• <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 ?

    Energy dissipation and power deposition of electromagnetic waves in the plasma sheath

    2021-03-01 08:09:58JiahuiZHANG張珈琿XinJI吉欣KeyuanYANG楊克元LeiSHI石磊andQingxiaWANG王青霞
    Plasma Science and Technology 2021年1期
    關(guān)鍵詞:石磊

    Jiahui ZHANG(張珈琿),Xin JI(吉欣),Keyuan YANG(楊克元),Lei SHI(石磊) and Qingxia WANG (王青霞)

    1 School of Aerospace Science and Technology, Xidian University, Xi’an 710071, People’s Republic of China

    2 China Academy of Space Technology, Xi’an 710100, People’s Republic of China

    Abstract Energy dissipation and power deposition of electromagnetic waves(EMW)in the reentry plasma sheath provide an opportunity to investigate ‘communication blackout’ phenomena.Based on a finite element method (FEM) simulation, we analyze variation of EMW energy dissipation and power deposition profiles dependent on the wave polarization, wave incident angle, plasma density profile and electron collision frequency.Cutoff and resonance of EMW in the plasma sheath are crucial in explaining the regulation of energy dissipation and power deposition.

    Keywords: electromagnetic wave, power deposition, plasma sheath

    1.Introduction

    A plasma sheath comes into being when a vehicle flies with hypersonic velocity.This is caused by the dissociation and ionization of the air molecules originating from the hightemperature shock wave heating of the air [1].The plasma sheath surrounds the hypersonic vehicle and acts as a dispersion medium for the electromagnetic waves (EMW) used for communication or radar detection [2, 3].In communication technology, the plasma sheath becomes a barrier for EMW and ‘communication blackout’ phenomena occur because of the reflection and absorption of EMW in the presence of the plasma sheath.In radar detection, the plasma sheath absorbs substantial energy from the EMW and reduces the efficiency of radar detection.Therefore, the concept of plasma stealth was developed and discussed[4].With respect to communication blackout research, the reflection of EMW caused by the plasma sheath and the corresponding conditions have been widely discussed [5].Blackout mitigation is of great importance and a few mechanisms have been developed to address this issue.Mechanisms such as aerodynamic shape modification[6],electrophilic fluid injection,surface catalysis effects[7]and E × B drift[8-10]mitigate the plasma sheath by reducing the electron plasma density.While other mechanisms keep the plasma sheath invariant, for example,wave frequency modification[11],laser communication[12],magnetic windows [13], resonant transmission [14], electron acoustic wave transmission [15] and three-wave interactions[16]comply with the plasma sheath and mitigate blackout by exploring and utilizing the EMW propagation characteristics in the plasma.However, EMW energy dissipation caused by the plasma sheath has not been focused on and the power deposition within the plasma sheath is ambiguous.This was the original motivation for this paper.On one hand, research of EMW energy dissipation in the plasma sheath can supply new insights into communication blackout.On the other hand, EMW energy dissipation regulations can be used to explain the phenomena relevant to the radar detection of a hypersonic vehicle enveloped by the plasma sheath.

    The simulation of EMW propagation is important in understanding the interaction between EMW and plasmas.USIM is a plasma simulation software based on magnetofluid theory and it is widely used in simulating EMW in the plasma sheath [17-19].The finite-difference time-domain method(FDTD)can give the EMW field evolution with time across the plasma sheath [20-22].The commercial code Ansoft and CST are convenient to simulate the communication antenna surrounded by the plasma sheath[23].However,additional plasma physical effects cannot be captured easily in the simulation.As an important supplement,COMSOL Multiphysics software can be used to analyze the physical effects,such as EMW cutoff and resonance in the plasma.Previously, we used COMSOL to analyze EMW field distributions[24]and the spatial dispersion effect[25]in a nonuniform plasma sheath.In this work,we will apply COMSOL to research EMW energy dissipation and power deposition in a nonuniform plasma sheath.

    The arrangement of this paper is as follows: the plane wave simulations are given in section 2.The full wave simulations based on realistic plasma sheath parameters are shown in section 3.Conclusions are drawn in section 4.

    2.Plane wave simulations

    2.1.Model and wave equations

    The EMW equation is solved in the frequency domain based on the finite element method.We assume that the variables of electromagnetic fields oscillate with eiωt, then the EMW equation in terms of the electric field can be given as:

    where the relative permittivity of the air or plasma is defied by εr′ and the wave number in the air is defied byk0.The relative permittivity of plasma is:

    where the angular frequency of the EMW is defined by ω,electron collision frequency is defied by νe, the plasma angular frequency is defined as

    neis the electron density,eis the electron charge, ε0is the permittivity of air andmeis the mass of the electron.

    Figure 1 shows the 2D model used to simulate the plane EMW across the reentry nonuniform plasma sheath caused by hypersonic flows.The plasma sheath is inserted into the air region.The electron density is assumed nonuniform inydirection and uniform inxdirection.The symmetry electron density distribution in the plasma region is given as:

    whereNis the maximum electron density aty=y0andLis the decay constant of the electron density.The electron collision frequency νeis treated as a constant in the plasma sheath.The permittivity of the plasma sheath can be imported by equation (2).The plane wave source is placed in the bottom air region and the wave vector k is set to be in thexoyplane.The input power of the EMW is 1 W.Periodic boundary conditions, which are consistent with the plane wave source, are assigned to the left and right boundaries.The relevant parameters are listed in table 1.

    Figure 1.Plane wave simulation model for EMW across the reentry nonuniform plasma sheath.The plane wave excitation is placed in the bottom air region.The wave vector k is set to be in the xoy plane.Periodic boundary conditions are assigned to the left and right boundaries.Perfect matched layers are applied to mimic the infinite boundary conditions for EMW.

    Table 1.The parameters in the simulation.

    Perfect matched layers (PMLs) are used to simulate the infinite boundary conditions for EMW.The property of the PML is the same as the air.We apply a polynomial stretching function in theydirection, which is defined by:where ξ is the dimensionless coordinate which varies from 0 to 1 over the PML,sis a scaling factor andpis a curvature parameter.The complex displacement for stretching in a single direction isis the original thickness of the PML and λ is a typical wavelength.To retain perfect absorption for plane waves incident at an angle α relative to the boundary normal,it is necessary to compensate for the longer wavelength seen by the PML in the stretching direction by setting the scaling factor:

    The curvature parameterpis equal to the default value 1.The quality of the PML is insensitive to the thicknessLPMLwhile eight mesh elements across the PML(in theydirection)must be satisfied.The grid dependency and validation of the simulation model have been discussed in detail in reference [24].

    Figure 2.The frequency response of the absorption coefficient CA with incidence angle(a)θ = 0°,(b)θ = 20°,(c)θ = 40°and(d)θ = 60°.The solid line denotes CA belonging to EMW with s polarization and the dashed line denotes CA belonging to EWMs with p polarization.The electron peak density is 5 × 1017 m?3,the decay constant of electron density L is 0.002 m and the collision frequency νe is 0.1 GHz.The other parameters are listed in table 1.

    In the beginning of this section, the basic parameters in this work need to be drawn.The range of electron density in the realistic plasma sheath is around 1015-1019m?3.So the moderate electron peak density, 5 × 1017m?3, is adopted in our simulation model.The range of EMW frequency is chosen as 1-20 GHz to cover the main communication frequency band.The input power of EMW is 1 W.The decay constantLin equation (4) can be used to adjust the electron density profile.

    For simplicity,the electron plasma frequency is defined as:

    This equation is relevant to EMW cutoff and resonance in the plasma.In the case of 1D nonuniform plasma, the cutoff frequency for EMW with vertical incidence in the local plasma region is given as:

    If taking EMW with oblique incidence into account,the more general form can be deduced:

    where θ is the incident angle of the EMW.The EMW resonance phenomenon in the plasma has been discussed in reference [24] and can be summarized as a sentence:p polarization EMW with oblique incidence can resonate with electron plasma when the condition off=fpeis satisfied in some local plasma regions.The preliminary knowledge here will be helpful to explain the characteristics of EMW power deposition in the plasma sheath.

    2.2.Dependence on incidence angle

    The frequency response of the absorption coefficientCAwith different incident angle is shown in figure 2.In each incident angles condition, the s polarization (Ex=Ey= 0,Ez≠ 0)case can be compared with the p polarization (Ex≠ 0,Ey≠ 0,Ez= 0) case.For the s polarization case, the wave frequency corresponding to the absorption maximum shifts with the incident angle.This phenomenon is closely related to the cutoff frequency of EMW in the nonuniform plasma sheath, which is defined in equation (8b).The cutoff frequency depends on the incident angle of EMW and the absorption coefficientCAalso maximizes near the frequency Max(fpe/cosθ).For the case of EMW with normal incidence in figure 2(a), the curve ofCAwith p polarization coincides with the one with s polarization.Nevertheless,for the case of an EMW with an oblique incidence angle, the curves ofCAwith p polarization deviate from the results with s polarization in the frequency band ranging from Min(fpe)to Max(fpe).The discrepancy originates from the resonance between EMW and Langmuir oscillation.The resonance can only take place for p polarization EMW with oblique incidence angle when Min(fpe) <f< Max(fpe).The absorption coefficientCAin this frequency band will be enhanced because of the resonance.The details of the resonance between EMW and Langmuir oscillation can be found in reference [24].The characteristic frequency values, Min(fpe), Max(fpe),Min(fpe/cosθ)and Max(fpe/cosθ)for various incident angles are listed in table 2.

    Figure 3.The power deposition profiles belonging to EMW with s polarization.(a) f = 4 GHz in the first column, (b) f = 6 GHz in the second column,(c)f = 8 GHz in the third column and(d)f = 10 GHz in the fourth column.The blue line in the first row denotes θ = 0°,the red line in the second row denotes θ = 20°,the green line in the third row denotes θ=40°,the cyan line in the fourth row denotes θ = 60°.The cutoff position of EMW near the input boundary is marked by the black dashed line if it exists in the plasma sheath.

    Table 2.The characteristic frequency values for various incident angles.

    The power deposition profiles of EMW with s polarization are shown in figure 3.Subplots in the same column have the same wave frequency and the subplots in the same row have the same incident angle.According to the relationship between the wave frequency and the cutoff frequency of plasma sheath, the power deposition profiles fall into three categories:

    f< Min(fpe/cosθ), Min(fpe/cosθ) <f< Max(fpe/cosθ) andf> Max(fpe/cosθ).Whenf< Min(fpe/cosθ), EMW are evanescent all over the plasma sheath and the power deposition concentrates near the left boundary of the plasma sheath (green line in the first column, cyan lines in the first and second columns).Iff> Max(fpe/cosθ),the power deposition can cover the whole plasma sheath and maximize near its center(blue lines in the third and fourth columns, red lines in the third and fourth columns,green line in the fourth column).The power deposition can permeate the plasma sheath inside a certain depth when Min(fpe/cosθ) <f< Max(fpe/cosθ).The penetration depth of power deposition is proportional to the depth of the first critical cutoff position of EMW.The first cutoff position of EMW near the input boundary is marked by the black dashed line(blue lines in the first and second columns,red lines in the first and second columns,green lines in the second and third columns,cyan lines in the third and fourth columns).It should be noted that the volume integration of the power deposition results in the absorption coefficientCA.

    Figure 4 shows the power deposition profiles of EMW with p polarization.Subplots in the same column have the same wave frequency and the subplots in the same row have the same incident angle.EMW with p polarization and oblique incident angle can resonate with electron plasma when the condition of Min(fpe) <f< Max(fpe) is satisfied.The absorption coefficient is much larger than the one with s polarization in the frequency range of Min(fpe) <f<Max(fpe) in figure 2.In this case, the power deposition concentrates on the left resonance position (red lines in the first and second columns, green lines in first and second columns, cyan lines in the first and second columns).Furthermore, the amplitude of the power deposition peak is sensitive to the incident angle of EMW and this is consistent with the absorption coefficient in figure 2.The power deposition rules without the resonance are no different from the case of s polarization EMW.

    Figure 4.The power deposition profiles belonging to EMW with p polarization.(a) f = 4 GHz in the first column, (b) f = 6 GHz in the second column,(c)f = 8 GHz in the third column and(d)f = 10 GHz in the fourth column.The blue line in the first row denotes θ = 0°,the red line in the second row denotes θ = 20°, the green line in the third row denotes θ = 40°, the cyan line in the fourth rowdenotes θ = 60°.

    2.3.Dependence on density profiles

    The electron density profiles can be adjusted by modifying the decay constant of electron densityLwhile the peak density remains the same.The symmetry electron density profiles with differentLare shown in figure 5.The smaller the decay constantLis, the steeper the density profile is, and the lower the edge electron density is.The frequency response of the absorption coefficientCAwith different decay constantLis shown in figure 6.The EMW incident angle is chosen to be 20° because a relative small incident angle is suitable for the realistic application scenario.In this case, the cutoff frequency Max(fpe/cosθ) of the plasma sheath is very close to Max(fpe).For s polarization EMW,the absorption coefficientCAmaximizes near the frequency of Max(fpe/cosθ).The peak amplitude ofCAincreases and the absorption bandwidth gets narrow when the decay constantLincreases.For p polarization EMW, the variation of the peak amplitude is not as large as it is for s polarization EMW.However, the bandwidth ofCAdecreases significantly withLincreasing.This is determined by the condition of EMW resonance with electron plasma, Min(fpe) <f< Max(fpe).The largerLresults in the larger Min(fpe) of the plasma sheath, which is the boundary of the absorption bandwidth.The characteristic frequency values, Min(fpe), Max(fpe), Min(fpe/cosθ) and Max(fpe/cosθ) for various decay constantsLare listed in table 3.

    Figure 5.The electron density profiles with different decay constants.

    Figure 6.The frequency response of the absorption coefficient CA with decay constant(a)L = 0.001 m,(b)L = 0.002 m,(c)L = 0.003 m and(d)L = 0.004 m.The solid line denotes CA belonging to EMW with s polarization and the dashed line denotes CA belonging to EWMs with p polarization.The incident angle of the EMW is 20°, the electron peak density is 5 × 1017 m?3 and the collision frequency νe is 0.1 GHz.The other parameters are listed in table 1.

    Table 3.The characteristic frequency values for various decay constants L.

    2.4.Dependence on peak electron density

    The peak electron number density is also the key factor to influence the energy dissipation of EMW.Figure 7 shows the frequency response of the absorption coefficientCAfor various peak electron densities.In all these cases,the absorption bands for p polarization are wider than those for s polarization.Furthermore, the absorption bands shift from the lowfrequency region to the high-frequency region when the peak electron number density increases.This phenomenon can be explained by the fact that the peak electron density determines Max(fpe) and Min(fpe) of the plasma sheath, as well as the cutoff and resonance condition of the EMW.The characteristic frequency values,Min(fpe),Max(fpe),Min(fpe/cosθ)and Max(fpe/cosθ) for various peak electron densities are listed in table 4.

    2.5.Dependence on electron collision frequency

    The electron collision frequency is another important parameter which influences the energy dissipation of EMW in the plasma sheath.The frequency response of the absorption coefficientCAwith various electron collision frequencies νeis shown in figure 8.Increasing the electron collision frequency νenot only enhances the amplitude peak ofCA, but also enlarges the frequency bandwidth of the absorption coefficient.It should also be noted that the discrepancy between s and p polarization tends to vanish when νeincreases.

    3.Full wave simulations

    3.1.Model

    Previously, we have obtained the EMW energy dissipation and power deposition regulations in the reentry plasma sheath based on plane wave model.In this section, we will proceed to the full wave simulation based on a 2D plasma model to mimic the realistic reentry plasma sheath.The full wave simulation model is shown in figure 9.The simulation region is surrounded by PMLs.In the simulation region, the plasma sheath is inserted into the air region.The electron density is assumed nonuniform inxandydirection as:

    Figure 7.The frequency response of the absorption coefficient CA with peak electron density(a)N = 1 × 1017 m?3,(b)N = 5 × 1017 m?3,(c) N = 1 × 1018 m?3 and (d) N = 5 × 1018 m?3.The solid line denotes CA belonging to EMW with s polarization and the dashed line denotes CA belonging to EWM with p polarization.The incident angle of the EMW is 20°,the decay constant of electron density L is 0.002 m, and the collision frequency νe is 0.1 GHz.The other parameters are listed in table 1.

    Table 4.The characteristic frequency values for various peak electron density.

    The profiles ofN(y)shown in figure 10 are fitted based on the reentry hypersonic fluid simulation results[26].The variation of the electron density in thexdirection is defined byLx.According to the characteristic of collision frequency distribution[26],the collision frequency is defined as uniform inydirection and nonuniform in thexdirection:

    The characteristic parameters of the plasma sheath with different altitudes are shown in table 5.The wave port is placed in the bottom air region and the main wave vector k is set to be normal to the plasma sheath boundary.The EMW input power is 1 W.

    3.2.Dependence on the altitude of the reentry vehicle

    The frequency responses of the absorption coefficientCAfor different altitudes of the reentry vehicle are shown in figure 11.High energy dissipation occurs at the altitude of 40 km and 60 km when the wave frequency is close to the plasma frequency.At the altitude of 40 km,the collision frequency is so large that the difference between s and p polarization is not obvious.Though the collision frequency at the altitude of 20 km is the largest, the energy dissipation is still very low.The reason is that the wave frequency is much larger than the plasma frequency and most wave energy gets through the plasma sheath.The energy dissipation at the altitude of 80 km is low because of the low collision frequency.In this case,most wave energy has been reflected.

    Figure 8.The frequency response of the absorption coefficient CA with collision frequency (a) νe = 0.05 GHz, (b) νe = 0.1 GHz, (c)νe = 0.5 GHz and (d) νe = 1 GHz.The solid line denotes CA belonging to EMW with s polarization and the dashed line denotes CA belonging to EWM with p polarization.The incident angle of the EMW is 20°, the electron peak density is 5 × 1017 m?3 and the decay constant of electron density L is 0.002 m.The other parameters are listed in table 1.

    Figure 9.Full wave simulation model for EMW across the reentry nonuniform plasma sheath.The wave port is placed in the bottom air region and the main wave vector k is set to be normal to the plasma sheath boundary.PMLs are applied to mimic the infinite boundary conditions for EMW.

    The power deposition distributions at the altitude of 40 km are shown in figure 12.The difference of the power deposition between s and p polarization is rather small for all the three frequencies.This is consistent with the conclusion deduced from figure 11.As for the power deposition at the altitude of 60 km in figure 13, the power deposition distributions with s and p polarization are different forf=5 GHz andf= 12 GHz.The light fringe in figures 13(d) and (e)caused by resonance between EMW and plasma can be observed.The light fringe vanishes in figure 13(f)because the wave frequencyf= 15 GHz has exceeded the maximum of the plasma frequency and the resonance condition is not satisfied.

    Figure 10.The electron density profiles with different altitudes of the reentry vehicle.

    Figure 11.The frequency response of the absorption coefficient for(a)high energy dissipation with altitude of 40 km and 60 km,and(b)low energy dissipation with altitudes of 20 km and 80 km.The solid line denotes CA belonging to EMW with s polarization and the dashed line denotes CA belonging to EWM with p polarization.

    Figure 12.EMW power deposition in the plasma sheath at the altitude of 40 km.(a)f = 5 GHz,(b)f = 12 GHz and(c)f = 15 GHz with s polarization.(d) f = 5 GHz, (e) f = 12 GHz and (f) f = 15 GHz with p polarization.

    4.Conclusions

    In this paper, we analyze the regulation of EMW energy dissipation and power deposition in the plasma sheath based on plane wave and full wave simulation models.The main conclusions deduced from the plane wave simulations can be summarized as follows:

    Figure 13.EMW power deposition in the plasma sheath at the altitude of 60 km.(a)f = 5 GHz,(b)f = 12 GHz and(c)f = 15 GHz with s polarization.(d) f = 5 GHz, (e) f = 12 GHz and (f) f = 15 GHz with p polarization.

    Table 5.The characteristic parameters of the plasma sheath with different altitudes.

    (1) The power deposition profiles with s polarization fall into three categories:f< Min(fpe/cosθ),Min(fpe/cosθ) <f< Max(fpe/cosθ) andf> Max(fpe/cosθ).Whenf< Min(fpe/cosθ), EMW are evanescent all over the plasma sheath and the power deposition concentrates near the plasma sheath boundary.Iff> Max(fpe/cosθ),the power deposition can cover the whole plasma sheath and maximize near the center of the plasma sheath.The power deposition can permeate the plasma sheath inside a certain depth when Min(fpe/cosθ) <f< Max(fpe/cosθ).

    (2) The power deposition profiles with p polarization and oblique incident angle concentrate on the first resonance position when the resonance between EMW and electron plasma oscillation takes place in the frequency range of Min(fpe) <f< Max(fpe).When the electron collision frequency increases, the resonance absorption peak of the power deposition profile decreases and broadens.The power deposition rules without resonance are similar to the case of s polarization EMW.

    (3) The volume integration of the power deposition results in the absorption coefficient.The characteristics of frequency response of the absorption coefficient are different for s and p polarization EMW.For the s polarization case, the absorption coefficient maximizes near the frequency of Max(fpe/cosθ).The absorption frequency bandwidth becomes narrower with the electron density gradient decreasing.However, increasing the electron collision frequency not only enhances the amplitude peak ofCA, but also enlarges the frequency bandwidth of the absorption coefficient.

    (4) For the p polarization case,the absorption coefficient in the frequency band where Min(fpe) <f< Max(fpe)will be much larger than that for s polarization case because of the EMW resonance with electron plasma oscillation.Variation of the plasma density profile or peak density can influence Min(fpe)or Max(fpe)as well as the bandwidth of the absorption coefficient.The effect of the collision frequency on the absorption coefficient for p polarization is similar to s polarization.In addition, the discrepancy between s and p polarization tends to vanish when collision frequency increases.

    The regulations above concluded from plane wave simulations can be used to explain the phenomena in the full wave simulations based on the realistic plasma sheath parameters at different altitudes of the reentry vehicle.High energy dissipation occurs at the altitudes of 40 km and 60 km when the wave frequency is close to the plasma frequency.

    The resonance of p polarization EMW in the plasma sheath can be distinguished from s polarization at the altitude of 60 km.The results in this paper can be useful in explaining the phenomena relevant to the radar detection of a hypersonic vehicle surrounded by a plasma sheath.

    Acknowledgments

    This research was partly funded by National Natural Science Foundation of China(Nos.61627901 and 61871302)and the Shaanxi National Natural Science Foundation under Grant No.2019JZ-15.

    猜你喜歡
    石磊
    “巨嬰”老公總讓我收拾爛攤子,忍無可忍我決定分居
    婦女生活(2025年2期)2025-02-20 00:00:00
    Nitrogen-tailored quasiparticle energy gaps of polyynes
    Momentum-space polarization fields in two-dimensional photonic-crystal slabs: Physics and applications
    Inverse synthetic aperture radar range profile compensation of plasma-sheathenveloped reentry object
    Adaptive protograph-based BICM-ID relying on the RJ-MCMC algorithm: a reliable and efficient transmission solution for plasma sheath channels
    PERIODIC AND ALMOST PERIODIC SOLUTIONS FOR A NON-AUTONOMOUS RESPIRATORY DISEASE MODEL WITH A LAG EFFECT*
    闕 題
    親愛的,你現(xiàn)在可以求婚了
    伴侶(2019年11期)2019-08-09 08:47:31
    Probabilistic Teleportation of an Arbitrary Two-Qubit State via Positive Operator-Valued Measurement with Multi Parties?
    昔日創(chuàng)客的美麗蝶變
    在线观看一区二区三区| 真人一进一出gif抽搐免费| 欧美色欧美亚洲另类二区| 成人美女网站在线观看视频| 小说图片视频综合网站| 国产不卡一卡二| 欧美性猛交╳xxx乱大交人| 久9热在线精品视频| 又爽又黄a免费视频| 内射极品少妇av片p| 国产av在哪里看| 国产精品日韩av在线免费观看| 99在线视频只有这里精品首页| 观看免费一级毛片| 成年女人看的毛片在线观看| 国产欧美日韩一区二区三| 亚洲国产欧洲综合997久久,| 欧美黄色片欧美黄色片| 久久精品久久久久久噜噜老黄 | 热99re8久久精品国产| 国产麻豆成人av免费视频| 国内精品久久久久久久电影| 久久久国产成人精品二区| 国产v大片淫在线免费观看| 丰满人妻熟妇乱又伦精品不卡| 国产高清三级在线| 怎么达到女性高潮| 少妇的逼水好多| 色5月婷婷丁香| 国产毛片a区久久久久| 黄色日韩在线| 性色av乱码一区二区三区2| 99在线视频只有这里精品首页| 美女cb高潮喷水在线观看| 毛片女人毛片| 别揉我奶头 嗯啊视频| 人人妻人人看人人澡| 激情在线观看视频在线高清| 亚洲一区二区三区色噜噜| 免费无遮挡裸体视频| 中文字幕免费在线视频6| 国产在视频线在精品| 久久久久精品国产欧美久久久| 精品久久久久久久人妻蜜臀av| 小说图片视频综合网站| 国内少妇人妻偷人精品xxx网站| 激情在线观看视频在线高清| 午夜a级毛片| 成人午夜高清在线视频| 国产在视频线在精品| 欧美区成人在线视频| 久久久久久久久大av| a在线观看视频网站| 99久久成人亚洲精品观看| 久久国产精品影院| 亚洲熟妇熟女久久| 国内精品久久久久久久电影| 黄色一级大片看看| 欧美在线黄色| 久久99热这里只有精品18| 一夜夜www| 成年免费大片在线观看| 看黄色毛片网站| 此物有八面人人有两片| 一区二区三区四区激情视频 | 嫩草影视91久久| 久久精品影院6| 最近在线观看免费完整版| 啦啦啦韩国在线观看视频| 久久久久久九九精品二区国产| 麻豆国产97在线/欧美| 99精品久久久久人妻精品| a级一级毛片免费在线观看| 欧美+亚洲+日韩+国产| 国产精品爽爽va在线观看网站| aaaaa片日本免费| 国产精品不卡视频一区二区 | 级片在线观看| 欧美三级亚洲精品| 欧美一区二区国产精品久久精品| 最新在线观看一区二区三区| av天堂中文字幕网| 国产av不卡久久| 国产麻豆成人av免费视频| 99久久99久久久精品蜜桃| 亚洲美女黄片视频| 日韩欧美精品免费久久 | 久久久久久久午夜电影| 欧美成人免费av一区二区三区| 少妇高潮的动态图| 亚洲av免费在线观看| 欧美成狂野欧美在线观看| 窝窝影院91人妻| 神马国产精品三级电影在线观看| 亚洲av熟女| 亚洲avbb在线观看| 九九在线视频观看精品| 麻豆国产97在线/欧美| x7x7x7水蜜桃| 久久久久国产精品人妻aⅴ院| 男人舔女人下体高潮全视频| 男插女下体视频免费在线播放| 日韩大尺度精品在线看网址| 少妇人妻一区二区三区视频| 一边摸一边抽搐一进一小说| 小蜜桃在线观看免费完整版高清| 精品国产三级普通话版| 日韩av在线大香蕉| 免费观看精品视频网站| 亚洲av成人不卡在线观看播放网| 亚洲精华国产精华精| 国产高清三级在线| 午夜福利18| 成人午夜高清在线视频| 午夜激情欧美在线| bbb黄色大片| 国内揄拍国产精品人妻在线| 99热只有精品国产| 国产欧美日韩精品亚洲av| 少妇的逼好多水| 毛片一级片免费看久久久久 | 久久久久国产精品人妻aⅴ院| 一进一出抽搐gif免费好疼| 国产三级在线视频| 国产成年人精品一区二区| 嫩草影院新地址| 中亚洲国语对白在线视频| 少妇人妻精品综合一区二区 | 99久国产av精品| 啦啦啦韩国在线观看视频| h日本视频在线播放| 精品一区二区三区人妻视频| 婷婷精品国产亚洲av在线| 变态另类丝袜制服| 国产视频内射| 夜夜看夜夜爽夜夜摸| 亚洲熟妇熟女久久| 中文字幕免费在线视频6| 亚洲中文字幕日韩| 亚洲性夜色夜夜综合| 老司机午夜福利在线观看视频| 99久久九九国产精品国产免费| 国产精品免费一区二区三区在线| 少妇人妻精品综合一区二区 | 最近视频中文字幕2019在线8| 又爽又黄无遮挡网站| 波野结衣二区三区在线| 哪里可以看免费的av片| 成年女人毛片免费观看观看9| 国语自产精品视频在线第100页| 国产高清视频在线观看网站| 国产精品伦人一区二区| 国产一级毛片七仙女欲春2| 国产黄a三级三级三级人| 国产视频内射| 亚洲国产高清在线一区二区三| 午夜福利免费观看在线| 国内久久婷婷六月综合欲色啪| 日本黄大片高清| 国产精品爽爽va在线观看网站| 成人亚洲精品av一区二区| 久久精品91蜜桃| 午夜福利免费观看在线| 内地一区二区视频在线| 成人国产一区最新在线观看| 18禁裸乳无遮挡免费网站照片| 免费一级毛片在线播放高清视频| av欧美777| 美女cb高潮喷水在线观看| 日韩欧美在线乱码| 精品乱码久久久久久99久播| 欧美中文日本在线观看视频| 午夜福利在线观看免费完整高清在 | 狂野欧美白嫩少妇大欣赏| 少妇熟女aⅴ在线视频| 日韩欧美三级三区| 色综合欧美亚洲国产小说| 亚洲电影在线观看av| 乱人视频在线观看| 99久久成人亚洲精品观看| 嫩草影视91久久| 免费人成视频x8x8入口观看| 国产亚洲精品综合一区在线观看| 在线免费观看的www视频| 午夜激情欧美在线| 小说图片视频综合网站| 亚洲人成电影免费在线| 搞女人的毛片| 久久久久久久午夜电影| 最近最新中文字幕大全电影3| 久久精品人妻少妇| 精品久久久久久久末码| 91九色精品人成在线观看| 他把我摸到了高潮在线观看| 男人狂女人下面高潮的视频| 不卡一级毛片| 一个人观看的视频www高清免费观看| 免费在线观看日本一区| www日本黄色视频网| 国产精华一区二区三区| 欧美日韩瑟瑟在线播放| 一二三四社区在线视频社区8| 首页视频小说图片口味搜索| 日本免费一区二区三区高清不卡| 欧美成人性av电影在线观看| 成人美女网站在线观看视频| www日本黄色视频网| 国产欧美日韩一区二区精品| 国产黄片美女视频| 综合色av麻豆| 午夜精品一区二区三区免费看| 搡老岳熟女国产| 国产欧美日韩一区二区精品| 国产精品1区2区在线观看.| a级毛片免费高清观看在线播放| 国产久久久一区二区三区| 国产爱豆传媒在线观看| 在线观看午夜福利视频| 黄色一级大片看看| 琪琪午夜伦伦电影理论片6080| 亚洲国产精品久久男人天堂| 久久人人精品亚洲av| 国产精品久久视频播放| 亚洲最大成人中文| 俄罗斯特黄特色一大片| 又黄又爽又刺激的免费视频.| 国产午夜精品久久久久久一区二区三区 | 亚洲电影在线观看av| 制服丝袜大香蕉在线| 国内精品久久久久精免费| 日韩中字成人| 女人被狂操c到高潮| 一区二区三区激情视频| 一区二区三区四区激情视频 | 欧美在线一区亚洲| 99久久99久久久精品蜜桃| 色吧在线观看| 日本在线视频免费播放| eeuss影院久久| 无人区码免费观看不卡| 悠悠久久av| 亚洲精品影视一区二区三区av| 国产在线男女| 深夜精品福利| 乱码一卡2卡4卡精品| 深夜a级毛片| 国产欧美日韩一区二区精品| 亚洲国产高清在线一区二区三| 亚洲七黄色美女视频| 看片在线看免费视频| 久久精品国产清高在天天线| 国产久久久一区二区三区| 国产av在哪里看| 精品欧美国产一区二区三| h日本视频在线播放| 最近视频中文字幕2019在线8| 国产精品一区二区免费欧美| 他把我摸到了高潮在线观看| 免费黄网站久久成人精品 | 国产精品久久电影中文字幕| 国产三级中文精品| 美女cb高潮喷水在线观看| 国产探花极品一区二区| 丰满乱子伦码专区| 啦啦啦观看免费观看视频高清| 国内揄拍国产精品人妻在线| 国产成人欧美在线观看| 午夜福利在线在线| 51国产日韩欧美| 亚洲人成网站在线播放欧美日韩| 69人妻影院| 美女被艹到高潮喷水动态| 国产私拍福利视频在线观看| 亚洲美女搞黄在线观看 | 亚洲成人久久性| 欧美zozozo另类| 中文资源天堂在线| 久久久精品欧美日韩精品| 亚洲在线观看片| 久久99热这里只有精品18| 一级av片app| 亚洲精品亚洲一区二区| 一级作爱视频免费观看| 国产免费一级a男人的天堂| 久久天躁狠狠躁夜夜2o2o| 91九色精品人成在线观看| 床上黄色一级片| 丰满人妻熟妇乱又伦精品不卡| 一级a爱片免费观看的视频| 国产精品美女特级片免费视频播放器| 999久久久精品免费观看国产| 亚洲国产精品成人综合色| 欧美+日韩+精品| 色综合站精品国产| 精品久久久久久久人妻蜜臀av| 精品乱码久久久久久99久播| 国产 一区 欧美 日韩| 久久精品夜夜夜夜夜久久蜜豆| 欧美3d第一页| 精品久久久久久,| 亚洲成人久久爱视频| 不卡一级毛片| 好男人在线观看高清免费视频| 小说图片视频综合网站| 97热精品久久久久久| 黄色一级大片看看| 99国产精品一区二区蜜桃av| 国产精品一区二区三区四区免费观看 | av天堂在线播放| 99精品久久久久人妻精品| 亚洲电影在线观看av| 一区二区三区免费毛片| 日本成人三级电影网站| 18禁裸乳无遮挡免费网站照片| 伦理电影大哥的女人| 俄罗斯特黄特色一大片| 国产亚洲精品av在线| 亚洲熟妇熟女久久| 中文字幕久久专区| 天堂动漫精品| 国产成人a区在线观看| 婷婷六月久久综合丁香| 午夜福利成人在线免费观看| 97人妻精品一区二区三区麻豆| 亚洲成a人片在线一区二区| 91午夜精品亚洲一区二区三区 | 免费观看精品视频网站| 天堂动漫精品| 午夜精品一区二区三区免费看| 久久中文看片网| www.熟女人妻精品国产| 国产精品一及| 久久久久久久亚洲中文字幕 | 午夜视频国产福利| 国产黄a三级三级三级人| 欧美一级a爱片免费观看看| 国产免费av片在线观看野外av| 国产v大片淫在线免费观看| 国产午夜精品久久久久久一区二区三区 | 中文字幕人成人乱码亚洲影| 精品99又大又爽又粗少妇毛片 | 毛片一级片免费看久久久久 | 日韩欧美 国产精品| 给我免费播放毛片高清在线观看| 不卡一级毛片| 国产人妻一区二区三区在| 三级男女做爰猛烈吃奶摸视频| 亚洲aⅴ乱码一区二区在线播放| 亚洲va日本ⅴa欧美va伊人久久| 日韩欧美免费精品| 成人高潮视频无遮挡免费网站| 精品免费久久久久久久清纯| 婷婷亚洲欧美| 色精品久久人妻99蜜桃| 国产乱人伦免费视频| 色播亚洲综合网| 激情在线观看视频在线高清| 午夜福利在线观看吧| 婷婷精品国产亚洲av| 欧美黑人巨大hd| 国语自产精品视频在线第100页| 夜夜爽天天搞| 欧美最新免费一区二区三区 | 国产精品乱码一区二三区的特点| 日本a在线网址| 亚洲一区二区三区不卡视频| 一级毛片久久久久久久久女| 国内精品一区二区在线观看| 中亚洲国语对白在线视频| 婷婷精品国产亚洲av| 最近中文字幕高清免费大全6 | 成人特级黄色片久久久久久久| 嫁个100分男人电影在线观看| 亚洲成人免费电影在线观看| 1024手机看黄色片| 国产乱人视频| 最新在线观看一区二区三区| 亚洲美女黄片视频| 欧美中文日本在线观看视频| av欧美777| 日本在线视频免费播放| 99热只有精品国产| 窝窝影院91人妻| 国产一区二区亚洲精品在线观看| 国产亚洲精品av在线| 俄罗斯特黄特色一大片| 757午夜福利合集在线观看| 亚洲av熟女| 国产白丝娇喘喷水9色精品| 亚洲aⅴ乱码一区二区在线播放| 黄色一级大片看看| 午夜老司机福利剧场| 亚洲电影在线观看av| 亚洲欧美日韩高清专用| 此物有八面人人有两片| 男人狂女人下面高潮的视频| 国产高清激情床上av| 亚洲美女搞黄在线观看 | 3wmmmm亚洲av在线观看| 黄色丝袜av网址大全| www.色视频.com| 国产 一区 欧美 日韩| 亚洲自偷自拍三级| 午夜视频国产福利| 天美传媒精品一区二区| 亚洲av五月六月丁香网| 午夜福利视频1000在线观看| 亚洲专区中文字幕在线| 久久久国产成人精品二区| eeuss影院久久| 别揉我奶头 嗯啊视频| 高清日韩中文字幕在线| 可以在线观看毛片的网站| 欧美性猛交黑人性爽| 91狼人影院| av视频在线观看入口| 免费av不卡在线播放| 男插女下体视频免费在线播放| 身体一侧抽搐| 简卡轻食公司| 日韩成人在线观看一区二区三区| 99久国产av精品| 久久这里只有精品中国| 久久久精品大字幕| 精品久久国产蜜桃| 国产免费男女视频| 国产精品久久视频播放| 国产极品精品免费视频能看的| 欧美日韩福利视频一区二区| 亚洲自拍偷在线| 99热这里只有精品一区| 日本精品一区二区三区蜜桃| 亚洲av中文字字幕乱码综合| 亚洲av第一区精品v没综合| 亚洲经典国产精华液单 | 国内精品美女久久久久久| 国产成人aa在线观看| 亚洲av成人不卡在线观看播放网| 精品日产1卡2卡| 久久久久久久久大av| 久久久久久久亚洲中文字幕 | 小蜜桃在线观看免费完整版高清| 精品免费久久久久久久清纯| 国产视频一区二区在线看| 毛片女人毛片| 99国产极品粉嫩在线观看| 久久久国产成人精品二区| 国产精华一区二区三区| 黄色日韩在线| 麻豆成人午夜福利视频| 最好的美女福利视频网| 久久精品国产亚洲av天美| 国产成年人精品一区二区| 国产av麻豆久久久久久久| 偷拍熟女少妇极品色| 国产白丝娇喘喷水9色精品| a在线观看视频网站| 欧美一区二区精品小视频在线| 狂野欧美白嫩少妇大欣赏| 成人三级黄色视频| 在线播放国产精品三级| 国产三级黄色录像| 欧美精品啪啪一区二区三区| 久久性视频一级片| 波多野结衣高清无吗| 人妻久久中文字幕网| 欧美午夜高清在线| 国产在线男女| 日韩av在线大香蕉| 永久网站在线| 女人被狂操c到高潮| 日本 av在线| 久久久久久久亚洲中文字幕 | 亚洲色图av天堂| 午夜福利视频1000在线观看| 亚洲精品亚洲一区二区| 中文字幕免费在线视频6| 宅男免费午夜| 欧美日本视频| 在线观看午夜福利视频| 久久热精品热| 如何舔出高潮| 在线免费观看的www视频| 色综合婷婷激情| 国产高清有码在线观看视频| 国产极品精品免费视频能看的| aaaaa片日本免费| 久久精品国产自在天天线| 99热这里只有是精品50| 乱人视频在线观看| 三级男女做爰猛烈吃奶摸视频| 亚洲欧美日韩高清专用| 91av网一区二区| 中文字幕人妻熟人妻熟丝袜美| 琪琪午夜伦伦电影理论片6080| 欧美精品啪啪一区二区三区| 免费观看的影片在线观看| av天堂在线播放| 亚洲avbb在线观看| 麻豆国产97在线/欧美| 国产精品99久久久久久久久| 一边摸一边抽搐一进一小说| 日韩欧美国产一区二区入口| 亚洲人成网站在线播| 一进一出好大好爽视频| 成人精品一区二区免费| 欧美黑人巨大hd| 1000部很黄的大片| 欧美成人免费av一区二区三区| 丰满人妻一区二区三区视频av| 9191精品国产免费久久| 亚洲精华国产精华精| 中文字幕av成人在线电影| 久久草成人影院| 亚洲自偷自拍三级| 91狼人影院| 一本久久中文字幕| 国产精品一区二区性色av| 国产成人欧美在线观看| 在线免费观看的www视频| 国产精品人妻久久久久久| 最近最新免费中文字幕在线| 精品人妻偷拍中文字幕| 欧洲精品卡2卡3卡4卡5卡区| 有码 亚洲区| 欧美不卡视频在线免费观看| 久久久国产成人免费| www日本黄色视频网| 国产大屁股一区二区在线视频| 欧美性猛交黑人性爽| 黄色配什么色好看| 久99久视频精品免费| 深夜a级毛片| 成人美女网站在线观看视频| 在线观看美女被高潮喷水网站 | 99国产精品一区二区蜜桃av| 永久网站在线| 亚洲欧美精品综合久久99| 丰满人妻一区二区三区视频av| 91狼人影院| 97热精品久久久久久| 日本五十路高清| 别揉我奶头 嗯啊视频| a级毛片a级免费在线| 激情在线观看视频在线高清| 真人一进一出gif抽搐免费| 婷婷色综合大香蕉| 国产在线精品亚洲第一网站| 听说在线观看完整版免费高清| 在线观看66精品国产| 在线看三级毛片| 久久久久久久久大av| 欧美日韩国产亚洲二区| 免费观看的影片在线观看| 成人三级黄色视频| 亚洲欧美日韩高清在线视频| 一夜夜www| 9191精品国产免费久久| 午夜福利在线观看吧| 亚洲精品一区av在线观看| av在线老鸭窝| 欧美日韩乱码在线| 国产一级毛片七仙女欲春2| 极品教师在线视频| 国产精品三级大全| 亚洲av二区三区四区| 在线看三级毛片| 免费av毛片视频| 韩国av一区二区三区四区| 国模一区二区三区四区视频| 亚洲专区中文字幕在线| 别揉我奶头 嗯啊视频| 黄色视频,在线免费观看| 小说图片视频综合网站| 又爽又黄无遮挡网站| 亚洲av美国av| 国产精品一区二区三区四区免费观看 | 丰满的人妻完整版| 啦啦啦韩国在线观看视频| 亚洲av第一区精品v没综合| 久久久久久九九精品二区国产| 亚洲男人的天堂狠狠| 国产一区二区激情短视频| 婷婷精品国产亚洲av| 久久99热6这里只有精品| 亚州av有码| 少妇高潮的动态图| 老司机午夜十八禁免费视频| 美女黄网站色视频| 亚洲国产精品合色在线| 午夜精品久久久久久毛片777| 99久久精品热视频| 国产精品人妻久久久久久| 国产亚洲精品久久久com| 少妇人妻一区二区三区视频| 丁香六月欧美| 毛片一级片免费看久久久久 | 美女黄网站色视频| 国产伦一二天堂av在线观看| 在现免费观看毛片| 美女免费视频网站| 少妇的逼水好多| 成人无遮挡网站| 精华霜和精华液先用哪个| 欧美最黄视频在线播放免费| 中国美女看黄片| 人人妻人人澡欧美一区二区| 免费在线观看日本一区| 嫩草影院入口| 成人三级黄色视频| 亚洲中文日韩欧美视频| 美女cb高潮喷水在线观看| 久久精品夜夜夜夜夜久久蜜豆| 真人做人爱边吃奶动态| 18禁裸乳无遮挡免费网站照片|