• <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 ?

    Rolling velocity and relative motion of particle detector in local granular flow

    2022-11-21 09:29:18RanLi李然BaoLinLiu劉寶林GangZheng鄭剛andHuiYang楊暉
    Chinese Physics B 2022年11期
    關(guān)鍵詞:鄭剛李然寶林

    Ran Li(李然) Bao-Lin Liu(劉寶林) Gang Zheng(鄭剛) and Hui Yang(楊暉)

    1School of Health Science and Engineering,University of Shanghai for Science and Technology,Shanghai 200093,China

    2School of Optical-Electrical and Computer Engineering,University of Shanghai for Science and Technology,Shanghai 200093,China

    The velocity of a particle detector in granular flow can be regarded as the combination of rolling and sliding velocities.The study of the contribution of rolling velocity and sliding velocity provides a new explanation to the relative motion between the detector and the local granular flow. In this study, a spherical detector using embedded inertial navigation technology is placed in the chute granular flow to study the movement of the detector relative to the granular flow. It is shown by particle image velocimetry(PIV)that the velocity of chute granular flow conforms to Silbert’s formula. And the velocity of the detector is greater than that of the granular flow around it. By decomposing the velocity into sliding and rolling velocity,it is indicated that the movement of the detector relative to the granular flow is mainly caused by rolling.The rolling detail shown by DEM simulation leads to two potential mechanisms based on the position and drive of the detector.

    Keywords: local velocity distribution,rolling velocity,inertial navigation technology,relative velocity dependent(RVD)rolling friction

    1. Introduction

    Traditional granular flow velocity distribution is studied usually[1]by using the monodisperse granular flow for the exploration of flow models[2,3]while the the research of polydisperse particle flow focuses on the mechanism of mixing and segregation.[4,5]However, there is a special particle flow of a few special particles worthy of attention in the nearly monodisperse granular flow,e.g.,rock landslides with accompanying debris flows are examples of such particle flows.[6]The number of special particles cannot form the statistical characteristics to support the segregation and mixing model exploration. The description of the movement of the special particles relative to the granular flow is very lacking. This process can be studied by placing inertial navigation detector into the chute granular flow,which can provide a valuable reference for the study of the movement process of special particles.

    In the absence of a unified framework,granular flows in a chute are commonly divided into three different regimes based on the inertial number.[7]This study focuses on the viscouslike regime. The material flow is more like a liquid with a shear-rate-dependent stress under this regime.[8]

    The local rheology is the most widely recognized mathematical model for viscous-like granular flow in an inclined chute.[9,10]Forterre and Pouliquen[11]and Tripathi and Khakha[12]summarized the local flow velocity distribution model as shown in Fig. 1(a). A granular layer of thicknesshflows down a rough plane inclined at an angle 8°<θ <12°.The force balance for steady uniform flows implies that the ratio between shear stress and normal stress is constant and equal to tanθ. Experimentally or numerically, the mean velocity varies as the power 3/2 of the depth and increases with inclination. The physical mechanism is the nonlinear correlation between the friction coefficientμand the inertial numberI[7,9]in the quasi static and kinetic regime,specifically

    which is shown in Fig.1(b).

    However,this model does not distinguish between the velocity caused by particle sliding and that by particle rolling.The latest research shows that rolling has an important influence on the movement of granular flow.[13,14]

    Wanget al. reported a study on the granular flow layers by using the embedded inertial navigation techniques.[15]This provides a new method of studying particle rolling in a particle flow. Caviezelet al.studied rockfall on Alps by using a detector equipped with a situ sensor,and successfully reconstructed the falling trajectory of the detector.[16,17]Zhuet al.improved the navigation techniques and applied them to the study of the funnel flow particle rolling in the laboratory, and accurately measured the angular velocity distribution of the tracer particles in the funnel flow.[18]It was found that there is a close relationship between rolling and the granular flow velocity distribution. This provides an important reference for the study of the relative particle flow motion of special particles.

    Fig.1. Local flow velocity distribution in chute granular flow:(a)schematic diagram of flat inclined chute and(b)nonlinear correlation between friction coefficient and inertial number.[11,12]

    It should be noted that the PIV method and the xray method will not interfere with the particle flow and are a reliable method to measure the particle flow velocity distribution.[19]Since x-ray may offset the inertial navigation device,the PIV is chosen to measure the velocity distribution of chute granular flow which is used as the baseline. However,there are physical parameters which cannot be obtained by the experimental technology. With the development of computer technology, the discrete element method (DEM) is increasingly used in the granular flow mechanism research field.[20,21]The DEM can track the real-time motion of each particle,and obtain the particle’s rotational motion information.[22]The influence of rolling friction coefficient was investigated in Yu and Saxen’s DEM study of Silo.[23]Tripathiet al.adopted the relative velocity dependent(RVD)rolling friction in quantitative DEM simulation of non-spherical particle.[24]Taking the rolling friction into consideration in the model,the consistency of simulation results and experimental results is improved.

    In this work,the data obtained from DEM simulation validated by spherical detector experiments are used to study the local granular flow,attempting to identify the velocity of particle as the rolling and sliding velocity in local flow velocity so as to provide a new perspective for the study of the movement of special particles relative to granular flow.

    2. Experimental setups

    2.1. Chute granular flow

    Based on the theoretical model,the experimental process in this study can be seen in Fig. 2. The chute granular flow lasted 2.7 s on average and 2.8 s in this experiment served as an example. Att0=0,the baffle is removed and the particles started to move. The velocity distribution is unstable initially but att1=0.6 s, the chute granular flow forms a stable local flow velocity distribution. Aftert2=1.2 s,owing to the inadequate thickness of the particle bed in the chute,the local flow velocity distribution cannot be maintained.

    We use the PIV technique to obtain the velocity on the side wall of the chute, as shown in Fig. 2(d). The detector is used as the special particle of concern (diameter of 30 mm),surrounded by small particles(diameter of 10 mm)inside the chute. The spherical detector can obtain the particle’s acceleration and rotation angular velocity. Therefore, the particle velocities of different initial heights in the chute and the composition of particle velocity under different inclination angles are studied.The position of the spherical detector isZ1,Z2,Z3,...,Z6, with a spacing of 15 mm. The thickness of the filled particles in the chute is 110 mm. The diameter of the filled particles is 10 mm,and the diameter of the spherical detector is 30 mm. To ensure that the velocity of the bottom particle is 0,a rough surface with a coefficient of friction of 0.8 is set as the bottom of the chute. More detailed description of the system is given in Refs.[14,15].

    Fig. 2. Snapshots of chute granular flow, showing granular profile at (a)t0 =0, (b)t1 =0.6 s, chute granular flow formed stable local flow velocity distribution;(c)after t2=1.2 s,local flow velocity distribution failing to be maintained due to the inadequate thickness of the particle bed in the chute;(d)example displaying the granular flow at t=1 s to show the PIV measurement results.

    2.2. Spherical detector based on embedded inertial navigation technology

    The spherical detector is used to measure the angular velocity,acceleration and other movement data during the experiment through using embedded inertial navigation technology.

    Any attitude in three-dimensional space can be represented concisely, intuitively by Euler angles. The aerial sequential Euler angles (shown in Fig. 3(a)) are used to represent the attitude of spherical detectors,φ,χ,Ψ, respectively,as the roll angle,pitch angle,and yaw angle. In the carrier coordinate system of the spherical detector,xbmoves to the right along the horizontal axis,ybmoves forward along the longitudinal axis,andzbmoves along the vertical axis. In the spatial coordinate system (E),xEis the projection ofxbon the horizontal plane,yEis perpendicular toxE,andzEis perpendicular to the horizontal plane.

    Fig. 3. (a) Schematic diagram of attitude angle of spherical detector, with ω′x,ω′y,ω′z,respectively,representing the components of original angular velocity of rolling around the x axis,y axis,and z axis,and ωy being the angular velocity of rolling around the y axis; (b) results from a typical experiment with two detectors placed side by side at Z1.[14,15]

    The Euler angle is adopted in the measurement system to represent the attitude,and a quaternion is used to represent the attitude when it is solved.[25,26]The attitude update equation of the inertial measurement unit(ωx,ωy,andωzare the values that are measured by the gyroscope)is given as follows:

    whereqis the quaternion expression.Nis the unit matrix,Ωnnbis the skew matrix of angular velocity, andTis the time interval.

    Therefore, the attitude of the spherical detector is converted into a quaternion representation through the following equation during the attitude solution:

    After the attitude solution is completed, the attitude is converted into Euler angles throughthe following equation:

    Through multiple experiments, the experimental results of spherical particle wireless measurement technology based on inertial navigation technology are validated and can be used to measure the angular velocity and translational velocity of particles in the chute system.[15,18]

    Figure 3(b)shows a typical experimental results obtained by using two spherical detectors placed atZ1. It can be found that the movement process of the detectors can be divided into stable stage and unstable stage by the rotating speed.[14]To discuss the rolling and sliding of the detector,we focus on the relationship between the particle flow velocity distribution and the special tracer particle velocity characteristic from 0.6 s to 1 s(stable stage).

    2.3. DEM simulation

    2.3.1. DEM contact model

    The most important step in DEM is to choose a reasonable physical contact model. The model of Hertz–Mindlin(no slip)with RVD rolling friction adjusts the calculation method of rolling friction to ensure that three dimensions have the proper functionality without affecting the calculation time. It is especially suitable for strong rotation systems that have strict requirements for particle rotation characteristics.[24]Therefore,in this paper DEM is used based on the model of the Hertz–Mindlin(no slip)with RVD rolling friction contact to simulate the discharge process of spherical particles in a chute.According to the relative rotational velocity between contact particles,the particle rolling friction is calculated as follows:[27]

    where torqueτrepresents the rolling friction of the particles,μris the rolling friction coefficient,Fnis the normal force between particles,R*is the equivalent radius between particles, ?ωrelis the unit vector of relative rotational velocity,E*is the equivalent Young’s modulus,andδnis the normal overlap amount.

    The equivalent radiusR*and the equivalent Young’s modulusE*are calculated from the following equations:

    whereiandjrepresent the two particles in contact,RiandRjare the radii of the contact particles,viandvjare the Poisson’s ratio,EiandEjare the Young’s moduli.

    2.3.2. Simulation setup

    Figure 4(a)shows the theoretical model of chute flow defined three layers based on the velocity distribution.[28]The experimental results presented in Ref. [15] indicate that the rolling contribution rate is an important factor affecting velocity composition.Figure 4(b)shows the simulation chute crosssectional surface sliced into 30×60 grids,and each grid is the smallest statistical unit with a size of 10 mm×20 mm×10 mm.In the simulation, the average movement information of the particles in each grid is used. The simulation process is the same as the experimental process shown in Fig. 2. Three particles (d= 1 cm) in each layer are marked. A detector(d=3 cm)is placed in the granular bed atZpoint,near particle B.

    During the simulation,the time interval for collecting particle motion data is set to be 0.01 s. In order to ensure the stability of experiment,the minimum time step in experiment is set to be 2.71×10-5s,which is less than the Rayleigh time of particle 5.82×10-5s.[29]Other system parameters of DEM simulation are shown in Table 1.

    Among them, the friction coefficient between particlesμp-pis obtained by measuring the repose angle of particle accumulation, and the coefficient of restitutioneis obtained by the particle rebound experiment.[30]

    Fig.4. Simulation based on the velocity layers: (a)schematic model of the chute system and(b)geometry of chute with an initial packed bed.

    Table 1. Physical parameters employed in experiments and simulations.

    3. Results and discussion

    3.1. Relative motion between detector and granular flow

    In the local granular flow model, it is believed that the flow velocityvx(z)is positively correlated withz3/2. The relationship between the flow velocity and the height of the chute can be expressed as(also known as Silbert’s formula)[7]

    whereIis the inertial number which increases with inclination angleθ, increasing,his the thickness of the filling particle,ρis the density of the filling particle,gis the acceleration of gravity,θis the angle between the chute and the ground,andzis the height of the chute. Based on Eq.(8),the calculated velocity of the granular flow is shown by the red line in Fig.5(a)whenθis 12°.

    Fig.5.(a)Comparison between theoretical curve and experimental curve of,chute height versus particle flow velocity,with red line representing velocity based on Eq.(8),where I=0.178,black line denoting averaged velocity measured by PIV method. and blue triangles referring to the velocities measured by using a spherical detector at six marked locations;and(b)curve of chute height versus relative velocity between the detector and the granular flow.

    We use the PIV method to obtain the averaged velocity profile on the side wall of the chute,and the detector to obtain the average velocity of special tracer particle during the stable period. It is shown in Fig.5(a)that the averaged velocity measured by the PIV method is similar to that obtained from the theoretical model,Eq.(8).The red line shows that the granular velocity at the bottom is not 0,whereas in Eq.(8)the grain at the bottom should not slip. This is because the chute does not use particle bed as bottom,so the granular layer at the bottom does not form complete stable state.

    The velocity measured by the detector at different values ofh(as shown by the blue points)is larger than the PIV results and increases linearly. This indicates that the detector moves faster than the surrounding particles. The relative velocity between the detector and the granular flow is shown by Fig.5(b).The biggest difference in velocity appears at the bottom.

    3.2. Rolling velocity and sliding velocity

    During the experiment, it can be observed in Fig. 2 that the particles in the chute have not only sliding motion, but also rolling motion. The velocity of the spherical detector is a combination of sliding velocity and rolling velocity as shown in Fig.6.

    Fig.6. Composition of velocity: sliding velocity vs and rolling velocity vr.

    The velocity along the flow directionvx(z)of the spherical detector can be expressed as

    Fig.7. Curves of chute height versus averaged angular veloci(z)of the spherical detector at different inclination angles.

    Fig. 8. Comparison of particle sliding velocity vs(z) among different values of inclination angle θ,with solid lines representing velocities calculated from Eq.(8),triangles denoting velocities measured by the spherical detector. Inertial number I =0.178 when θ =12°, I =0.140 when θ =10°.I=0.125 when θ =8°.

    As shown in Fig. 8, the sliding velocities measured by detector and calculated from Eq.(8)are matched. At the free surface of the chute,the growth pattern of particle sliding velocityvs(z)tends to be flat. This is one of the characteristics of the local flow model,indicating that the sliding velocity of the detector is mainly driven by the local granular flow. Correspondingly, the velocity of the detector relative to the surrounding particles is mainly due to rolling.

    3.3. Relative motion based on simulation results

    Using the detector and PIV technology,the measurement results show that rolling and relative motion are statistically correlated. For further investigation,the results obtained from the DEM simulation (Fig. 4) are analyzed. The area in the middle of the chute is considered as the area that contains valid granular flow velocity distribution as shown in the inset of Fig.9. The velocities of each particle are shown by the black triangles. Calculations from Eq. (8) are shown by the red line. It can be observed that the simulation results are in line with the experimental results as shown by the blue line(the same as the red line in Fig. 5). The slight difference inIbetween 0.178 in experiment result and 0.182 in simulation result may be due to the ideal shear process obtained by simulation.

    Fig. 9. Simulated velocity distributions, with inset showing measured area,triangles representing velocities of particles in measured area,red line(I =0.182) and blue line (I =0.178) denoting calculations from Eq. (8)based on the simulation and the experimental results.

    By tracking the labeled particles, simulation results provide the accurate trajectories and real-time rolling velocities that cannot be obtained experimentally.

    Figure 10(a)shows the rolling velocities of 3 labeled particles. The rolling velocity of particle A is larger than those of the other two labeled particles. The velocityvxof particle A located in the surface layer (Fig. 4) is significantly higher than those in the other layers. It takes less than 2 s to move out of the chute. This is consistent with the theory presented in Subsection 3.1.

    The velocityωyof particle B is slightly larger than that of particle C in the stable stage. After 1.5 s, the values ofωyof particles B and C are the same. By tracking the labeled particles, it is found that particle B falls in height as it follows granular flow and approaches to particle C in a time between 0.5 s and 1.5 s. This causes relative motion between particle B and the core layer. After 1.5 s, particles B and C follow similar trajectories moving out of the chute. So a similarωyis obtained.

    Because of the difference invx, the particles in different layers have obvious relative motions. The relative motion trajectory is consistent with that of velocityωy.

    Figure 10(b)shows time-dependentωyof the detector and particle B.The detector moves faster,leaving the chute 0.55 s earlier than particle B at a similar initial position. Comparing withωyin the moving duration,the rotation of the detector is more stable and larger than the particle B on average. Several larger pulses in red line indicate that particle B moves intensely when there is a gap.

    Fig. 10. (a) Curve of time-dependent angular velocity ωy of particles A(blue line),B(red line),and C(black line)on surface,core,and basal layer.(b)Curve of time-dependent angular velocity ωy of detector(blue line)and particle B(red line)located at similar initial position.

    Fig. 11. Two potential mechanisms of ωy of detector: (a) detector surrounded by granular flow; (b) detector driven by the unbalanced granular flow;(c)detector starting to surface the granular flow;(d)detector driven by gravity.

    Based on theωy,two potential mechanisms of the detector rolling are presented in Fig. 11. During the stable stage,the detector is surrounded by the granular flow as shown in Fig. 11(a). Because of the difference invxat different values ofh,the detector rolls forward under the drive unbalanced granular flow as shown in Fig.11(b).

    During the unstable stage, the upper part of the detector is not covered by the granular flow. Figure 11(c) shows the moment when the detector surfaces the granular flow. It can be observed thatvxbelow the detector is not uniform. At this stage, the detector is driven by gravity, moving to the region with highervx.

    Further investigation of the detector trajectory shows that the mechanism ofωyof the detector is correlated with the layer at which the detector is located. In the surface and basal layer,the detector has a higher probability of moving upwards. The direction is similar to that shown in Fig. 11(d). In the core layer,the trajectory of the detector is very complex. The motion directions indicated by both mechanisms occur. The relationship between rolling mechanism and time-space will be the focus of further research.

    4. Conclusions

    We experimentally studied a special particle moving in the local granular flow and consider that the velocity of the special particle should be divided into sliding velocityvs(z)and rolling velocityvr(z). Ashincreases, the sliding velocityvs(z) of particles increases, but rolling velocityvr(z)decreases. The velocityvx(z) of particles presents a linear growth,andωy(z)can be obtained by a spherical detector,thus the rolling velocity of the particlevr(z)can be obtained. Two potential mechanisms ofωyare presented based on the DEM simulation with RVD rolling friction model,andωyof the detector changes in different flow stages and layers. In further studies, the relationship between mechanism ofωyand timespace of the detector needs to be analyzed precisely and compared with theoretical models.

    Acknowledgements

    We would like to express our gratitude to Prof. V.Zivkovic from Newcastle University for his careful guidance and help.

    Project supported by the National Natural Science Foundation of China (Grant Nos. 11972212, 12072200, and 12002213).

    猜你喜歡
    鄭剛李然寶林
    《力量》
    Adaptive synchronization of chaotic systems with less measurement and actuation?
    Reptiles Are Great!
    Great Vacation Places
    春曉
    鄭剛辭職,馬仿列接掌北汽新能源
    汽車觀察(2019年2期)2019-03-15 06:00:12
    Analysis on the Pharmacists Intervention Results of the Problems from 2000 Prescriptions of Chinese Herbal Pieces
    Reduced technique for modeling electromagnetic immunity on braid shielding cable bundles?
    “養(yǎng)路鐵人”金寶林
    北方人(2017年10期)2017-07-03 14:07:24
    如果所有的愿望都能成真
    精品午夜福利在线看| 精品熟女少妇av免费看| 国产在线视频一区二区| 国产在线视频一区二区| 视频在线观看一区二区三区| 国产精品欧美亚洲77777| 亚洲av免费高清在线观看| 极品少妇高潮喷水抽搐| 亚洲人成77777在线视频| 日本午夜av视频| 少妇的丰满在线观看| 国产av国产精品国产| 国产精品国产三级国产专区5o| 久久久a久久爽久久v久久| 久久精品人人爽人人爽视色| 日本av免费视频播放| 伦理电影免费视频| 激情视频va一区二区三区| 另类亚洲欧美激情| 22中文网久久字幕| 一级毛片黄色毛片免费观看视频| 五月伊人婷婷丁香| 免费大片18禁| 黄片播放在线免费| 国产亚洲最大av| xxx大片免费视频| 黑人高潮一二区| 午夜激情久久久久久久| 成人漫画全彩无遮挡| 嫩草影院入口| a级毛片黄视频| 18禁动态无遮挡网站| 一二三四在线观看免费中文在 | 黄色一级大片看看| 欧美激情极品国产一区二区三区 | 久久ye,这里只有精品| 亚洲精品久久午夜乱码| 免费观看无遮挡的男女| 黄色视频在线播放观看不卡| 精品人妻在线不人妻| 大话2 男鬼变身卡| 国产精品欧美亚洲77777| 曰老女人黄片| 亚洲图色成人| 又黄又粗又硬又大视频| 草草在线视频免费看| 亚洲欧美成人综合另类久久久| 亚洲精品日韩在线中文字幕| 国产免费福利视频在线观看| 欧美激情极品国产一区二区三区 | 久久人妻熟女aⅴ| 精品人妻偷拍中文字幕| 人人妻人人澡人人看| 97在线视频观看| 热re99久久国产66热| 五月天丁香电影| 最后的刺客免费高清国语| 最近手机中文字幕大全| 中文字幕精品免费在线观看视频 | 伦精品一区二区三区| 99re6热这里在线精品视频| 成人亚洲精品一区在线观看| 国产一区二区三区综合在线观看 | 成人国产av品久久久| 99视频精品全部免费 在线| 亚洲欧洲国产日韩| 亚洲精品国产av成人精品| 免费黄频网站在线观看国产| 亚洲激情五月婷婷啪啪| 午夜免费鲁丝| 亚洲少妇的诱惑av| 伊人亚洲综合成人网| 一级片'在线观看视频| 女性被躁到高潮视频| 乱人伦中国视频| 国产不卡av网站在线观看| 91精品三级在线观看| 99精国产麻豆久久婷婷| 亚洲一码二码三码区别大吗| 亚洲精品美女久久久久99蜜臀 | 国产精品不卡视频一区二区| 国产精品国产av在线观看| 国产成人精品在线电影| 国产亚洲欧美精品永久| 少妇人妻精品综合一区二区| 日韩,欧美,国产一区二区三区| 欧美人与性动交α欧美精品济南到 | 成年人免费黄色播放视频| 国产熟女午夜一区二区三区| 一级毛片我不卡| 国产亚洲精品第一综合不卡 | 99热6这里只有精品| 日韩在线高清观看一区二区三区| 欧美bdsm另类| 精品卡一卡二卡四卡免费| 日日啪夜夜爽| 成人毛片a级毛片在线播放| 国产精品三级大全| 女人被躁到高潮嗷嗷叫费观| 老司机影院毛片| 一区二区av电影网| 免费日韩欧美在线观看| 久久这里有精品视频免费| 视频在线观看一区二区三区| 一二三四中文在线观看免费高清| 国产高清三级在线| 亚洲av国产av综合av卡| 9色porny在线观看| 午夜精品国产一区二区电影| 亚洲第一区二区三区不卡| 2018国产大陆天天弄谢| 一二三四在线观看免费中文在 | 午夜久久久在线观看| 韩国av在线不卡| 亚洲,欧美,日韩| 久久久久精品久久久久真实原创| 五月天丁香电影| 考比视频在线观看| 看非洲黑人一级黄片| 99久久综合免费| 午夜福利视频在线观看免费| 久久99精品国语久久久| 99久久综合免费| 涩涩av久久男人的天堂| 亚洲精品乱码久久久久久按摩| 日韩伦理黄色片| 啦啦啦中文免费视频观看日本| 亚洲精品第二区| 丝袜喷水一区| 欧美亚洲 丝袜 人妻 在线| 中文字幕最新亚洲高清| 热99国产精品久久久久久7| 99热6这里只有精品| 一级黄片播放器| 国产一级毛片在线| 久久狼人影院| 国产男女超爽视频在线观看| 69精品国产乱码久久久| 久久ye,这里只有精品| www日本在线高清视频| 国产深夜福利视频在线观看| 欧美日本中文国产一区发布| 亚洲国产av新网站| 欧美xxxx性猛交bbbb| 日韩,欧美,国产一区二区三区| 色婷婷av一区二区三区视频| 免费日韩欧美在线观看| 欧美激情 高清一区二区三区| 国产一区二区在线观看日韩| 美女国产高潮福利片在线看| 欧美激情极品国产一区二区三区 | 亚洲丝袜综合中文字幕| 日韩精品有码人妻一区| 国产成人aa在线观看| 99re6热这里在线精品视频| 亚洲国产av新网站| 国产精品国产三级国产专区5o| 精品酒店卫生间| 少妇人妻久久综合中文| 国产日韩欧美视频二区| 插逼视频在线观看| 制服人妻中文乱码| 免费黄网站久久成人精品| 免费观看在线日韩| 精品一区在线观看国产| 如何舔出高潮| 亚洲第一区二区三区不卡| 久久ye,这里只有精品| 天天躁夜夜躁狠狠躁躁| 日韩人妻精品一区2区三区| 天堂8中文在线网| 国产在线一区二区三区精| 国产成人精品无人区| 久久热在线av| tube8黄色片| av在线观看视频网站免费| 亚洲高清免费不卡视频| 97超碰精品成人国产| 草草在线视频免费看| 欧美日韩av久久| 国产一区二区三区综合在线观看 | 熟女av电影| 亚洲av成人精品一二三区| 亚洲精品日本国产第一区| 熟女av电影| 亚洲丝袜综合中文字幕| 波多野结衣一区麻豆| 亚洲精品国产av成人精品| 亚洲精品一二三| 国产精品秋霞免费鲁丝片| 人妻少妇偷人精品九色| 亚洲av电影在线进入| 午夜久久久在线观看| 中文字幕制服av| 国产成人精品久久久久久| 9色porny在线观看| 少妇精品久久久久久久| 亚洲欧洲国产日韩| 亚洲人与动物交配视频| 黑丝袜美女国产一区| 男女高潮啪啪啪动态图| 国产精品麻豆人妻色哟哟久久| 人成视频在线观看免费观看| 久久99热这里只频精品6学生| 亚洲天堂av无毛| 免费看av在线观看网站| 最新的欧美精品一区二区| 在线亚洲精品国产二区图片欧美| 国产无遮挡羞羞视频在线观看| 免费看av在线观看网站| 成年女人在线观看亚洲视频| 五月开心婷婷网| 久久99一区二区三区| 男人操女人黄网站| 777米奇影视久久| 校园人妻丝袜中文字幕| 亚洲人与动物交配视频| 亚洲欧美色中文字幕在线| 91精品三级在线观看| 亚洲激情五月婷婷啪啪| 国产熟女午夜一区二区三区| 亚洲国产欧美在线一区| 黄片播放在线免费| av电影中文网址| 青春草国产在线视频| 久久精品久久久久久久性| 亚洲国产欧美日韩在线播放| 少妇 在线观看| 妹子高潮喷水视频| 自线自在国产av| 男人添女人高潮全过程视频| 免费大片黄手机在线观看| 交换朋友夫妻互换小说| 一区在线观看完整版| 高清av免费在线| 91在线精品国自产拍蜜月| 亚洲国产精品成人久久小说| 男女午夜视频在线观看 | 搡老乐熟女国产| 青青草视频在线视频观看| a 毛片基地| 18禁动态无遮挡网站| 成年动漫av网址| 在线天堂中文资源库| 亚洲国产精品999| 秋霞伦理黄片| 尾随美女入室| 99精国产麻豆久久婷婷| 亚洲av欧美aⅴ国产| 视频在线观看一区二区三区| 一区二区三区精品91| 1024视频免费在线观看| 女人精品久久久久毛片| 男女国产视频网站| 亚洲国产最新在线播放| 99热全是精品| 国产xxxxx性猛交| 国产成人精品在线电影| 欧美日韩视频精品一区| 国产激情久久老熟女| 欧美日韩国产mv在线观看视频| 欧美 日韩 精品 国产| 午夜福利,免费看| 久久久亚洲精品成人影院| 国产成人91sexporn| 少妇熟女欧美另类| 亚洲av日韩在线播放| 免费观看无遮挡的男女| 一本一本久久a久久精品综合妖精 国产伦在线观看视频一区 | 91aial.com中文字幕在线观看| 一本大道久久a久久精品| 欧美日本中文国产一区发布| 两个人看的免费小视频| 日韩欧美一区视频在线观看| 少妇的丰满在线观看| 国产精品蜜桃在线观看| 欧美亚洲 丝袜 人妻 在线| 国产精品久久久久成人av| 国产探花极品一区二区| av天堂久久9| 久久久久久久亚洲中文字幕| 日韩制服骚丝袜av| 久久久久久人人人人人| 久久99蜜桃精品久久| 亚洲国产精品成人久久小说| 成年美女黄网站色视频大全免费| 久久精品国产综合久久久 | 精品国产国语对白av| 亚洲,欧美,日韩| 日本猛色少妇xxxxx猛交久久| 内地一区二区视频在线| 亚洲天堂av无毛| 亚洲人与动物交配视频| 成人毛片a级毛片在线播放| 久久午夜福利片| 人妻一区二区av| 视频区图区小说| av国产久精品久网站免费入址| 国产毛片在线视频| 爱豆传媒免费全集在线观看| 国产有黄有色有爽视频| 亚洲精品久久午夜乱码| 国产成人一区二区在线| 精品第一国产精品| 午夜免费男女啪啪视频观看| 91久久精品国产一区二区三区| 午夜影院在线不卡| 色吧在线观看| 国产亚洲av片在线观看秒播厂| 美女主播在线视频| 飞空精品影院首页| 免费观看a级毛片全部| 秋霞在线观看毛片| 日韩av在线免费看完整版不卡| 国产亚洲精品久久久com| 久久久久久久久久久免费av| 中文字幕av电影在线播放| av福利片在线| 丰满少妇做爰视频| 午夜福利乱码中文字幕| 中文欧美无线码| 久久 成人 亚洲| 久久精品熟女亚洲av麻豆精品| 国产一区二区在线观看日韩| 下体分泌物呈黄色| 国产精品.久久久| 有码 亚洲区| 国产欧美日韩一区二区三区在线| 亚洲国产精品一区二区三区在线| 日本av手机在线免费观看| tube8黄色片| 一区在线观看完整版| 老司机亚洲免费影院| 高清视频免费观看一区二区| 在线观看三级黄色| 蜜桃国产av成人99| www.av在线官网国产| 亚洲欧美成人综合另类久久久| 婷婷色综合www| 人妻 亚洲 视频| 欧美精品一区二区免费开放| 亚洲综合精品二区| 色5月婷婷丁香| 成人国语在线视频| 丰满饥渴人妻一区二区三| 最近中文字幕2019免费版| 中文字幕最新亚洲高清| 精品人妻一区二区三区麻豆| 只有这里有精品99| 人妻人人澡人人爽人人| 国产精品国产av在线观看| av福利片在线| 日韩免费高清中文字幕av| 午夜免费男女啪啪视频观看| 成人国产麻豆网| 亚洲精品成人av观看孕妇| 欧美最新免费一区二区三区| 免费久久久久久久精品成人欧美视频 | 大陆偷拍与自拍| 少妇的逼好多水| 香蕉精品网在线| 亚洲成av片中文字幕在线观看 | 午夜免费鲁丝| 亚洲国产欧美日韩在线播放| 22中文网久久字幕| 久久午夜福利片| 久久久久久久久久成人| 国产精品欧美亚洲77777| 亚洲国产精品国产精品| 91国产中文字幕| 欧美 亚洲 国产 日韩一| 国产成人一区二区在线| 久久久国产一区二区| 午夜精品国产一区二区电影| 日韩人妻精品一区2区三区| av卡一久久| 99re6热这里在线精品视频| 精品久久国产蜜桃| 久久精品国产鲁丝片午夜精品| 一级,二级,三级黄色视频| 99久久综合免费| 蜜桃在线观看..| 亚洲av成人精品一二三区| 99热全是精品| 天堂中文最新版在线下载| av在线播放精品| 久久毛片免费看一区二区三区| av片东京热男人的天堂| 天堂俺去俺来也www色官网| 男女下面插进去视频免费观看 | 黄色配什么色好看| 男女高潮啪啪啪动态图| 97在线人人人人妻| 菩萨蛮人人尽说江南好唐韦庄| 亚洲精品456在线播放app| 男女啪啪激烈高潮av片| 日韩免费高清中文字幕av| 捣出白浆h1v1| 精品一区在线观看国产| 日韩视频在线欧美| 草草在线视频免费看| 亚洲五月色婷婷综合| 免费高清在线观看日韩| 2018国产大陆天天弄谢| 熟妇人妻不卡中文字幕| 国产成人精品久久久久久| 男女边吃奶边做爰视频| 性色av一级| 精品国产一区二区三区久久久樱花| 国产片内射在线| 丝袜喷水一区| 免费观看a级毛片全部| a 毛片基地| 在线天堂最新版资源| 黄色怎么调成土黄色| 人妻 亚洲 视频| 一级毛片 在线播放| 亚洲国产欧美日韩在线播放| 视频在线观看一区二区三区| 免费日韩欧美在线观看| 色网站视频免费| 91在线精品国自产拍蜜月| 亚洲精品一二三| 五月玫瑰六月丁香| 天天躁夜夜躁狠狠躁躁| 日韩av不卡免费在线播放| 9191精品国产免费久久| 尾随美女入室| 日韩av免费高清视频| 亚洲伊人色综图| 国产一区二区三区av在线| 人妻少妇偷人精品九色| 久久99精品国语久久久| 纯流量卡能插随身wifi吗| 国产麻豆69| 日本91视频免费播放| 自拍欧美九色日韩亚洲蝌蚪91| 亚洲精品久久成人aⅴ小说| 搡老乐熟女国产| 久久婷婷青草| 日韩中文字幕视频在线看片| 日韩一区二区三区影片| 亚洲精品久久成人aⅴ小说| 亚洲国产精品专区欧美| 黑人巨大精品欧美一区二区蜜桃 | 在线观看免费日韩欧美大片| 天堂俺去俺来也www色官网| 国产精品偷伦视频观看了| 欧美xxxx性猛交bbbb| 肉色欧美久久久久久久蜜桃| 亚洲 欧美一区二区三区| 国产成人一区二区在线| 国产精品一区二区在线不卡| av视频免费观看在线观看| 免费久久久久久久精品成人欧美视频 | 亚洲图色成人| 日本av免费视频播放| 在线免费观看不下载黄p国产| 亚洲欧美一区二区三区黑人 | 人妻少妇偷人精品九色| 国产福利在线免费观看视频| 热99国产精品久久久久久7| 日韩熟女老妇一区二区性免费视频| 精品第一国产精品| 亚洲性久久影院| 伦理电影免费视频| 国产免费又黄又爽又色| 精品午夜福利在线看| 日日爽夜夜爽网站| 看十八女毛片水多多多| 国内精品宾馆在线| 18在线观看网站| 欧美成人精品欧美一级黄| av片东京热男人的天堂| 赤兔流量卡办理| av国产精品久久久久影院| 在线天堂最新版资源| 51国产日韩欧美| 五月伊人婷婷丁香| 国产成人精品一,二区| 激情五月婷婷亚洲| 久久久久国产网址| 夜夜骑夜夜射夜夜干| 日韩人妻精品一区2区三区| 国产精品久久久久久久久免| 少妇的丰满在线观看| 亚洲精品一二三| 男男h啪啪无遮挡| 久久国产精品大桥未久av| 精品卡一卡二卡四卡免费| 国产成人精品在线电影| 亚洲综合精品二区| 亚洲一码二码三码区别大吗| 在线 av 中文字幕| 美女大奶头黄色视频| 亚洲欧美中文字幕日韩二区| 人妻人人澡人人爽人人| 少妇 在线观看| 男女免费视频国产| 欧美精品亚洲一区二区| 在线天堂中文资源库| 久久韩国三级中文字幕| 国产伦理片在线播放av一区| 最近中文字幕高清免费大全6| 捣出白浆h1v1| 久久青草综合色| 日韩在线高清观看一区二区三区| 国产精品免费大片| 宅男免费午夜| 久久午夜综合久久蜜桃| 成年动漫av网址| 国国产精品蜜臀av免费| 老女人水多毛片| 亚洲一级一片aⅴ在线观看| 十八禁高潮呻吟视频| 日韩中字成人| 侵犯人妻中文字幕一二三四区| av网站免费在线观看视频| 国产精品久久久久成人av| 国产免费一级a男人的天堂| 91精品国产国语对白视频| 在线天堂中文资源库| 亚洲高清免费不卡视频| 亚洲成人av在线免费| 亚洲av免费高清在线观看| 久久人妻熟女aⅴ| 亚洲国产精品成人久久小说| 成人毛片60女人毛片免费| 亚洲欧美一区二区三区国产| 成人亚洲欧美一区二区av| 99九九在线精品视频| 国产精品久久久久久久电影| 我要看黄色一级片免费的| h视频一区二区三区| 香蕉国产在线看| 18禁动态无遮挡网站| 一级毛片 在线播放| 成年动漫av网址| 久久综合国产亚洲精品| 久久久久精品人妻al黑| 丰满少妇做爰视频| 全区人妻精品视频| 亚洲精品日本国产第一区| 亚洲精品日韩在线中文字幕| 我的女老师完整版在线观看| 日本91视频免费播放| 久久久国产一区二区| 18禁国产床啪视频网站| 中文字幕av电影在线播放| 国产高清不卡午夜福利| 99久久精品国产国产毛片| 日韩一本色道免费dvd| 久久精品久久久久久久性| 久久久久精品久久久久真实原创| 欧美成人精品欧美一级黄| 菩萨蛮人人尽说江南好唐韦庄| 亚洲三级黄色毛片| 国产视频首页在线观看| 亚洲中文av在线| 午夜福利影视在线免费观看| av网站免费在线观看视频| 三级国产精品片| 波多野结衣一区麻豆| 自线自在国产av| 久久久久视频综合| av视频免费观看在线观看| av又黄又爽大尺度在线免费看| 蜜桃在线观看..| 男女高潮啪啪啪动态图| 国产一区二区激情短视频 | 日本免费在线观看一区| 在现免费观看毛片| 22中文网久久字幕| 久热久热在线精品观看| 日日撸夜夜添| 亚洲第一av免费看| 黑人猛操日本美女一级片| 久久av网站| 校园人妻丝袜中文字幕| 99精国产麻豆久久婷婷| 成年人午夜在线观看视频| freevideosex欧美| 飞空精品影院首页| 最近最新中文字幕免费大全7| 久久精品aⅴ一区二区三区四区 | 一本色道久久久久久精品综合| 亚洲国产毛片av蜜桃av| av一本久久久久| 精品酒店卫生间| 男人爽女人下面视频在线观看| 男女啪啪激烈高潮av片| 中文字幕亚洲精品专区| 亚洲av男天堂| 国产精品麻豆人妻色哟哟久久| 在线观看国产h片| 亚洲中文av在线| 亚洲欧美中文字幕日韩二区| 国产精品一国产av| 老女人水多毛片| 一本—道久久a久久精品蜜桃钙片| 国产亚洲av片在线观看秒播厂| www.色视频.com| 精品视频人人做人人爽| 欧美精品国产亚洲| 日韩成人伦理影院| 国产成人免费无遮挡视频| 免费女性裸体啪啪无遮挡网站| 麻豆乱淫一区二区| 最新中文字幕久久久久| 成年女人在线观看亚洲视频| 国产综合精华液| 成人亚洲欧美一区二区av| 亚洲精品日本国产第一区| 汤姆久久久久久久影院中文字幕| 自线自在国产av|