Method for obtaining acoustic transmission characteristic relationship of sea pipe system

Abstract

The application discloses a kind of acquisition methods for the acoustic transfer characteristics of a through-hull piping system, which comprises the following steps: obtaining the acoustic transfer characteristics of the piping system in the frequency range of 5Hz-1st critical frequency, drawing the relationship curve, and taking the 1st peak point on the curve; determining each high-order critical frequency, calculating and obtaining the relationship between the amplitude A of the peak point in the acoustic transfer characteristics relationship curve of the piping system and the frequency f; drawing the relationship curve between the amplitude of the peak point and the frequency, and determining the peak point of each frequency band on the curve, and calculating the acoustic transfer characteristics relationship of the corresponding peak point frequency band. The beneficial effects of the present application are: based on the traditional method, the peak point-frequency relationship of the acoustic transfer characteristics curve of the through-hull piping system is given, and an acquisition method for the acoustic transfer characteristics of the through-hull piping system is proposed, which can be used for the evaluation of the acoustic transfer characteristics of the system piping in the frequency band of 5Hz-1000Hz in the preliminary design stage of the through-hull system.

Description

Technical Field

[0001] This invention relates to the field of acoustic design of submarine sea passage systems, and specifically to a method for obtaining the acoustic transmission characteristics of a sea passage pipeline system. Background Technology

[0002] The noise from the pump units of a submarine's sea passage system, especially the blade frequency line spectrum noise, propagates along the sea passage pipeline through the internal fluid medium and radiates outward at the sea passage opening, generating prominent line spectrum radiated noise. This is a key factor affecting the overall acoustic stealth performance. Typically, for sea passage system noise, the radiated noise energy is mainly concentrated in the "5Hz–1000Hz" frequency band, with the pump unit blade frequency at sea passage not exceeding 500Hz. Therefore, in the early preliminary design stages of sea passage systems, it is necessary to conduct preliminary assessments of the pipe outlet radiated noise in the 5Hz–1000Hz frequency band. This provides technical support for the acoustic optimization design of the sea passage system pipeline configuration, enabling the selection of the optimal noise control scheme from various configuration options.

[0003] Traditionally, methods for assessing radiated noise at the outlets of sea passage systems are based on the propagation of plane waves through the pipes. These methods provide formulas for calculating the first-order critical frequency (typically less than 150Hz) and estimating radiated noise in the 5Hz to critical frequency band. However, for frequency bands above the first-order critical frequency, the minimum values ​​of the frequency bands below the first-order critical frequency are directly used, which fails to meet the accuracy requirements for estimating the line spectrum noise of actual shipboard sea passage systems. While the acoustic finite element method can accurately calculate the acoustic transmission characteristic curves of the pipe system across the entire frequency band, its heavy reliance on the three-dimensional geometry of the pipe system limits its applicability to optimizing the acoustic parameters of pipe systems with various diameters and lengths. Summary of the Invention

[0004] The purpose of this invention is to provide a method for obtaining acoustic transmission relationships in a marine pipeline system, addressing the shortcomings of existing technologies.

[0005] The technical solution adopted in this invention is: a method for obtaining the acoustic transmission characteristics of a submarine pipeline system, the method comprising the following steps:

[0006] Step 1: Obtain the acoustic transmission characteristic relationship of the pipeline system in the frequency range of 5Hz to the first critical frequency, plot the relationship curve, and take the first peak point on the curve.

[0007] Step 2: Determine each higher-order critical frequency, and calculate and obtain the relationship between the amplitude A and frequency f at the peak point in the acoustic transmission characteristic curve of the pipeline system;

[0008] Step 3: Plot the relationship curve between the amplitude and frequency of the peak point, determine the peak point of each frequency band on the curve, and calculate the acoustic transmission characteristic relationship of the corresponding peak point frequency band.

[0009] According to the above scheme, in step one, the relationship between sound pressure level difference and frequency is used to characterize the acoustic transmission characteristics of the pipeline system.

[0010] According to the above scheme, in step one, the acoustic transmission characteristics within the frequency band of 5Hz to the first critical frequency satisfy the following relationship:

[0011]

[0012] in:

[0013]

[0014]

[0015]

[0016]

[0017]

[0018] In the above formulas, 5Hz≤f <f 1st ;TL total Total transmission loss, in dB; d is the pipe diameter, in meters; e is the base of the natural logarithm, a constant 2.71828; dimensionless; α, β, and z are process parameters introduced to simplify the calculation formula, dimensionless; f is the frequency, in Hz; l is the pipe length, in meters; C is the underwater acoustic velocity in the pipe, in meters per second; h is the pipe wall thickness, in meters; E is the elastic modulus of the pipe material, in MPa; f 1st This is the first critical frequency of the pipeline system, measured in Hz.

[0019] According to the above scheme, in step two, each higher-order critical frequency is an integer multiple of the first-order critical frequency, that is: the critical frequencies of each order of the total transmission loss curve of the pipeline system in the 5Hz to 1000Hz frequency band are fi, fj ... 1st 2f 1st ...nf 1st .

[0020] According to the above scheme, in step two, the functional relationship between the amplitude A of the peak point in the acoustic transmission characteristic curve and the frequency f is:

[0021]

[0022] In the formula, A0 is the amplitude auxiliary calculation coefficient, and the calculation formula is as follows:

[0023]

[0024] According to the above plan, the specific method for step three is as follows:

[0025] Using the amplitude of the first peak point as a reference, the peak point normalization process is performed on the acoustic transmission characteristic curve in the frequency band from 5Hz to the first critical frequency, as shown in the following formula:

[0026]

[0027] In the above formula, A1 represents the amplitude of the first peak point, in dB;

[0028] Accordingly, for (i-1)f 1st ~if 1st For a frequency band where i>1, with the center frequency within that band as the axis of symmetry, calculate the normalized acoustic transmission characteristics data of the peak point of that frequency band. The calculation formula is as follows:

[0029]

[0030]

[0031] In the above two formulas, TL dimensionless (f) is the dimensionless transmission loss, which has no unit; χ is the introduced process parameter, with the unit being Hz;

[0032] (i-1)f 1st ~if 1st The amplitude A at the peak point of the frequency band acoustic transfer characteristic curve i for:

[0033]

[0034] Then, (i-1)f 1st ~if 1st The acoustic transmission characteristics of a frequency band pipeline system satisfy the following equation:

[0035]

[0036] In the formula, (i-1)f 1st ≤f <if 1st , i>1; TL i (f) is the i-th frequency interval (i-1)f 1st ~if 1st The transmission loss on the line is expressed in dB.

[0037] The beneficial effects of this invention are as follows: Based on traditional methods, this invention provides the peak point-frequency relationship of the acoustic transmission characteristic curve of a sea-crossing pipeline system, and proposes a method for obtaining the acoustic transmission characteristic relationship of a sea-crossing pipeline system. This method can be used to evaluate the acoustic transmission characteristics of the system pipeline in the 5Hz-1000Hz frequency band during the preliminary design stage of a sea-crossing system. Compared with traditional methods, it broadens the frequency application range while maintaining the advantages of parametric calculation. Compared with the finite element method, it is more suitable for multi-parameter optimization design of sea-crossing systems and can provide technical support for the acoustic optimization design of sea-crossing systems. Attached Figure Description

[0038] Figure 1 This is a schematic diagram of the acoustic transmission characteristics relationship (i.e., the relationship curve between total transmission loss and frequency) and the first peak point in the frequency band from 5Hz to the first critical frequency in this embodiment.

[0039] Figure 2 This is a schematic diagram of the critical frequencies and peak points of each order in this embodiment.

[0040] Figure 3 This is the total transmission loss curve for the 5Hz to 1000Hz frequency band in this embodiment.

[0041] Figure 4 This is a schematic diagram comparing the calculated relationship curve and the simulated curve in this embodiment. Detailed Implementation

[0042] To better understand the present invention, it will be further described below with reference to the accompanying drawings and specific embodiments.

[0043] A method for obtaining the acoustic transmission characteristics of a marine pipeline system, comprising the following steps:

[0044] Step 1: Obtain the acoustic transmission characteristic formula for the frequency range of 5Hz to the first critical frequency, plot the relationship curve, and take the first peak point on the curve: the low frequency band, i.e., the frequency f is 5Hz to f 1st f 1st This is the first-order critical frequency.

[0045] Based on traditional methods for assessing acoustic transmission loss and orifice radiation impedance in pipeline systems, this paper calculates the sound pressure level at the sound source and the radiated noise sound pressure level at the orifice. The acoustic transmission characteristics of the pipeline system are characterized by the relationship between the sound pressure level difference (the difference between the sound pressure level at the sound source and the radiated noise sound pressure level at the orifice, i.e., the total transmission loss) and frequency. The acoustic transmission characteristics within the frequency band from 5 Hz to the first critical frequency satisfy the following relationship:

[0046]

[0047] in:

[0048]

[0049]

[0050]

[0051]

[0052]

[0053] In the above formulas, 5Hz≤f <f 1st ;TL total Total transmission loss, in dB; d is the pipe diameter, in meters; e is the base of the natural logarithm, a constant 2.71828; dimensionless; α, β, and z are process parameters introduced to simplify the calculation formula, dimensionless; f is the frequency, in Hz; l is the pipe length, in meters; C is the underwater acoustic velocity in the pipe, in meters per second; h is the pipe wall thickness, in meters; E is the elastic modulus of the pipe material, in MPa; f 1st This is the first critical frequency of the pipeline system, measured in Hz.

[0054] For the acoustic transmission characteristic curves in the frequency band from 5Hz to the first critical frequency, the peak point is obtained at 5Hz. See details. Figure 1 As shown.

[0055] Step 2: Determine the critical frequencies of each order, and calculate and obtain the relationship between the amplitude A at the peak point and the frequency f in the acoustic transmission characteristic curve.

[0056] Finite element analysis revealed that above the first critical frequency, there exist second, third...nth critical frequencies, and each higher-order critical frequency is an integer multiple of the first-order critical frequency. Specifically, the critical frequencies for each order of the total transmission loss curve of the pipeline system in the 5Hz–1000Hz frequency band are fi, fj ... 1st 2f 1st ...nf 1st (f 1st 2f 1st ...nf 1st Let f represent the first critical frequency, the second critical frequency, ..., the nth critical frequency, respectively. The acoustic transmission characteristic curves in the frequency region between adjacent critical frequencies have peak points. Through numerical fitting of the finite element calculation results, the functional relationship between the amplitude A of the peak points in the acoustic transmission characteristic curves and the frequency f is obtained as follows:

[0057]

[0058] In the formula, A0 is the amplitude auxiliary calculation coefficient, and the calculation formula is as follows:

[0059]

[0060] Step 3: Plot the curve showing the relationship between the amplitude A and frequency f at the peak point, and determine the peak point of each frequency band on the curve. Calculate the acoustic transmission characteristic relationship of the corresponding peak point frequency band.

[0061] The specific method for this step is as follows: normalization processing to obtain the variation of transmission loss with frequency. The amplitude of the first peak point is used as a reference; see appendix for details. Figure 1 The peak point normalization of the acoustic transmission characteristic curves in the frequency band from 5Hz to the first critical frequency is shown in the following formula:

[0062]

[0063] In the above formula, A1 represents the amplitude of the first peak point, in dB.

[0064] Accordingly, for (i-1)f 1st ~if 1st For a frequency band where i>1, with the center frequency within that band as the axis of symmetry, calculate the normalized acoustic transmission characteristics data of the peak point of that frequency band. The calculation formula is as follows:

[0065]

[0066]

[0067] In the above two formulas, TL dimensionless (f) is the dimensionless transmission loss, which has no unit; χ is a process parameter introduced to simplify the calculation formula, and its unit is Hz;

[0068] Based on the functional relationship between the amplitude and frequency at the peak point, it is clear that (i-1)f 1st ~if 1st The amplitude A at the peak point of the frequency band acoustic transfer characteristic curve i for:

[0069]

[0070] Then, (i-1)f 1st ~if 1st The acoustic transmission characteristics of a frequency band pipeline system satisfy the following equation:

[0071]

[0072] In the formula, (i-1)f 1st ≤f <if 1st , i>1; TL i (f) is the i-th frequency interval (i-1)f1st ~if 1st The transmission loss is expressed in dB.

[0073] Finally, the results can be verified through simulation. This invention can be used to evaluate the acoustic transmission characteristics of system pipelines in the 5Hz–1000Hz frequency band during the preliminary design phase of a marine pipeline system.

[0074] In this embodiment, the method for obtaining the acoustic transmission characteristics of a 4.3m long inlet pipe of a water cooling system is as follows:

[0075] First, calculate the acoustic transmission characteristic curves for the first critical frequency and the frequency band from 5Hz to the first critical frequency, and give the first peak point of the curve (see appendix). Figure 1 As shown;

[0076] Secondly, the second, third, ..., critical frequencies are determined respectively, and the amplitude-frequency relationship curves of the peak points of the acoustic transmission characteristics are given. The second, third, ..., nth peak points are marked on the curves to determine the amplitude of each peak point. (See Appendix) Figure 2 As shown.

[0077] Finally, based on each peak point, the acoustic transfer characteristic relationship curves between the corresponding peak points in the frequency bands are calculated, as shown in the appendix. Figure 3 As shown in the figure. A comparison with simulation results is shown in the appendix. Figure 4 As shown, the maximum peak point deviation is about 2.5dB, with a relative deviation of only 3.9%; the first-order critical frequency deviation is 1Hz, with a relative deviation of only 0.72%.

[0078] 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 method for obtaining the acoustic transmission characteristics of a submarine pipeline system, characterized in that, The method includes the following steps: Step 1: Obtain the acoustic transmission characteristic relationship of the pipeline system in the frequency range of 5Hz to the first critical frequency, plot the relationship curve, and take the first peak point on the curve. Step 2: Determine the higher-order critical frequencies, and calculate and obtain the amplitude A and frequency of the peak point in the acoustic transmission characteristic curve of the pipeline system. f Relationship; Step 3: Plot the relationship curve between the amplitude and frequency of the peak point, determine the peak point of each frequency band on the curve, and calculate the acoustic transmission characteristic relationship of the corresponding peak point frequency band; In step one, the relationship between sound pressure level difference and frequency is used to characterize the acoustic transmission characteristics of the pipeline system; In step two, the amplitude of the peak point in the acoustic transmission characteristic curve. A With frequency f The functional relationship between them is: (2)； In the formula, The auxiliary calculation coefficient for amplitude is calculated using the following formula: （3）； The specific method for step three is as follows: Using the amplitude of the first peak point as a reference, the peak point normalization process is performed on the acoustic transmission characteristic curve in the frequency band from 5Hz to the first critical frequency, as shown in the following formula: （4）； In the above formula, A1 represents the amplitude of the first peak point, in dB; Accordingly, for Frequency bands, among which Using the center frequency within this frequency band as the axis of symmetry, the normalized acoustic transmission characteristics data of the peak point in this frequency band are calculated using the following formula: (5)， ， In the above two formulas, This is a dimensionless transmission loss, with no unit. The introduced process parameter is in Hz; The amplitude of the peak point in the frequency band acoustic transfer characteristic relationship curve A i for: （6）， but, The acoustic transmission characteristics of a frequency band pipeline system satisfy the following equation: （7）； In the formula, , ; For the i-th frequency interval Transmission loss, expressed in dB; In the above formula, Total transmission loss, in dB; d The pipe diameter is in meters (m); e is the base of the natural logarithm, a constant of 2.71828; it has no unit. f Frequency, in Hz; The length of the pipeline is in meters (m). The velocity of sound in the pipeline is m / s; The pipe wall thickness is in meters (m). This is the first critical frequency of the pipeline system, measured in Hz.

2. The method for obtaining the acoustic transmission characteristics of a marine pipeline system as described in claim 1, characterized in that, In step one, the acoustic transmission characteristics within the frequency band of 5Hz to the first critical frequency satisfy the following relationship: （1）， in: Of the above formulas, ; Total transmission loss, in dB; d The pipe diameter is in meters (m); e is the base of the natural logarithm, a constant of 2.71828; it has no unit. All are introduced process parameters and have no units. f Frequency, in Hz; The length of the pipeline is in meters (m). The velocity of sound in the pipeline is m / s; The pipe wall thickness is in meters (m). The elastic modulus of the pipe material is given in MPa. This is the first critical frequency of the pipeline system, measured in Hz.

3. The method for obtaining the acoustic transmission characteristics of a marine pipeline system as described in claim 1, characterized in that, In step two, each higher-order critical frequency is an integer multiple of the first-order critical frequency. That is, the critical frequencies of each order in the total transmission loss curve of the pipeline system in the 5Hz~1000Hz frequency band are respectively... .

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