CN112240907B - Acoustic propagation calculation method considering influence of bubble mixing layer under shallow-sea fluctuating sea surface - Google Patents
Acoustic propagation calculation method considering influence of bubble mixing layer under shallow-sea fluctuating sea surface Download PDFInfo
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Abstract
The invention discloses an acoustic propagation calculation method considering the influence of a bubble mixing layer under a shallow-sea fluctuating sea surface, which comprises the following steps: generating a one-dimensional fluctuating sea surface by a Monte Carlo method to obtain sea surface parameters; correcting the underwater sound velocity profile without the bubble layer to obtain a sound velocity profile parameter; calculating an attenuation coefficient of the bubble mixing layer caused by scattering absorption to obtain an absorption attenuation parameter; carrying out horizontal non-uniform treatment on the bubble mixing layer, and correcting sound velocity profile parameters and absorption attenuation parameters in depth to obtain the bubble mixing layer with consistent fluctuation with the sea surface; and writing the sea surface parameter, the corrected sound velocity profile parameter and the corrected absorption attenuation parameter into an input file, inputting the input file into a parabolic model, and outputting sound field data. The method provided by the invention can make up the defect that the conventional sound propagation calculation method under the fluctuating sea surface does not consider the factors of the bubble mixing layer, and more comprehensively considers the influence of sea surface stormy waves on sound propagation.
Description
Technical Field
The invention relates to the field of underwater sound physics, in particular to an acoustic propagation calculation method considering the influence of a bubble mixing layer under a shallow-sea fluctuating sea surface.
Background
The problem of sound propagation is always a hotspot and a difficulty of research of underwater sound workers, the sea surface serving as an upper boundary of an ocean waveguide has important influence on sound propagation, and the sea surface is generally regarded as an absolutely soft ideal boundary for a flat sea surface without wind wave influence, has a good reflection effect on underwater incident sound waves, and almost has no boundary reflection loss. Unfortunately, the sea surface is often fluctuated and uneven due to the influence of sea surface wind waves, and the rough sea surface boundary has both reflection and scattering effects on incident sound waves, so that the reflection loss of the sea surface can be caused; over the past several decades, there has been some progress in research work on the propagation of sound under rough sea caused by wind and waves.
The traditional acoustic propagation model under the rough sea surface is a simple normal wave model (Krakenc), a parabolic model (Ramsurf) and the like, wherein the parabolic model can generate a one-dimensional rough sea surface through a Monte Carlo method to be used as sea surface parameter input of the model, and finally, the acoustic propagation calculation under the rough sea surface can be carried out, but the influence of a near-sea-surface bubble mixed layer on the acoustic propagation caused by stormy wave stirring is not considered.
In practical situations, when rough sea surface is caused by heavy waves, a bubble mixing layer close to the sea surface can be formed by stirring of the heavy waves, the bubble mixing layer has scattering and absorbing effects on sound waves, the original sound velocity profile structure can be changed, and sound transmission is influenced to different degrees.
Disclosure of Invention
The invention aims to overcome the technical defects and provide the sound propagation calculation method considering the influence of the bubble mixing layer under the fluctuating sea surface on the basis of the parabolic model, the method is suitable for sound propagation calculation in the heavy-wave weather, the influence of two factors of the fluctuating sea surface and the bubble mixing layer on the offshore surface on sound propagation under the heavy wave is comprehensively considered, and the sound propagation calculation precision is improved.
In order to achieve the above object, the present invention provides an acoustic propagation calculation method considering the influence of a bubble mixing layer under a shallow sea surface, the method including:
generating a one-dimensional fluctuating sea surface by a Monte Carlo method to obtain sea surface parameters;
correcting the underwater sound velocity profile without the bubble layer to obtain a sound velocity profile parameter;
calculating an attenuation coefficient of the bubble mixing layer caused by scattering absorption to obtain an absorption attenuation parameter;
carrying out horizontal non-uniform treatment on the bubble mixing layer, and correcting sound velocity profile parameters and absorption attenuation parameters in depth to obtain the bubble mixing layer with consistent fluctuation with the sea surface;
and writing the sea surface parameter, the corrected sound velocity profile parameter and the corrected absorption attenuation parameter into an input file, inputting the input file into a parabolic model, and outputting sound field data.
As an improvement of the above method, the generating a one-dimensional undulating sea surface by a monte carlo method to obtain the sea surface parameters specifically includes:
step 1-1) calculating power spectral density S (k) of rough sea surfacej) Comprises the following steps:
wherein, a0＝8.1×10-3β is 0.74, g is the acceleration of gravity, v19.5The wind speed is the wind speed at the height of 19.5m above the sea surface, and the unit is m/s; discrete wave number kjIs expressed as kj2 pi j/L, L being the total length of the rough surface sample;
step 1-2) generating a wave number spectrum F (k) by using Monte Carlo simulationj)：
Wherein, Δ k is the spatial wavenumber difference of adjacent harmonic samples in the spectral domain; n (0,1) represents a normally distributed random number with a mean value of 0 and a variance of 1; when j > 0, F (k)j) Satisfy the conjugate symmetry relationship F (k)j)＝F(k-j)*；
Step 1-3) for F (k)j) Fourier transformation is carried out to obtain a one-dimensional undulating sea surface f (x) with the length of Ln)：
Wherein x isnWhere n Δ x denotes the nth sample point on the rough surface, Δ x is roughSampling interval of rough surface, n ═ M/2+1, …, M/2; l is the total length of the rough surface sample, L ═ M × Δ x;
step 1-4) the one-dimensional fluctuating sea surface is (x)n,f(xn) The sea surface parameter is (x)n,f(xn)-min(f(xn)))。
As an improvement of the above method, the modifying the underwater sound velocity profile without the bubble layer to obtain the sound velocity profile parameter specifically includes:
if the size of the radius of the bubble is between 10 μm and 1000 μm, the distribution function of the bubble group is:
wherein a is the radius of the bubble, z is the depth of the water, v10The wind speed is 10m above the sea surface,
wherein: a isref(z)＝54.4+1.984×10-6z，
The method for correcting the sound velocity in water containing the bubble layer comprises the following steps:
wherein, cwIs the speed of sound in water without bubbles, cm(z) is the corrected speed of sound in water; where P (z) is the absolute hydrostatic pressure in the water, U (z) is the air pressure created by the bubble layer in the water:
wherein, amin10 μm is the minimum radius of the bubble; a ismax1000 μm is the maximum radius of the bubble;
the sound velocity profile parameters are as follows: (z, c)m(z))。
As an improvement of the method, the attenuation coefficient of the bubble mixed layer due to scattering absorption is calculated to obtain an absorption attenuation parameter; the method specifically comprises the following steps:
calculating attenuation coefficient alpha of the bubble mixed layer caused by scattering absorptionb(z)：
Wherein, Y ═ frF, f is the acoustic frequency, frIs the resonant frequency of the bubble with radius a at water depth z, and δ is the damping constant; the absorption attenuation parameter is (z, alpha)b(z))。
As an improvement of the method, the horizontal non-uniformity processing is carried out on the bubble mixing layer, and the sound velocity profile parameter and the absorption attenuation parameter are corrected in depth to obtain the bubble mixing layer with consistent undulation with the sea surface; the method specifically comprises the following steps:
for the sound velocity profile parameter (z, c)m(z)) and absorption attenuation parameters (z, α)b(z)) makes a correction in depth: (z + f (x)n)-min(f(xn))，cm(z)) and (z + f (x)n)-min(f(xn))，αb(z)); obtaining the corrected sound velocity profile parameter (z + f (x)n)-min(f(xn))，αb(z)) and a corrected absorption attenuation parameter (z + f (x)n)-min(f(xn))，αb(z))。
As an improvement of the above method, the sea surface parameter, the corrected sound velocity profile parameter, and the corrected absorption attenuation parameter are written into an input file, and then input into a parabolic model, and output sound field data, specifically:
the sea surface parameter (x)n,f(xn)-min(f(xn)))、
Corrected sound velocity profile parameter (z + f (x)n)-min(f(xn))，αb(z))
And the corrected absorption attenuation parameter (z + f (x)n)-min(f(xn)))
And writing the data into an input file of the parabolic sound field model Ramsurf, and outputting sound field data.
The invention has the advantages that:
1. the method comprehensively considers the influence of the fluctuating sea surface and the bubble mixing layer on sound propagation under the heavy stormy waves, and provides an algorithm model support for shallow sea sound field forecast in the heavy stormy weather;
2. the acoustic propagation calculation method considering the influence of the bubble mixing layer under the rough sea surface can make up the defect that the conventional acoustic propagation calculation method under the rough sea surface does not consider the factor of the bubble mixing layer, and more comprehensively considers the influence of sea surface stormy waves on acoustic propagation.
Drawings
FIG. 1 is a schematic view of a rough sea surface and a bubble-mixed layer under high winds and waves;
FIG. 2 is a graph of the correction of the acoustic velocity in water for a hybrid layer containing bubbles;
FIG. 3 is an in-water attenuation coefficient for a mixed layer containing bubbles;
FIG. 4 is a graph of acoustic propagation loss at a wind speed of 10 m/s;
FIG. 5 is a graph of sound propagation loss at a wind speed of 13 m/s.
Detailed Description
The technical solution of the present invention will be described in detail below with reference to the accompanying drawings.
The method generates a one-dimensional fluctuating sea surface as the sea surface parameter of the model by a Monte Carlo method, calculates the attenuation coefficient of the bubble mixing layer caused by scattering absorption as the absorption attenuation parameter of the model, and corrects the underwater sound velocity profile without the bubble layer as the sound velocity profile parameter of the model.
The acoustic propagation calculation method comprises the five steps of generating a one-dimensional fluctuating sea surface, calculating an acoustic attenuation coefficient caused by the bubble mixing layer, correcting a sound velocity profile of the bubble mixing layer, processing horizontal non-uniformity of the bubble mixing layer and inputting a parabolic model to obtain a sound field:
step 1) generation of one-dimensional fluctuating sea surface:
and generating a PM spectrum one-dimensional fluctuating sea surface by using a Monte Carlo method.
The relief surface is considered to be formed by the superposition of a large number of harmonics, the amplitudes of which are independent gaussian random variables, the variance of which is proportional to the power spectrum S (k) of a specific wave numberj). One-dimensional rough surface samples of length L can be generated by:
wherein x isnWhere (n) denotes the nth sample point on the rough surface, wave number spectrum F (k) represents (M/2 +1, …, M/2) ═ n Δ xj) And f (x)n) Called Fourier transform pair, defined as:
wherein a discrete wave number k is definedjIs expressed as kj2 pi j/L, Δ k is the spatial wavenumber difference of adjacent harmonic samples in the spectral domain, S (k)j) The power spectral density of a rough sea surface represents the distribution of ocean wave energy relative to spatial wave numbers. N (0,1) represents a normally distributed random number with a mean of 0 and a variance of 1. When j > 0, F (k)j) Satisfy the conjugate symmetry relationship F (k)j)＝F(k-j)*。
The power spectral density of the PM spectrum is:
step 2) sound velocity profile correction of bubble mixing layer
The bubble swarm model adopts Hall-Novarini (HN) bubble swarm model, and the distribution function of the bubble swarm is as follows, assuming that the radius of the bubbles is between 10 mu m and 1000 mu m:
wherein a is the radius of the bubble, z is the depth of the water, v10Wind speed 10m above sea surface, in addition:
the method for correcting the sound velocity in water containing the bubble layer comprises the following steps:
wherein c iswIs the speed of sound in water without bubbles, cmIs the corrected speed of sound in water. Where P (z) is the absolute hydrostatic pressure in water and U (z) is the air pressure in water, the expression for U (z) at different wind speeds is derived as follows:
wherein, amin10 μm is the minimum radius of the bubble; a ismax1000 μm is the maximum radius of the bubble;
the sound velocity profile parameters are as follows: (z, c)m(z))。
Step 3) calculating the attenuation coefficient of sound wave caused by the bubble mixing layer
The bubbles in the water have a scattering and absorbing effect on the acoustic energy, causing attenuation of the acoustic energy. The calculation method of the attenuation coefficient comprises the following steps:
wherein, Y ═ frF, f is the acoustic frequency, frIs the resonant frequency of the bubble with radius a at water depth z, and δ is the damping constant.
The absorption attenuation parameter is (z, alpha)b(z))。
Step 4) horizontal non-uniform treatment of the bubble mixing layer
As shown in fig. 1, since the sea surface is undulating, the bubble mixed layer is also uneven in the horizontal direction and is horizontally non-uniform. Therefore, the bubble layer needs to be horizontally non-uniformly treated: and vertically displacing the bubble mixing layer, wherein the vertical displacement is equivalent to the displacement of the undulating sea surface relative to the sea level.
At the nth sampling point xnThe bubble mixing layer is displaced in depth by a distance f (x)n) The purpose of which is to mix the layer of bubbles with the one-dimensional undulating sea surface (x)n,f(xn) Have consistent undulations; the horizontal non-uniformity processing of the bubble mixing layer is embodied in the input file of the model, and is the horizontal non-uniformity of the sound velocity profile and the horizontal non-uniformity of the absorption attenuation coefficient. Thus, "at sample point n" xnThe bubble mixing layer is displaced in depth by a distance f (x)n) "for the sound velocity profile parameters (z, c)m(z)) and absorption attenuation parameters (z, α)b(z)) makes a correction in depth: (z + f (x)n)-min(f(xn))，cm(z)) and (z + f (x)n)-min(f(xn))，αb(z))；
Obtaining the corrected sound velocity profile parameter (z + f (x)n)-min(f(xn))，αb(z)) andcorrected absorption attenuation parameter (z + f (x)n)-min(f(xn))，αb(z))。
The horizontal non-uniformity processing of the bubble mixing layer is embodied in the input file of the model, and is the horizontal non-uniformity of the sound velocity profile and the horizontal non-uniformity of the absorption attenuation coefficient.
Step 5) said determining sea surface parameters (x)n,f(xn)-min(f(xn) X), absorption attenuation parameter (z + f (x))n)-min(f(xn))，cm(z)), sound velocity profile parameter (z + f (x)n)-min(f(xn))，αb(z)) writing the data into an input file of the parabolic sound field model Ramsurf, and outputting sound field data, wherein the data specifically comprises:
the input files are used as input files of a parabolic sound field model Ramsurf, and Ramsurf is operated to obtain sound field data considering the influence of a bubble mixing layer under shallow-sea fluctuating sea surfaces
The parabolic sound field model Ramsurf is a sound field calculation model under a fluctuating sea surface, and the format of an input file is as follows:
file name
Sound field frequency parameter, transmission depth parameter, reception depth parameter
Calculated level parameters: comprises calculating maximum horizontal distance, horizontal step length, and horizontal output step length
The calculated depth parameter: comprises calculating maximum depth, depth step length, depth output step length, and maximum sea depth
Reference sound velocity, Pedet approximation order, stability control coefficient, and stability control distance
Parameters of undulating sea surface
End mark of rough sea surface parameters: -1-1
Sea floor topography parameters
End mark of submarine topography parameters: -1-1
Sound velocity profile parameters (z + f (0) -min (f (0)), cm(z))
Sound velocity profile parameter end flag: -1-1
Absorption attenuation coefficient by bubble (z + f (0) -min (f (0)), αb(z))
End of bubble-induced absorption attenuation coefficient flag: -1-1
The subsea parameters include: seafloor acoustic velocity, seafloor density, seafloor attenuation.
Δx
Sound velocity profile parameters (z + f (Δ x) -min (f (Δ x)), cm(z))
Sound velocity profile parameter end flag: -1-1
Absorption attenuation coefficient by bubble (z + f (Δ x) -min (f (Δ x)), αb(z))
End of bubble-induced absorption attenuation coefficient flag: -1-1
The subsea parameters include: seafloor acoustic velocity, seafloor density, seafloor attenuation.
End of sea floor parameter marking: -1-1
2*Δx
Sound velocity profile parameters (z + f (2 x Δ x) -min (f (2 x Δ x)), cm(z))
Sound velocity profile parameter end flag: -1-1
Absorption attenuation coefficient by bubble (z + f (2. DELTA.x) -min (f (2. DELTA.x)), αb(z))
End of bubble-induced absorption attenuation coefficient flag: -1-1
The subsea parameters include: sea bottom sound velocity, sea bottom density, sea bottom attenuation
End of sea floor parameter marking: -1-1
3*Δx
Sound velocity profile parameters (z + f (3 Δ x) -min (f (3 Δ x)), cm(z))
Sound velocity profile parameter end flag: -1-1
Absorption attenuation coefficient by bubble (z + f (3. DELTA.x) -min (f (3. DELTA.x)), αb(z))
End of bubble-induced absorption attenuation coefficient flag: -1-1
The subsea parameters include: sea bottom sound velocity, sea bottom density, sea bottom attenuation
End of sea floor parameter marking: -1-1
●
●
●
M*Δx
Sound velocity profile parameters (z + f (M Δ x) -min (f (M Δ x)), cm(z))
Sound velocity profile parameter end flag: -1-1
Absorption attenuation coefficient by bubble (z + f (M.DELTA.x) -min (f (M.DELTA.x)), alphab(z))
End of bubble-induced absorption attenuation coefficient flag: -1-1
The subsea parameters include: sea bottom sound velocity, sea bottom density, sea bottom attenuation
End of sea floor parameter marking: -1-1
Example (c):
in an underwater acoustic environment with the water depth of 80m, the sound source depth is 20m, and the receiving depth is 20 m. The sound velocity profile in water containing no bubbles was 1500m/s, the sound velocity profile corrected by equation (5) is shown in FIG. 2, and the absorption attenuation profile calculated by equation (6) is shown in FIG. 3.
Carrying out horizontal non-uniform treatment on the bubble mixing layer to enable the bubble mixing layer to present the fluctuation consistent with the sea surface, as shown in figure 1; horizontal non-uniformity of the sound velocity profile and horizontal non-uniformity of the absorption attenuation coefficient are reflected in the input file. And (3) generating a random fluctuating sea surface every time by Monte Carlo, calculating the vertical displacement h (r) of the fluctuating sea surface relative to the sea level, and performing the same vertical displacement h (r) on the corrected sound velocity profile and the absorption attenuation coefficient on the basis, namely performing horizontal non-uniform treatment on the bubble mixing layer. And calculating a propagation loss curve with the center frequency of 3kHz and the bandwidth of one third octave bandwidth, wherein the frequency interval is 10 Hz. An average of 50 monte carlo methods was performed for each frequency.
FIG. 4 is a graph comparing a propagation loss curve at a smooth undersea (wind speed of 0m/s) with a propagation loss curve at a wind speed of 10 m/s; FIG. 5 is a graph comparing a propagation loss curve at a smooth sea surface with a propagation loss curve at a wind speed of 13 m/s. At a horizontal distance of 10km, the propagation loss at a wind speed of 10m/s is 10dB greater than the propagation loss at a wind speed of 0 m/s; at a horizontal distance of 10km, the propagation loss at a wind speed of 13m/s is 12dB greater than that at a wind speed of 0 m/s.
Finally, it should be noted that the above embodiments are only used for illustrating the technical solutions of the present invention and are not limited. Although the present invention has been described in detail with reference to the embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted without departing from the spirit and scope of the invention as defined in the appended claims.
Claims (5)
1. An acoustic propagation calculation method considering the influence of a bubble-mixed layer under a shallow sea fluctuating surface, the method comprising:
generating a one-dimensional fluctuating sea surface by a Monte Carlo method to obtain sea surface parameters;
correcting the underwater sound velocity profile without the bubble layer to obtain a sound velocity profile parameter;
calculating an attenuation coefficient of the bubble mixing layer caused by scattering absorption to obtain an absorption attenuation parameter;
carrying out horizontal non-uniform treatment on the bubble mixing layer, and correcting sound velocity profile parameters and absorption attenuation parameters in depth to obtain the bubble mixing layer with consistent fluctuation with the sea surface;
writing the sea surface parameter, the corrected sound velocity profile parameter and the corrected absorption attenuation parameter into an input file, then inputting the input file into a parabolic model, and outputting sound field data;
the method for generating the one-dimensional fluctuating sea surface through the Monte Carlo method to obtain the sea surface parameters specifically comprises the following steps:
step 1-1) calculating power spectral density S (k) of rough sea surfacej) Comprises the following steps:
wherein, a0＝8.1×10-3β is 0.74, g is the acceleration of gravity, v19.5The wind speed is the wind speed at the height of 19.5m above the sea surface, and the unit is m/s; discrete wave number kjIs expressed as kj2 pi j/L, L being the total length of the rough surface sample;
step 1-2) generating a wave number spectrum F (k) by using Monte Carlo simulationj)：
Wherein, Δ k is the spatial wavenumber difference of adjacent harmonic samples in the spectral domain; n (0,1) represents a normally distributed random number with a mean value of 0 and a variance of 1; when j > 0, F (k)j) Satisfy the conjugate symmetry relationship F (k)j)＝F(k-j)*；
Step 1-3) for F (k)j) Fourier transformation is carried out to obtain a one-dimensional undulating sea surface f (x) with the length of Ln)：
Wherein x isnN Δ x denotes the nth sampling point on the rough surface, Δ x is the sampling interval of the rough surface, n ═ M/2+1, …, M/2; l is the total length of the rough surface sample, L ═ M × Δ x;
step 1-4) the one-dimensional fluctuating sea surface is (x)n,f(xn) The sea surface parameter is (x)n,f(xn)-min(f(xn)))。
2. The acoustic propagation calculation method considering the influence of the bubble-mixed layer under the shallow sea fluctuating sea surface according to claim 1, wherein the step of correcting the underwater sound velocity profile without the bubble layer to obtain the sound velocity profile parameters specifically comprises the steps of:
if the size of the radius of the bubble is between 10 μm and 1000 μm, the distribution function of the bubble group is:
wherein a is the radius of the bubble, z is the depth of the water, v10The wind speed 10m above the sea surface，
Wherein: a isref(z)＝54.4+1.984×10-6z，
The method for correcting the sound velocity in water containing the bubble layer comprises the following steps:
wherein, cwIs the speed of sound in water without bubbles, cm(z) is the corrected speed of sound in water; where P (z) is the absolute hydrostatic pressure in the water, U (z) is the air pressure created by the bubble layer in the water:
wherein, amin10 μm is the minimum radius of the bubble; a ismax1000 μm is the maximum radius of the bubble;
the sound velocity profile parameters are as follows: (z, c)m(z))。
3. The acoustic propagation calculation method considering the influence of the bubble mixing layer under the shallow sea undulating surface according to claim 2, wherein the attenuation coefficient of the bubble mixing layer due to scattering absorption is calculated to obtain an absorption attenuation parameter; the method specifically comprises the following steps:
calculating attenuation coefficient alpha of the bubble mixed layer caused by scattering absorptionb(z)：
Wherein, Y ═ frF, f is the acoustic frequency, frIs the resonant frequency of the bubble with radius a at water depth z, and δ is the damping constant; the absorption attenuation parameter is (z, alpha)b(z))。
4. The acoustic propagation calculation method considering the influence of the bubble mixing layer under the shallow-sea undulating sea surface according to claim 3, wherein the bubble mixing layer is subjected to horizontal non-uniform processing, and the acoustic velocity profile parameter and the absorption attenuation parameter are corrected in depth to obtain the bubble mixing layer having consistent undulation with the sea surface; the method specifically comprises the following steps:
for the sound velocity profile parameter (z, c)m(z)) and absorption attenuation parameters (z, α)b(z)) makes a correction in depth: (z + f (x)n)-min(f(xn))，cm(z)) and (z + f (x)n)-min(f(xn))，αb(z)); obtaining the corrected sound velocity profile parameter (z + f (x)n)-min(f(xn))，αb(z)) and a corrected absorption attenuation parameter (z + f (x)n)-min(f(xn))，αb(z))。
5. The acoustic propagation calculation method considering the influence of the bubble mixing layer under the shallow-sea fluctuating sea surface according to claim 4, wherein the sea surface parameters, the corrected sound velocity profile parameters, and the corrected absorption attenuation parameters are written in an input file, and then input into a parabolic model, and output acoustic field data, specifically:
the sea surface parameter (x)n,f(xn)-min(f(xn)))、
Corrected sound velocity profile parameter (z + f (x)n)-min(f(xn))，αb(z))
And the corrected absorption attenuation parameter (z + f (x)n)-min(f(xn)))
And writing the data into an input file of the parabolic sound field model Ramsurf, and outputting sound field data.
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