• <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 ?

    Electro-osmotic flow of a second-grade fluid in a porous microchannel subject to an AC electric field*

    2013-06-01 12:29:57MISRA
    水動力學研究與進展 B輯 2013年2期
    關鍵詞:液硫噴射器焚燒爐

    MISRA J. C.

    Department of Mathematics, Institute of Technical Education and Research, Siksha O Anusandhan University, Bhubaneswar, India, E-mail:misrajc@gmail.com

    CHANDRA S.

    Department of Physics, Sabang S. K. Mahavidyalaya, Vidyasagar University, Midnapore, India

    Electro-osmotic flow of a second-grade fluid in a porous microchannel subject to an AC electric field*

    MISRA J. C.

    Department of Mathematics, Institute of Technical Education and Research, Siksha O Anusandhan University, Bhubaneswar, India, E-mail:misrajc@gmail.com

    CHANDRA S.

    Department of Physics, Sabang S. K. Mahavidyalaya, Vidyasagar University, Midnapore, India

    (Received May 17, 2012, Revised August 7, 2012)

    Studies on electro-osmotic flows of various types of fluids in microchannel are of great importance owing to their multifold applications in the transport of liquids, particularly when the ionized liquid flows with respect to a charged surface in the presence of an external electric field. In the case of viscoelastic fluids, the volumetric flow rate differs significantly from that of Newtonian fluids, even when the flow takes place under the same pressure gradient and the same electric field. With this end in view, this paper is devoted to a study concerning the flow pattern of an electro-osmotic flow in a porous microchannel, which is under the action of an alternating electric field. The influence of various rheological and electro-osmotic parameters, e.g., the Reynolds number, Debye-Huckel parameter, shape factor and fluid viscoelasticity on the kinematics of the fluid, has been investigated for a secondgrade viscoelastic fluid. The problem is first treated by using analytical methods, but the quantitative estimates are obtained numerically with the help of the software MATHEMATICA. The results presented here are applicable to the cases where the channel height is much greater than the thickness of the electrical double layer comprising the Stern and diffuse layers. The study reveals that a larger value of the Debye-Huckel parameter creates sharper profile near the wall and also that the velocity of electro-osmotic flow increases as the permeability of the porous microchannel is enhanced. The study further shows that the electro-osmotic flow dominates at lower values of Reynolds number. The results presented here will be quite useful to validate the observations of experimental investigations on the characteristics of electro-osmotic flows and also the results of complex numerical models that are necessary to deal with more realistic situations, where electro-osmotic flows come into the picture, as in blood flow in the micro-circulatory system subject to an electric field.

    electrical double layer, Debye length, second-grade fluid, Ionic energy

    Introduction

    In recent years microfluidics has emerged as an important branch of fluid mechanics. It has occupied a central position in scientific research and has profuse applications not only in engineering and technology, but also in various branches of science, including physiological and medical sciences. Studies on electroosmotic flow in microchannels have been receiving growing interest of researchers in recent years, because of their wide range of applications in many biomedical lab-on-a-chip devices to transport liquids in narrow confinements like sample injection, in the investigation of bio-chemical reactions and in the process of species separation[1-3]. Owing to the developments in micro-fabrication technologies, there has been an urgent need of research on various aspects of miniaturized fluidic systems in order that they can be utilized in a better way for drug delivery, DNA analysis/sequencing systems as well as in the improvement of biological/chemical agent detection sensors.

    When a solid surface comes in contact with an aqueous solution of an electrolyte, a structure is formed that comprises a layer of charges of one polarity on the solid side and a layer of charges of opposite polarity on the liquid side of the solid-liquid interface. This phenomenon is known as the Electrical Double Layer (EDL). In order to resolve problems arising out of highly charged double layers, Stern suggested the consideration of an additional internal layer, where the ions are strongly bound.

    The Stern layer is formed in the immediate vicinity of the wall with charges opposite to that of the wall and has a typical thickness of one ionic diameter. The ions within the Stern layer are attracted towards the wall with very strong electrostatic forces. But the ions in the outer diffuse layer are less associated and when these free ions experience a force due to the influence of an external electric field, there occurs a bulk motion of the liquid. This type of flow is termed as electro-osmotic flow.

    The concept of electro-osmosis has been established experimentally. Several studies on electro-osmosis in microchannels were carried out by some researchers in the recent past[4-7]. Different aspects of electro-osmotic flow in microchannels were investigated by them. All these studies were, however, confined to simple Newtonian fluids. But the flow behavior of a non-Newtonian fluid is of greater interest in many areas of science and technology, including physiology and medicine. Many physiological fluids such as blood, saliva and DNA solutions have been found to be viscoelastic in nature. It is now well known that changes due to different diseases or surgical interventions can be readily identified, considering blood viscoelasticity as a useful clinical parameter. Tang et al.[8]studied the electro-osmotic flow of a non-Newtonian viscous fluid described by the power law model, using the lattice Boltzmann method. Zhao et al.[9]presented a detailed account of studying the effect of dynamic viscosity on the velocity of the electro-osmotic flow of power-law fluids.

    Analysis, prediction and simulation of the behaviour of viscoelastic fluids by the use of Newtonian fluid models have been made in the past and they also have been adopted in many industries. But the flow behavior of viscoelastic fluids exhibits wide departure from that of Newtonian fluids. Various non-Newtonian models have been tried by several investigators to explain the complex behavior of viscoelastic fluids. Among them the second grade fluid models have become quite popular. One of the reasons for their popularity is that it has been possible to derive analytical solutions of different problems by adopting the second-grade fluid model and to explore thereby different characteristics of viscoelastic fluids. From the analytical solutions it is also possible to derive various information by using the method of parametric variation.

    There is another more important reason for considering second-grade viscoelastic fluid model in preference to other non-Newtonian fluid models. In a recent communication by Misra et al.[I0]it has been mentioned that the second-grade fluid model is compatible with the principles of thermodynamics. Moreover, the specific Helmholtz free energy is minimum in the equilibrium state of the fluid. This is owing to the fact that for a second-grade fluid, all of the following three conditions are met simultaneously whereμrepresents the fluid viscosity coefficient and a1,a2are normal stress moduli. It is worthwhile to emphasize that as a1<0, the fluid exhibits an anomalous behavior, even if the two other conditions are satisfied and therefore, that sort of fluid model is not suitable for use in any study of rheological fluids.

    It may further be mentioned that all porous media are stable both mechanically and chemically. Poroelastic and poroviscoelastic media possess the characteristics of porosity and permeability both. By utilizing the porosity factor, it is possible to control the fluid flow[10].

    Due to inherent analytical difficulties introduced by more complex constitutive equations, studies of non-Newtonian fluids have been limited to simple inelastic fluid models, such as the power-law model. Influences of viscosity index and electro-kinetic effects on the velocity of a third-grade fluid between microparallel plates were demonstrated by Akgul and Pakdemirli[11]. Dhinakaran et al.[12]presented a solution for a viscoelastic fluid model using the Phan-Thien-Tanner model. Some different aspects of electro-osmotic flow of a viscoelastic fluid in a channel was studied by Misra et al.[13]who also illustrated the applicability of their theoretical analysis to physiological fluid dynamics. But all these studies were limited to the steady case of electro-osmotic flow, where the external electric field was of DC nature, which requires extremely large voltages for producing significant electro-kinetic forces for a controlled transport of the fluid. To maintain controlled micro-bio-fluidic transport, a periodic electric field is better than a DC electric field in multiple ways. Moreover, in the study of some pathological situations as well as in various medical treatment methods, studies on flows in porous channels find significant applications. But all the investigations referred to above are not suitable to depict the exact behavioral pattern of fluid flow through a porous channel.

    The present study is motivated towards investigating the flow behavior of a second-grade viscoelastic fluid between two porous plates executing oscillatory motion, under the influence of electro-kinetic forces. In this study, an AC electric field is considered and for the sake of generality, the frequency of the oscillatory plates and that of the electric field are considered to be different. By adopting appropriate constitutive equations, a mathematical analysis has been presented with the purpose of examining the effect of the viscoelastic parameter in the ionized motion of the viscoelastic fluid. Analytical solutions are derived and the derived expressions have been computed numerically for aspecific situation. The numerical estimates obtained on the basis of our computational work, for different physical quantities of special interest are presented graphically. The results will be highly beneficial for validating the results of complex numerical models required for dealing with more realistic situations and also for establishing related experimental observations.

    1. The model and its analysis

    The constitutive equation of an incompressible second-grade fluid is of the form[14]

    where T is the Cauchy stress tensor,pis the pressure,-pIdenotes the indeterminate spherical stress andu,α1and α2are measurable material constants which denote, respectively, the viscosity, elasticity and cross-viscosity. These material constants can be determined from viscometric flows for any real fluid. A1and A2are the Rivlin-Ericksen tensors[14]and they denote, respectively, the rate of strain and acceleration.A1and A2are defined as

    whereu is the velocity vector,?, the gradient operator,T, the transpose andd/dtthe material time derivative.

    The basic equations governing the motion of an incompressible fluid are

    in which ρrepresents the fluid density,J, the current density,Hthe total magnetic field,μm, the magnetic permeability,E, the total electric field and kp, the permeability of the porous channel.

    Considering the flow to be symmetric, we can confine the analysis of the model to the region0≤y≤h, for Ex[0,L], whereL represents the length of the channel (cf. Fig.1) The effect of gravity and the Joule heating effect, being quite small for the situation taken up for the present study, will be disregarded. The Debye lengthλis assumed to be much smaller than the channel height2h . Further, h is supposed to be much smaller than the widthw and the lengthL of the channel.

    Fig.1 Physical sketch of the problem

    Inserting Eq.(2) into Eq.(6) and making use of Eqs.(3), (4) and (7) and assuming Boussinesq incomepressible fluid model yield the boundary-layer equations[15,16]governing the second grade viscoelastic fluid in the presence of a time-periodic electric field

    The charge density and electric potential are related to each other according to Gauss’s law of charge distribution. The relation is given by the equation

    where ρe=2 n0ez sinh(e z/ KBTψ)represents the distribution of net electric charge density in equilibrium near a charged surface, as in a fully developed flow, weis the angular velocity of the AC electric field,Exis the amplitude of the field andt denotes the time. The electrical double layers are considered to be so thin that there is no mutual interference between the walls. The symbolsv,K,ρand kpdenote respectively the kinematic viscosity, viscoelastic coefficient, density and porous medium permeability coefficient.

    Let us now introduce the following set of non-dimensional variables:

    In Eqs.(11) and (12),UHSdenotes the Helmholtz-Smoluchowski electro-osmotic velocity, which is defined by

    in which M stands for the mobility,ζfor the zeta potential,εfor the dielectric constant of the medium and u =ρvis the dynamic viscosity.

    In terms of the dimensionless variables defined in Eqs.(11) and (12), Eqs.(8)-(10) can be rewritten in the form

    where m2is called the Debye-Huckel parameter (in the non-dimensional form) and is defined by

    λbeing the thickness of the Debye layer.

    The solution of Eq.(16) subject to the boundary conditions

    In the sequel, we shall drop the superscript “?” to give a more convenient look to the equations involving non-dimensional variables. To solve the Eqs.(14), (15) and (16), we further write the velocityuas u= useiw1t, whereusrepresents the steady part of the velocity (independent of time).

    Now the boundary conditions applicable to our flow problem are,

    Making use of these boundary conditions and the Eq.(14), we have derived the following equation

    where w =we-ω1represents the difference between the angular velocity of the applied electric field and that of the oscillatory motion of the plates.

    來自各級硫冷凝器的液硫隨重力自流至液硫池(S-301),在液硫池中通過Black&Veatch的專利技術(shù)MAG○R脫氣工藝可將液硫中的硫化氫質(zhì)量分數(shù)脫除至15×10-6以下[2]。MAG○R液硫脫氣工藝無需采用任何化學添加劑,其工藝原理為:液硫在液硫池的不同分區(qū)中循環(huán)流動,并通過一、二級噴射器(EJ-302/303)進行機械攪動,溶解在液硫中的硫化氫釋放到氣相中并由蒸汽抽空器(EJ-301A/B)送入尾氣焚燒爐焚燒[3]。

    Solving the Eq.(20) subject to the boundary condition (19), we obtain,

    Equation (21) gives the required solution for the steady part of the electro-osmotic flow velocity, while for the problem under consideration at any instant, the fluid velocity is given by u= useiω1t. The numerical estimates of the velocity variations have been computed and presented graphically in the section that follows. They are quite useful to derive a variety of information in respect of different bio-medical applications.

    2. Application: Quantitative estimates for physiological flows

    In this section we want to present some numerical estimates that are useful to examine the variation in velocity distribution as well as the change in velocity as time progresses for different values of the parameters involved in the analysis of the problem. The software MATHEMATICA has been used for the purpose of computational work. In order to illustrate the applicability of the mathematical analysis presented in Section 1, we consider an example concerning the physiological problem of the hemodynamical channel flow of blood under the action of an applied alternating electric field. We have confined our computational work to electro-osmotic flows of blood in the microcirculatory system. With this end in view, the effects of the blood viscoelasticity parameter K, the Reynolds numberRe , the porous medium shape factor parameterD , the Debye-Huckel parameterm on velocity distribution of blood flow has been investigated thoroughly. For the purpose of computation of the concerned analytical expressions, we have made use of experimental data for different parameters for blood and its flow, as available from Refs.[17]-[20].

    Fig.2 Distribution of blood velocity during electro-osmotic flow, in lower range values of Reynolds number Re, when m =50,t =5,D =0.1,B =30,K =0.005, we=50,ω1=20

    Fig.3 Distribution of blood velocity during electro-osmotic flow, in higher range values of Reynolds number Re, when m =50,t =5,D =0.1,B =30,K =0.005, we=50,ω1=20

    Figure 2 provides an idea of the velocity distribution in the lower range of the Reynolds number Re. This figure reveals that with an increase in the Reynolds numberRe, the velocity of blood in a micro-channel decreases. But from Fig.3, it is revealed that the velocity increases with the increase in the Reynolds number (at a higher range values ofRe). Physically, the Reynolds number can be defined as a ratio between the inertia force and the viscous force. So, logically any increase in the Reynolds number causes a rise in the magnitude of the inertia force, and so the velocity should increase. But, for an electroosmotically actuated flow at lower values ofRe, flow due to electro-osmosis dominates first and with an increase in the value ofRe, the flow gradually turns out to be controlled by the inertia force arising out of the increasing value of Reynolds number. It is also to be observed from Fig.3 that the electrokinetic force is more dominant near the vicinity of the wall due to the formation of electrical double layer.

    From Fig.4 it is observed that the velocity increases with a rise in porous medium shape factorD. The shape factor of porous medium is the ratio between the permeability coefficient and the square of the height of the channel. So, any increase in theporous medium permeability coefficient causes a rise in the velocity of the fluid (blood). Figure 5 illustrates that the amplitude of oscillation of blood velocity u increases as the value of the shape factorD is enhanced.

    Fig.4 Variation in distribution of blood velocity during electroosmotic flow, for different values of porous medium shape factor parameter D, when m =50,t =5,Re= 0.001,B =30,K =0.005,we=50,ω1=20

    Fig.5 Variation in velocity field during electro-osmotic flow of blood with change in porous medium shape factor parameter D, when m =50,y =0.95,Re =0.01,B =30, K =0.005,we=5,ω1=2

    Fig.6 Variation in velocity distribution in electro-osmotic blood flow with change in blood viscoelasticity (K), when m =50,t =5,D =0.1,B =30,Re =0.01,we=50, ω1=20

    Fig.7 Change in velocity field of blood during electro-osmotic flow, with change in blood viscoelasticity (K), when m =50,y =0.9,D =0.1,B =30,Re =0.01,we= 5,ω1=2

    Fig.8 Change in distribution of electro-osmotic flow velocity of blood, as the value of the Debye-Huckel parameter m changes, where Re =0.1,t =10,D =0.1,B =30, K =0.005,we=500,ω1=200

    Fig.9 Change in distribution of electro-osmotic flow velocity with time as the value of the Debye-Huckel parameter m changes, when Re =0.1,y =0.9,D =0.1,B= 30,K =0.005,we=50,ω1=20

    3. Concluding remark

    The study has been motivated by recent developments of bio-sensing and high thought-put screening technologies for several important applications, such as sample collection for detection of viruses like adenovirus and Dengue Hemorrhagic fever. Basically the problem is formulated as a boundary-value problem concerning the flow of a second-grade viscoelastic fluid under the influence of electro-kinetic forces. The object of this theoretical investigation has been to have an idea of the distribution of the fluid velocity through a porous channel, with the change in different parameters of interest in the viscoelastic fluid flow pattern. The study serves as a first step towards a better understanding of the role of electro-osmosis in the viscoelastic flow pattern, which is oscillatory in nature, when influenced by an alternating electric field. The numerical estimates presented in the preceding section bear the potential of throwing some light on the electro-osmotic flow behavior of blood in the micro-circulatory system, when the system is under the influence of an external electric field. These results are expected to be of immense interest to clinicians and bio-engineers.

    Acknowledgement

    The authors wish to express their deep sense of gratitude to the esteemed reviewers for their comments on original version of the manuscript, based on which the revised manuscript has been prepared.

    [1] STONE H. A., STROOCK A. D. and AJDARI A. Engineering flows in small devides: Microfluidics toward a lab-on-a-chip[J]. Annual Review and Fluid Mechanics, 2004, 36: 381-411.

    [3] HLUSHKOU D., KANDHAI D. and TALLAREK U. Coupled lattice-Boltzmann and finite-difference simulation of velectroosmosis in microfluidic channels[J]. International Journal of Numerical Methods Fluids, 2004, 46(5): 507-532.

    [4] HERR A. E., MOLHO J. I. and SANTIAGO J. G. et al. Electro-osmotic capillary flow with non-uniform zeta potential[J]. Analytical Chemistry, 2000, 72: 1053-1057.

    [5] CHEN C.-I., CHEN C.-K. and LIN H.-J. Analysis of unsteady flow through a microtube with wall slip and given inlet volume flow variations[J]. Journal of Applied Mechanics, 2008, 75(1): 014506.

    [6] YANG R. J., FU L. M. and LIN Y. C. Electro-osmotic flow in microchannels[J]. Journal of Colloid Interface Science, 2001, 239: 98-105.

    [7] PIKAL M. J. The role of electroosmotic flow in transdermal ionotophoresis[J]. Advance Drug Delivery Reviews, 2001, 46(1-3): 281-305.

    [8] TANG G. H., LI X. F. and HE Y. L. et al. Electroosmotic flow of non-Newtonian fluid in microchannels[J]. Journal of Non-Newtonian Fluid Mechanics, 2009, 157(1-2): 133-137.

    [9] ZHAO C., ZHOLKOVSKIJ E. and JACOB H. et al. Analysis of electroosmotic flow of power-law fluids in a slit microchannel[J]. Journal of Colloid Interface Science, 2008, 326(2): 503-510.

    [10] MISRA J. C., SINHA A. and SHIT G. C. Flow of a biomagnetic viscoelastic fluid: Application to estimation of blood flow in arteries during electromagnetic hyperthermia, a therapautic procedure for cancer treatment[J]. Applied Mathematics Mechanics, 2010, 31(11): 1405-1420.

    [11] AKGUL M. B., PAKDEMIRLI M. Analytical and numerical solutions of electro-osmotically driven flow of a third-grade fluid between micro-parallel plates[J]. International Journal of Non-Linear Mechanics, 2008, 43(9): 985-992.

    [12] DHINAKARAN S., AFONSO A. M. and ALVES M. A. et al. Steady viscoelastic fluid flow between parallel plates under electro-osmotic forces: Phan-Thien-Tanner model[J]. Journal of Colloid Interface Science, 2010, 344(2): 513-520.

    [13] MISRA J. C., SHIT G. C. and CHANDRA S. et al. Electro-osmotic flow of a vis-coelastic fluid in a channel: Applications to physiological fluid mechanics[J]. Applied Mathematics and Computation, 2011, 217: 7932-7939.

    [14] RIVLIN R. S., ERICKSEN J. L. Stress deformation relations for isotropic materials[J]. Journal of Rational Mechanics Analysis, 1955, 4: 323-425.

    [15] MAKINDE O. D., MHONE P. Y. Heat transfer to MHD oscillatory flow in a channel filled with porous medium[J]. Rom Journal of Physics, 2005, 50(9-10): 931-938.

    [16] HAMZA M. M., ISAH B. Y. and USMAN H. Unsteady heat transfer to MHD oscillatory flow through a porous medium under slip condition[J]. International Journal of Computer Applications, 2011, 33(4): 12-17.

    [17] MISRA J. C., SHIT G. C. and RATH H. J. Flow and heat transfer of a MHD viscoelastic fluid in a channel with stretching wall: Some applications to hemodynamics[J]. Computers and Fluids, 2008, 37(1): 1-11.

    [18] MISRA J. C., SHIT G. C. and CHANDRA S. et al. Hydromagnetic flow and heat transfer of a second-grade viscoelastic fluid in a channel with oscillatory stretching walls: Application to the dynamics of blood flow[J]. Journal of Engineering Mathematics, 2011, 69(1): 91-100.

    [19] PAPADOPOULOS P. K., TZIRTZILAKIS E. E. Biomagnetic flow in a curved square duct under the influence of an applied magnetic field[J]. Physics of Fluids, 2004, 16(8): 29-52.

    [20] TZIRTZILAKIS E. E. A mathematical model for blood flow in magnetic field[J]. Physics of Fluids, 2005, 17(7): 07710.

    Nomenclature

    (x, y)– Space coordinates in Cartesian system

    u– Velocity of the fluid along x-direction

    us– The steady value of the velocity

    L– Length of the channel

    Ex– Amplitude of the instantaneous electric field applied externally

    E– Value of dc electric field

    v – The kinematic viscosity

    K– The coefficient of viscoelasticity

    kp– Porous medium permeability coefficient

    e– Charge of an electron

    z – Absolute value of the ionic valance

    KB– Boltzmann constant

    T– Temperature in Kelvin scale

    no– Ionic number concentration

    ω– The angular velocity

    ψ– Potential field in the transverse direction (induced)

    ζ– Wall zeta potential

    ε– Dielectric constant

    ρ– Density of the fluid

    ρe– Electric charge density

    v – The kinematic viscosity

    m– Non-dimensional Debye-Huckel parameter

    μ– Dynamicor viscometric viscosity

    p– Pressure

    D =k/h2– Porous medium shape factor parameter

    p

    λ– The thickness of electrical double layer

    B– Amplitude of the instantaneous pressure

    ωe– Angular velocity of the applied electric field ω1– Angular velocity of the oscillatory plates

    M– Mobility

    h– Half-width of the channel

    Re – Reynolds number

    10.1016/S1001-6058(13)60368-6

    * Biography: MISRA J. C. (1944-), Male, Ph. D., Professor

    猜你喜歡
    液硫噴射器焚燒爐
    尾氣處理工藝中尾氣焚燒爐的控制原理及應用
    液硫輸送和液位測量技改實踐
    垃圾焚燒爐的專利技術(shù)綜述
    含堿廢液焚燒爐耐火材料研究進展
    硫化氫制酸焚燒爐的模擬分析
    山東化工(2020年9期)2020-06-01 06:56:48
    液硫噴射鼓泡脫氣工藝運行及設計總結(jié)
    大型液硫脫氣裝置改造
    超深高含硫氣藏氣—液硫兩相滲流實驗
    噴射器氣體動力函數(shù)法的真實氣體修正
    喉嘴距可調(diào)的組裝式噴射器
    国产成人精品久久二区二区免费| 国产在线视频一区二区| 国产成人精品久久久久久| 99热国产这里只有精品6| 久久午夜综合久久蜜桃| 曰老女人黄片| 精品一品国产午夜福利视频| 国产免费福利视频在线观看| 一级片'在线观看视频| 女人爽到高潮嗷嗷叫在线视频| 悠悠久久av| 久久亚洲国产成人精品v| 男女免费视频国产| 成年女人毛片免费观看观看9 | 黄网站色视频无遮挡免费观看| 国产淫语在线视频| 中国美女看黄片| 久久久国产一区二区| 日韩免费高清中文字幕av| 嫩草影视91久久| 亚洲国产精品999| 电影成人av| 亚洲免费av在线视频| 久久 成人 亚洲| 国产一级毛片在线| 午夜福利免费观看在线| 十分钟在线观看高清视频www| 男男h啪啪无遮挡| 女人被躁到高潮嗷嗷叫费观| 日韩,欧美,国产一区二区三区| 国产色视频综合| 中文字幕最新亚洲高清| 秋霞在线观看毛片| 久久av网站| 免费看十八禁软件| 中国国产av一级| 又紧又爽又黄一区二区| 国产伦理片在线播放av一区| 亚洲熟女精品中文字幕| 91精品伊人久久大香线蕉| 悠悠久久av| 精品人妻熟女毛片av久久网站| 久久精品亚洲av国产电影网| 久久精品久久精品一区二区三区| 亚洲 国产 在线| 大香蕉久久网| 精品久久久久久电影网| 一本综合久久免费| 免费黄频网站在线观看国产| 精品国产一区二区三区久久久樱花| 国产成人一区二区三区免费视频网站 | 欧美少妇被猛烈插入视频| 手机成人av网站| 美女午夜性视频免费| 成年美女黄网站色视频大全免费| 国产精品 欧美亚洲| 下体分泌物呈黄色| 人妻一区二区av| 1024视频免费在线观看| 黄片播放在线免费| 久久精品久久久久久久性| 1024香蕉在线观看| 精品免费久久久久久久清纯 | 美女午夜性视频免费| 国产成人精品无人区| 成人国产av品久久久| 国产又爽黄色视频| 国产精品麻豆人妻色哟哟久久| 久久精品熟女亚洲av麻豆精品| www.999成人在线观看| 欧美日韩综合久久久久久| 在线看a的网站| 亚洲熟女精品中文字幕| 日韩大片免费观看网站| 校园人妻丝袜中文字幕| 女人爽到高潮嗷嗷叫在线视频| 久久久久网色| 黄色 视频免费看| 嫩草影视91久久| 美女中出高潮动态图| 中文字幕人妻丝袜一区二区| 最近中文字幕2019免费版| 99国产精品一区二区蜜桃av | 成人国产av品久久久| 19禁男女啪啪无遮挡网站| 国产成人精品无人区| 婷婷色综合大香蕉| xxx大片免费视频| 亚洲欧美日韩高清在线视频 | 又大又黄又爽视频免费| 久久ye,这里只有精品| 午夜福利影视在线免费观看| 在线观看人妻少妇| 亚洲欧美一区二区三区黑人| 午夜激情久久久久久久| 建设人人有责人人尽责人人享有的| 免费在线观看完整版高清| 欧美日韩视频精品一区| 好男人视频免费观看在线| 涩涩av久久男人的天堂| 婷婷色麻豆天堂久久| 亚洲情色 制服丝袜| 国产成人欧美| 国产精品av久久久久免费| 少妇的丰满在线观看| 国产精品熟女久久久久浪| 日韩 欧美 亚洲 中文字幕| 天天躁夜夜躁狠狠久久av| 欧美大码av| 韩国高清视频一区二区三区| 国产男女超爽视频在线观看| 亚洲精品国产一区二区精华液| 亚洲精品第二区| 欧美黑人欧美精品刺激| 亚洲伊人久久精品综合| 97人妻天天添夜夜摸| 亚洲精品日韩在线中文字幕| 精品熟女少妇八av免费久了| 咕卡用的链子| 赤兔流量卡办理| 超色免费av| 国产99久久九九免费精品| 纯流量卡能插随身wifi吗| 欧美黄色片欧美黄色片| 性高湖久久久久久久久免费观看| 亚洲国产精品一区二区三区在线| 亚洲av成人精品一二三区| 丰满人妻熟妇乱又伦精品不卡| 人人澡人人妻人| 久久精品亚洲熟妇少妇任你| 美女视频免费永久观看网站| 久久狼人影院| 人人妻人人爽人人添夜夜欢视频| 久久人妻熟女aⅴ| 汤姆久久久久久久影院中文字幕| 国产极品粉嫩免费观看在线| 一级片'在线观看视频| 男男h啪啪无遮挡| 97精品久久久久久久久久精品| 无遮挡黄片免费观看| 国产欧美亚洲国产| 久久精品熟女亚洲av麻豆精品| 在线精品无人区一区二区三| 天天操日日干夜夜撸| 国产欧美日韩综合在线一区二区| 午夜91福利影院| 男人添女人高潮全过程视频| 国产成人影院久久av| 久久久久久久精品精品| 久久国产精品男人的天堂亚洲| 婷婷色麻豆天堂久久| 国产99久久九九免费精品| 精品亚洲成a人片在线观看| 大型av网站在线播放| 欧美国产精品一级二级三级| 男人舔女人的私密视频| 亚洲激情五月婷婷啪啪| 91精品伊人久久大香线蕉| 国产又爽黄色视频| 日本午夜av视频| 午夜福利影视在线免费观看| 亚洲av美国av| 狂野欧美激情性xxxx| 一级黄色大片毛片| 欧美日韩亚洲综合一区二区三区_| av网站在线播放免费| 国产精品国产三级国产专区5o| 在线天堂中文资源库| 一本—道久久a久久精品蜜桃钙片| 777久久人妻少妇嫩草av网站| 深夜精品福利| 中文精品一卡2卡3卡4更新| 亚洲成人免费电影在线观看 | 咕卡用的链子| 亚洲,欧美,日韩| 菩萨蛮人人尽说江南好唐韦庄| 亚洲精品日本国产第一区| 国产午夜精品一二区理论片| 国产成人精品久久久久久| 亚洲国产欧美在线一区| netflix在线观看网站| 超碰97精品在线观看| 亚洲精品久久成人aⅴ小说| 国产免费现黄频在线看| 大香蕉久久成人网| 亚洲精品国产一区二区精华液| 久久国产亚洲av麻豆专区| 日本欧美国产在线视频| 中文字幕亚洲精品专区| 深夜精品福利| 国产精品偷伦视频观看了| 男女国产视频网站| 亚洲精品成人av观看孕妇| 亚洲精品久久成人aⅴ小说| 精品福利永久在线观看| 一级片'在线观看视频| 高清欧美精品videossex| 国产亚洲精品第一综合不卡| 色网站视频免费| 黄色片一级片一级黄色片| 啦啦啦在线免费观看视频4| 亚洲欧美日韩另类电影网站| 日韩精品免费视频一区二区三区| 性色av乱码一区二区三区2| 婷婷色综合大香蕉| 亚洲情色 制服丝袜| 精品少妇一区二区三区视频日本电影| 国产xxxxx性猛交| 成人亚洲精品一区在线观看| 亚洲七黄色美女视频| 亚洲五月婷婷丁香| 亚洲伊人久久精品综合| 欧美中文综合在线视频| 老司机影院成人| 国产免费又黄又爽又色| 成年美女黄网站色视频大全免费| 日韩大片免费观看网站| 夜夜骑夜夜射夜夜干| 极品少妇高潮喷水抽搐| 成人免费观看视频高清| 免费在线观看黄色视频的| 精品少妇内射三级| 99re6热这里在线精品视频| 一本—道久久a久久精品蜜桃钙片| 精品国产超薄肉色丝袜足j| 国产有黄有色有爽视频| 真人做人爱边吃奶动态| 久热这里只有精品99| 视频区图区小说| 国产精品99久久99久久久不卡| 午夜福利免费观看在线| 欧美久久黑人一区二区| 久久精品aⅴ一区二区三区四区| 久久精品久久久久久噜噜老黄| 九色亚洲精品在线播放| 51午夜福利影视在线观看| xxxhd国产人妻xxx| 亚洲成人国产一区在线观看 | 乱人伦中国视频| 十八禁人妻一区二区| av电影中文网址| 亚洲精品美女久久久久99蜜臀 | 亚洲成av片中文字幕在线观看| 一本色道久久久久久精品综合| 欧美亚洲日本最大视频资源| 婷婷色麻豆天堂久久| 一本久久精品| 在线天堂中文资源库| 欧美国产精品一级二级三级| 涩涩av久久男人的天堂| 少妇人妻 视频| 亚洲中文字幕日韩| 亚洲国产欧美一区二区综合| 久久精品亚洲熟妇少妇任你| 叶爱在线成人免费视频播放| 在线观看免费高清a一片| 欧美变态另类bdsm刘玥| 亚洲综合色网址| 久久久久久人人人人人| 成年人黄色毛片网站| 国产精品久久久久久精品电影小说| 人人妻人人澡人人爽人人夜夜| 中国国产av一级| 美女午夜性视频免费| 国产麻豆69| 亚洲av综合色区一区| 国产女主播在线喷水免费视频网站| 黄色毛片三级朝国网站| 欧美黑人欧美精品刺激| 日本猛色少妇xxxxx猛交久久| 女人高潮潮喷娇喘18禁视频| 亚洲色图 男人天堂 中文字幕| 亚洲午夜精品一区,二区,三区| 亚洲人成77777在线视频| 黄色a级毛片大全视频| 一区福利在线观看| 久久久久国产一级毛片高清牌| 中文字幕制服av| 麻豆av在线久日| 欧美人与性动交α欧美软件| 老司机影院毛片| 一级毛片女人18水好多 | 男男h啪啪无遮挡| 免费在线观看完整版高清| 精品熟女少妇八av免费久了| 国产在视频线精品| 精品国产一区二区三区久久久樱花| 大码成人一级视频| 国产日韩欧美视频二区| 国产成人精品无人区| 一级毛片我不卡| 五月开心婷婷网| 青青草视频在线视频观看| 在线观看免费视频网站a站| 亚洲免费av在线视频| 久久久久久久国产电影| 欧美日韩一级在线毛片| 亚洲中文字幕日韩| 麻豆av在线久日| 欧美精品啪啪一区二区三区 | 日韩av在线免费看完整版不卡| 欧美人与性动交α欧美软件| 中文字幕人妻丝袜制服| 精品国产国语对白av| 看免费成人av毛片| 成人18禁高潮啪啪吃奶动态图| 日韩电影二区| 欧美日韩亚洲国产一区二区在线观看 | 国产一区二区三区综合在线观看| 久久综合国产亚洲精品| 亚洲av美国av| 国产成人av激情在线播放| 天天影视国产精品| 男人操女人黄网站| 国产精品久久久久久精品电影小说| 久久鲁丝午夜福利片| 国产精品一区二区在线不卡| 亚洲成人国产一区在线观看 | 捣出白浆h1v1| 久久青草综合色| 人妻一区二区av| 亚洲欧洲精品一区二区精品久久久| 巨乳人妻的诱惑在线观看| 女人精品久久久久毛片| 老熟女久久久| 少妇人妻久久综合中文| 精品人妻一区二区三区麻豆| 亚洲欧洲国产日韩| 91字幕亚洲| 亚洲天堂av无毛| 亚洲中文字幕日韩| 中文欧美无线码| 久久人人爽人人片av| 男女下面插进去视频免费观看| 亚洲精品国产av成人精品| 天天添夜夜摸| 亚洲精品国产av成人精品| 老司机影院毛片| 亚洲中文日韩欧美视频| 成在线人永久免费视频| 美国免费a级毛片| 国产精品一区二区在线观看99| 久久综合国产亚洲精品| 久久精品国产亚洲av涩爱| 9色porny在线观看| 精品人妻熟女毛片av久久网站| 大片电影免费在线观看免费| 超碰97精品在线观看| 久久人妻熟女aⅴ| 欧美乱码精品一区二区三区| av有码第一页| 亚洲综合色网址| av天堂在线播放| 久9热在线精品视频| 亚洲精品在线美女| 美女主播在线视频| 日韩制服丝袜自拍偷拍| e午夜精品久久久久久久| 午夜免费成人在线视频| 国产成人欧美在线观看 | 成人国语在线视频| 亚洲精品第二区| 男女免费视频国产| 手机成人av网站| 中文字幕另类日韩欧美亚洲嫩草| 国产高清国产精品国产三级| 亚洲av在线观看美女高潮| 欧美日韩福利视频一区二区| 三上悠亚av全集在线观看| 别揉我奶头~嗯~啊~动态视频 | 欧美激情极品国产一区二区三区| 校园人妻丝袜中文字幕| 国产亚洲欧美在线一区二区| 咕卡用的链子| 久久精品国产亚洲av高清一级| 免费日韩欧美在线观看| 黄频高清免费视频| 国产片特级美女逼逼视频| 欧美在线一区亚洲| 亚洲精品一卡2卡三卡4卡5卡 | 少妇人妻 视频| 黑人巨大精品欧美一区二区蜜桃| 99热网站在线观看| 亚洲欧美色中文字幕在线| 亚洲国产欧美在线一区| 考比视频在线观看| 成人18禁高潮啪啪吃奶动态图| 免费在线观看完整版高清| 国产精品一区二区免费欧美 | 美女主播在线视频| 久久精品国产a三级三级三级| 国产一区二区在线观看av| 亚洲图色成人| 日韩中文字幕视频在线看片| 久久久精品免费免费高清| 久久久精品94久久精品| 亚洲国产精品999| 校园人妻丝袜中文字幕| 人人妻人人澡人人爽人人夜夜| netflix在线观看网站| 国产熟女欧美一区二区| 中文乱码字字幕精品一区二区三区| cao死你这个sao货| 亚洲五月色婷婷综合| 男女边摸边吃奶| 亚洲自偷自拍图片 自拍| 欧美激情 高清一区二区三区| 日本一区二区免费在线视频| 老司机亚洲免费影院| 女性生殖器流出的白浆| 日本猛色少妇xxxxx猛交久久| 国产成人欧美| 母亲3免费完整高清在线观看| 精品国产国语对白av| 在线天堂中文资源库| 黄色a级毛片大全视频| 亚洲视频免费观看视频| 狂野欧美激情性xxxx| av在线app专区| 欧美亚洲 丝袜 人妻 在线| 久久精品亚洲熟妇少妇任你| videosex国产| 亚洲情色 制服丝袜| h视频一区二区三区| 亚洲av男天堂| 欧美成人精品欧美一级黄| 婷婷色麻豆天堂久久| 国精品久久久久久国模美| 新久久久久国产一级毛片| 母亲3免费完整高清在线观看| 天天躁日日躁夜夜躁夜夜| 亚洲国产精品999| 国产精品欧美亚洲77777| 在线观看一区二区三区激情| 午夜av观看不卡| 亚洲熟女毛片儿| 欧美精品一区二区大全| 丰满少妇做爰视频| 国产精品.久久久| 一区二区三区四区激情视频| 国产欧美日韩一区二区三 | 午夜福利,免费看| 免费在线观看黄色视频的| 国产免费一区二区三区四区乱码| 亚洲国产看品久久| 波多野结衣一区麻豆| 秋霞在线观看毛片| 男女免费视频国产| av电影中文网址| 久久鲁丝午夜福利片| 久久久精品国产亚洲av高清涩受| 久久久久精品国产欧美久久久 | 母亲3免费完整高清在线观看| 18禁裸乳无遮挡动漫免费视频| 午夜日韩欧美国产| 黑人巨大精品欧美一区二区蜜桃| 久久鲁丝午夜福利片| 后天国语完整版免费观看| 久久午夜综合久久蜜桃| 97精品久久久久久久久久精品| 精品国产一区二区三区四区第35| 一级毛片黄色毛片免费观看视频| 亚洲国产av影院在线观看| 国产免费视频播放在线视频| 女人被躁到高潮嗷嗷叫费观| 亚洲成av片中文字幕在线观看| 91国产中文字幕| av天堂久久9| 麻豆乱淫一区二区| 热99久久久久精品小说推荐| 日韩av不卡免费在线播放| 午夜久久久在线观看| 曰老女人黄片| 男女无遮挡免费网站观看| 亚洲国产精品成人久久小说| 国产男女超爽视频在线观看| 日韩一卡2卡3卡4卡2021年| 精品国产国语对白av| 极品少妇高潮喷水抽搐| 亚洲九九香蕉| 亚洲精品乱久久久久久| av不卡在线播放| 国产又爽黄色视频| 大型av网站在线播放| 亚洲欧洲日产国产| 国产亚洲av高清不卡| 亚洲视频免费观看视频| 欧美亚洲 丝袜 人妻 在线| 黑人欧美特级aaaaaa片| 亚洲av综合色区一区| 欧美激情极品国产一区二区三区| 日韩伦理黄色片| 91精品伊人久久大香线蕉| 极品少妇高潮喷水抽搐| 性色av乱码一区二区三区2| 成人三级做爰电影| 狂野欧美激情性bbbbbb| 久久天堂一区二区三区四区| 超色免费av| 一区二区三区四区激情视频| 黑人巨大精品欧美一区二区蜜桃| 国产av精品麻豆| 爱豆传媒免费全集在线观看| 男人爽女人下面视频在线观看| 午夜免费观看性视频| 免费人妻精品一区二区三区视频| 日本av手机在线免费观看| 91字幕亚洲| 男女之事视频高清在线观看 | 久久精品久久精品一区二区三区| 999久久久国产精品视频| 久久中文字幕一级| 国产成人啪精品午夜网站| 午夜两性在线视频| 黄色视频不卡| 成人国语在线视频| 777久久人妻少妇嫩草av网站| 久久av网站| 久久这里只有精品19| 亚洲精品日本国产第一区| 亚洲精品一二三| 国产国语露脸激情在线看| 我要看黄色一级片免费的| 99国产综合亚洲精品| 成人三级做爰电影| 啦啦啦啦在线视频资源| 午夜福利在线免费观看网站| 精品久久蜜臀av无| 日韩中文字幕欧美一区二区 | 欧美中文综合在线视频| 欧美日韩黄片免| 99精国产麻豆久久婷婷| 国产精品 欧美亚洲| 亚洲国产欧美日韩在线播放| 中文字幕另类日韩欧美亚洲嫩草| 丰满人妻熟妇乱又伦精品不卡| 国产成人欧美| 欧美xxⅹ黑人| 久久人人爽av亚洲精品天堂| 精品人妻一区二区三区麻豆| 色精品久久人妻99蜜桃| 中文字幕av电影在线播放| 国产在线观看jvid| 久久九九热精品免费| 女人爽到高潮嗷嗷叫在线视频| 国产精品久久久人人做人人爽| 日韩伦理黄色片| 手机成人av网站| 19禁男女啪啪无遮挡网站| 中文精品一卡2卡3卡4更新| 国产精品久久久久久精品古装| 精品国产一区二区三区久久久樱花| www.熟女人妻精品国产| 久久人人97超碰香蕉20202| 男的添女的下面高潮视频| 啦啦啦视频在线资源免费观看| 午夜福利乱码中文字幕| 中文字幕最新亚洲高清| 国产在线视频一区二区| 精品国产国语对白av| 国产亚洲精品久久久久5区| 中文字幕最新亚洲高清| 新久久久久国产一级毛片| 免费人妻精品一区二区三区视频| 午夜日韩欧美国产| 蜜桃在线观看..| 七月丁香在线播放| 性色av一级| 99国产精品一区二区蜜桃av | 99香蕉大伊视频| 午夜激情av网站| 最近中文字幕2019免费版| 一区福利在线观看| 另类亚洲欧美激情| 国产男人的电影天堂91| 亚洲国产毛片av蜜桃av| 日韩制服骚丝袜av| 亚洲av成人不卡在线观看播放网 | 夫妻性生交免费视频一级片| 国语对白做爰xxxⅹ性视频网站| 亚洲九九香蕉| 国产99久久九九免费精品| 久久毛片免费看一区二区三区| 一本色道久久久久久精品综合| 欧美日韩亚洲高清精品| 最新的欧美精品一区二区| 无限看片的www在线观看| 亚洲,欧美,日韩| 亚洲欧美一区二区三区黑人| 日日爽夜夜爽网站| 熟女av电影| 亚洲国产中文字幕在线视频| 男女午夜视频在线观看| 中文字幕人妻熟女乱码| 亚洲中文字幕日韩| 电影成人av| 色婷婷久久久亚洲欧美| 久久国产精品大桥未久av| 脱女人内裤的视频| 免费在线观看完整版高清| 国产成人啪精品午夜网站| 欧美精品高潮呻吟av久久| 老司机午夜十八禁免费视频| 飞空精品影院首页| 国产精品偷伦视频观看了| 亚洲欧美一区二区三区国产| 性色av乱码一区二区三区2| 精品卡一卡二卡四卡免费| 日韩,欧美,国产一区二区三区| 精品第一国产精品| 亚洲人成网站在线观看播放| 又粗又硬又长又爽又黄的视频| 日本五十路高清| 视频区图区小说| 纯流量卡能插随身wifi吗|