crossbars. The middle parts of two adjacent uprights are connected by several inclined reinforcing bars.

3. The direct radiation component testing system for sea passage pipe flow noise as described in claim 2, characterized in that, The uprights, crossbars, and reinforcing bars are all cylindrical components.

4. A method for obtaining the direct radiation component of the sea passage flow noise based on the test system described in any one of claims 1 to 3, characterized in that, The method includes the following steps: Step 1: Design the test bench as shown above; Step 2: Select a lake with a water depth of more than 10m, and set up the test platform as described above, so that the installation platform is higher than the lake surface; Step 3: Fabricate a test pipeline according to the actual ship's pipeline length and diameter. Connect the outlet of the test pipeline to the inlet of the sea-crossing pump, and the inlet of the test pipeline to the sea-crossing outlet; reserve a guide pipe at the bottom of the lake. Step 4: Set up radiated noise measurement points at the estuary and install underwater acoustic sensors at the measurement point locations; Step 5: Start the estuary pump. The pump set is started at various speeds. Under each speed condition, the sound pressure level of the radiated noise at the estuary is measured when the guide pipe is not connected. L p1 And the underwater radiated noise sound pressure level at the pipe inlet when connecting the guide pipe to the sea mouth. L p2 The direct radiation component of the flow noise was calculated using the principle of acoustic energy superposition. L p-fluid .

5. The method for testing the direct radiation component of flow noise at a sea passage as described in claim 4, characterized in that, In step five, L p-fluid The calculation formula is: 。 6. The method for testing the direct radiation component of flow noise at a sea passage as described in claim 4, characterized in that, In step three, the guide pipe is located in front of the estuary, and the axes of the two are parallel; the diameter of the guide pipe is not less than the diameter of the test pipeline.

7. The method for testing the direct radiation component of flow noise at a sea outlet as described in claim 4, characterized in that, In step three, the total water depth at the estuary... H Not less than 10m.

8. The method for testing the direct radiation component of flow noise at a sea passage as described in claim 4, characterized in that, In step four, the radiated noise measurement points at the sea outlet are arranged on an axis outside the critical distance from the sea outlet, and the distance between the measurement points and the sea outlet is... r The following relationship must be satisfied: a 2 / λ <r<2d / 3 ， in, This is the critical distance; The diameter of the estuary is in meters (m). The wavelength of the sound wave is in meters (m). d Let be the distance, in meters, from the geometric center of the estuary to the water surface.

9. The method for testing the direct radiation component of flow noise at a sea passage as described in claim 4, characterized in that, In step four, the distance between the geometric center of the estuary and the water surface... d Satisfy 5 a < d <0.5 H ,in H The total water depth at the estuary is in meters (m). The diameter of the estuary is in meters (m).

10. The method for testing the direct radiation component of flow noise at a sea passage as described in claim 5, characterized in that, Flow noise radiation energy ratio β The calculation formula is: 。

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