• <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 ?

    Hydrodynamic metamaterials for flow manipulation:Functions and prospects

    2022-09-24 08:03:46BinWang王斌andJipingHuang黃吉平
    Chinese Physics B 2022年9期
    關(guān)鍵詞:王斌

    Bin Wang(王斌) and Jiping Huang(黃吉平)

    1School of Mechanical and Power Engineering,East China University of Science and Technology,Shanghai 200237,China

    2Department of Physics,State Key Laboratory of Surface Physics,and Key Laboratory of Micro and Nano Photonic Structures(MOE),Fudan University,Shanghai 200438,China

    Keywords: flow control,metamaterials,hydrodynamic cloaks,drag reduction,liquid diodes

    1. Introduction

    Flow control can be divided into macroscopic flow control and microscopic flow control(i.e.,microfluidics). Macroscopic flow control usually includes drag reduction, lift enhancement, transition delay, separation postponement, turbulence augmentation,and noise suppression,among others.[1,2]For microfluidics, flows can be manipulated precisely with microscale devices, which are involved in the semiconductor industry, the micro-electromechanical systems (MEMS)field,lab-on-a-chip technologies,and bio-fabrication research,among numerous other areas.[3,4]Efficient flow control systems can not only save billions of dollars annually in fuel costs for air, land, and sea vehicles, but also enable industrial processes involving flow control to become more precise as well as more economically and environmentally competitive. Therefore, the ability to actively or passively manipulate the flow field to achieve desired changes according to human wishes undoubtedly becomes crucial. For example,the resistance of a traveling object (such as a car, submarine,airplane,etc.) is generally proportional to the square of the object’s velocity, and the power consumed is proportional to the third power of the velocity. Namely, whenever the velocity increases two times, the resistance will increase four times, and then the power consumption is increased to eight times. However,if an object is in a hydrodynamically perfect cloaking state,then its drag force can become zero in motion,and in turn this object will not need additional boosters and power consumption. Thus, zero energy consumption can be achieved,which would be very exciting.

    The emergence of metamaterials of optical cloaks allows light or electromagnetic waves to propagate around an object as a fluid, leading to the cloaking of the object.[5,6]Consequently, it has inspired numerous studies on metamaterials in different fields, such as optics,[5,6]electromagnetics,[6,7]acoustics,[8,9]mechanics,[10,11]and thermodynamics.[12,13]However,how to achieve accurate manipulation of the flow remains a huge challenge because the Navier-Stokes equations governing fluid flow constitute a nonlinear set of equations,rendering studies of hydrodynamic metamaterials more challenging than those of other metamaterials, and consequently slower than the development of other metamaterials by many years. Fortunately,after these years of development,hydrodynamic metamaterials have gradually become an emerging hot research area.

    To provide the readers with a clear understanding of the history, physical mechanisms, and future trends of hydrodynamic metamaterials,we would like to review the major milestones of hydrodynamic metamaterials. In this review, we first introduce the theory and experiment of various kinds of hydrodynamic cloaking metamaterials in porous media and non-porous media. Then, we introduce other hydrodynamic metamaterials beyond cloaking. Finally, we present an outlook on the development of this appealing field and raise the challenges to be addressed.

    2. Hydrodynamic cloaking metamaterials

    To understand the basic fundamentals of hydrodynamic metamaterials, we start with their governing equations. The continuity equation and Navier-Stokes equations for incompressible flows at steady state without the influence of body forces can be written as

    whereρ,μ,u, andpdenote density, dynamic viscosity, velocity vector,and pressure,respectively.

    2.1. Hydrodynamic metamaterials in porous media

    For creeping flows in porous media, the inertia termρu·?uin Eq.(2)can be neglected. Hence,equation(2)can be simplified to the Brinkman-Stokes equation[14]

    Matching each term with Eqs. (1) and (5) subsequently provides us the fundamental equations for hydrodynamic transformation media[15]

    Similarly, hydrodynamic concentrators, hydrodynamic rotators, and hydrodynamic camouflage devices under creeping flows all can be obtained by coordinate transformation theory, as shown in Table 1. In addition, to extend metamaterials to the non-creeping flow circumstances,the stabilization of the hydrodynamic cloak in laminar-flow conditions[16,17]and the wave reduction resistance of the hydrodynamic cloak in turbulent-flow conditions[18]are successively studied. However,owing to the huge resistance of fluid flow in porous media,it is extremely difficult to provide a high Reynolds number for practical situations.

    Table 1. The most common cylindrical hydrodynamic metadevices in porous media and non-porous media based on transformation hydrodynamics.

    To further extend the hydrodynamic metamaterials to the area of convective thermal metamaterials, by coupling Eqs.(1)and(4)and energy transport equation,the authors in Refs. [19,20] successively studied convective thermal metamaterials from both steady-state and transient perspectives.After the extension of hydrodynamic metamaterials to the area of thermal metamaterials, numerous thermal metamaterials with various functions have been studied,[21-26]enabling the application of hydrodynamic metamaterials to be expanded from the area of nonlinear hydrodynamic metamaterials containing thermo-hydrodynamic coupling.

    Since the above hydrodynamic metamaterials are obtained based on the theory of porous media, they cannot be applied in the environment without porous media. For this reason, numerous researchers have started to investigate hydrodynamic metamaterials in the non-porous media environment.

    2.2. Hydrodynamic metamaterials in non-porous media

    Inspired by the fact that magnetohydrodynamic (MHD)effects[27]can be used to eliminate vortices, an active magnetohydrodynamic metamaterial is studied.[28]This study demonstrates that the metamaterials can eliminate the wake behind the cylinder at a fixed volume force distribution under forced laminar flow over a wide range of Reynolds numbers.However, these magnetohydrodynamic metamaterials cannot achieve perfect cloaking. To establish a design theory for fabricating perfect hydrodynamic metamaterials, the authors in Ref.[29]first proved that equations(1)and(2)(neglecting the inertia term)in creeping flows satisfy the coordinate transformation invariance and established the transformation hydrodynamics. Because the fluid flow bounds in the boundary layer are rotational, the governing equations do not satisfy the coordinate transformation invariance. To provide a clearer and more concise proof,according to Ref.[30],under irrotationalflow idealization (i.e.viscous potential flows), equations (1)and(2)can be transformed into Laplace equations as

    If we assume the flow is creeping flows, thenQ=p.Comparing Eq.(10)with Eq.(5)reveals that they are both in the form of Laplace’s equation. Obviously, we can similarly introduce the spatial coordinate transformation matrixJsuch that equations(9)and(10)from the virtual spacex(x,y,z)to the physical spacex'(x,y,z)satisfy

    Since equations (11) and (12) satisfy the coordinate transformation invariance,similar to the previous design of hydrodynamic metamaterials in porous media, we can choose different coordinate transformations and then use the transformation matrixJto calculate differentμ'. Eventually,it is possible to design hydrodynamic metamaterials with different functions in non-porous media. For the hydrodynamic cloak in nonporous media, the parameters can be obtained from Eq. (13),as shown below[29](Fig.1(a)):

    Inspired by the use of microfabricated arrays to steer,refract and focus the flow of biomaterials by Ref. [31], the hydrodynamic cloak for Hele-Shaw flows[32]is also experimentally fabricated.[29]It proves both theoretically and experimentally that the cloak can realize zero drag force.

    Similarly, hydrodynamic concentrators can be designed by varying the coordinate transformation of the expansion and compression of different regions in the axial direction[33](Fig. 1(b)), hydrodynamic rotators can be designed by varying the coordinate transformation of the rotation angle[34](Fig.1(c)),and hydrodynamic camouflage devices can be designed by adding the corresponding camouflage based on hydrodynamic cloaks[35](Figs. 1(d) and 1(e)). These four hydrodynamic devices are summarized in Table 1. Noteworthily,when two coordinate transformations of hydrodynamic rotators and hydrodynamic concentrators are combined,a venturieffect rotating concentrator in varying arbitrary directions can be fabricated.[36]This study also reveals that changing the sequence of rotation and aggregation results in nonreciprocity of coordinate transformations,i.e.,rotational coordinate transformations are performed first,followed by aggregation transformations, compared with the opposite order of coordinate transformations, one of which exhibits a rotational hysteresis effect.

    Since the shapes of objects in real life usually come in complex shapes,the authors in Ref.[37]designed a complexshaped cloak in Hele-Shaw flows by assembling different shaped cloaks, such as the square, triangular, and exemplary three-dimensional house-shaped cloaks. This study provides practical ideas for designing cloaks with different structures.In addition, the authors in Ref.[38]investigated the cloaking and drag reduction properties of cylinders, elliptic cylinders,vertical flat plates, and airfoils by using coordinate transformation theory, respectively. The study demonstrates that although the cloak designed by the coordinate transformation theory can achieve perfect cloaking only in the creeping Hele-Shaw flow situation, the drag reduction performance of the cloak remains excellent for the modest Reynolds number situation. It is remarkable that most of the above metamaterials obtained based on coordinate transformation theory are either obtained by linear coordinate transformation (transformation parameters are independent of other variables) or by background fluid being a single-phase flow. The investigation of hydrodynamic metamaterials in the case of nonlinear coordinate transformation and multiphase flow remains to be further explored, to which references[39,40]may provide inspiration.It is noticeable that when we introduce nonlinear coordinate transformation or multiphase flow, we need to pay attention to whether the original simplified equations (Eqs. (11) and(12)) are still applicable. For nonlinear problems, it is usually necessary to exploit a new theory. Subsequently,coupling the fluid dynamics and energy transport equations, the theory of transformation heat transfer in creeping flows is developed,which allows the design of different convective thermalmetamaterial devices,[41-43]and these findings will help to further explore nonlinear hydrodynamic metamaterials containing thermo-hydrodynamic coupling.

    In order to promote the cloak to the non-creeping flows,the authors in Ref. [44] theoretically designed a cloak in the laminar flows by coordinate-transforming the density and the viscosity coefficient simultaneously. However, transforming the density means that the flow is treated as a compressible flow,so the simultaneous manipulation of density and viscosity coefficients is difficult to achieve from the current physical viewpoint,and perhaps the technology in the future could realize the simultaneous manipulation of both. Due to the limitation of anisotropy of metamaterials using coordinate transformation theory design, the authors in Ref. [45] used scattering cancellation method to theoretically and experimentally implement a metamaterial-free cloak by adjusting the height of the cloak. However, the method enables cloaking in twodimensional flows by sacrificing the flow in the third dimension, which is only valid at very low Reynolds numbers. Besides, the authors in Ref. [46] experimentally designed a microfluidic cloak that does not require metamaterials by using 3D printing and two inlet and outlet flow filters; and the authors in Ref.[47]used deep-reinforcement-learning to achieve hydrodynamic active cloaking, but these cloaks still fail to achieve perfect cloaking.

    To homogenize the hydrodynamic cloak,[29]the authors in Ref. [35] then simplified the anisotropic inhomogeneous cloak to an anisotropic homogeneous cloak by using the integral median theorem and coordinate transformation theory.It is concluded that the drag force on the cloak in creeping flows becomes zero,and the cloak continues to exhibit remarkably strong drag reduction characteristics in laminar flows.Aiming to enable the cloak to be constant and extendable to non-creeping flows, the authors in Ref. [35] utilized the convection-diffusion-balance method, to solve Eqs. (9) and(10)analytically,and designed a microscale cylindrical cloak effective in a certain Reynolds number range (Re ≤42), the parameters of which are only related to the radius of the object and the cloak (μ2=(R22-R21)/(R22+R21)μb,μbis the background fluid viscosity coefficient), which greatly reduces the difficulty of cloak fabrication(Fig.2). Moreover,the study offers the possibility of realizing perfect cloaking by utilizing external fields(e.g.,temperature fields,external forces,and other methods). Subsequently, the authors in Ref. [48] achieved laminar hydrodynamic cloaking and hydrodynamic shielding at microscale from both numerically and experimentally by exploiting the electroosmotic flow-control method (Fig. 3).In addition, the method can achieve cloaking for arbitrarily shaped objects at the microscale.

    Fig. 2. Velocity distributions superimposed with streamlines (black lines) and isobars (white lines) of the hydrodynamic cloak at various laminar Reynolds numbers.[30]

    Fig. 3. Hydrodynamic cloaking and shielding in the presence of cylindrical objects.[48] (a)-(c) Theoretical pressure profile (color map) and streamlines(white lines)corresponding to(a)pressure-driven flow,(b)shielding,and(c)cloaking. (d)-(f)Experimental velocity fields(blue arrows)and resulting streamlines(black lines)corresponding to(d)pressure-driven flow,(e)shielding,and(f)cloaking.

    It is noteworthy that although zero-drag hydrodynamic cloaks for non-creeping flows have been extensively studied,[30,44,48]these hydrodynamic cloaks are still mainly limited to low Reynolds numbers. How to improve the applicability of hydrodynamic cloaks to the high Reynolds numbers will be a very challenging direction in the future. Research in high Reynolds-number cloaking will not only enable us to achieve zero energy consumption cloaking motion, but also allow us to escape extreme natural disasters, such as typhoons, tornadoes, and tsunamis,etc. Besides, if we can design hydrodynamic metamaterials under high Reynolds numbers,we can even regulate these natural disasters and convert them into electrical energy for the benefit of mankind; alternatively,we can even regulate the climate as well as make climate weapons.[49-52]

    3. Hydrodynamic metamaterials beyond cloaking

    In addition to hydrodynamic cloaking metamaterials,numerous other hydrodynamic metamaterials are not intended for cloaking purposes, such as liquid diodes,[64,65,65-69]liquid gates,[70-72]among other aspects. Since these studies have already been reviewed in the relevant literature,we will not expand too much on them.For this reason,we selectively choose some typical hydrodynamic metamaterials for a brief introduction,hoping to inspire relevant studies.

    3.1. Liquid diodes

    The directional and passive transport of water droplets is a universal phenomenon in nature and plays a key role in a variety of practical applications in the fields of energy,materials, physics, chemistry, biology, and medicine.[53-63]Hence, numerous researchers have investigated bionic liquid diodes.[64-69]Similar to an electronic diode that can conduct current in the forward direction and block it in the reverse direction, a liquid device that can rectify liquids to flow in a directional manner can be treated as a “l(fā)iquid diode”. It is noteworthy that although traditional mechanical valves can also perform unidirectional transport functions,traditional mechanical valves are relatively bulky compared to liquid diodes.Moreover,unlike traditional valves,the primary regulation of liquid diodes is based on surface chemistry and topography,which is mainly used in microfluidics and biology. Besides,as opposed to electronic diodes that work on semiconductor materials by applying an external voltage, ideal liquid diodes are able to deliver liquids in a directional manner on a variety of materials regardless of the need for any external energy entry.[66]If liquid diodes could be built as liquid logic gates or even logic gate arrays, then liquid “l(fā)ogic circuits” could be built and their applications would be very exciting. Finally,the dependence of liquid diodes on surface topography leads to the existence of hysteresis resistance,which limits their transport distance and velocity significantly. How to overcome the hindering liquid self-transfer on the liquid diode will be an important challenge for it.

    3.2. Liquid gates

    Controllable fluid transport[73-76]plays an important role in multiphase separations,[77,78]energy harvesting,[79,80]microfluidics,[81]chemical analyses,[82,83]smart valves,[84,85]and other fields. In recent years, researchers have proposed an emerging liquid gating technology that uses liquids as dynamic structural materials,breaking through the limitations of a single solid material with properties such as anti-pollution,energy saving,and functional controllability,and has received considerable attention as a novel method to control fluid transport. The mechanism of this technology adopts the unique mobility of liquid as a dynamic“gate”to realize the“opening”and“closing”of the pore channel under certain pressure[70,71]or photothermal induction.[72]Meanwhile, due to the difference of interfacial tension between different kinds of transport fluids and gating fluids, it features specific gating thresholds for each type of transport fluid,so that transport control of different fluids under different conditions can be implemented. It is worth noting that liquid gates are affected by a variety of factors such as pressure,temperature and surface tension,among others,their stability and application is extremely demanding on the environment. Therefore,it will be a great challenge to design a stable liquid gate for a wide range of applications.

    4. Summary and outlook

    In this review,we introduce the recent progress of hydrodynamic metamaterials. The current studies of hydrodynamic metamaterials mainly focus on the use of coordinate transformation theory,analytical solution methods,machine learning,and external field control. However, previous studies are still mainly limited to the moderate Reynolds number range,which is mainly due to the Navier-Stokes equations are a nonlinear system of equations as well as the coordinate transformation theory is only valid in the creeping flow and shallow channel flows. Therefore,the current research scope of hydrodynamic metamaterials is still mainly in the field of microfluidics,and many aspects remain to be further explored. For this reason,we propose several prospects here.

    (i)Since microfluidics has been extensively studied in the field of biofabrication,[86]related manipulation tools, such as optical,magnetical,electrical,mechanical,and combined manipulation techniques,may contribute in the future to diversify the fabrication of hydrodynamic metamaterials.

    (ii) The hydrodynamic metamaterials in this review are mainly for the flow control of conventional fluids, and few hydrodynamic metamaterials have been reported for the design of some exotic fluids, such as supercritical fluids,[87-89]superfluids,[90-93]liquid metal,[94-97]metafluids,[98-100]multiphase flows,[101-103]among others. These exotic fluids may be very different from conventional fluids in terms of flow control because of their different fluid properties,which will probably provide directions for the development of the investigation scope of hydrodynamic metamaterials.

    (iii)Because both the Stokes and Brinkman-Stokes equations at the steady state can be transformed into the Laplace equation,which is consistent with the steady-state form of the heat conduction equation. Therefore,many current innovative ideas for thermal metamaterials[104-109]can be applied to the design of hydrodynamic metamaterials. In addition,due to the control of thermal metamaterials mainly includes three basic forms of thermal conduction,thermal convection and thermal radiation,the development of the area of hydrodynamic metamaterials will help to reveal the manipulation mechanism of convective thermal metamaterials and further promote the development of thermal metamaterials.

    (iv) Noteworthily, because of the zero-drag characteristic of hydrodynamic cloaks, one of the most challenging and attractive research directions in the future lies in the design of hydrodynamic cloaks in high Reynolds numbers. If the high-Reynolds-number hydrodynamic cloak is implemented,the human energy consumption will be significantly reduced,which is extremely beneficial to the development of aeronautics and astronautics, as well as to utilize or defend against typhoons,tornadoes,and other harsh natural environments.

    (v)As a new branch of flow control,hydrodynamic metamaterials facilitate the understanding of fluid transport mechanisms which plays a critical role in understanding the mechanism of turbulent flows. Hence,comprehension to mechanism of turbulent flows will be promoted with the further advancement of hydrodynamic metamaterials. Because traditional fluid mechanics treats the dynamic viscosity as a fundamental property of a fluid,it may limit our understanding of fluid transport.In contrast,most of the parameters of hydrodynamic metamaterials are presented in the form of a tensor that varies with space, for example, the dynamic viscosity tensor exists in the limit values of infinity and zero. Understanding the dynamic viscosity or other parameters with space can deepen the understanding of the essence of fluid flows. Because turbulence can be understood mathematically and physically as the limit of fluid mechanics at zero viscosity. However,this limit comes as a singularity, because if we set the viscosity term directly to zero, we will not obtain turbulence using the Euler equation. This is because the viscous dissipation vanishes as the viscosity becomes smaller and smaller. Therefore, if we examine the nature of hydrodynamics with the perspective of asymptotically varying viscosity coefficients, it may help to reveal the nature of turbulence in the future. Perhaps this research direction,when flourished,could be called“metahydrodynamics”.

    Acknowledgements

    Project supported by Shanghai Science and Technology Development Funds (Grant No. 22YF1410600), the National Natural Science Foundation of China (Grant Nos. 11725521 and 12035004), and the Fund from the Science and Technology Commission of Shanghai Municipality (Grant No.20JC1414700).

    猜你喜歡
    王斌
    習(xí)作轉(zhuǎn)化創(chuàng)作
    質(zhì)子泵抑制劑對(duì)反流性咽喉炎的療效研究
    Device physics and design of FD-SOI JLFET with step-gate-oxide structure to suppress GIDL effect?
    王斌陶藝設(shè)計(jì)作品選
    王斌陶藝設(shè)計(jì)作品選
    公租房性猝死事件:貪個(gè)租金倒賠45萬
    Nutrient-enhanced n-alkanes biodegradation and succession of bacterial communities*
    Microbial ecological associations in the surface sediments of Bohai Strait*
    高考化學(xué)計(jì)算型習(xí)題常見解法例析
    不給禮金不準(zhǔn)結(jié)婚,女婿偽造存折弄巧成拙被判刑
    国产av国产精品国产| 亚洲欧美日韩另类电影网站| 天天添夜夜摸| 两个人免费观看高清视频| 热99国产精品久久久久久7| 久久精品国产综合久久久| 中文字幕av电影在线播放| 国产成人精品久久二区二区免费| 美国免费a级毛片| 少妇猛男粗大的猛烈进出视频| 香蕉久久夜色| 国产精品久久久久久精品电影小说| 侵犯人妻中文字幕一二三四区| 黄色 视频免费看| 亚洲伊人色综图| 午夜福利乱码中文字幕| 女性生殖器流出的白浆| 老司机影院毛片| 国产亚洲精品久久久久5区| 别揉我奶头~嗯~啊~动态视频| 成人18禁高潮啪啪吃奶动态图| 亚洲色图av天堂| 久久国产精品男人的天堂亚洲| 亚洲性夜色夜夜综合| av福利片在线| 男男h啪啪无遮挡| av天堂久久9| 91老司机精品| 久久婷婷成人综合色麻豆| 亚洲,欧美精品.| 最近最新免费中文字幕在线| 欧美大码av| 亚洲专区国产一区二区| 亚洲男人天堂网一区| 90打野战视频偷拍视频| 19禁男女啪啪无遮挡网站| 我要看黄色一级片免费的| 免费日韩欧美在线观看| a级毛片黄视频| 久久久久久免费高清国产稀缺| videos熟女内射| 在线观看免费视频网站a站| 精品少妇黑人巨大在线播放| 国产一区二区激情短视频| 黄色视频,在线免费观看| 满18在线观看网站| 一边摸一边抽搐一进一小说 | 午夜福利免费观看在线| 99热网站在线观看| 亚洲午夜理论影院| 国产男靠女视频免费网站| 国产一区二区三区在线臀色熟女 | 国产黄色免费在线视频| 久久午夜综合久久蜜桃| 精品一区二区三区视频在线观看免费 | 国产成人免费观看mmmm| a级毛片黄视频| 久久国产精品男人的天堂亚洲| 亚洲av第一区精品v没综合| 首页视频小说图片口味搜索| 在线十欧美十亚洲十日本专区| 欧美精品高潮呻吟av久久| 免费观看人在逋| 首页视频小说图片口味搜索| 国产精品99久久99久久久不卡| 午夜福利乱码中文字幕| 香蕉国产在线看| 久久久久久久久免费视频了| 亚洲国产毛片av蜜桃av| 亚洲七黄色美女视频| 中文字幕色久视频| 亚洲专区国产一区二区| 一二三四社区在线视频社区8| 成年人黄色毛片网站| 久久午夜综合久久蜜桃| 久久久久久人人人人人| 香蕉丝袜av| 国产单亲对白刺激| 侵犯人妻中文字幕一二三四区| 在线观看免费视频网站a站| 久久久久久久久久久久大奶| 久久热在线av| 大型黄色视频在线免费观看| 久久精品亚洲精品国产色婷小说| 免费在线观看影片大全网站| 99精国产麻豆久久婷婷| 免费久久久久久久精品成人欧美视频| 日韩中文字幕欧美一区二区| 午夜福利免费观看在线| 18禁裸乳无遮挡动漫免费视频| 国产亚洲精品一区二区www | 欧美激情高清一区二区三区| 大码成人一级视频| 午夜激情av网站| avwww免费| 中亚洲国语对白在线视频| 亚洲欧洲精品一区二区精品久久久| 成人特级黄色片久久久久久久 | 国产区一区二久久| 亚洲欧洲日产国产| 亚洲成国产人片在线观看| av福利片在线| 欧美人与性动交α欧美精品济南到| 日本av免费视频播放| 在线av久久热| 高清av免费在线| 亚洲欧洲精品一区二区精品久久久| 国产精品久久久久成人av| 两性午夜刺激爽爽歪歪视频在线观看 | 老熟妇乱子伦视频在线观看| 黑人巨大精品欧美一区二区mp4| 12—13女人毛片做爰片一| av线在线观看网站| 久久亚洲精品不卡| 99在线人妻在线中文字幕 | 99精品欧美一区二区三区四区| 成人亚洲精品一区在线观看| 天堂中文最新版在线下载| a在线观看视频网站| 一本—道久久a久久精品蜜桃钙片| 我的亚洲天堂| 黄色视频在线播放观看不卡| 国产日韩欧美在线精品| 久久中文看片网| 男女免费视频国产| 久久影院123| 国产精品免费视频内射| 99在线人妻在线中文字幕 | av网站在线播放免费| 老司机亚洲免费影院| av欧美777| 亚洲五月婷婷丁香| 午夜福利影视在线免费观看| 午夜福利,免费看| 国产成人av教育| 久久精品亚洲精品国产色婷小说| 欧美黑人精品巨大| 亚洲人成电影免费在线| 色播在线永久视频| 精品人妻在线不人妻| 国产精品偷伦视频观看了| 国精品久久久久久国模美| 国产日韩欧美亚洲二区| 人成视频在线观看免费观看| 中文字幕色久视频| 精品卡一卡二卡四卡免费| 水蜜桃什么品种好| 久久精品国产a三级三级三级| 另类亚洲欧美激情| 日韩欧美免费精品| 国产成人一区二区三区免费视频网站| 黑人欧美特级aaaaaa片| a级毛片黄视频| 日韩成人在线观看一区二区三区| 亚洲精品粉嫩美女一区| 久久九九热精品免费| 搡老乐熟女国产| 黄色成人免费大全| 国产在线观看jvid| 国产精品一区二区在线观看99| 如日韩欧美国产精品一区二区三区| www.精华液| 在线十欧美十亚洲十日本专区| 免费黄频网站在线观看国产| 免费高清在线观看日韩| 高清av免费在线| 另类精品久久| 一夜夜www| 国产日韩一区二区三区精品不卡| 动漫黄色视频在线观看| 精品国产乱码久久久久久男人| 一级毛片电影观看| av天堂在线播放| a级毛片在线看网站| 免费在线观看日本一区| 日韩 欧美 亚洲 中文字幕| 在线观看免费日韩欧美大片| 欧美精品啪啪一区二区三区| 国产欧美亚洲国产| www.精华液| 久久久久久久大尺度免费视频| 性色av乱码一区二区三区2| 国产亚洲午夜精品一区二区久久| 日本五十路高清| 中亚洲国语对白在线视频| 国产精品电影一区二区三区 | 久久人妻福利社区极品人妻图片| 50天的宝宝边吃奶边哭怎么回事| 日韩熟女老妇一区二区性免费视频| 青草久久国产| 国产老妇伦熟女老妇高清| 精品人妻熟女毛片av久久网站| 一区二区av电影网| 国产精品一区二区精品视频观看| 国产成人精品在线电影| 国产aⅴ精品一区二区三区波| 自线自在国产av| 亚洲av欧美aⅴ国产| 制服人妻中文乱码| 日韩欧美国产一区二区入口| tocl精华| 久久国产精品影院| 性色av乱码一区二区三区2| 两个人看的免费小视频| 成年动漫av网址| 亚洲人成电影免费在线| 国产视频一区二区在线看| 亚洲性夜色夜夜综合| 成人影院久久| 天天影视国产精品| 18禁黄网站禁片午夜丰满| 国产精品99久久99久久久不卡| 国产精品九九99| 熟女少妇亚洲综合色aaa.| 亚洲国产欧美日韩在线播放| 男女下面插进去视频免费观看| 免费av中文字幕在线| 激情在线观看视频在线高清 | 日韩大码丰满熟妇| 精品高清国产在线一区| 亚洲成人免费av在线播放| 90打野战视频偷拍视频| 黑人猛操日本美女一级片| 色老头精品视频在线观看| 久久久欧美国产精品| 极品人妻少妇av视频| 女同久久另类99精品国产91| 18禁美女被吸乳视频| 午夜免费鲁丝| 80岁老熟妇乱子伦牲交| 欧美一级毛片孕妇| av天堂在线播放| a在线观看视频网站| 美国免费a级毛片| 深夜精品福利| 国产精品 欧美亚洲| 自线自在国产av| 老鸭窝网址在线观看| 脱女人内裤的视频| 国产欧美日韩一区二区三| 最新在线观看一区二区三区| 妹子高潮喷水视频| 久久久久久久精品吃奶| 精品久久久精品久久久| 99精品欧美一区二区三区四区| 777米奇影视久久| 建设人人有责人人尽责人人享有的| 欧美日韩亚洲综合一区二区三区_| 国产日韩一区二区三区精品不卡| 国产精品香港三级国产av潘金莲| 日本wwww免费看| 香蕉久久夜色| 五月开心婷婷网| 免费久久久久久久精品成人欧美视频| 十八禁高潮呻吟视频| 欧美日韩成人在线一区二区| 欧美精品啪啪一区二区三区| 成在线人永久免费视频| 啦啦啦在线免费观看视频4| 男女无遮挡免费网站观看| 欧美日韩福利视频一区二区| 国产精品亚洲一级av第二区| 日本a在线网址| 欧美久久黑人一区二区| 精品一品国产午夜福利视频| 日韩中文字幕视频在线看片| 国产在线一区二区三区精| a在线观看视频网站| 无限看片的www在线观看| 啦啦啦 在线观看视频| 亚洲精品国产一区二区精华液| 黑人巨大精品欧美一区二区蜜桃| 十八禁人妻一区二区| av电影中文网址| 国产欧美亚洲国产| 青青草视频在线视频观看| 老司机午夜福利在线观看视频 | 日韩欧美免费精品| 色综合婷婷激情| 国产精品二区激情视频| 男女高潮啪啪啪动态图| 色在线成人网| 亚洲人成伊人成综合网2020| 久久久久久久大尺度免费视频| 日韩人妻精品一区2区三区| 啦啦啦中文免费视频观看日本| 亚洲专区中文字幕在线| 在线天堂中文资源库| 久久免费观看电影| 精品欧美一区二区三区在线| 色播在线永久视频| 黄色 视频免费看| 成人免费观看视频高清| 老司机午夜十八禁免费视频| 热99国产精品久久久久久7| 久久精品aⅴ一区二区三区四区| 亚洲精品自拍成人| 精品第一国产精品| 在线亚洲精品国产二区图片欧美| 亚洲av日韩精品久久久久久密| 两人在一起打扑克的视频| 曰老女人黄片| 欧美激情 高清一区二区三区| 欧美人与性动交α欧美精品济南到| 天天躁日日躁夜夜躁夜夜| 日韩欧美一区二区三区在线观看 | 天堂中文最新版在线下载| 久久 成人 亚洲| 亚洲男人天堂网一区| 一级片'在线观看视频| 99国产极品粉嫩在线观看| 成年人黄色毛片网站| 九色亚洲精品在线播放| 久久人妻熟女aⅴ| 日日夜夜操网爽| 1024香蕉在线观看| 亚洲欧洲精品一区二区精品久久久| 亚洲欧美色中文字幕在线| 嫁个100分男人电影在线观看| 成人18禁高潮啪啪吃奶动态图| 久久久久久久大尺度免费视频| 黑丝袜美女国产一区| 怎么达到女性高潮| 国产欧美日韩一区二区三| 18禁裸乳无遮挡动漫免费视频| 中文字幕制服av| 精品国产乱码久久久久久男人| 中文字幕av电影在线播放| 日本精品一区二区三区蜜桃| 午夜久久久在线观看| 欧美激情 高清一区二区三区| 午夜福利欧美成人| 免费人妻精品一区二区三区视频| 水蜜桃什么品种好| 久久免费观看电影| 手机成人av网站| 精品久久久久久久毛片微露脸| 国精品久久久久久国模美| 蜜桃在线观看..| 久久久久国产一级毛片高清牌| 国产精品影院久久| 亚洲国产av影院在线观看| av不卡在线播放| 久久久精品免费免费高清| 国产成人欧美在线观看 | 男女无遮挡免费网站观看| 国产成人免费观看mmmm| 国产精品影院久久| 国产区一区二久久| 国产精品亚洲一级av第二区| 大香蕉久久网| 色婷婷av一区二区三区视频| 我要看黄色一级片免费的| a级片在线免费高清观看视频| 视频在线观看一区二区三区| 啦啦啦中文免费视频观看日本| 欧美成人午夜精品| 男女之事视频高清在线观看| 人人妻人人添人人爽欧美一区卜| 99久久人妻综合| 十八禁人妻一区二区| 日日夜夜操网爽| 午夜福利一区二区在线看| 菩萨蛮人人尽说江南好唐韦庄| 99久久99久久久精品蜜桃| 人人妻人人爽人人添夜夜欢视频| 自拍欧美九色日韩亚洲蝌蚪91| 中文字幕制服av| 99国产精品一区二区蜜桃av | 夜夜骑夜夜射夜夜干| 亚洲,欧美精品.| 美女主播在线视频| 亚洲精品一卡2卡三卡4卡5卡| 视频区欧美日本亚洲| 午夜成年电影在线免费观看| 亚洲欧美色中文字幕在线| 两性夫妻黄色片| 久久久久网色| 国产一区二区三区在线臀色熟女 | av有码第一页| 久久久国产一区二区| 国产高清视频在线播放一区| 69av精品久久久久久 | 亚洲人成77777在线视频| 高清av免费在线| 亚洲全国av大片| 午夜福利在线观看吧| 不卡av一区二区三区| 国产精品免费一区二区三区在线 | 亚洲人成电影观看| 一区二区三区国产精品乱码| 热99久久久久精品小说推荐| 一本—道久久a久久精品蜜桃钙片| 欧美成人午夜精品| 久久精品人人爽人人爽视色| www.精华液| 飞空精品影院首页| 桃红色精品国产亚洲av| 亚洲一区中文字幕在线| 19禁男女啪啪无遮挡网站| 夫妻午夜视频| 新久久久久国产一级毛片| 国产黄频视频在线观看| 中文字幕高清在线视频| 日韩欧美三级三区| 国产精品亚洲av一区麻豆| 一级a爱视频在线免费观看| 免费观看人在逋| 国产精品电影一区二区三区 | 无遮挡黄片免费观看| 久久午夜亚洲精品久久| 9191精品国产免费久久| 另类亚洲欧美激情| 操出白浆在线播放| 不卡av一区二区三区| 亚洲精品美女久久av网站| 大码成人一级视频| 欧美日韩亚洲高清精品| 免费观看av网站的网址| 久久人人爽av亚洲精品天堂| 欧美av亚洲av综合av国产av| 一区在线观看完整版| 久久久久网色| 岛国毛片在线播放| 丰满人妻熟妇乱又伦精品不卡| 国产日韩欧美亚洲二区| 国产av又大| 老司机在亚洲福利影院| 90打野战视频偷拍视频| 中文字幕最新亚洲高清| 国产一区有黄有色的免费视频| tocl精华| 黄色视频在线播放观看不卡| 99精国产麻豆久久婷婷| 两个人看的免费小视频| 国产成人系列免费观看| 精品国产乱码久久久久久小说| 国产精品98久久久久久宅男小说| 国产日韩欧美亚洲二区| 午夜两性在线视频| 一夜夜www| 亚洲午夜理论影院| 久久中文看片网| 久久久久久亚洲精品国产蜜桃av| 欧美亚洲日本最大视频资源| 亚洲av日韩在线播放| 中文字幕最新亚洲高清| 国产精品影院久久| 制服诱惑二区| 亚洲欧美精品综合一区二区三区| 久久精品人人爽人人爽视色| av一本久久久久| h视频一区二区三区| 视频区图区小说| 亚洲国产成人一精品久久久| 亚洲五月婷婷丁香| 中文字幕av电影在线播放| 啦啦啦免费观看视频1| 日本vs欧美在线观看视频| 久久久精品区二区三区| a级毛片在线看网站| 日日爽夜夜爽网站| 久久毛片免费看一区二区三区| 中文字幕色久视频| 亚洲精品在线观看二区| 99热国产这里只有精品6| 动漫黄色视频在线观看| av网站免费在线观看视频| 日韩免费高清中文字幕av| 成人免费观看视频高清| 国产在线精品亚洲第一网站| 久久精品aⅴ一区二区三区四区| 十分钟在线观看高清视频www| 激情视频va一区二区三区| 狠狠狠狠99中文字幕| 色综合婷婷激情| 久久婷婷成人综合色麻豆| 国产精品久久久久久人妻精品电影 | av一本久久久久| 超碰97精品在线观看| 纵有疾风起免费观看全集完整版| 在线观看免费高清a一片| 国产精品二区激情视频| 亚洲伊人久久精品综合| a级毛片黄视频| 99在线人妻在线中文字幕 | 国产成人免费观看mmmm| 亚洲国产欧美日韩在线播放| 高清黄色对白视频在线免费看| 青青草视频在线视频观看| 一区福利在线观看| 精品国产乱码久久久久久小说| 黄色视频在线播放观看不卡| 久久精品人人爽人人爽视色| svipshipincom国产片| 97在线人人人人妻| 最黄视频免费看| 热re99久久精品国产66热6| 啦啦啦 在线观看视频| www.熟女人妻精品国产| 少妇粗大呻吟视频| 天天添夜夜摸| 2018国产大陆天天弄谢| 欧美日韩黄片免| 高清毛片免费观看视频网站 | 欧美亚洲日本最大视频资源| 高清黄色对白视频在线免费看| 亚洲专区字幕在线| 欧美日本中文国产一区发布| 婷婷丁香在线五月| 搡老岳熟女国产| 啪啪无遮挡十八禁网站| 免费av中文字幕在线| 亚洲精品一二三| 婷婷丁香在线五月| 人人妻,人人澡人人爽秒播| 免费看十八禁软件| www日本在线高清视频| 久久久欧美国产精品| 大片电影免费在线观看免费| 亚洲伊人色综图| 99精品久久久久人妻精品| 动漫黄色视频在线观看| 少妇裸体淫交视频免费看高清 | 一级,二级,三级黄色视频| 丝袜美足系列| 国产一区二区三区在线臀色熟女 | 又大又爽又粗| 黄网站色视频无遮挡免费观看| 黄片大片在线免费观看| 欧美成人午夜精品| 这个男人来自地球电影免费观看| 国产精品98久久久久久宅男小说| 国产精品.久久久| 日日摸夜夜添夜夜添小说| 亚洲熟妇熟女久久| 国产在线精品亚洲第一网站| 宅男免费午夜| 高清av免费在线| 少妇精品久久久久久久| 亚洲一卡2卡3卡4卡5卡精品中文| 中文亚洲av片在线观看爽 | 久久精品人人爽人人爽视色| 久久久久视频综合| 少妇精品久久久久久久| 久久久久久亚洲精品国产蜜桃av| 午夜免费成人在线视频| 日韩有码中文字幕| 欧美av亚洲av综合av国产av| 国产国语露脸激情在线看| 99国产极品粉嫩在线观看| 性少妇av在线| 国产精品麻豆人妻色哟哟久久| 99热网站在线观看| 欧美精品高潮呻吟av久久| 欧美一级毛片孕妇| h视频一区二区三区| √禁漫天堂资源中文www| 欧美变态另类bdsm刘玥| 黄色丝袜av网址大全| 美女高潮喷水抽搐中文字幕| 青青草视频在线视频观看| 女性生殖器流出的白浆| 国产亚洲精品一区二区www | 亚洲精品自拍成人| 国产精品久久久久久精品古装| 别揉我奶头~嗯~啊~动态视频| av天堂在线播放| 成人国语在线视频| 啦啦啦免费观看视频1| 夫妻午夜视频| 欧美老熟妇乱子伦牲交| 色视频在线一区二区三区| 久久av网站| 国产一区二区 视频在线| 国产午夜精品久久久久久| 99精品在免费线老司机午夜| 亚洲av日韩精品久久久久久密| 亚洲国产欧美网| 天堂中文最新版在线下载| 老司机在亚洲福利影院| 十八禁人妻一区二区| 中文字幕制服av| 性少妇av在线| 搡老岳熟女国产| 久久久久精品国产欧美久久久| 高清视频免费观看一区二区| 黄色毛片三级朝国网站| 日韩欧美免费精品| 老熟妇乱子伦视频在线观看| 久久精品成人免费网站| 亚洲精品国产区一区二| 在线观看免费午夜福利视频| 国产亚洲精品第一综合不卡| 色综合欧美亚洲国产小说| 80岁老熟妇乱子伦牲交| 久久久久久久久免费视频了| videosex国产| av不卡在线播放| 国产黄色免费在线视频| 亚洲精品国产区一区二| 欧美日韩福利视频一区二区| 精品亚洲乱码少妇综合久久| 一本色道久久久久久精品综合| 久久精品熟女亚洲av麻豆精品| 午夜成年电影在线免费观看| 亚洲第一青青草原| 我的亚洲天堂| 亚洲精品国产精品久久久不卡| 亚洲欧美一区二区三区久久| 久久久国产精品麻豆| 美国免费a级毛片| 国产伦人伦偷精品视频| 精品久久久精品久久久| 久久人妻熟女aⅴ|