• <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 ?

    The effect of free surface on cloud cavitating flow around a blunt body *

    2017-03-14 07:06:30ChangXu徐暢YiweiWang王一偉ChenguangHuang黃晨光JianHuang黃薦
    水動力學研究與進展 B輯 2017年6期
    關鍵詞:晨光

    Chang Xu (徐暢), Yi-wei Wang (王一偉), Chen-guang Huang (黃晨光), Jian Huang (黃薦),

    Chao Yu (余超)1,2,

    1. Key Laboratory for Mechanics in Fluid Solid Coupling Systems, Institute of Mechanics, Chinese Academy of Sciences, Beijing 100190, China

    2. School of Engineering Science, University of Chinese Academy of Sciences, Beijing 100049, China,

    E-mail: xuchang@imech.ac.cn

    Introduction

    The cavitation is one of the classic problems in high-speed hydrodynamics when underwater vehicles move in great speed[1-4]. The induced instable phenomena can cause serious consequences, such as noises,erosion, and vibrations of the structure. The problem becomes complicated when the interaction between the free surface and the cloud cavitating flow on the model is considered. The water tunnel[5]and water tank[6,7]tests are usually performed to analyze the problem. In recent years, the CFD method becomes one of the main research methods used for the cavitation flow, including the potential flow theory[8,9],the boundary element method (BEM)[10-12], the large eddy simulation (LES)[13-16], and other approaches[17-19]with commercial software, such as the CFX, the FLUENT[20,21]and other open source software, such as the OpenFOAM[22-24].

    The interaction between the free surface and the cavitating flow is a very complex and interesting problem. Based on the numerical and experimental methods mentioned above, the flow characteristics and the mechanism of unsteady cavities were studied.The mechanism of main control parameters, such as the submerged depth, the cavitation number, the Froude number, and the gravity, which affect the cavitating flow, were analyzed based on experiments and numerical simulations[1,9,25]. Wang[13,26]studied the cloud cavitating flow around an axisymmetric projectile near the free surface, including the effect of the free surface on the cavity shape, the cavity evolution process, the re-entrant jet inside the cavity,and the vortex structure. The CFD simulations were conducted, and the results were found to be consistent with the water tank experiment data. Moreover, the atmospheric ventilation flow around a blunt body near the free surface was discussed[27]. Ventilated cavitation occurs when the model is sufficiently close to the free surface. The entrainment of a strong air into the ca-vity on the upper side of the blunt body induces a large and stable cavity. The effects of other boundary conditions, such as that of the near-wall on the cloud cavitating flow around vehicles were also discussed in the recent studies[28-30].

    Fig.1 Water tank test facilities

    In this work, the water tank experiments and the numerical simulations are performed to analyze the effect of the free surface on the cloud cavitating flow around a blunt body in various submerged depths. The accuracy of the numerical method and the mesh independence are verified. The cavity evolution processes,including the cavity growth, the re-entrant jet, the cavity shedding, and the collapse, can be observed through the experimental data. We first discuss the effects of the free surface on the cavity length, the thickness, and the cavity evolution period. Then, the effects of the free surface on the cavity stability, the asymmetry, and the thickness and the velocity of the re-entrant jet inside the cavity of various submerged depths are examined under a series of working conditions.

    1. Water tank experiment

    The water tank test facilities are shown in Fig.1.The tested model in the experiment is a slender,polished stainless-steel cylinder of 37 mm in diameter.The launching process is based on the Split-Hopkinson pressure bar technology[6], which could accelerate the launched model to a speed of 18.5 m/s in less than 50 μs. The entire cavity evolution process could be recorded by a high-speed camera with 25 000 frames per second. The water temperature is approximately 20oC. In the following sections, the cavity evolution will be mainly discussed based on experimental pictures and numerical results. The cavity shape changes with the submerged depth at the launch time, the cavitation phenomenon can be classified by the shape development into the cloud cavitation[13],the natural ventilation[27]and the supercavitation as the submerged depth decreases. We mainly focus on the cloud cavitating flow in this paper with the submerged depth varying from 15 mm to 40 mm. There will be no free surface effect on the cloud cavi- tating flow around the projectile when the distance between the upper side of the projectile and the free surface exceeds 40 mm.

    2. Numerical methods

    2.1 Governing equations

    The multiphase flow equations are extensively used for solving the water-liquid/water-vapor twophase flow problems. The governing and momentum equations are expressed as:

    whereiu is the velocity component in the i direction, ρ is the mixture density, p is the pressure, and μ is the laminar viscosity, which can be defined as

    where α is the volume fraction of the different phases, and l and v represent the liquid water and the water vapor, respectively. The mixture density ρ is defined as

    The transport equation of the water vapor volume fraction is

    Table 1 Numerical schemes and parameters

    where R =10-6mis the generalized bubble radius,

    B pv=2340Pais the saturated vapor pressure,anuc=5× 1 0-4is the nucleation site volume fraction,Fvap=50 is the evaporation coefficient, and Fcond=

    0.01 is the condensation coefficient. The selected parameter values are based on the work of Zwart et al..The parameters are evaluated and found to work well for a variety of fluids and devices. The parameters and the recommended values of the cavitation model were extensively used[13]. In addition, several studies indicated that the parameters had a small effect on the results of the cloud cavitating flow within a certain range[32].

    2.2 Numerical schemes and parameters

    In this study, the commercial software FLUENT is used for simulating the cloud cavitating flow around a blunt body near the free surface. The 1.2 m×0.8 m×0.4 m computational domain and the defined boundary conditions include the velocity-inlet, the pressure-outlet, and no-slip wall, as shown in Fig.2, where half of the model is considered. The depth between the upper side of the blunt body and the free surface(15 mm) and the simulated velocity (18.5 m/s) are the same as those in the water tank experiment. The tail effect on the cavity is neglected by using a semiinfinite projectile model. Other simulation conditions are consistent with the experimental conditions.During the calculation, the VOF method and the LES approach with the Smagorinsky-Lilly model are used for simulating the turbulent flow. Other detailed numerical schemes and parameters are shown in Table 1.

    Fig.2 Computational domain and boundary conditions

    Fig.3 Mesh near the head of the projectile

    Fig.4 Comparison of cavity lengths on the upper and lower sides of the model between the experimental and simulated results

    2.3 Validation

    Fig.5 Comparison of simulated results of cavity length at the upper and lower sides of the model of original mesh and refined mesh, and experimental results

    The numerical results of a block-structured mesh(Fig.3) with a cell number of approximately 4×106are compared with the water tank experimental data in Fig.4. l is the distance between the upper side of the projectile and the free surface, t is time. The first layer height is set at 1 m to ensure that+Y is approximately equal to 1. The total cell number is approximately 4×106with a good orthogonality, which is refined around the model and near the free surface.The results are consistent with each other, which validates the accuracy of the numerical methods. The cavity evolution process shown in the figure includes four stages: the cavity growth, the re-entrant jet, the cavity shedding, and the collapse.

    2.4 Mesh independence study

    Based on the original mesh plan, a refined mesh is generated with a total cell number of 3×107. The mesh independence is confirmed by comparing the cavity length at the upper and lower sides of the blunt body among the experimental results, and the simulated results with the original mesh, and the refined mesh, as shown in Fig.5. The results of the new mesh plan are in good agreement with those of the previous models. The cavity shapes of the simulated results are also compared in Fig.6, which shows that the refined mesh simulation results are consistent with the original results of the cavity evolution. As the main features of the cavity evolution are our concern to a greater extent than other attributes, the mesh independence of the simulation method can be verified. The LES approach is widely used in the calculation of the cavitating flow nowadays, but without much validation and verification (V&V) study[33]. The V&V is necessary for numerical calculations[34]and the V&V research for the LES methods will be conducted in the future.

    3. Results and discussions

    Figure 7 shows the comparison of cavity patterns between the experiment and simulation results during the cavity evolution process. The preceding four stages mentioned above can be clearly observed through the figures. The cavity is generated in the first stage. The re-entrant jet appears inside the end of the cavity and moves toward the shoulder of the model when the cavity turns into a stable shape. In the third stage, the re-entrant jet removes the cavity by interfering with the outside flow. Thereafter, the cavity shedding occurs. In the last stage, the cavity collapses,and the cavity length is significantly decreased. The differences of the cavity shape between the upper and lower sides of the body reflect the effect of the free surface on the cavitating flow. With a small upper constraint and the effect of the free surface, the upper side of the cavity has a larger curvature than that of the lower side cavity. Cavities can be thick and short near the free surface. The entire cavity evolution period is also shortened. Detailed discussions and analyses of the flow characteristics and the mechanism of the cavity are given in Ref.[13].

    Fig.6 (Color online) Comparison of the cavity evolutions between simulated results with the original mesh and the refined mesh

    Fig.7 (Color online) Comparison of cavity patterns between experiment and simulation results at =t 2 ms, 4 ms, 6 ms,8 ms, 10 ms, 12 ms and 16 ms. Re-entrant jets are marked by red lines

    In this study, various submerged depths (15 mm,20 mm, 25 mm, 30 mm and 40 mm) are considered to analyze the cavity stability and the asymmetry, the re-entrant jet thickness, and the velocity with the free surface effect. If the submerged depth is reduced, a natural ventilation will occur[27].

    3.1 The effect of free surface on cavity stability and asymmetry

    Plotted data are shown in Figures 8 and 9. The cavity stability on the upper side of the blunt body increases with the decrease of the submerged depth,whereas the stability on the lower side cavity is generally unchanged. The cavity asymmetry increases with the decrease of the submerged depth. The relationship between the average cavity length difference and the submerged depth can be expressed by the following equation

    where l is the cavity length, and d is the submerged depth.

    Fig.8 Standard deviation of cavity length ()lσ on the upper and lower sides of blunt body at 1 ms-17 ms

    3.2 The effect of free surface on re-entrant jet thickness and velocity

    Fig.10 (Color online) Comparison of simulation results for various submerged depths (15 mm, 20 mm, 25 mm, 30 mm and 40 mm) at 6 ms (velocity contour charts show the velocity distribution around the model at the added symmetry plane)

    Fig.11 Thickness of re-entrant jet inside the cavity for various submerged depths (15 mm, 20 mm, 25 mm, 30 mm and 40 mm) at 6 ms

    The re-entrant jet is one of the important factors for the cavity instability. By putting the velocity contour charts on the symmetry plane of the model,we can clearly see the re-entrant jet inside the cavity based on the numerical results. Figure 10 shows the velocity distribution around the blunt body and the cavitating flow on the model at =6 mst . With the increase of the distance between the free surface and the model, the difference between the cavity length on the upper and lower sides of the body decreases. The thickness of the re-entrant jet inside the cavity at t =6 ms is plotted in Fig.11, which shows that the thickness of the re-entrant jet is proportional to the water layer thickness. When the model is sufficiently close to the free surface, the re-entrant jet on the upper side is very thin and does not have a sufficient strength to remove the cavity. Thus, several fluctuations of the cavity shape are found on the upper side; however, no shedding occurs[27]. The thin re-entrant jet also induces a stable cavity when the blunt body moves close to the free surface. The relationship between the reentrant jet thickness and the submerged depth can be expressed by the following linear equation

    where δ is the re-entrant jet thickness.

    The re-entrant jet inside the cavity moves toward the shoulder of the blunt body during the cavity evolution. The re-entrant jet profiles are marked by red lines in Fig.12. Finally, the main cavity is removed by interfering with the outside flow at t = 8ms . Figures 13 and 14 compare the re-entrant jet velocities (Vre-entryjet) of the simulated cases with various submerged depths (15 mm, 20 mm, 25 mm,30 mm and 40 mm) in terms of the re-entrant jet length from the end of the main cavity to the re-entrant jet front inside the cavity. Generally, the re-entrant jet velocity increases as the submerged depth decreases. The re-entrant jet inside the upper side cavity of the blunt rapidly moves under the free surface effect. The re-entrant jet takes a considerable time to reach the leading edge of the hydrofoil due to the increase of the cavity length and the decrease of the speed of the re-entrant jet.

    Fig.12 (Color online) Cavity evolution of simulation results with submerged depth of 15 mm at 2 ms, 4 ms, 6 ms and 8 ms (velocity contour charts show the velocity distribution around the model at the added symmetry plane)

    Fig.13 The re-entrant jet velocities of the simulated cases with various submerged depths (15 mm, 20 mm, 25 mm,30 mm and 40 mm) at 6 ms

    Fig.14 The re-entrant jet velocities of the simulated cases with various submerged depths (15 mm, 20 mm, 25 mm,30 mm and 40 mm) at 6 ms

    4. Conclusions

    In this study, the effect of the free surface on the cloud cavitating flow around an underwater- launched blunt body is analyzed. The results of the water tank experiment and the CFD simulation are in good agreement. The mesh independence study is also carried out.The results of a series of water tank experiments and simulations for various submerged depths are analyzed.

    Generally, the effect of the free surface on the cavitating flow around the blunt body is enhanced with the decrease of the submerged depth. The cavity on the upper side of the model is stable, thick, and short under the free surface effect. The cavity asymmetry, the difference between the upper and lower side cavities, increases as the submerged depth decreases.

    The thickness of the re-entrant jet is proportional to the water layer thickness as shown by the simulation results. Therefore, the thin re-entrant jet also induces a stable cavity when the blunt body moves close to the free surface. In addition, the re-entrant jet velocity increases as the submerged depth decreases.The free surface effect near the blunt body can induce a fast re-entrant jet inside the upper side cavity.

    The cavitating flow around the model near the free surface is complex. Apart from the submerged depth of the model, many other control parameters,such as the head type of the projectile and the boundary conditions, may influence the cavity. The author will focus on the effect of the free surface on the cavitating flow in case of wave movement in the future. Further study on the V&V research with the LES methods is also necessary. In this study, the results are limited to typical working conditions for a typically shaped model, and an in-depth analysis is required.

    [1] Franc J. P., Michel J. M. Fundamentals of cavitation [J].Fluid Mechanics and Its Applications, 2005, 76(11): 1-46.

    [2] Wang G., Senocak I., Wei S. et al. Dynamics of attached turbulent cavitating flows [J]. Progress in Aerospace Sciences, 2001, 37(6): 551-581.

    [3] Knapp R. T., Daily J. W., Hammitt F. G. Cavitation [M].New York, USA: McGraw-Hill, 1970.

    [4] Brennen C. E. Cavitation and bubble dynamics [M].Oxford, UK: Oxford University Press, 1995.

    [5] Leroux J. B., Coutierdelgosha O., Astolfi J. A. A joint experimental and numerical study of mechanisms associated to instability of partial cavitation on two-dimensional hydrofoil [J]. Physics of Fluids, 2005, 17(5):515-13.

    [6] Wei Y. P., Wang Y. W., Fang X. et al. A scaled underwater launch system accomplished by stress wave propagation technique [J]. Chinese Physics Letters, 2011,28(2): 024601-72.

    [7] Hu C. L., Wang G. Y., Huang B. et al. The inception cavitating flows over an axisymmetric body with a blunt head-form [J]. Journal of Hydrodynamics, 2015, 27(3):359-366.

    [8] Faltinsen O. M. Hydrodynamics of high-speed marine vehicles [M]. Cambridge, UK: Cambridge University Press, 2005.

    [9] Faltinsen O. M., Semenov Y. A. The effect of gravity and cavitation on a hydrofoil near the free surface [J]. Journal of Fluid Mechanics, 2008, 597: 371-394.

    [10] Bal S. High-speed submerged and surface piercing cavitating hydrofoils, including tandem case [J]. Ocean Engineering, 2007, 34(14): 1935-1946.

    [11] Bal S. The effect of finite depth on 2D and 3D cavitating hydrofoils [J]. Journal of Marine Science and Technology,2011, 16(2): 129-142.

    [12] Bal S, Kinnas S. A. A BEM for the prediction of free surface effects on cavitating hydrofoils [J]. Computational Mechanics, 2002, 28(3-4): 260-274.

    [13] Wang Y., Wu X., Huang C. et al. Unsteady characteristics of cloud cavitating flow near the free surface around an axisymmetric projectile [J]. International Journal of Multiphase Flow, 2016, 85: 48-56.

    [14] Ji B., Long Y., Long X. P. et al. Large eddy simulation of turbulent attached cavitating flow with special emphasis on large scale structures of the hydrofoil wake and turbulence-cavita-tion interactions [J]. Journal of Hydrodynamics, 2017, 29(1): 27-39.

    [15] Ji Bin, Luo X. W., Peng X. X. et al. Three-dimensional large eddy simulation and vorticity analysis of unsteady cavitating flow around a twisted hydrofoil [J]. Journal of Hydrodynamics, 2013, 25(4): 510-519.

    [16] Xu C., Wang Y., Huang C. et al. Cloud cavitating flow that surrounds a vertical hydrofoil near the free surface [J].Journal of Fluids Engineering, 2017, 139(10): 101302.

    [17] Ma J., Hsiao C. T., Chahine G. L. A physics based multiscale modeling of cavitating flows [J]. Computers and Fluids, 2017, 145: 68-84.

    [18] Ma J., Oberai A. A., Drew D. A. et al. A quantitative subgrid air entrainment model for bubbly flows–plunging jets[J]. Computers and Fluids, 2010, 39(1): 77-86.

    [19] Cheng H. Y., Long X. P., Ji B. et al. Numerical investigation of unsteady cavitating turbulent flows around twisted hydrofoil from the Lagrangian viewpoint [J].Journal of Hydrodynamics, 2016, 28(4): 709-712.

    [20] Kanfoudi H., Lamloumi H., Zgolli R. Numerical investigation for steady and unsteady cavitating flows, advances in modeling of fluid dynamics [M]. Rijeka, Croatia:INTECH Open Access Publisher, 2012.

    [21] Wu Q., Huang B., Wang G. Numerical simulation of transient flows around a 3D pitching hydrofoil [J]. Advances in Mechanical Engineering, 2014, 7(2): 808034.

    [22] Yu X. X., Huang C. G., Du T. Z. et al. Study of characteristics of cloud cavity around axisymmetric projectile by large eddy simulation [J]. Journal of Fluids Engineering,2014, 136(5): 051303.

    [23] Bensow R. E., Bark G. Implicit LES predictions of the cavitating flow on a propeller [J]. Journal of Fluids Engineering, 2010, 132(4): 041302.

    [24] Pendar M. R., Roohi E. Investigation of cavitation around 3D hemispherical head-form body and conical cavitators using different turbulence and cavitation models [J].Ocean Engineering, 2016, 112: 287-306.

    [25] Dawson T. E. An experimental investigation of a fully cavitating two-dimensional flat plate hydrofoil near a free surface [J]. California Institute of Technology, 1959,11(12): 1651-1655.

    [26] Wang Y. W., Xu C., Huang J. et al. Study on flow characteristics and stability mechanism of unsteady cavitating flow near the free surface [C]. Proceedings of the 14th National congress on Hydrodynamics and the 28th National Conference on Hydrodynamics. Changchun,2017, 94-104(in Chinese).

    [27] Wang Y. W., Xu C., Wu X. C. et al. Ventilated cloud cavitating flow around a blunt body close to the free surface[J]. Physical Review Fluids, 2017, 2(8): 084303.

    [28] Yu C., Wang Y. W., Huang C. G. et al. Experimental and numerical investigation on cloud cavitating flow around an axisymmetric projectile near the wall with emphasis on the analysis of local cavity shedding [J]. Ocean Engineering, 2017, 140: 377-387.

    [29] Xu C., Wang Y. W., Huang C. G. et al. Analysis of Nearwall effect on cloud cavitating flow that surrounds an axisymmetric projectile using large eddy simulation with Cartesian cut-cell mesh method [J]. European Journal of Mechanics-B/Fluids, 2018, 67: 15-24.

    [30] Xu C., Yu C., Huang J. et al. Experimental and numerical analysis of cloud cavitating flow that surrounds an axisymmetric projectile in shallow water [C]. Proceedings of the 14th National Congress on Hydrodynamics and the 28th National Conference on Hydrodynamics. Changchun,China, 2017, 518-524(in Chinese).

    [31] Zwart P. J., Gerber A G., Belarmri T. A two-phase on model for predicting cavitation dynamics [C]. Fifth International Conference on Multi-phase Flow. Yokohama,Japan, 2004.

    [32] Yu X., Wang Y., Huang C. et al. Study on the influence of phase change rate on cloud cavitation [J]. Procedia Engineering, 2013, 61(7): 204-206.

    [33] Long Y., Long X. P., Ji B. et al. Verification and validation of URANS simulations of the turbulent cavitating flow around the hydrofoil [J]. Journal of Hydrodynamics,2017, 29(4): 610-620.

    [34] Xing T. A general framework for verification and validation of large eddy simulation [J]. Journal of Hydrodynamics, 2015, 27(2): 163-175.

    猜你喜歡
    晨光
    牛來了
    瓷上賞青花
    大雁銜魚來
    航天晨光
    中國核電(2021年3期)2021-08-13 08:57:00
    晨光
    晨光與小鹿
    中外文摘(2020年23期)2020-01-01 13:56:52
    灞橋月
    晨光改造大多數(shù)
    晨光
    讀者(2016年3期)2016-01-13 16:50:34
    晨光
    海燕(2015年2期)2015-10-12 10:11:38
    久久久久久久亚洲中文字幕| 在线观看三级黄色| 天天躁日日操中文字幕| 女的被弄到高潮叫床怎么办| 中国美白少妇内射xxxbb| 国产熟女欧美一区二区| 久久久成人免费电影| 校园人妻丝袜中文字幕| 免费看av在线观看网站| 亚洲性久久影院| 国产女主播在线喷水免费视频网站| 亚洲国产精品专区欧美| 国语对白做爰xxxⅹ性视频网站| 欧美极品一区二区三区四区| 成年版毛片免费区| 3wmmmm亚洲av在线观看| 色播亚洲综合网| 婷婷色av中文字幕| 看免费成人av毛片| 亚洲美女视频黄频| 国模一区二区三区四区视频| 国产大屁股一区二区在线视频| 99久久九九国产精品国产免费| 国产精品成人在线| av在线天堂中文字幕| 精品一区二区三区视频在线| 中文字幕久久专区| 亚洲av欧美aⅴ国产| 大码成人一级视频| 亚洲av免费高清在线观看| 国产久久久一区二区三区| 色综合色国产| 哪个播放器可以免费观看大片| 成人漫画全彩无遮挡| 亚洲欧美日韩另类电影网站 | 午夜精品国产一区二区电影 | 久久久久久国产a免费观看| 2021少妇久久久久久久久久久| 99久久人妻综合| 国产成人精品福利久久| 亚洲伊人久久精品综合| 99久久精品国产国产毛片| av在线app专区| 国产探花极品一区二区| 日韩精品有码人妻一区| 六月丁香七月| 亚洲精品乱码久久久v下载方式| 免费大片黄手机在线观看| 97人妻精品一区二区三区麻豆| 国产精品女同一区二区软件| 久热久热在线精品观看| 久久女婷五月综合色啪小说 | 日本黄色片子视频| 国产欧美亚洲国产| 亚洲国产精品专区欧美| 亚洲国产色片| 国产淫语在线视频| 汤姆久久久久久久影院中文字幕| 久久久久久久精品精品| av线在线观看网站| 午夜福利在线观看免费完整高清在| 国产成人91sexporn| 欧美成人一区二区免费高清观看| 精品亚洲乱码少妇综合久久| 寂寞人妻少妇视频99o| 国产欧美另类精品又又久久亚洲欧美| 国产亚洲精品久久久com| 老女人水多毛片| 精品国产一区二区三区久久久樱花 | 边亲边吃奶的免费视频| 舔av片在线| 免费在线观看成人毛片| 成人高潮视频无遮挡免费网站| 哪个播放器可以免费观看大片| av国产精品久久久久影院| 如何舔出高潮| h日本视频在线播放| 国产精品av视频在线免费观看| 91精品伊人久久大香线蕉| 亚洲久久久久久中文字幕| h日本视频在线播放| 99热网站在线观看| 水蜜桃什么品种好| 久久亚洲国产成人精品v| 一区二区三区精品91| 偷拍熟女少妇极品色| 啦啦啦啦在线视频资源| 久久鲁丝午夜福利片| 国产一区二区在线观看日韩| 2021少妇久久久久久久久久久| 亚洲三级黄色毛片| 91久久精品电影网| av在线播放精品| 内地一区二区视频在线| 国产精品一区二区性色av| 麻豆国产97在线/欧美| 日韩 亚洲 欧美在线| 国产精品人妻久久久久久| 国产黄频视频在线观看| 卡戴珊不雅视频在线播放| 九九爱精品视频在线观看| 老司机影院毛片| 日日撸夜夜添| 在现免费观看毛片| 91狼人影院| 国产一区二区在线观看日韩| 最近手机中文字幕大全| 国产探花在线观看一区二区| 蜜臀久久99精品久久宅男| 超碰av人人做人人爽久久| 国产精品蜜桃在线观看| 三级经典国产精品| 国产男人的电影天堂91| 在线观看一区二区三区激情| 日韩成人伦理影院| 亚洲成色77777| 亚洲内射少妇av| 欧美xxⅹ黑人| 国内揄拍国产精品人妻在线| 69人妻影院| 在线观看三级黄色| 免费看a级黄色片| 国产免费福利视频在线观看| 黄色欧美视频在线观看| 美女视频免费永久观看网站| 精品人妻熟女av久视频| 免费观看性生交大片5| 黑人高潮一二区| 日本与韩国留学比较| 亚洲欧美一区二区三区黑人 | 欧美三级亚洲精品| 尾随美女入室| 亚洲国产精品999| 乱码一卡2卡4卡精品| 久久久久国产精品人妻一区二区| 一本久久精品| 性插视频无遮挡在线免费观看| 一级毛片电影观看| 国产精品精品国产色婷婷| 日韩三级伦理在线观看| 亚洲怡红院男人天堂| 久久久久精品久久久久真实原创| 男女边摸边吃奶| 精品国产一区二区三区久久久樱花 | 国产精品人妻久久久久久| 真实男女啪啪啪动态图| 极品教师在线视频| 最近2019中文字幕mv第一页| 色婷婷久久久亚洲欧美| 97热精品久久久久久| 欧美日韩国产mv在线观看视频 | 亚洲精品一二三| 国产 一区 欧美 日韩| 看十八女毛片水多多多| 青春草视频在线免费观看| 国产乱人视频| 国产探花极品一区二区| 免费看光身美女| 寂寞人妻少妇视频99o| 精品人妻偷拍中文字幕| 国产高潮美女av| 亚洲av国产av综合av卡| 午夜福利高清视频| av在线蜜桃| 欧美精品人与动牲交sv欧美| 欧美精品一区二区大全| 午夜福利网站1000一区二区三区| av.在线天堂| 九九在线视频观看精品| 亚洲欧美一区二区三区黑人 | 国产高清不卡午夜福利| 人体艺术视频欧美日本| 熟女电影av网| 22中文网久久字幕| 亚洲精品亚洲一区二区| 街头女战士在线观看网站| 精品国产乱码久久久久久小说| 亚洲av成人精品一二三区| 亚洲精品乱久久久久久| 777米奇影视久久| 国产精品爽爽va在线观看网站| av在线天堂中文字幕| 丝袜美腿在线中文| 97热精品久久久久久| 成年人午夜在线观看视频| 亚洲欧美日韩另类电影网站 | 国产一区二区亚洲精品在线观看| 高清av免费在线| 久久久精品欧美日韩精品| 精品少妇久久久久久888优播| 男男h啪啪无遮挡| 好男人在线观看高清免费视频| 久久久久国产精品人妻一区二区| 日韩一区二区三区影片| 国产精品伦人一区二区| 99热6这里只有精品| 超碰av人人做人人爽久久| 亚洲av福利一区| 国产精品av视频在线免费观看| 日日撸夜夜添| 中文精品一卡2卡3卡4更新| 亚洲自偷自拍三级| 麻豆国产97在线/欧美| 搡老乐熟女国产| 女人十人毛片免费观看3o分钟| 69人妻影院| 中文乱码字字幕精品一区二区三区| 欧美xxxx性猛交bbbb| av线在线观看网站| 国产在线男女| 国产精品一区二区三区四区免费观看| 寂寞人妻少妇视频99o| 免费观看a级毛片全部| 国产成人福利小说| 久久精品久久精品一区二区三区| 国产老妇伦熟女老妇高清| 免费看日本二区| videos熟女内射| 国产精品人妻久久久久久| 99精国产麻豆久久婷婷| 成人毛片60女人毛片免费| 亚洲精品成人久久久久久| 亚洲自偷自拍三级| 久久精品久久精品一区二区三区| 在现免费观看毛片| 成人二区视频| 国产色婷婷99| 黄色配什么色好看| 成人毛片a级毛片在线播放| 最新中文字幕久久久久| 大片电影免费在线观看免费| 69人妻影院| 欧美xxxx性猛交bbbb| 精品亚洲乱码少妇综合久久| 久久久欧美国产精品| 久久久久久久久久久免费av| 亚洲av中文av极速乱| www.色视频.com| 国产高清国产精品国产三级 | 毛片一级片免费看久久久久| 亚洲精品成人av观看孕妇| 国产亚洲av片在线观看秒播厂| 色5月婷婷丁香| 日本黄大片高清| 久久久久久伊人网av| 成人国产麻豆网| 国产精品精品国产色婷婷| 男人和女人高潮做爰伦理| 成人亚洲精品av一区二区| 联通29元200g的流量卡| 久久久久国产网址| 日韩中字成人| 国产男人的电影天堂91| 69av精品久久久久久| 麻豆精品久久久久久蜜桃| 欧美一级a爱片免费观看看| 亚洲色图av天堂| 国产精品成人在线| 啦啦啦在线观看免费高清www| 18禁在线无遮挡免费观看视频| 国产乱来视频区| 日本一本二区三区精品| 精品少妇黑人巨大在线播放| 国内精品美女久久久久久| 欧美日韩精品成人综合77777| 国产男女内射视频| 男插女下体视频免费在线播放| 极品教师在线视频| 日韩在线高清观看一区二区三区| 熟女电影av网| 97人妻精品一区二区三区麻豆| 久久精品综合一区二区三区| 国模一区二区三区四区视频| 婷婷色av中文字幕| 亚洲人成网站在线观看播放| 高清午夜精品一区二区三区| 婷婷色综合大香蕉| 麻豆国产97在线/欧美| 亚洲国产精品成人综合色| 在线免费观看不下载黄p国产| 精品久久久噜噜| 欧美最新免费一区二区三区| 国产真实伦视频高清在线观看| 精品一区在线观看国产| 午夜老司机福利剧场| 欧美丝袜亚洲另类| 男人添女人高潮全过程视频| 99精国产麻豆久久婷婷| 精品国产乱码久久久久久小说| 成人漫画全彩无遮挡| 国产精品嫩草影院av在线观看| 亚洲av在线观看美女高潮| 99re6热这里在线精品视频| 91久久精品电影网| 大码成人一级视频| 精品久久久久久久末码| 又爽又黄无遮挡网站| 小蜜桃在线观看免费完整版高清| 欧美日韩综合久久久久久| 欧美bdsm另类| 观看美女的网站| 国产成人aa在线观看| 午夜视频国产福利| 亚洲第一区二区三区不卡| 日日撸夜夜添| 国产免费一区二区三区四区乱码| 男人狂女人下面高潮的视频| 亚洲欧美成人精品一区二区| 成人毛片60女人毛片免费| 亚洲av福利一区| 热99国产精品久久久久久7| 直男gayav资源| h日本视频在线播放| 亚洲熟女精品中文字幕| 久久ye,这里只有精品| 亚洲欧美日韩另类电影网站 | 亚洲四区av| 熟妇人妻不卡中文字幕| 黄色配什么色好看| 日韩伦理黄色片| 国产av国产精品国产| 性色av一级| 搞女人的毛片| 国产精品成人在线| 观看美女的网站| 欧美3d第一页| 熟女av电影| 寂寞人妻少妇视频99o| xxx大片免费视频| 中文乱码字字幕精品一区二区三区| 亚洲av在线观看美女高潮| 久久久久久久久久久免费av| 最新中文字幕久久久久| 日本爱情动作片www.在线观看| 国产精品久久久久久久久免| 99re6热这里在线精品视频| 少妇人妻一区二区三区视频| 69人妻影院| 欧美日韩亚洲高清精品| 五月开心婷婷网| 久久99热这里只有精品18| 少妇猛男粗大的猛烈进出视频 | 自拍偷自拍亚洲精品老妇| 国产亚洲最大av| 天堂俺去俺来也www色官网| 91狼人影院| 日产精品乱码卡一卡2卡三| 一级二级三级毛片免费看| 国产成人aa在线观看| 另类亚洲欧美激情| 蜜臀久久99精品久久宅男| 亚洲精品国产成人久久av| 久久精品国产亚洲网站| 亚洲无线观看免费| 久久99精品国语久久久| 亚洲精品国产成人久久av| 少妇熟女欧美另类| 国产亚洲午夜精品一区二区久久 | .国产精品久久| 日日撸夜夜添| 亚洲精品日本国产第一区| 日韩欧美一区视频在线观看 | 日韩免费高清中文字幕av| 亚洲av不卡在线观看| 国产精品.久久久| 亚洲av男天堂| 国模一区二区三区四区视频| 最近最新中文字幕大全电影3| 日本-黄色视频高清免费观看| 亚洲自偷自拍三级| 国产 精品1| 国产精品不卡视频一区二区| 黄片无遮挡物在线观看| 女人十人毛片免费观看3o分钟| 直男gayav资源| 久久99精品国语久久久| 最近中文字幕高清免费大全6| 国产精品蜜桃在线观看| 亚洲经典国产精华液单| 亚洲国产av新网站| 亚洲综合精品二区| 精品视频人人做人人爽| 日韩av在线免费看完整版不卡| 日韩成人av中文字幕在线观看| 蜜桃久久精品国产亚洲av| 在线a可以看的网站| 国产精品国产三级国产av玫瑰| 精品一区二区三区视频在线| 成人欧美大片| 久久99精品国语久久久| 国产黄片视频在线免费观看| av在线app专区| 你懂的网址亚洲精品在线观看| 黑人高潮一二区| 麻豆成人午夜福利视频| 色5月婷婷丁香| 婷婷色综合大香蕉| 一二三四中文在线观看免费高清| 亚洲av在线观看美女高潮| 日韩欧美 国产精品| 成人漫画全彩无遮挡| 在线亚洲精品国产二区图片欧美 | 人妻 亚洲 视频| 日产精品乱码卡一卡2卡三| 亚洲色图综合在线观看| 国产日韩欧美亚洲二区| 久久热精品热| 久久久久久久精品精品| 九九爱精品视频在线观看| 夜夜看夜夜爽夜夜摸| 啦啦啦在线观看免费高清www| 99热这里只有是精品在线观看| 99久久九九国产精品国产免费| av免费在线看不卡| 国产成人aa在线观看| 一个人看视频在线观看www免费| 视频区图区小说| 免费观看的影片在线观看| 18+在线观看网站| 国产一区二区在线观看日韩| 欧美日韩国产mv在线观看视频 | 国产精品麻豆人妻色哟哟久久| 日韩一本色道免费dvd| 天美传媒精品一区二区| videos熟女内射| 亚洲一区二区三区欧美精品 | 赤兔流量卡办理| 国产精品偷伦视频观看了| 亚洲欧美日韩卡通动漫| 伊人久久国产一区二区| 久久热精品热| 超碰av人人做人人爽久久| 久久久久久久久久久丰满| 国产乱人视频| av国产精品久久久久影院| 亚洲精品一区蜜桃| 男女啪啪激烈高潮av片| 国产免费视频播放在线视频| 小蜜桃在线观看免费完整版高清| 久久精品久久久久久噜噜老黄| 男插女下体视频免费在线播放| 国产精品不卡视频一区二区| 久久久久久伊人网av| 在线免费观看不下载黄p国产| 国产精品.久久久| 麻豆国产97在线/欧美| 亚洲国产成人一精品久久久| 一级毛片黄色毛片免费观看视频| 亚洲精品国产色婷婷电影| 精品99又大又爽又粗少妇毛片| 精品熟女少妇av免费看| 国产一区有黄有色的免费视频| 日韩欧美 国产精品| 久久97久久精品| 亚洲丝袜综合中文字幕| 国产一区二区在线观看日韩| av女优亚洲男人天堂| 亚洲最大成人中文| 九色成人免费人妻av| 香蕉精品网在线| 成人毛片60女人毛片免费| 舔av片在线| 国产在线一区二区三区精| 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| 国产探花在线观看一区二区| 日韩中字成人| 国产片特级美女逼逼视频| 日韩,欧美,国产一区二区三区| 亚洲av.av天堂| 日韩 亚洲 欧美在线| 精品酒店卫生间| 欧美另类一区| 国产亚洲av片在线观看秒播厂| 日本色播在线视频| 在线免费十八禁| 老司机影院毛片| 国产精品精品国产色婷婷| 狠狠精品人妻久久久久久综合| 国产av码专区亚洲av| 一级毛片 在线播放| 少妇人妻久久综合中文| 亚洲人成网站在线播| 深夜a级毛片| 婷婷色av中文字幕| av免费在线看不卡| 免费av观看视频| 免费观看无遮挡的男女| 国产成人精品久久久久久| 国产视频内射| 亚洲av男天堂| 亚洲精品一二三| 欧美成人a在线观看| 国产免费福利视频在线观看| 国产精品99久久99久久久不卡 | 国产v大片淫在线免费观看| 日日撸夜夜添| 亚洲精品一二三| 大片免费播放器 马上看| 大话2 男鬼变身卡| 色视频www国产| 亚洲av.av天堂| 久久久欧美国产精品| 亚洲欧美日韩卡通动漫| 国产成人精品久久久久久| 久久精品久久久久久久性| 亚洲av成人精品一二三区| 可以在线观看毛片的网站| 少妇裸体淫交视频免费看高清| 免费大片黄手机在线观看| 欧美xxxx黑人xx丫x性爽| 国产午夜福利久久久久久| 色视频www国产| 国产精品一及| kizo精华| 性插视频无遮挡在线免费观看| 成人毛片a级毛片在线播放| 欧美 日韩 精品 国产| 在线观看三级黄色| 日本熟妇午夜| 99久国产av精品国产电影| av在线观看视频网站免费| 国产久久久一区二区三区| 欧美国产精品一级二级三级 | 熟女av电影| 天天躁日日操中文字幕| 亚洲激情五月婷婷啪啪| 国产在线一区二区三区精| 男女国产视频网站| 成人亚洲欧美一区二区av| 亚洲精品成人av观看孕妇| 久久久成人免费电影| 人人妻人人看人人澡| 一个人观看的视频www高清免费观看| 91久久精品电影网| 亚洲美女搞黄在线观看| a级毛片免费高清观看在线播放| 亚洲经典国产精华液单| 秋霞在线观看毛片| 精品一区二区免费观看| 熟女av电影| 亚洲精品国产av成人精品| 国产精品偷伦视频观看了| 最近最新中文字幕大全电影3| 18禁在线播放成人免费| 国产av码专区亚洲av| 色视频www国产| 亚洲av免费在线观看| 高清视频免费观看一区二区| 热99国产精品久久久久久7| 亚洲成人中文字幕在线播放| 午夜精品一区二区三区免费看| av在线播放精品| av在线蜜桃| 国产爽快片一区二区三区| 欧美另类一区| 人体艺术视频欧美日本| 免费看av在线观看网站| 久久人人爽人人爽人人片va| 大香蕉久久网| 熟女人妻精品中文字幕| 亚洲伊人久久精品综合| 免费av观看视频| 精品久久久精品久久久| 亚洲欧美日韩无卡精品| 精品视频人人做人人爽| 六月丁香七月| 日日啪夜夜撸| 国产一区有黄有色的免费视频| 久久精品久久精品一区二区三区| 欧美精品人与动牲交sv欧美| 亚洲av在线观看美女高潮| 国产精品精品国产色婷婷| 制服丝袜香蕉在线| 99热这里只有精品一区| 97在线视频观看| 人体艺术视频欧美日本| 婷婷色av中文字幕| 国产黄a三级三级三级人| 久久女婷五月综合色啪小说 | 午夜福利网站1000一区二区三区| 欧美高清性xxxxhd video| 一级毛片电影观看| 在线天堂最新版资源| 干丝袜人妻中文字幕| 国产男女内射视频| 成人亚洲欧美一区二区av| 婷婷色av中文字幕| 男女边吃奶边做爰视频| 99视频精品全部免费 在线| 性色av一级| 九色成人免费人妻av| 国产男女超爽视频在线观看| 成人鲁丝片一二三区免费| 国产男女内射视频| 亚洲成人av在线免费| 免费看日本二区| 久久久久久久午夜电影| 国产老妇女一区| 欧美丝袜亚洲另类| 欧美精品国产亚洲| 免费av不卡在线播放| 免费看av在线观看网站| 国产亚洲午夜精品一区二区久久 | 一级黄片播放器| 亚洲自偷自拍三级| h日本视频在线播放| 国产69精品久久久久777片| 国产男女内射视频| 九九在线视频观看精品| 在线亚洲精品国产二区图片欧美 | 波野结衣二区三区在线| 青春草国产在线视频| 国产国拍精品亚洲av在线观看| 久久久久久久久久人人人人人人|