• <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
    欧美少妇被猛烈插入视频| 美女国产视频在线观看| 高清毛片免费看| 99热6这里只有精品| 国产精品一及| 交换朋友夫妻互换小说| 欧美高清成人免费视频www| 直男gayav资源| xxx大片免费视频| 在线观看免费高清a一片| 久久精品国产亚洲av涩爱| 婷婷色av中文字幕| 久久99热这里只频精品6学生| freevideosex欧美| 久久精品国产亚洲av涩爱| 99热这里只有精品一区| 久久韩国三级中文字幕| 久久99热这里只有精品18| 伊人久久精品亚洲午夜| 久久99热6这里只有精品| 91狼人影院| 嘟嘟电影网在线观看| 听说在线观看完整版免费高清| 肉色欧美久久久久久久蜜桃 | 国产白丝娇喘喷水9色精品| 亚洲国产色片| 美女国产视频在线观看| 亚洲精品aⅴ在线观看| 一级爰片在线观看| 晚上一个人看的免费电影| 精品一区二区三区视频在线| 能在线免费看毛片的网站| 亚洲精品国产成人久久av| 少妇人妻久久综合中文| 黄色日韩在线| 伊人久久精品亚洲午夜| 久久人人爽人人片av| 久久99精品国语久久久| 精品99又大又爽又粗少妇毛片| 欧美日韩国产mv在线观看视频 | 国产精品成人在线| 欧美最新免费一区二区三区| 国产淫语在线视频| 狂野欧美白嫩少妇大欣赏| 久久人人爽av亚洲精品天堂 | 亚洲成人精品中文字幕电影| 国产熟女欧美一区二区| 91精品一卡2卡3卡4卡| 亚洲图色成人| 国产美女午夜福利| 久久6这里有精品| 国国产精品蜜臀av免费| 国产精品秋霞免费鲁丝片| 国产伦在线观看视频一区| 99久久精品热视频| 国产高潮美女av| 美女脱内裤让男人舔精品视频| 特级一级黄色大片| 美女高潮的动态| 嫩草影院入口| 在线观看国产h片| 最近中文字幕高清免费大全6| 日本av手机在线免费观看| 国产免费视频播放在线视频| 国产精品爽爽va在线观看网站| 免费电影在线观看免费观看| 国内精品美女久久久久久| 色网站视频免费| 亚洲欧美日韩东京热| 欧美+日韩+精品| 国产毛片在线视频| 久久亚洲国产成人精品v| 人妻 亚洲 视频| 国产毛片在线视频| 欧美zozozo另类| 99九九线精品视频在线观看视频| 日韩欧美精品v在线| 精品少妇黑人巨大在线播放| 亚洲欧美中文字幕日韩二区| 亚洲婷婷狠狠爱综合网| 成人国产av品久久久| 中文字幕制服av| 亚洲精品中文字幕在线视频 | 观看免费一级毛片| 亚洲精品一区蜜桃| 欧美成人精品欧美一级黄| 婷婷色综合www| 久久精品久久精品一区二区三区| 精品人妻偷拍中文字幕| 如何舔出高潮| 国产中年淑女户外野战色| 久久午夜福利片| 美女xxoo啪啪120秒动态图| 在线观看免费高清a一片| 色播亚洲综合网| 97在线视频观看| 七月丁香在线播放| 自拍欧美九色日韩亚洲蝌蚪91 | 一级a做视频免费观看| 成人国产av品久久久| 大又大粗又爽又黄少妇毛片口| 国产视频内射| 欧美xxxx性猛交bbbb| 99九九线精品视频在线观看视频| 国产高清不卡午夜福利| 免费少妇av软件| 久久久a久久爽久久v久久| 91久久精品国产一区二区成人| 精品久久国产蜜桃| 亚洲内射少妇av| 丰满乱子伦码专区| 国产视频首页在线观看| 色哟哟·www| 欧美精品国产亚洲| 国产男人的电影天堂91| 男女国产视频网站| 免费看a级黄色片| 亚洲一区二区三区欧美精品 | av一本久久久久| 免费观看a级毛片全部| 成年版毛片免费区| 精品酒店卫生间| 夜夜爽夜夜爽视频| 国产亚洲av片在线观看秒播厂| 老女人水多毛片| 大又大粗又爽又黄少妇毛片口| 99久久精品一区二区三区| 国产伦理片在线播放av一区| av在线亚洲专区| 大又大粗又爽又黄少妇毛片口| 国产色爽女视频免费观看| 男女那种视频在线观看| 晚上一个人看的免费电影| 久久久久九九精品影院| 国产av不卡久久| 亚洲精品视频女| 国产女主播在线喷水免费视频网站| 亚洲成人av在线免费| www.av在线官网国产| 国产伦在线观看视频一区| 免费av观看视频| 久久精品国产亚洲av涩爱| 国产成人精品福利久久| 欧美+日韩+精品| 国产成人freesex在线| 日本熟妇午夜| 精品一区二区三卡| 中文字幕制服av| 国产综合懂色| 国产日韩欧美亚洲二区| 乱码一卡2卡4卡精品| 联通29元200g的流量卡| 亚洲欧美成人精品一区二区| 内射极品少妇av片p| 亚洲丝袜综合中文字幕| 久久久久久久久久久丰满| 狠狠精品人妻久久久久久综合| 中文字幕亚洲精品专区| 高清在线视频一区二区三区| 成人亚洲精品av一区二区| 亚洲不卡免费看| 别揉我奶头 嗯啊视频| 中文在线观看免费www的网站| 成人综合一区亚洲| 97超碰精品成人国产| 国产探花极品一区二区| 亚洲国产高清在线一区二区三| 亚洲精品亚洲一区二区| 国产免费福利视频在线观看| 国产一区二区三区综合在线观看 | 美女脱内裤让男人舔精品视频| 国产欧美亚洲国产| av在线app专区| 80岁老熟妇乱子伦牲交| 熟女av电影| 国产毛片在线视频| 在线天堂最新版资源| 国产免费福利视频在线观看| 美女主播在线视频| 2018国产大陆天天弄谢| 精品久久久精品久久久| 日本一二三区视频观看| 51国产日韩欧美| 亚洲国产成人一精品久久久| 别揉我奶头 嗯啊视频| 日韩电影二区| 亚洲欧美日韩另类电影网站 | 又爽又黄a免费视频| 亚洲欧美日韩卡通动漫| 国国产精品蜜臀av免费| 久久97久久精品| 毛片一级片免费看久久久久| 美女视频免费永久观看网站| 成人免费观看视频高清| 久久久亚洲精品成人影院| 国产精品一及| 麻豆久久精品国产亚洲av| 日韩国内少妇激情av| 人人妻人人爽人人添夜夜欢视频 | 久久女婷五月综合色啪小说 | 亚洲精品aⅴ在线观看| av播播在线观看一区| 欧美bdsm另类| 亚洲精品国产色婷婷电影| 搡老乐熟女国产| 国语对白做爰xxxⅹ性视频网站| 五月天丁香电影| 亚洲国产色片| 中文字幕人妻熟人妻熟丝袜美| 久热久热在线精品观看| 又黄又爽又刺激的免费视频.| 人人妻人人看人人澡| 美女脱内裤让男人舔精品视频| av在线观看视频网站免费| 99热网站在线观看| 亚洲精品乱久久久久久| 男女边吃奶边做爰视频| 在线观看美女被高潮喷水网站| 国产精品久久久久久av不卡| 男人爽女人下面视频在线观看| 青春草国产在线视频| 性色avwww在线观看| 久久久久网色| 亚洲不卡免费看| 成人综合一区亚洲| 一个人看的www免费观看视频| 熟女电影av网| 亚洲自拍偷在线| 精品一区二区免费观看| 欧美少妇被猛烈插入视频| 性插视频无遮挡在线免费观看| 女人被狂操c到高潮| 国产视频内射| 国产大屁股一区二区在线视频| 在线亚洲精品国产二区图片欧美 | 一边亲一边摸免费视频| 777米奇影视久久| 2018国产大陆天天弄谢| 日韩强制内射视频| 亚洲欧美日韩卡通动漫| 99久国产av精品国产电影| 中文字幕亚洲精品专区| a级一级毛片免费在线观看| 成人亚洲欧美一区二区av| 日韩av在线免费看完整版不卡| 久久99热这里只有精品18| 色视频在线一区二区三区| 国产亚洲精品久久久com| 在现免费观看毛片| 美女内射精品一级片tv| 韩国av在线不卡| 亚洲精品中文字幕在线视频 | 新久久久久国产一级毛片| 国产免费又黄又爽又色| kizo精华| 欧美最新免费一区二区三区| 日日摸夜夜添夜夜添av毛片| 久久久久久久久久人人人人人人| 亚洲第一区二区三区不卡| 1000部很黄的大片| 婷婷色综合大香蕉| 中国三级夫妇交换| 我要看日韩黄色一级片| 亚洲aⅴ乱码一区二区在线播放| 中文乱码字字幕精品一区二区三区| 又爽又黄无遮挡网站| 直男gayav资源| 另类亚洲欧美激情| 国内精品美女久久久久久| 亚洲国产av新网站| 69人妻影院| 亚洲精品中文字幕在线视频 | 国产精品蜜桃在线观看| 精品久久久噜噜| 国产成人一区二区在线| 欧美最新免费一区二区三区| 黄片无遮挡物在线观看| 亚洲av.av天堂| 国产av国产精品国产| 欧美xxxx性猛交bbbb| 真实男女啪啪啪动态图| 成年版毛片免费区| 交换朋友夫妻互换小说| 国产伦精品一区二区三区视频9| 国产黄a三级三级三级人| 精品久久久精品久久久| 国产一级毛片在线| 午夜免费男女啪啪视频观看| 国产欧美日韩精品一区二区| 亚洲av中文字字幕乱码综合| 熟妇人妻不卡中文字幕| 日本三级黄在线观看| av在线亚洲专区| 色5月婷婷丁香| 22中文网久久字幕| 2021天堂中文幕一二区在线观| 免费电影在线观看免费观看| 一本色道久久久久久精品综合| 国产黄a三级三级三级人| 一区二区三区四区激情视频| 麻豆成人午夜福利视频| 蜜桃久久精品国产亚洲av| 特级一级黄色大片| 久久99精品国语久久久| 菩萨蛮人人尽说江南好唐韦庄| 亚洲色图综合在线观看| 在线免费观看不下载黄p国产| 亚洲三级黄色毛片| 亚洲色图av天堂| 久久99蜜桃精品久久| 又大又黄又爽视频免费| 中文精品一卡2卡3卡4更新| 国产综合精华液| 久久午夜福利片| av女优亚洲男人天堂| 中文字幕亚洲精品专区| 国产伦精品一区二区三区四那| 国产男女超爽视频在线观看| 街头女战士在线观看网站| 国产av不卡久久| 天天躁日日操中文字幕| 下体分泌物呈黄色| 日日啪夜夜爽| 成年版毛片免费区| 男女啪啪激烈高潮av片| 国产精品三级大全| 男的添女的下面高潮视频| 美女国产视频在线观看| 精品久久久久久久末码| 免费看av在线观看网站| 午夜视频国产福利| 男的添女的下面高潮视频| 午夜激情久久久久久久| 国产老妇伦熟女老妇高清| 在线观看一区二区三区激情| 全区人妻精品视频| 亚洲av男天堂| 一级毛片我不卡| 涩涩av久久男人的天堂| 亚洲色图av天堂| 亚洲一区二区三区欧美精品 | 日韩制服骚丝袜av| 国产成人a∨麻豆精品| 久热久热在线精品观看| 人人妻人人看人人澡| 欧美亚洲 丝袜 人妻 在线| 97热精品久久久久久| 国产v大片淫在线免费观看| 日韩国内少妇激情av| 男女啪啪激烈高潮av片| 欧美精品国产亚洲| av在线天堂中文字幕| 热re99久久精品国产66热6| 欧美高清性xxxxhd video| 国产成人a区在线观看| 色综合色国产| 亚洲精品乱码久久久久久按摩| 亚洲怡红院男人天堂| 亚洲av一区综合| 久久久久网色| tube8黄色片| 人人妻人人看人人澡| 老司机影院毛片| 国产精品一及| 国产片特级美女逼逼视频| 又爽又黄a免费视频| 99视频精品全部免费 在线| 日日撸夜夜添| 欧美成人a在线观看| 国产综合懂色| 插逼视频在线观看| 日韩不卡一区二区三区视频在线| 国精品久久久久久国模美| 日日啪夜夜爽| 中文天堂在线官网| 午夜免费鲁丝| 九九爱精品视频在线观看| 天堂网av新在线| 纵有疾风起免费观看全集完整版| 一区二区av电影网| 国产成人免费无遮挡视频| 欧美成人精品欧美一级黄| 免费看光身美女| 美女主播在线视频| 一区二区三区四区激情视频| 男人狂女人下面高潮的视频| 日日摸夜夜添夜夜添av毛片| 亚洲精品自拍成人| 国产黄片视频在线免费观看| 亚洲美女搞黄在线观看| 午夜福利在线观看免费完整高清在| 少妇裸体淫交视频免费看高清| 免费在线观看成人毛片| 美女脱内裤让男人舔精品视频| 国产 一区精品| 亚洲色图综合在线观看| 精品人妻一区二区三区麻豆| 国产精品一区二区性色av| 激情五月婷婷亚洲| 亚洲久久久久久中文字幕| 国产高清不卡午夜福利| 草草在线视频免费看| av国产久精品久网站免费入址| 成年女人在线观看亚洲视频 | 久久久国产一区二区| 久久久久久久大尺度免费视频| 综合色av麻豆| 国产男女内射视频| 综合色av麻豆| 亚洲国产最新在线播放| 精品人妻熟女av久视频| 国产高清国产精品国产三级 | 久久精品综合一区二区三区| 国产精品久久久久久av不卡| 最近手机中文字幕大全| 如何舔出高潮| av天堂中文字幕网| 91在线精品国自产拍蜜月| 亚洲精品一区蜜桃| 国内少妇人妻偷人精品xxx网站| 国产精品女同一区二区软件| 亚洲不卡免费看| 中文天堂在线官网| 亚洲av一区综合| 观看免费一级毛片| 国产成人精品久久久久久| 中国国产av一级| 国产91av在线免费观看| 三级国产精品欧美在线观看| 一级毛片久久久久久久久女| 99久久人妻综合| 三级国产精品欧美在线观看| 亚洲色图综合在线观看| 涩涩av久久男人的天堂| 亚洲精品,欧美精品| 精品久久久精品久久久| 亚洲av中文字字幕乱码综合| 免费看a级黄色片| 校园人妻丝袜中文字幕| av在线老鸭窝| 97人妻精品一区二区三区麻豆| 国产免费一区二区三区四区乱码| 日本一本二区三区精品| 汤姆久久久久久久影院中文字幕| 国模一区二区三区四区视频| 国产在线男女| 国产一区二区在线观看日韩| 亚洲欧美日韩卡通动漫| 日日啪夜夜爽| 亚洲电影在线观看av| 啦啦啦在线观看免费高清www| 超碰97精品在线观看| 制服丝袜香蕉在线| 久久精品综合一区二区三区| 成人鲁丝片一二三区免费| 亚洲色图av天堂| 搡女人真爽免费视频火全软件| 日日摸夜夜添夜夜爱| 亚洲图色成人| 亚洲国产高清在线一区二区三| 久久99热这里只有精品18| 日本猛色少妇xxxxx猛交久久| 麻豆精品久久久久久蜜桃| 波野结衣二区三区在线| 777米奇影视久久| 国产视频内射| 五月开心婷婷网| 亚洲欧洲国产日韩| 成年人午夜在线观看视频| 日韩视频在线欧美| 国产精品福利在线免费观看| 亚洲精品国产av成人精品| 亚洲性久久影院| 高清日韩中文字幕在线| 少妇人妻精品综合一区二区| 亚洲欧美日韩东京热| 黑人高潮一二区| 97精品久久久久久久久久精品| av福利片在线观看| 国产成年人精品一区二区| 久久久久性生活片| 人体艺术视频欧美日本| 一本—道久久a久久精品蜜桃钙片 精品乱码久久久久久99久播 | videossex国产| 久久久久久久久久成人| 日日撸夜夜添| 国产精品一二三区在线看| 亚洲第一区二区三区不卡| 色视频在线一区二区三区| av在线老鸭窝| 精华霜和精华液先用哪个| 毛片一级片免费看久久久久| 久久久久久久亚洲中文字幕| 成人毛片a级毛片在线播放| 亚洲精品,欧美精品| 久久99热这里只频精品6学生| 国产综合懂色| 1000部很黄的大片| 亚洲精品影视一区二区三区av| 亚洲最大成人中文| 国产亚洲91精品色在线| 丝瓜视频免费看黄片| 精品久久久久久久久亚洲| 国产成人aa在线观看| www.av在线官网国产| 有码 亚洲区| 国产 一区 欧美 日韩| 深夜a级毛片| 亚洲欧美中文字幕日韩二区| 国产一区二区三区综合在线观看 | 如何舔出高潮| 亚洲激情五月婷婷啪啪| 国产成人免费无遮挡视频| 99热这里只有是精品50| 哪个播放器可以免费观看大片| 国语对白做爰xxxⅹ性视频网站| 亚洲在线观看片| 男女下面进入的视频免费午夜| 免费看av在线观看网站| 国产免费一级a男人的天堂| 久久精品久久精品一区二区三区| 国产成人精品一,二区| 97人妻精品一区二区三区麻豆| 亚洲精品日本国产第一区| 免费大片黄手机在线观看| 亚洲内射少妇av| 别揉我奶头 嗯啊视频| 少妇人妻一区二区三区视频| 五月天丁香电影| 成人亚洲欧美一区二区av| 国产亚洲午夜精品一区二区久久 | 看黄色毛片网站| 日韩不卡一区二区三区视频在线| 秋霞在线观看毛片| av天堂中文字幕网| av卡一久久| 国产又色又爽无遮挡免| 国产精品久久久久久精品电影| 亚洲精品成人av观看孕妇| 身体一侧抽搐| 国产成人免费无遮挡视频| 午夜免费观看性视频| 丰满人妻一区二区三区视频av| 青春草国产在线视频| 免费av不卡在线播放| 男女国产视频网站| 午夜免费观看性视频| 少妇人妻久久综合中文| 亚洲精品456在线播放app| 最近中文字幕2019免费版| av在线天堂中文字幕| 国产色婷婷99| 看非洲黑人一级黄片| 美女高潮的动态| av网站免费在线观看视频| 婷婷色综合www| 亚洲在久久综合| 亚洲精品亚洲一区二区| 亚州av有码| 国产亚洲av嫩草精品影院| 九九爱精品视频在线观看| 国产又色又爽无遮挡免| 精品人妻偷拍中文字幕| 一边亲一边摸免费视频| 国产在视频线精品| 日本三级黄在线观看| 九草在线视频观看| 26uuu在线亚洲综合色| 女人十人毛片免费观看3o分钟| 18禁动态无遮挡网站| 国产高清不卡午夜福利| av免费在线看不卡| 2021少妇久久久久久久久久久| 久久精品国产a三级三级三级| 黄色一级大片看看| av免费在线看不卡| 人妻系列 视频| 精品少妇黑人巨大在线播放| av播播在线观看一区| 国产免费一区二区三区四区乱码| 真实男女啪啪啪动态图| 国产高潮美女av| 久久99热这里只频精品6学生| 午夜精品国产一区二区电影 | a级一级毛片免费在线观看| 在线看a的网站| 少妇的逼好多水| 国产中年淑女户外野战色| www.av在线官网国产| eeuss影院久久| 在现免费观看毛片| 免费观看av网站的网址| 91精品伊人久久大香线蕉| 亚洲在久久综合| 亚洲精品久久午夜乱码| 免费看光身美女| 卡戴珊不雅视频在线播放| 白带黄色成豆腐渣| 成人无遮挡网站| 欧美日韩综合久久久久久| videossex国产| 亚洲欧美精品自产自拍| 好男人在线观看高清免费视频| 亚洲精品aⅴ在线观看| 欧美xxxx性猛交bbbb| 少妇熟女欧美另类| 中文字幕av成人在线电影| 一级黄片播放器| 蜜臀久久99精品久久宅男| 免费在线观看成人毛片| 国产亚洲5aaaaa淫片| 午夜福利高清视频| 热99国产精品久久久久久7| 成年女人看的毛片在线观看| 午夜爱爱视频在线播放|