• <tr id="yyy80"></tr>
  • <sup id="yyy80"></sup>
  • <tfoot id="yyy80"><noscript id="yyy80"></noscript></tfoot>
  • 99热精品在线国产_美女午夜性视频免费_国产精品国产高清国产av_av欧美777_自拍偷自拍亚洲精品老妇_亚洲熟女精品中文字幕_www日本黄色视频网_国产精品野战在线观看 ?

    High-order Bragg forward scattering and frequency shift of low-frequency underwater acoustic field by moving rough sea surface

    2024-03-25 09:30:28YaXiaoMo莫亞梟ChaoJinZhang張朝金LiChengLu鹿力成QiHangSun孫啟航andLiMa馬力
    Chinese Physics B 2024年3期
    關(guān)鍵詞:馬力

    Ya-Xiao Mo(莫亞梟), Chao-Jin Zhang(張朝金), Li-Cheng Lu(鹿力成),Qi-Hang Sun(孫啟航), and Li Ma(馬力)

    1Key Laboratory of Underwater Acoustic Environment,Institute of Acoustics,Chinese Academy of Sciences(CAS),Beijing 100190,China

    2China State Shipbuilding Corporation Systems Engineering Research Institute,Beijing 100094,China

    3Little Bird Co.,Ltd,Beijing 100089,China

    Keywords: high-order Bragg scattering,frequency shift,low-frequency acoustic field,moving rough sea surface

    1.Introduction

    As a key component of underwater acoustic waveguide,the undulation of the sea surface induces an evident acoustic scattering modulation, which is an important topic in underwater acoustic research,particularly in the reverberation of active sonar detection.[1]To directly describe the acoustic scattering field, empirical formulas, perturbation theory, Kirchhoff approximation, small-slope approximation methods, and their combined methods have been widely used.[2,3]Moreover,for the sea surface acoustic scattering in underwater acoustic propagation, range-dependent models are effectively established by using parabolic equation methods, ray methods,coupled normal wave methods,and other methods.[4,5]In addition to conventional backscattering, forward scattering has attracted considerable attention with the development of multistatic underwater acoustic detection.[6,7]

    Comparing with a static rough sea surface,[8,9]the acoustic scattering modulation effect of a moving rough sea surface has been rarely studied.In theory, the motion of the waveguide boundary produces a Doppler frequency shift.According to the sound field calculation model of moving medium in aeroacoustics,[10,11]the Doppler frequency shift and spectrum expansion of the received signal are not prominent when the sea surface is regard as a context of waveguide medium.This can be explained by the Mach number, which is the ratio of the motion speed of the medium to the speed of sound.Meanwhile, based on the conventional acoustic Doppler frequency shift analysis,[12]the frequency shift depends on the sound frequency and relative speed between the source and receiver.The frequency shift is almost negligible for the lowfrequency acoustic band.

    Low-frequency acoustic detection experiments near the coast[13]and simulation calculations[14]have obtained inconsistent frequency modulation effects.Obvious frequency shift and frequency expansion phenomena are observed when lowfrequency acoustic waves are scattered by a moving rough sea surface.According to the results of frequency modulation,the rough sea surface moving in the acoustic field cannot be simply equated with the relative motion of the medium or sound source-receiver.Instead, it should be similar to “grating” to form the Bragg scattering phenomenon and modulate the frequency of the acoustic scattering field.The Bragg scattering process of a sea surface is equivalent to the Fourier series expansion of the sea surface period under the Rayleigh assumption.[15,16]Compared with limited research on underwater acoustic, numerous studies have focused on the Bragg scattering of a moving rough sea surface in an electromagnetic wave area, which has been applied to monitor sea surface fluctuations and differentiate the types of sea surfaces.[17]Even if the high-order perturbation theory in underwater sound is adopted, the high-order Bragg scattering in the above lowfrequency acoustic detection test and simulation calculation is not well explained except for the first order Bragg scattering.Especially in shallow sea environment, the waveguide effect makes the resonant Bragg scattering no longer a second-order effect, and the regular perturbation theory fails.For this reason, a singular perturbation theory allowing for strong scattering was introduced.[18]Based on the singular perturbation theory and the multiple scale analysis, the first-order Bragg scattering is studied for only one guide mode in shallow water.

    For underwater acoustic simulation and detection, the rough sea surface is often directly generated by wind waves or a Gaussian spectrum,[2,6,8]however, the different characteristics of the various types of sea surface waves are often ignored.According to their causes,the undulation of a rough sea surface can be divided into swell wave and wind wave,which generate different characteristics, such as wave crest lines and wave periods.[19,20]Existing researches of underwater acoustic propagation mainly focus on wind waves,whereas swell waves are rarely considered.On the northern continental slope of the South China Sea, experiments showed that swell waves have a strong influence on the acoustic propagation in the surface sound channel.In particular,the swell wave causes a difference of 10 dB in the acoustic field loss prediction over a distance of tens of kilometers.[21]

    Herein, high-order Bragg forward scattering of lowfrequency acoustic field under a moving rough sea surface is analyzed.Moreover, the acoustic scattering and frequency shifts under swell wave and wind wave are compared with each other.The rest of this paper is organized as follows.In Section 2, two acoustic models are derived by qualitative approach and quantitative approach, respectively.The scattering intensity of a moving rough surface model is obtained from the integral equation in the qualitative approach, and the acoustic scattering field model is developed by using the parabolic equation and nonuniform grid meshing in the quantitative approach.In Section 3,according to the integral equation method and parabolic equation model, the acoustic scattering field and frequency shift phenomenon under a singleperiod rough sea surface are simulated.The characteristics of the high-order Bragg forward scattering and frequency shift are expounded by using the principle of grating and constructive interference.Furthermore, the acoustic scattering field and frequency shift under the sea surface of swell,fully grown wind,unsteady wind,and mixed waves are compared in Section 4.The conclusions are drawn from the present study in Section 5.

    2.Acoustic scattering field model under rough sea surface

    2.1.Acoustic scattering field model based on integral equation

    The integral equation can accurately and reliably simulate a typical acoustic field and compute typical acoustic field characteristics.Therefore, for the qualitative approach, underwater acoustic scattering field model is derived from the integral equation in a moving rough surface environment.To simplify the analysis, a one-dimensional (1D) moving rough sea surface at momenttswis expressed asz=f(x;tsw) and a rectangular coordinate system is adopted.For the sea surface motion associated with gravity waves, it is so slow that the wavy surface appears frozen relative to the motion caused by sound.[18]The ocean waveguide with a moving rough sea surface can be viewed as a seriestswof relatively stationary range-dependent waveguides.

    When a distant acoustic field is incident on the rough sea surface at the relatively stationary momenttsw,the Helmholtz integral formula satisfied by the total acoustic fieldp(r;tsw)=pi(r;tsw)+ps(r;tsw)with a single frequencyωcan be written as[16]

    Fig.1.Helmholtz contour integral path for rough sea surface.

    According to the division of the integral path and definingrs=|r-r′|:

    ForLε(tsw), considering that its radius tends to approach 0,this path is almost a contour path around the singularity and the outer normal direction of this overall path is the inner normal direction of the small-radius contour path, that is,?/?n′=-?/?rs.Considering the polar coordinate system and asymptotic expansion of the Hankel function,the last term on the left-hand in Eq.(2)can be written as

    ForLR(tsw), when its radius tends to approach infinity, according to the Helmholtz integral formula in a homogeneous medium and radiation condition of the scattered field,we obtain

    Therefore,the total acoustic pressure field can be obtained as follows:

    Due to the difference in acoustic impedance between air and water,the transmitted acoustic intensity in air is much smaller than the acoustic field in water.Even in the case of normal incidence, the transmitted acoustic intensity is much weaker than that in water.Meanwhile, considering that the fluctuation of the sea surface is relatively smooth on a low-frequency acoustic wavelength scale, the acoustic boundary condition can be viewed as absolute soft boundary for sea surface in the case of low-frequency acoustic wave incidence.As a result,we can obtain the low-frequency acoustic pressure field on the rough sea surface:p(r′;tsw)||r′=LS(tsw)≡0, and equation (5)can be written as

    The first term and the second term on the right side of Eq.(6)are the contributions of the incident acoustic wave and the scattered acoustic wave by the rough interface to the total acoustic field,respectively.

    For the moving rough sea surfacez=f(x;tsw), i.e.,r=(x,f(x;tsw)), considering the pressure-release boundary condition, the integral equation on the moving rough sea surface can be written as

    Based on the incident acoustic wave field and derivative of the rough sea surface along the discretizing rough sea surface,?p(r′;tsw)/?n′will be calculated in all discretized areas, and this matrix equation obtained by discrete processing can be written as

    Considering the singularity of the Hankel function,am(tsw),Amn(tsw),andbn(tsw)are represented as follows:[6]

    whereeis a natural constant,am(tsw) is the incident acoustic field,Amnis theN-th-order symmetric matrix of the zeroorder Hankel function,rm(tsw)=xm?x+f(xm;tsw)?z,xm=(m-1/2)Δx-L/2,Δx=L/N,andLis the calculated length of the sea surface.

    According to Eq.(6) and the far-field approximation of the Hankel function, the acoustic scattering field atr=(x,z)can be expressed as

    2.2.Acoustic field model based on parabolic equation

    For actual ocean sound waveguides with rough sea surface, the calculation method based on the integral equation has limited the capability in quantifying the acoustic scattering field.Considering the ocean waveguide environment characteristics,the low-frequency band,and multistatic acoustic detection, an acoustic forward scattering field model is derived from the parabolic equation for the quantitative approach.Like the integral equation, we assume that the sea surface motion related to gravity waves is so slow that the wavy surface appears frozen relative to the motion caused by sound.[18]Consequently,the ocean waveguide with a moving rough sea surface can be viewed as a series of relatively stationary range-dependent waveguides.

    At the range-dependent waveguide in each stationary momenttsw,the harmonic acoustic fieldp(r,z;tsw)is generated by continuous source with a time factor exp(-iω0t)and is governed by the Hemholtz equation:

    wherek1,2=ω0/cis the acoustic wave number,andω0is the angular frequency of the acoustic wave.Based on Fourier transform theory and the acoustic fieldp(r,z;tsw) in the series oftsw, the modulated acoustic field frequency spectrumˉp(r,z;ω)with acoustic frequencyωcan be written as

    The acoustic fieldp(r,z;tsw) at the momenttswis shown in Fig.2,and based on the step approximation and energy conservation,the parabolic equation satisfied by harmonic the acoustic field can be obtained as follows:

    wherek0=ω0/c0is a reference sound number,withc0being a reference sound velocity.

    According to the high-order Pad′e rational approximation and taking the horizontal recursion step size as Δr,we obtain

    According to the spatial variation scale of the sea surface and seabed and wavelength characteristics of the lowfrequency sound field, the operator can be solved by the Galerkin nonuniform discretion of a limitedzspace; the nonuniform discrete division is shown in Fig.2.The area near the sea surface is divided into small steps to fully characterize the influence of the rough sea surface.Meanwhile, the area below the sea surface after several wavelengths is divided into a sparse discrete area with a large step size to achieve rapid calculation.A transition discrete area exists between these two areas to avoid the large difference in step length, which may cause numerical instability.At the same time,a perfectly matched layer with functiong(z)is adopted to avoid affecting the reflection field at the boundary of the seabed truncation,and the calculation amount in the vertical direction is effectively reduced.The operator function of each vertical discrete pointzj(j=Nzs(r),...,Nz)can then be expressed as

    3.High-order scattering mechanism of moving rough sea surface based on Bragg theory

    3.1.Scattering intensity of sinusoidal rough sea surface

    Regardless of swell, wind, and mixed waves, the rough sea surface can decompose into harmonics.Therefore,to characterize the effect of an actual rough sea surface, a rough sea surface composed of a single harmonic wave is analyzed.Considering the gravity force as the restoring force in rough sea surface,the following dispersion relation is satisfied by the sea surface wave numberksw=2π/λswand the sea surface wave angular frequencyωsw=2π fsw:[21]

    Fig.3.Sinusoidal rough sea surface.

    When the modified Gaussian beams with different sound frequencies are incident at 30°, the comb-shaped distribution of the acoustic scattering intensity at a depth of 1 m is shown in Fig.4.In addition to the mirror reflection, multiple strong acoustic scattering sidelobes are noted along the discrete grazing angle.The strong scattering sidelobe distribution is consistent with the Fourier series result of the sea surface period under a Rayleigh assumption.[16]With the increase of acoustic wave frequency, the strong scattering sidelobe becomes narrower and the number of sidelobe increases.Furthermore,according to the dispersion of the gravity wave, the decrease in the frequency of the sea surface causes the sea surface wavelength to grow considerably.For instance,when the rough sea surface frequency decreases from 0.2 Hz to 0.1 Hz,the sea surface wavelength increases from 39 m to 156 m.This change in the sea surface wavelength considerably increases the number of strong scattering side lobes.

    Fig.4.Acoustic scattering intensities of sinusoidal rough sea surface at(a)sea surface frequency=0.1 Hz(a)and 0.2 Hz(b).

    3.2.High-order Bragg scattering and frequency shift under sinusoidal rough sea surface

    Based on the first-order Bragg scattering theory and higher-order perturbation theory, Lynch and D’Spain discussed the first-order strong scattering sidelobe.[13]The firstorder Bragg scattering theory explains the generation of the first-order strong scattering sidelobe, the higher-order perturbation theory predicts its strength, consistent with the measurements.However,the higher-order perturbation theory cannot accurately predict higher-order scattering sidelobes.Thus,we use the high-order Bragg scattering theory to analyze the high-order strong acoustic scattering process.

    The acoustic wavelength isλ,the incident acoustic beam isθi,the scattering acoustic beam isθs,and the grazing angle is taken to be positive in the counterclockwise direction.The periodic rough sea surface can be regarded as a“grating”with equal interval lengths, which is the wavelength of the rough sea surfaceλsw(Fig.5).The difference in path of the forward scattering field between adjacent acoustic beams is

    When acoustic waves numberk=2π/λand path differenceLsatisfykL=±2nπ, the adjacent acoustic beams will form a constructive interference.Therefore, in addition to the mirror reflection, there are strong acoustic scattering side lobes in constructive interference directions.These directions of the strong acoustic scattering sidelobes are described by

    Fig.5.The high-order Bragg scattering under a rough sea surface.

    Because|cosθs|≤1 and|cosθi|≤1 in Eq.(24), the order of the strong scattering sidelobe is affected by the incident acoustic wavelength and the rough sea surface wavelength.As the acoustic wave wavelength increases,the number of strong acoustic scattering side lobes will decrease.Meanwhile, as the sea surface wavelength increases,the number of the strong scattering side lobes will increase.These results are consistent with the simulated scattering intensity based on the integral equation.

    When the rough sea surface moves horizontally at a velocityvsw=ωswλsw/(2π),the frequency of the coherent angular acoustic scattering field is obtained from the Doppler frequency shift as follows:

    wherecis the acoustic speed in water.When the rough sea surface velocity direction is consistent with the horizontalrdirection, +vswis used; otherwise,-vswis used.By defining the rough sea surface velocity sign operator [vsw]=±vsw/|vsw|and according to Eqs.(24)and(25),we obtain

    which shows that the strong scattering sidelobe Doppler frequency shift caused by the time-evolving sea surface is only related to the sidelobe ordernand frequency of the moving rough sea surfaceωsw.The frequency of the incident acoustic wave is unrelated to the sidelobe Doppler frequency shift.Even if the frequency of incident acoustic is very low,the scattering effect of the moving sea surface can produce an obvious frequency shift, which is different from the conventional Doppler frequency shift of moving sound source and receiver.

    The periodic rough sea surface is represented aszsrf(r,tsw)=Hswsin(ωswtsw+2πr/λsw), and the sea surface movement direction is opposite to the horizontal direction(i.e.rdirection).The rough sea surface amplitude is 0.8 m,and the sea surface frequency is 0.2 Hz.Gravity is considered as the sea surface restoring force, that is,ω2sw=gcksw.The ocean sound velocity is 1500 m/s, the density is 1.0 g/cm3, and the sea water depth is 1800 m.The acoustic source frequency is 500 Hz, whereby the acoustic beam is uniformly distributed in 600 m-1000 m,and the grazing angle of the main acoustic wave beam is 30°.Based on this uniformly distributed acoustic source with wave beam towards sea surface, the effect of seabed is not considered to avoid further complications in the high-order Bragg scattering field,though this effect can be calculated by the parabolic equation.The acoustic field loss distributions under rough and smooth sea surfaces are shown in Fig.6.

    Fig.6.Acoustic field loss distribution under high-order Bragg acoustic scattering in(a)rough sea surface case, (b)smooth sea surface case,and for(c)differences in acoustic field loss distribution.

    It can be seen that the constructive interference can cause the periodic rough sea surface to produce a multiorder obvious scattering field distribution as marked by the white dotted lines in Fig.6.The Bragg scattering angle distribution is consistent with the strong scattering sidelobe angle distribution in Fig.4(b).According to Eq.(24),multiorder Bragg scattering will appear in the positivendirection,whereas only one order Bragg scattering will appear in the negativendirection.However,in addition to these Bragg scattering fields at an incident angle of 30°, the other interference pattern represents higherorder Bragg scattering that can be observed outsiden=-1 andn=3,which can be explained by the acoustic field computation.Although the incident acoustic beam limits the grazing angle to 30°, additional grazing angle is considered the inappropriate local line source along the vertical direction in the parabolic equation.As shown in Fig.6, there are trajectories outside the main incident acoustic beam,which generate additional high-order Bragg scattering field after being incident on the rough sea surface.

    When the underwater acoustic wave with a frequency of 500 Hz is incident on the rough sea surface,the periodic rough sea surface frequency represented aszsrf(r,t)=Hswsin(ωswt+2πr/λsw) is 0.2 Hz.The forward acoustic fields can be calculated at different time and sea surface states.Based on the fast Fourier transform of forward acoustic fields,the frequency shifts of the forward acoustic field at different receiving positions (r,zr) can be obtained, and the results are shown in Fig.7.After deducting,xaxis indicates the frequency shift from acoustic frequency.

    Fig.7.Acoustic frequency shift distribution under high-order Bragg scattering at receiver locations of (a) (2 km, 400 m) and (b) (4 km,500 m).

    As shown in Fig.7,besides the 0 Hz frequency shift corresponding to mirror reflection, periodic sea surface motion produces an obvious frequency shift, which is a multiple of the moving rough sea surface frequency.It should be noted that the frequency shifts and scattering intensities are different at different receiver positions.For the receiver location(2 km,400 m), there is a strong first-order Bragg scattering control area,corresponding to the source at a depth of 600 m.Therefore,it has a strong positive frequency shift of 0.2 Hz with the acoustic wave amplitude similar to the mirror reflection wave amplitude.For the receiver location (4 km, 500 m), there is a strong first-order Bragg scattering control area corresponding to the source at a depth of 1000 m.Therefore, a strong positive frequency shift of 0.2 Hz is created, and its acoustic wave amplitude is higher than that of the mirror reflection wave without the frequency shift.That is,the peak frequency of the received acoustic wave signal may deviate from the actual incident acoustic frequency.At the same time,the calculated frequency shift order is higher than frequency shift order of the Bragg scattering,as shown by the white dotted lines in Fig.6, which further verifies the high-order Bragg scattering caused by the inappropriate local line source in the acoustic beam simulation.

    4.Frequency shift of low-frequency acoustic field under wind and swell waves

    4.1.Simulation of a moving rough sea surface under wind and swell waves

    The actual sea surface is considerably more complicated than the assumed sinusoidal periodic sea surface.In particular, the sea surface waves are composed of wind wave and swell wave, which appear out of different causes.As such,they have different characteristic parameters,such as spectral peak frequency,wave height,and spectral moment,which are standards for their separation.

    Fig.8.Spectral densities of different wave spectra under different wind speeds: (a) PM spectrum and (b) JONSWAP spectrum (wind distance of 7 km).

    Considering the wind speed at the sea surface,wind area length, and sea depth, various wave spectra have been developed to describe rough sea surface, such as the Pierson-Moskowitz (PM) and Joint North Sea Wave Project (JONSWAP) spectra.Figure 8 illustrates the power spectral density under different wind speed parameters calculated from the PM spectrum and JONSWAP spectrum, which represent steady sea surface and unsteady sea surface,respectively.

    The simulation results show that the fully grown sea surface waves represented by the PM spectrum have a low spectral peak frequency distribution and a steep spectral density distribution.The insufficiently grown sea surface waves represented by the JONSWAP spectrum have a flatter power spectral density distribution and a higher spectral peak frequency distribution.Swell waves are low-frequency components propagated by the fully grown sea surface waves at a distance,with their high-frequency sea surface components attenuated rapidly.Conversely, wind waves are affected by the local wind.Therefore, the sea surface under swell waves is smooth and can be depicted as a sine wave, whereas the sea surface under wind waves is randomly rough and has a higher sea surface high-frequency distribution and can be simulated by the Monte-Carlo and wave spectrum methods.According to the Monte-Carlo method, a sea surface with wind waves comprises multiple harmonic components, which have their own random intensity and phase.For a single-dimensional rough sea surface with lengthLand discrete numberN, the moving sea surface direction is opposite to the horizontalrdirection and the random rough sea surface height at discrete sampling pointsrnat timetcan be expressed as

    whereS(kswj) is the power spectral density of the rough surface,ωswjis the angular frequency of the sea surface corresponding to wave numberkswj,andN(0,1)is a standard normal distribution random number.The harmonic spectrum of the negative wavenumberkswj=2π j/L(j=-N/2,...,-1)is the complex conjugate of the positive wavenumber harmonic spectrum.Based on this method,the sea surface of the wind waves represented by the PM spectrum is simulated,and the results are shown in Fig.9.The sea surface simulation of the swell wave is also depicted as a sine wave with a spectral peak frequency of 0.1 Hz,which is identical to that of the PM spectrum wind wave.

    Fig.9.Sea surface simulations with the swell and fully grown wind waves: (a) sea surface with swell wave and (b) sea surface with wind waves(PM spectrum).

    It can be seen from Fig.9 that both swell wave with a spectral peak frequency of 0.1 Hz and fully grown wind wave have identical amplitude peaks of approximately 2.5 m.The oblique stripes reflect the sea surface wave propagation characteristics.Compared with the swell waves simulated as sine waves,the wind waves have significant random and highfrequency components,which are reduced periodic regularity.

    4.2.High-order Bragg scattering and frequency shift of rough sea surface with wind and swell waves

    For the sea surface with swell waves and fully grown wind waves, when an acoustic wave with a frequency of 200 Hz is incident,the acoustic scattering field distribution and frequency shift can be calculated by the same method as that in Figs.6 and 7.Besides the acoustic wave frequency,other parameters are similar to those in the simulation in Fig.6.The results of the acoustic scattering field distribution and frequency shift at(3 km,250 m)with swell waves and fully grown wind waves are shown in Figs.10 and 11, respectively.The simulations illustrate that the sea surface with swell waves and fully grown wind waves can cause an obvious acoustic scattering field and frequency shift for low frequency acoustic wave.However, for the sea surfaces with different wave types, the acoustic scattering field and frequency shift are obviously different.

    Fig.10.Higher-order Bragg scattering of rough sea surface with swell waves: (a) acoustic scattering field loss distribution and (b) frequency shift at(3 km,250 m).

    Fig.11.Higher-order Bragg scattering of rough sea surface with fully grown wind waves: (a)acoustic scattering field loss distribution and(b)frequency shift at(3 km,250 m).

    As shown in Fig.10, the Bragg acoustic scattering field under the periodically time-evolving sea surface is not related to the incident acoustic wave frequency.It multiplies with the sea surface periodical frequency.Therefore, multiple frequency shifts of 0.1 Hz are noted.The sea surface with a large wave height produces a more obvious scattering field and frequency shift.At (3 km, 250 m), the Bragg scattering frequency shifts of ordersn=-1 andn=-2 are consistent with the scattering field distribution in Fig.10(a).Moreover,the acoustic intensity after the frequency shift is considerably higher than that of the mirror reflection without the frequency shift.Compared with the moving sea surface with swell waves characterized by a single frequency,the rough sea surface with fully grown wind waves has a more complex scattering field as shown in Fig.11.For the sea surface with fully grown wind waves, the interference of the sea surface wave with multiple fluctuating frequencies changes the strength of the acoustic scattering field.In addition to the strong Bragg acoustic scattering,a frequency shift is noted from-0.4 Hz to 0.4 Hz,and the strongest frequency shift is slightly different from the multiple with the wind wave spectral peak frequency of 0.1 Hz,as shown in Fig.8(a).For this difference in the strongest frequency shift, it can be explained from the wavelength selection of Bragg scattering and the interference between acoustic scattering beams.During the Bragg scattering of rough sea surface, only a narrow part of the sea spectrum gives rise to strong scattering,while the remaining part of the spectrum produces second order effects.[18]Meanwhile, corresponding to each spatial distributed acoustic source in these simulations,the incident acoustic beam is modulated by the rough sea surface,and the strong acoustic scattering field is produced along the respective Bragg scattering direction.The strong acoustic scattering fields from different acoustic sources will be interfere with each other, creating an additional pattern where the scattering waves with different frequency shifts either cancel out or reinforce each other.

    For the wind wave at an average wind speed of 10 m/s at 10 m above the sea surface and a wind distance of 7 km,the rough sea surface with insufficiently grown wind waves is simulated by the JONSWAP spectrum.Figure 12 shows the sea surface under unsteady wind waves and mixed waves.The mixed wave is the superposition of the simulated insufficiently grown wind wave and swell wave,the spectral peak frequency of insufficiently grown wind wave and swell wave are 0.4 Hz and 0.1 Hz, respectively.The wave height of the rough sea surface with wind waves (Fig.12(a)) is smaller than that under swell waves and fully grown wind waves.Because of the randomness of the wind waves,the wave height of the sea surface under mixed waves (Fig.12(b)) is also random.With the acoustic wave with acoustic beam parameters,as shown in Fig.10,the acoustic scattering field under the sea surface with insufficiently grown wind and mixed waves can be calculated,and the results are shown in Figs.13 and 14,respectively.

    Fig.12.Sea surface simulations with (a) insufficiently grown wind waves(JONSWAP spectrum)and(b)mixed waves.

    Fig.13.Higher-order Bragg scattering of a rough sea surface with insufficiently grown wind waves: (a)acoustic scattering field loss distribution and(b)frequency shift at(3 km,250 m).

    Figure 13 shows that the reflection acoustic field accounts for the absolute main component when the sea surface is affected by insufficiently grown wind waves,and the scattering acoustic field is weaker than that of the other rough sea surface wave cases.The absence of a frequency shift in Fig.13(b)further verifies this reflection acting as the main component of the acoustic field.In other simulation cases, the Bragg scattering field at the receiving position of (3 km, 250 m) has higher acoustic intensity,whereas the frequency shift with insufficiently grown wind waves is negligible in a weak case at 0.32 Hz only.The weak frequency shift results from the lower height of the unsteady rough sea surface.In particular, the wave spectrum of the unsteady sea surface has a wider frequency band that results in the interference of more harmonic components of the frequencies, reducing the scattering intensity and frequency shift.Meanwhile, the frequency shift for the sea surface with unsteady wind waves is not proportional to the wind spectrum peak frequency as shown in Fig.8(b),which is similar to the results shown in Fig.11.

    Fig.14.Higher-order Bragg scattering of rough sea surface with mixed waves: (a) acoustic scattering field loss distribution and (b) frequency shift at(3 km,250 m).

    Comparing with the single insufficiently grown wind wave, the acoustic scattering field and frequency shift are very obvious in the case of the sea surface with mixed waves(Fig.14).Further,the acoustic scattering field distribution and frequency shift are almost consistent with those observed in the case of the sea surface with swell waves(Fig.10).In particular, there are multi-order high-intensity Bragg scatterings and a proportional frequency shift of 0.1 Hz.The highest order obvious frequency shift is 0.4 Hz.The frequency shift also preliminarily reflects the influence of the insufficiently grown wind waves,and the comb-shaped multi-order frequency shift is superimposed on the small frequency-shift fluctuations in the case of the sea surface with insufficiently grown wind waves.

    5.Conclusions

    Based on the sea surface acoustic scattering obtained by the integral equation and forward acoustic field calculation method through using the parabolic equation, the acoustic scattering and frequency shift caused by a moving rough sea surface are calculated and analyzed.The simulation results show that the acoustic scattering field is enhanced at a series of discrete scatter angles stratified by constructive interference,which produces the comb-like high-order Bragg scattering and frequency shifts.The acoustic scattering field has an obvious strong scattering sidelobe along multiple Bragg scattering angle, and its scattering intensity is slightly lower than that of the mirror reflection field.The order of the Bragg acoustic scattering field is directly proportional to the frequency of incident acoustic wave, but inversely proportional to the frequency of sea surface fluctuations.Even if the frequency of incident acoustic is low, Bragg scattering is generated under an actual periodic moving sea surface.The acoustic field along each Bragg scattering angle direction has an obvious frequency shift caused by the periodic sea surface, which is considerably different from the conventional acoustic Doppler frequency shift.In particular, this is attributed to the Bragg scattering order and moving sea surface frequency, but is unrelated to the incident acoustic wave frequency.Considerable frequency shift is noted with low or ultralow incident acoustic frequencies.Therefore, the frequency shift is non-negligible for underwater low-frequency and extremely low-frequency acoustic measurement.

    Meanwhile, the acoustic scattering field and frequency shift distribution for a rough sea surface with typical swell,wind, and mixed waves are analyzed.There are obvious differences in the Bragg acoustic scattering field and frequency shift between the sea surface with swell waves and the sea surface with wind waves.Based on the high-order Bragg acoustic scattering field and acoustic frequency shift,different types of sea wave spectrum peak frequencies and other characteristics are obtained.Compared with the sea surface with fully and insufficiently grown wind waves, the sea surface with swell waves is dominated by a single harmonic component,forming a considerable multi-order Bragg acoustic scattering field and comb-like frequency shift that is a multiple of the wave frequency.The sea surface with fully grown wind waves exhibits multi-order Bragg acoustic scattering field and frequency shift.However, the comb-like frequency shift is less obvious than that under the sea surface with swell waves.The strongest frequency shift is not proportional to the peak frequency of the wind wave spectrum.The insufficiently grown wind wave spectrum has a wider frequency distribution and higher peak frequency, while the Bragg acoustic scattering field and frequency shift distribution are extremely weaker.Under low wind speed and short wind distance, an inconspicuous frequency shift is noted on the acoustic wave, which was not proportional to the peak frequency of the wind wave spectrum either.When the insufficiently grown wind waves and swell waves are mutually superposed to form mixed waves,the Bragg acoustic scattering field and frequency shift are mainly due to the effect of the swell sea surface under the sea surface with mixed waves.

    Acknowledgements

    Project supported by the IACAS Young Elite Researcher Project(Grant No.QNYC201703),the Rising Star Foundation of Integrated Research Center for Islands and Reefs Sciences,CAS(Grant No.ZDRW-XH-2021-2-04),and the Key Laboratory Foundation of Acoustic Science and Technology (Grant No.2021-JCJQ-LB-066-08).

    猜你喜歡
    馬力
    走進(jìn)綠水青山 聚焦退耕還林
    說(shuō)說(shuō)“馬力”
    反問俗語(yǔ)
    超級(jí)馬力歐 色彩奇遇記
    優(yōu)雅(2017年11期)2017-11-11 11:24:28
    馬力全開肌膚加油站
    Coco薇(2017年9期)2017-09-07 21:18:27
    行攝藏地
    “馬力”是一種什么力
    毛衣鏈 給冬日摩登感加大馬力
    Coco薇(2016年2期)2016-03-22 02:25:19
    雪之魅
    馬力出手
    西部(2012年3期)2012-04-29 00:44:03
    香蕉国产在线看| 国产精品电影一区二区三区| 精品久久久精品久久久| 女性被躁到高潮视频| 亚洲欧美日韩另类电影网站| 一级毛片精品| av电影中文网址| 欧美成人午夜精品| 涩涩av久久男人的天堂| 国产精品国产av在线观看| 视频区欧美日本亚洲| 免费人成视频x8x8入口观看| 夜夜夜夜夜久久久久| 欧美日韩黄片免| 欧美+亚洲+日韩+国产| av欧美777| 十八禁网站免费在线| 久久人妻福利社区极品人妻图片| 欧美乱妇无乱码| 国产97色在线日韩免费| 久久热在线av| 老司机亚洲免费影院| 悠悠久久av| 美女大奶头视频| 免费高清视频大片| 狠狠狠狠99中文字幕| 波多野结衣一区麻豆| av网站在线播放免费| 亚洲精品久久午夜乱码| 国产精品98久久久久久宅男小说| 国产在线观看jvid| 欧美日韩中文字幕国产精品一区二区三区 | 免费看十八禁软件| 久久草成人影院| 9色porny在线观看| 热99国产精品久久久久久7| 999精品在线视频| 国产精品香港三级国产av潘金莲| 丝袜美腿诱惑在线| 精品日产1卡2卡| 国产激情欧美一区二区| 亚洲色图av天堂| 日韩欧美国产一区二区入口| 亚洲中文av在线| 这个男人来自地球电影免费观看| 色综合欧美亚洲国产小说| 亚洲精品av麻豆狂野| 国产乱人伦免费视频| 18禁观看日本| 18禁国产床啪视频网站| 国产欧美日韩一区二区精品| 精品第一国产精品| 欧美日韩瑟瑟在线播放| 国产野战对白在线观看| 十八禁网站免费在线| 免费搜索国产男女视频| 亚洲成a人片在线一区二区| 在线国产一区二区在线| 韩国精品一区二区三区| 国产精品一区二区三区四区久久 | 国产精品永久免费网站| 在线国产一区二区在线| 日韩精品青青久久久久久| 宅男免费午夜| 亚洲一码二码三码区别大吗| 99久久国产精品久久久| 午夜福利影视在线免费观看| 亚洲av成人不卡在线观看播放网| 亚洲精品国产精品久久久不卡| 18美女黄网站色大片免费观看| 两人在一起打扑克的视频| 美女福利国产在线| 无遮挡黄片免费观看| 久久中文字幕人妻熟女| 人妻久久中文字幕网| 一本大道久久a久久精品| 波多野结衣高清无吗| 久久久久久大精品| 两人在一起打扑克的视频| 国产成+人综合+亚洲专区| 久久久国产欧美日韩av| av网站免费在线观看视频| 成人亚洲精品av一区二区 | 69av精品久久久久久| 少妇的丰满在线观看| 美国免费a级毛片| av超薄肉色丝袜交足视频| 无人区码免费观看不卡| 在线观看舔阴道视频| 乱人伦中国视频| 成人亚洲精品一区在线观看| 欧美中文日本在线观看视频| 91九色精品人成在线观看| 午夜影院日韩av| 欧美日韩中文字幕国产精品一区二区三区 | avwww免费| 美女高潮到喷水免费观看| 免费人成视频x8x8入口观看| av网站在线播放免费| 韩国av一区二区三区四区| 天堂俺去俺来也www色官网| 天天躁狠狠躁夜夜躁狠狠躁| 免费在线观看完整版高清| 国产精品98久久久久久宅男小说| 少妇粗大呻吟视频| 黄片小视频在线播放| 国产精品久久久久久人妻精品电影| 欧美一级毛片孕妇| 久久人人爽av亚洲精品天堂| 午夜免费成人在线视频| 国产一区二区在线av高清观看| 亚洲人成电影观看| 9色porny在线观看| 侵犯人妻中文字幕一二三四区| 国产av在哪里看| 国产一区二区激情短视频| 久久久久久久久久久久大奶| 精品欧美一区二区三区在线| 精品卡一卡二卡四卡免费| 日韩中文字幕欧美一区二区| 久久久国产精品麻豆| 亚洲人成伊人成综合网2020| 精品国产乱子伦一区二区三区| 香蕉久久夜色| 国产精品免费视频内射| 久久精品国产亚洲av香蕉五月| 国产精品九九99| 中文欧美无线码| 国产精品永久免费网站| 欧美日韩精品网址| 亚洲精品一二三| 一个人观看的视频www高清免费观看 | 9色porny在线观看| 久久精品亚洲熟妇少妇任你| www.999成人在线观看| 嫁个100分男人电影在线观看| 大码成人一级视频| 欧美日韩瑟瑟在线播放| 国产黄a三级三级三级人| 欧美精品一区二区免费开放| 啦啦啦在线免费观看视频4| 99国产精品一区二区三区| 国产成人系列免费观看| 国产av精品麻豆| 日本一区二区免费在线视频| 精品久久久精品久久久| 妹子高潮喷水视频| 91精品三级在线观看| 亚洲人成电影观看| 久久久久久久久免费视频了| 女性被躁到高潮视频| 午夜免费观看网址| 嫁个100分男人电影在线观看| 级片在线观看| 妹子高潮喷水视频| 亚洲av成人av| 麻豆国产av国片精品| 两个人看的免费小视频| 久久久久久免费高清国产稀缺| 欧美黑人精品巨大| 大型av网站在线播放| 在线播放国产精品三级| 一边摸一边抽搐一进一出视频| 国产真人三级小视频在线观看| 国产黄色免费在线视频| svipshipincom国产片| 亚洲午夜精品一区,二区,三区| 久久狼人影院| 久久久久国内视频| 性少妇av在线| a级毛片黄视频| 美女午夜性视频免费| 精品免费久久久久久久清纯| 亚洲精品国产色婷婷电影| 免费在线观看日本一区| 99久久久亚洲精品蜜臀av| 亚洲熟妇中文字幕五十中出 | 亚洲人成网站在线播放欧美日韩| 亚洲视频免费观看视频| 国产精品美女特级片免费视频播放器 | 香蕉国产在线看| 丰满迷人的少妇在线观看| 国产欧美日韩一区二区三区在线| 成人亚洲精品一区在线观看| 精品午夜福利视频在线观看一区| 亚洲精品在线美女| 亚洲精品一二三| 久久午夜亚洲精品久久| 精品高清国产在线一区| 日本免费一区二区三区高清不卡 | 成人手机av| 中文字幕高清在线视频| 亚洲片人在线观看| 97超级碰碰碰精品色视频在线观看| 一边摸一边抽搐一进一出视频| 国产精品一区二区三区四区久久 | 国产精品爽爽va在线观看网站 | 亚洲九九香蕉| 人人澡人人妻人| 亚洲伊人色综图| 免费女性裸体啪啪无遮挡网站| 久久这里只有精品19| 国产精品国产高清国产av| 亚洲av美国av| 在线av久久热| 日本免费一区二区三区高清不卡 | 欧美黄色淫秽网站| 亚洲中文字幕日韩| 亚洲欧美一区二区三区黑人| 亚洲色图综合在线观看| av视频免费观看在线观看| 亚洲一卡2卡3卡4卡5卡精品中文| 少妇 在线观看| 欧美激情极品国产一区二区三区| 黑人猛操日本美女一级片| 精品国产亚洲在线| 精品免费久久久久久久清纯| 亚洲中文日韩欧美视频| a级片在线免费高清观看视频| 99久久国产精品久久久| 亚洲五月色婷婷综合| 国产精品日韩av在线免费观看 | 美女福利国产在线| 国产精品久久久av美女十八| 人成视频在线观看免费观看| 免费一级毛片在线播放高清视频 | 国产在线观看jvid| 欧美乱妇无乱码| 人人妻人人添人人爽欧美一区卜| 夜夜看夜夜爽夜夜摸 | 日韩欧美一区二区三区在线观看| 日本撒尿小便嘘嘘汇集6| 欧美最黄视频在线播放免费 | 熟女少妇亚洲综合色aaa.| 国产成+人综合+亚洲专区| 每晚都被弄得嗷嗷叫到高潮| 国产亚洲欧美在线一区二区| 又大又爽又粗| 亚洲va日本ⅴa欧美va伊人久久| 国产欧美日韩一区二区三| 久久久国产欧美日韩av| 最近最新免费中文字幕在线| 免费不卡黄色视频| 12—13女人毛片做爰片一| a级片在线免费高清观看视频| av片东京热男人的天堂| 欧美精品亚洲一区二区| 免费在线观看日本一区| 国产亚洲精品第一综合不卡| 国产黄a三级三级三级人| 久久中文看片网| 五月开心婷婷网| 欧美 亚洲 国产 日韩一| 老司机亚洲免费影院| 日韩国内少妇激情av| 国产又爽黄色视频| 高清毛片免费观看视频网站 | 亚洲精品久久午夜乱码| 老熟妇仑乱视频hdxx| av中文乱码字幕在线| 久久久精品欧美日韩精品| 成年人黄色毛片网站| 啦啦啦在线免费观看视频4| ponron亚洲| 亚洲中文av在线| 99香蕉大伊视频| 亚洲精品久久午夜乱码| 男男h啪啪无遮挡| 欧美日本亚洲视频在线播放| 少妇裸体淫交视频免费看高清 | 99精品欧美一区二区三区四区| 99riav亚洲国产免费| 久久国产精品人妻蜜桃| 欧美日韩亚洲高清精品| 国产精品av久久久久免费| av片东京热男人的天堂| 99国产精品99久久久久| 波多野结衣av一区二区av| 18禁美女被吸乳视频| 自拍欧美九色日韩亚洲蝌蚪91| 岛国在线观看网站| 亚洲精品一二三| 一级片免费观看大全| 人人澡人人妻人| 一区福利在线观看| 三级毛片av免费| 老司机深夜福利视频在线观看| 国产黄a三级三级三级人| e午夜精品久久久久久久| 美女扒开内裤让男人捅视频| 99久久久亚洲精品蜜臀av| 国产精品自产拍在线观看55亚洲| 亚洲男人的天堂狠狠| 久久国产精品影院| av在线播放免费不卡| 嫁个100分男人电影在线观看| 久久精品亚洲熟妇少妇任你| 亚洲精品美女久久av网站| 99香蕉大伊视频| 国产成人免费无遮挡视频| 亚洲av美国av| 女人被狂操c到高潮| 色哟哟哟哟哟哟| 嫩草影院精品99| 国产成人av教育| 亚洲人成网站在线播放欧美日韩| 嫩草影院精品99| 精品一区二区三区av网在线观看| 色在线成人网| 99国产精品一区二区蜜桃av| 真人做人爱边吃奶动态| 日本欧美视频一区| 99久久精品国产亚洲精品| 真人做人爱边吃奶动态| 国产一区二区三区综合在线观看| 18美女黄网站色大片免费观看| 国产极品粉嫩免费观看在线| 精品第一国产精品| 一边摸一边做爽爽视频免费| 亚洲一区二区三区色噜噜 | 女人被狂操c到高潮| 黑人猛操日本美女一级片| 美女福利国产在线| 午夜免费成人在线视频| 黄色片一级片一级黄色片| 精品国产乱子伦一区二区三区| 亚洲熟女毛片儿| 午夜福利一区二区在线看| 波多野结衣一区麻豆| 多毛熟女@视频| 久久久久亚洲av毛片大全| 老司机靠b影院| 国产高清激情床上av| 日韩av在线大香蕉| av福利片在线| www.精华液| 国产成+人综合+亚洲专区| 好男人电影高清在线观看| 中文字幕另类日韩欧美亚洲嫩草| 亚洲精华国产精华精| 午夜福利,免费看| 精品福利永久在线观看| 操美女的视频在线观看| 在线av久久热| 热99国产精品久久久久久7| 亚洲美女黄片视频| 精品国产美女av久久久久小说| 国产精品日韩av在线免费观看 | 99久久久亚洲精品蜜臀av| 久久国产乱子伦精品免费另类| 1024香蕉在线观看| 亚洲第一欧美日韩一区二区三区| 老鸭窝网址在线观看| 三级毛片av免费| 女人爽到高潮嗷嗷叫在线视频| 三上悠亚av全集在线观看| 亚洲精品在线观看二区| 国产精品九九99| 青草久久国产| 成熟少妇高潮喷水视频| 美国免费a级毛片| 亚洲美女黄片视频| 亚洲av日韩精品久久久久久密| 精品国产一区二区久久| 99久久99久久久精品蜜桃| 国产三级在线视频| av在线天堂中文字幕 | 狠狠狠狠99中文字幕| 青草久久国产| 亚洲精品国产一区二区精华液| 韩国av一区二区三区四区| 精品乱码久久久久久99久播| 日韩三级视频一区二区三区| a级片在线免费高清观看视频| 大香蕉久久成人网| 亚洲男人的天堂狠狠| 国产精品99久久99久久久不卡| av视频免费观看在线观看| 在线观看午夜福利视频| www国产在线视频色| 午夜福利影视在线免费观看| 久久狼人影院| 免费女性裸体啪啪无遮挡网站| 欧美日韩亚洲国产一区二区在线观看| 国产亚洲av高清不卡| 免费在线观看完整版高清| 一级片'在线观看视频| 欧美 亚洲 国产 日韩一| 婷婷精品国产亚洲av在线| 91成年电影在线观看| av网站免费在线观看视频| 中出人妻视频一区二区| 欧美激情久久久久久爽电影 | 亚洲免费av在线视频| 国产av一区在线观看免费| 欧美精品亚洲一区二区| 1024香蕉在线观看| 69av精品久久久久久| 精品久久蜜臀av无| 老熟妇乱子伦视频在线观看| 巨乳人妻的诱惑在线观看| 男女下面进入的视频免费午夜 | 久久欧美精品欧美久久欧美| 亚洲精品国产精品久久久不卡| 欧美色视频一区免费| www.精华液| 国产精品亚洲一级av第二区| 日韩欧美在线二视频| 亚洲成国产人片在线观看| √禁漫天堂资源中文www| 在线十欧美十亚洲十日本专区| 久久久久国产精品人妻aⅴ院| 午夜影院日韩av| 男人的好看免费观看在线视频 | 男人操女人黄网站| 俄罗斯特黄特色一大片| 国产麻豆69| 国产av一区在线观看免费| 日韩精品中文字幕看吧| 国产三级在线视频| av在线天堂中文字幕 | 亚洲精品久久成人aⅴ小说| 91成年电影在线观看| 夜夜夜夜夜久久久久| 水蜜桃什么品种好| 久久久久亚洲av毛片大全| 麻豆成人av在线观看| 日韩成人在线观看一区二区三区| 高清黄色对白视频在线免费看| av天堂在线播放| 国产又爽黄色视频| 一二三四社区在线视频社区8| 久久精品亚洲av国产电影网| 久9热在线精品视频| 国产99久久九九免费精品| 久久国产精品男人的天堂亚洲| 亚洲av第一区精品v没综合| av视频免费观看在线观看| 免费在线观看亚洲国产| 妹子高潮喷水视频| 久久精品91无色码中文字幕| 免费看十八禁软件| 高清在线国产一区| 国产精品乱码一区二三区的特点 | 女生性感内裤真人,穿戴方法视频| 国产成人精品无人区| 成人18禁在线播放| 999精品在线视频| 99精国产麻豆久久婷婷| 免费不卡黄色视频| 亚洲一区中文字幕在线| 久久中文看片网| 两性夫妻黄色片| av国产精品久久久久影院| 国产三级在线视频| 国产黄色免费在线视频| 50天的宝宝边吃奶边哭怎么回事| 国产无遮挡羞羞视频在线观看| 一级片免费观看大全| 精品日产1卡2卡| 不卡av一区二区三区| 久久精品人人爽人人爽视色| 色婷婷av一区二区三区视频| 欧美精品啪啪一区二区三区| 久久狼人影院| 99riav亚洲国产免费| 中文字幕高清在线视频| 女人高潮潮喷娇喘18禁视频| 一夜夜www| 黄色丝袜av网址大全| 亚洲精品在线美女| 88av欧美| 99久久国产精品久久久| 亚洲va日本ⅴa欧美va伊人久久| 亚洲国产看品久久| 一级,二级,三级黄色视频| 中文字幕av电影在线播放| 在线观看www视频免费| av视频免费观看在线观看| 免费av中文字幕在线| 嫩草影视91久久| 久久天躁狠狠躁夜夜2o2o| 欧美久久黑人一区二区| 三上悠亚av全集在线观看| 亚洲七黄色美女视频| 老司机福利观看| 国产熟女xx| 国产精品久久久人人做人人爽| 久久久久国内视频| 激情在线观看视频在线高清| 51午夜福利影视在线观看| 日韩免费高清中文字幕av| 五月开心婷婷网| 怎么达到女性高潮| 久久精品国产清高在天天线| 精品久久久久久成人av| 搡老岳熟女国产| 精品午夜福利视频在线观看一区| 波多野结衣高清无吗| 国产极品粉嫩免费观看在线| 亚洲 国产 在线| 香蕉国产在线看| 日韩中文字幕欧美一区二区| 国产成人影院久久av| 又黄又爽又免费观看的视频| 好男人电影高清在线观看| 精品国产乱码久久久久久男人| 在线av久久热| 丰满饥渴人妻一区二区三| 久久久久久大精品| 多毛熟女@视频| 欧美日韩黄片免| 国产精品九九99| 色婷婷av一区二区三区视频| 一级黄色大片毛片| 亚洲av美国av| 久9热在线精品视频| a级毛片黄视频| 视频区欧美日本亚洲| svipshipincom国产片| 999久久久国产精品视频| 成在线人永久免费视频| 丝袜人妻中文字幕| 亚洲va日本ⅴa欧美va伊人久久| 亚洲精品粉嫩美女一区| 久久久国产成人精品二区 | av福利片在线| 欧美丝袜亚洲另类 | 51午夜福利影视在线观看| 亚洲欧洲精品一区二区精品久久久| 一二三四在线观看免费中文在| 宅男免费午夜| x7x7x7水蜜桃| 在线观看免费高清a一片| 99re在线观看精品视频| 国产欧美日韩综合在线一区二区| 国产精品国产高清国产av| 亚洲人成77777在线视频| 亚洲avbb在线观看| 欧美激情极品国产一区二区三区| 中文字幕av电影在线播放| 88av欧美| 看片在线看免费视频| 日本黄色日本黄色录像| 热99国产精品久久久久久7| 久久人妻福利社区极品人妻图片| 老司机深夜福利视频在线观看| 大型av网站在线播放| 高清在线国产一区| 啦啦啦 在线观看视频| 国产1区2区3区精品| 纯流量卡能插随身wifi吗| 99香蕉大伊视频| 女性被躁到高潮视频| 十八禁网站免费在线| 免费在线观看日本一区| 亚洲中文av在线| 午夜91福利影院| 大陆偷拍与自拍| 欧美日韩国产mv在线观看视频| 国产激情欧美一区二区| 免费看a级黄色片| 一级片'在线观看视频| 亚洲国产看品久久| 日韩欧美在线二视频| 国产真人三级小视频在线观看| 亚洲五月天丁香| 国产精品电影一区二区三区| 久久人人精品亚洲av| 精品一区二区三区四区五区乱码| 老司机靠b影院| 热99re8久久精品国产| 久久精品国产亚洲av香蕉五月| 成人影院久久| 色在线成人网| 久久草成人影院| 一二三四社区在线视频社区8| 久久人妻av系列| 成人亚洲精品一区在线观看| 久久久久久久久中文| 色婷婷久久久亚洲欧美| 18禁黄网站禁片午夜丰满| 国产欧美日韩一区二区三| 级片在线观看| 一区福利在线观看| 日韩欧美在线二视频| 啦啦啦 在线观看视频| www.熟女人妻精品国产| 亚洲专区字幕在线| 成在线人永久免费视频| 在线av久久热| www日本在线高清视频| 免费少妇av软件| 免费观看精品视频网站| 亚洲av成人av| 亚洲色图av天堂| 国产麻豆69| 人人妻,人人澡人人爽秒播| 亚洲男人的天堂狠狠| 国产成人精品在线电影| 成人三级做爰电影| videosex国产| 99久久99久久久精品蜜桃| 亚洲精华国产精华精| 亚洲少妇的诱惑av| av片东京热男人的天堂| 男女床上黄色一级片免费看| 亚洲午夜精品一区,二区,三区| 老司机午夜十八禁免费视频| 国产精品免费一区二区三区在线| 黄色a级毛片大全视频| 欧美成人性av电影在线观看| 曰老女人黄片| 亚洲人成伊人成综合网2020| 巨乳人妻的诱惑在线观看|