• <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 ?

    Investigation of rotating stall for a centrifugal pump impeller using various SGS models*

    2017-04-26 06:00:50PeijianZhou周佩劍FujunWang王福軍ZhengjunYang楊正軍JiegangMou牟介剛
    關(guān)鍵詞:佩劍

    Pei-jian Zhou (周佩劍), Fu-jun Wang (王福軍), Zheng-jun Yang (楊正軍), Jie-gang Mou (牟介剛)

    1.College of Water Resources and Civil Engineering, China Agricultural University, Beijing 100083, China

    2.College of Mechanical Engineering, Zhejiang University of Technology, Hangzhou 310014, China,

    E-mail: peijianzhou@gmail.com

    Investigation of rotating stall for a centrifugal pump impeller using various SGS models*

    Pei-jian Zhou (周佩劍)1,2, Fu-jun Wang (王福軍)1, Zheng-jun Yang (楊正軍)1, Jie-gang Mou (牟介剛)2

    1.College of Water Resources and Civil Engineering, China Agricultural University, Beijing 100083, China

    2.College of Mechanical Engineering, Zhejiang University of Technology, Hangzhou 310014, China,

    E-mail: peijianzhou@gmail.com

    The accurate modeling and prediction of the rotating stall in a centrifugal pump is a significant challenge. One of the modeling techniques that can improve the accuracy of the flow predictions is the large eddy simulation (LES). The quality of the LES predictions depends on the sub-grid-scale (SGS) model implemented in the LES. This paper assesses the influence of various SGS models that are suitable for predicting rotating stall in a low-specific speed centrifugal pump impeller. The SGS models considered in the present work include the Smagorinsky model (SM), the dynamic Smagorinsky model (DSM), the dynamic non-linear model (DNM), the dynamic mixed model (DMM) and the dynamic mixed non-linear model (DMNM). The results obtained from these models are compared with the PIV and LDV experimental data. The analysis of the results shows that the SGS models have significant influences on the flow field. Among the models, the DSM, the DMM and the DMNM can successfully predict the“two-channel” stall phenomenon, but not the SM and the DNM. According to the simulations, the DMNM gives the best prediction on the mean velocity flow field and also indicates improvements for the simulation of the turbulent flow. Moreover, the high turbulent kinetic energy predicted by the DMNM is in the best agreement with the experiment data.

    Centrifugal impeller, rotating stall, large eddy simulation, sub-grid-scale (SGS) model

    Introduction

    The rotating stall is a key issue for the stable operation of centrifugal pumps[1,2]. This phenomenon often occurs under a part load condition and is usually accompanied with a large flow separation and strong anisotropy, which serves as a very severe test for the flow simulation by turbulence models based on the linear eddy viscosity concept. It is a challenging task to accurately predict the rotating stall within a pump.

    The improvements in the computer power make it possible to implement advanced models such as the LES to study the performance of pumps. The application of the LES for pumps becomes a widely used technique in recent years. Byskov et al.[3]applied the LES and the RANS models to a centrifugal pump impeller containing two bladed channels. The results indicate that the LES results are in superior agreement with the measurements as compared to the RANS ones, particularly at the stall point. Feng et al.[4]implemented the hybrid RANS-LES approach to predict a “two-channel” stall phenomenon in the impeller, where the RNGand SSG models fail to provide such predictions. Lucius and Brenner[5,6]used another hybrid RANS-LES method called the scaleadaptive simulation to determine the rotating stall in a centrifugal pump, while Hasmatuchi[7]also applied the same methodology to investigate the stall flow in a pump-turbine. Tao et al.[8]considered a novel rotating correction on the RANS, to improve the accuracy under the designed condition. However, a large deviation can still be observed during the stall flow. In the study presented by Braun[9], numerical investigations of the rotating stall in a pump-turbine were performed. The results indicate that the SSTmodel fails toaccurately reproduce the phenomenon. Pacot et al.[10]investigated the rotating stall phenomena in a pumpturbine under a part load condition. The results demonstrate that unlike the RANS approach, the LES is a powerful tool to predict the stall flow.

    According to the literature, the reliability of the LES relies on the performance of the employed SGS model. The early work presented by Kato et al.[11]shows that the stall point predicted by the SM for a mixed-flow pump is at a slightly lower flow-rate ratio, as compared to the measurements. Posa et al.[12]tested the SM and the filtered structured function (FSF) model for a mixed-flow pump, and it is shown that the FSF model performs better for the complex flow under the off-design condition. Yang et al.[13]evaluated SGS models including the SM, the DSM and the DMM for the LES in a shrouded six-bladed centrifugal pump impeller under the design condition. Among the models, the DMM showed improvement in predictions of both the surface shear stress and the velocity distributions. Furthermore, Yang and Wang[14]proposed a dynamic mixed nonlinear model (DMNM) which combines the advantages of the DMM and the DNM. Their study shows that the DMNM can capture the detailed vortex characteristics more accurately. The SGS models have great effects on the rotating stall in a pump. According to the knowledge of the authors, it is still not clear which SGS model can provide better predictions under similar circumstances. It is an urgent task to evaluate the performance of various SGS models.

    The present study investigates the performance of five SGS models (SM, DSM, DNM, DMM and DMNM) in the internal flow prediction of a low specific speed centrifugal pump impeller under the stall condition. Various features studied include velocities, vortices and the turbulent kinetic energy, and the results predicted by the SGS models are compared with available experimental data obtained from the PIV and the LDV.

    1. Description of SGS models

    In the LES, the effects of large-scale eddies are considered while small-scale eddies are modeled according to a pattern. Compared to the original N-S governing equations, the LES involves an additional SGS stress tensor termwithin the governing equation. This term can be modeled with various SGS models such as SM, DSM, DNM, DMM and DMNM.

    1.1Smagorinsky model (SM)

    One of the earliest SGS model is proposed by Smagorinsky[15]for weather report. It is referred to as SM. The stress term of the SGS can be computed as

    where the over-bar represents the spatial filter ring for a filtered sizeis the magnitude ofandis the Smagorinsky coefficient.

    This model requires a small amount of computation and can be quite accurate in describing the subgrid dissipation characteristics. However, it has the following drawbacks:is a constant coefficient (the value of which depends on experience), it cannot describe the asymptotic behavior near the wall and it does not allow the SGS energy backscatter to the resolved scales.

    1.2Dynamic Smagorinsky model (DSM)

    Afterwards, a more comprehensive model (referred to as DSM) as compared to the SM was proposed[16]. This model overcomes some of the drawbacks of the SM and can be regarded as a modified SM[17]. The stress tensor can be expressed as

    where the tilde denotes the test filtering at a test filter scaleis the resolved velocity componentis the SGS stress foris the so-called Leonard stress tensor which can be computed by the resolved scales.

    Applying the SM to model the SGS stress, we have

    The DSM coefficient is calculated by using the least-squares method[15]

    The DSM is one of the most popular SGS models due to its robustness, its ease to implement and the low computational cost. Also, it has many other desirable features, i.e., it requires only one input parameter,it has the correct asymptotic behavior near the wall and in laminar flows, and it does not prohibit the energy backscatter. However, the DSM has several aspects that require improvements. The model assumes that the SGS stress is only dependent on the resolved strain rate tensor. The principal axes of the SGS stress tensor are to be aligned with those of the resolved strain rate tensor. This model requires a slightly more computational time than the SM.

    1.3Dynamic mixed model (DMM)

    Singh and You[18]presented a DMM which employs a mixed model as the basis model. The anisotropic part of the SGS stress at a grid filter scale is expressed as follows

    The anisotropic part of the SGS stress at a test filter scale is expressed as

    The mixed SGS models have several advantages: (1) they require less sophisticated modeling due to the explicit calculation of the modified Leonard term, and only the residual stresses have to be modeled, (2) the modified Leonard term can provide the energy backscatter to the resolved scales, (3) the models will reduce the excessive backscatter represented by the eddy viscosity model which causes the previously mentioned numerical instability, and (4) they do not require alignment of the principal axes of the SGS stress tensor and the resolved strain rate tensor. Note that the DMM requires more computational time than the DSM.

    1.4Dynamic non-linear model (DNM)

    In the study presented by Yang et al.[19], the SGS was expressed in a general third-order formulation. In the current study, the modified cross term and the modified SGS Reynolds stress are modeled by using the following equation

    The anisotropic part of the SGS stress at a test filter scale is expressed as:

    The two coefficients can be obtained by:

    The SGS stress expression includes tensors of the resolved strain rate and the rotation rate, which represent the anisotropy of the rotating flows. Unlike the SM, it does not require an alignment between the SGS stress tensor and the resolved strain rate tensor. Also this model reflects both the forward and the backward scatters of the SGS turbulence kinetic energy between the filtered and the SGS motions, however, it does not consider the Leonard term. The amount of computations required by the DNM is almost the same as the DMM.

    1.5Dynamic mixed non-linear model (DMNM)

    Yang and Wang[14]developed a new model (known as DMNM) that retains the resolved modified Leonard term along with the modified expressions for the cross term and the SGS Reynolds stress. The SGS stress can be expressed as:

    By substituting Eq.(15) and Eq.(16) into Eq.(3), the following equation is obtained

    A similar approach in the DSM is implemented by using the least squares minimization of the error. The two coefficients in the DMNM are obtained by using the following equations:

    This model combines the advantages of the DMM and the DNM, however, it needs the largest amount of computational time among the discussed SGS models. Yang and Wang[14]showed that the DMNM is more suitable for high curvature and strong rotational turbulence calculations as it considers the turbulent anisotropic properties.

    2. The investigated pump impeller and simulation details

    As shown in Fig.1, the considered pump impeller in this study is a shrouded, low specific-speed centrifugal impeller. The pump flow rate isand the head isunder the design condition. The simulation of the off-design condition(=Qis performed in this paper. The main geometry data of the impeller are summarized in Table 1. Note that more detailed geometry and experimental data are available in Ref.[20].

    Fig.1 Geometry of the impeller

    Table 1 Impeller geometry

    The full passages of the impeller are simulated in the present work. To reduce the boundary influence, extensions are made at the outlet and the inlet of the flow passage, respectively. Due to the complexity of the computational domain, an unstructured hexahedron mesh is employed as it enjoys a good adaptability. In the near-wall regions, the mesh is refined according to the requirement of the LES. The grid stretching factor is selected to allow the wall-adjacent cells to be located within 0.02 mm of the surface corresponding tovalues, less than 5 near the wall, whereas the grids are also refined in the stream-wise and span-wise directions. A mesh of totally 2 381 970 cells is selected as the best adjustment between the solution accuracy requirements and the computer resources. Increasing the number of grids does not show a significant change of the results as shown by the grid independent test. Figure 2 represents the mesh construction of the full passage. The stretching factor near the wall is 1.1 and the value of the maximum aspect ratio is 218.

    Fig.2 Computational grid

    The rotation reference frame is adopted for the flow passage with the rotation speed being set to the rotation speed of the impeller. The inlet velocity boundary condition is determined by the flow rate, whichincludes some fluctuated velocity components normal to the inlet boundary. The Neumann conditionis adopted for the pressure. The value of the pressure is given at the outlet of the passage and the Neumann condition is taken into account for the velocity. Note that no-slip wall condition is adopted as

    The time step is set as 0.00023 s that corresponds to a Courant number estimation of less than 10, i.e., overall 360 time steps per impeller revolution. The residual convergence criterion for each time step is reduced to 1.0×10-5, while the allowed maximum number of iterations per time step is limited to 15.

    The introduced five SGS models are considered in the simulation and the calculated results are compared with the PIV and LDV experimental data taken from Ref.[20]. According to the standard error of the PIV data estimates and based on 1000 statistically uncorrelated samples, the statistical uncertainty in the mean velocities is set to 1.2. The statistical uncertainties in the LDV mean velocities are estimated to be 0.7%[20].

    Fig.3 (Color online) Time-averaged velocity fields obtained by various SGS models

    Fig.4 Radial and tangential velocities

    3. Mean velocity field predicted

    The following results are presented for the impeller mid-height. Figures.3(a)-3(e) show the time-averaged streamlines computed by using the SGS models and Fig.3(f) demonstrates the velocity vectors measured by the LDV. As shown in the LDV experiment, the blocked passage and the unblocked passage occur alternately in the impeller. This “two channel” phenomenon consisting of the alternated stalled and un-stalled passages, is captured by the DSM, the DMM and the DMNM, but not the SM and the DNM. The predictions are almost consistent with the measurement results, however an unreal small vortex is found for these three models in the blade suction of the un-stalled passage. This remarkable difference ismainly caused by the pre-rotation disregarded in the simulations[3]. According to the results, the size and the shape of the vortex computed by three models are different as the calculated vortex near the outlet obtained by the DMM is much smaller than those obtained by the other two models.

    Fig.5 (Color online) Contour plots of the0.5)

    In order to further examine the performance of the three SGS models in simulating the rotating stall phenomena, the radial and tangential velocities at theare compared for the points at the radial positions of(as shown in Fig.4). The velocity profiles at 0.25demonstrate a decent periodicity for every two passages within the full annulus. Therefore, only the results within a circumferential range ofare presented in the following sections, which contain two adjacent passages: A is the un-stalled passage, and B is the stalled passage. The results of the DNM and the SM are not presented in Fig.4 as these models fail to do the job. At0.5, the PIV measurements reveal that the velocity profiles in the passage A are skewed towards the suction side. However, all simulations predict velocity profiles that are displaced to the pressure side. This remarkable difference is mainly associated to the effects of pre-rotation[3]. According to Fig.4, in the passage B, the radial and tangential velocities illustrate a reversed flow along the suction side. The results of the DMNM and the DSM are in a decent agreement with the PIV results, however the DMM’s performance is not within the acceptable range. At, the performances of four models are almost the same in the passage A. Nevertheless in the passage B, the performance of the DMNM is in better agreement with the PIV results. At, all models appear to give predictions substantially deviated from the measurements of the radial velocity of the passage A. However, the predicted variation trend by the DMNM is in the best agreement with the experimental data. The tangential velocities of the passage B, predicted by the DMNM are in the best agreement with the PIV data. According to this detailed analysis of the models, the DMNM enjoys the highest accuracy in predicting the flow behavior.

    4. Vorticity analysis

    Figure 5 shows the time-averagedvorticity computed by using the SGS models. As shown in Fig.5(d), it presents the signi ficant strength of the inlet stall cell in passage B. According to this figure, avorticity of pronounced large magnitude is obtained across the inlet. Additional small clockwise rotating vortex is also observed to be shed from the pressure leading edge. It is clearly shown that thevorticity predicted by the DMM remarkably deviates from the measurements. Both the DMNM and the DSM have successfully captured small clockwise rotating vortices in the passage, however the size and the shape of the vortices still substantially deviate from the PIV results. Furthermore, the large value region in the DSM is larger than the region predicted by the DMNM and is more consistent with the PIV results.

    5. Turbulence behavior analysis

    Figure 6 illustrates the distribution of the twodimensional turbulent kinetic energyat the middle sectionof the impeller. This kinetic energy characterizes the extent of the instantaneous velocity deviation from the mean velocity, which is defined asNote thatu′ andare values of the instantaneous velocity rootmean square (rms) inplane. The stall phenomenon in passage B is associated with the high turbulence activity. Furthermore, the strong reversed flow from the vortex in the outlet region of the passage B gives rise to a signi ficant turbulence intensity. In the passage A, the DMM overestimates the turbulent kinetic energy. Also, a low value region is created near the entrance by using the DSM and the DMNM, which is in agreement with the PIV results. However, the DMM fails to predict such region. In the passage B, the DMM also gives an over-prediction at the passage entrance. In addition, the high value area predicted by the DSM has a lower value than the DMNM. The above explanations show that the predicted results by the DMNM are more consistent with the PIV results as compared to the results predicted by the other SGS models.

    Fig.6 (Color online) Contours of the turbulent kinetic energy

    In order to further evaluate the performance of the presented SGS models in the turbulence intensity prediction, the comparisons of the blade-to-blade distribution of the turbulence intensity are presented in Fig.7 at two radial positions, i.e.,and. According to this figure, atthe DMM over-predictsextensively as compared to PIV results. In the passage A, the DSM and the DMNM appear to be more reasonable, although both models predict profiles that are flatter than the PIV results due to the pre-rotation. In the passage B, the two models give the same peak magnitudes of the turbulent intensity in agreement with the PIV data. Nonetheless, when different positions are considered, the DMNM is more accurate than the DSM. Based on the results obtained atin the passage A, all predicted profiles for the turbulence intensity see higher values than the PIV results. Also, the models can not predict the peak value at the suction side. In the passage B, the DMNM and the DSM give results in a good agreement with the PIV results, unlike the DMM which gives a lower estimation of the turbulence intensity. Thus, it can be concluded that the twodimensional turbulent kinetic energy predicted by the DMNM is in the best agreement with the experimental values.

    Fig.7 Turbulence intensity profiles

    6. Conclusions

    The internal flow in a shrouded six-bladed centri-fugal pump impeller under the stall condition is investigated in this paper by considering five different SGS models: SM, DSM, DNM, DMM and DMNM. The qualitative and quantitative comparisons are conducted between the simulation results and experimental tests.

    Based on the results presented in this paper, the DMNM has great potentials to be used by pump designers to predict the flow performance under the stall condition of the pump.

    [1] Luo X., Ji B., Tsujimoto Y. A review of cavitation in hydraulic machinery [J].Journal of Hydrodynamics, 2016, 28(3): 335-358.

    [2] Zhou P. J., Wang F. J., Yao Z. F. Study on effects of blade number on stall characteristics for centrifugal pump impeller [J].Journal of Mechanical Engineering, 2016, 52(10): 207-215(in Chinese).

    [3] Byskov R. K., Jacobsen C. B., Pedersen N. Flow in a centrifugal pump impeller at design and off-design conditions-Part II: Large eddy simulations [J].Journal of Fluids Engineering, 2003, 125(1): 73-83.

    [4] Feng J., Benra F., Dohmen H. J. Application of different turbulence models in unsteady flow simulations of a radial diffuser pump [J].Forschung Im Ingenieurwesen, 2010, 74(3): 123-133.

    [5] Lucius A., Brenner G. Numerical simulation and evaluation of velocity fluctuations during rotating stall of a centrifugal pump [J].Journal of Fluids Engineering, 2011, 133(8): 081102.

    [6] Lucius A., Brenner G. Unsteady CFD simulations of a pump in part load conditions using scale-adaptive simulation [J].International Journal of Heat and Fluid Flow, 2010, 31(6): 1113-1118.

    [7] Hasmatuchi V., Roth S., Botero F. et al. Hydrodynamics of a pump-turbine at off-design operating conditions: Numerical simulation [C].Proceeding of ASME-JSMEKSME Joint Fluids Engineering Conference. Shizuoka, Japan, 2011.

    [8] Tao R., Xiao R., Yang W. et al. A comparative assessment of Spalart-Shur rotation/curvature correction in RANS simulations in a centrifugal pump impeller [J].Mathematical Problems in Engineering, 2014, 2014: 342905.

    [9] Braun O. Part load flow in radial centrifugal pumps [D]. Doctoral Thesis, Lausanne, Switzerland: école Polytechnique Fédérale de Lausanne, 2009.

    [10] Pacot O., Kato C., Avellan F. High-resolution LES of the rotating stall in a reduced scale model pump-turbine [C].27th IAHR Symposium on Hydraulic Machinery and Systems (IAHR 2014). Montreal, Canada, 2014.

    [11] Kato C., Mukai H., Manabe A. Large-eddy simulation of unsteady flow in a mixed-flow pump [J].International Journal of Rotating Machinery, 2003, 9(5): 345-351.

    [12] Posa A., Lippolis A., Verzicco R. et al. Large-eddy simulations in mixed-flow pumps using an immersed-boundary method [J].Computers and Fluids, 2011, 47(1): 33-43.

    [13] Yang Z., Wang F., Zhou P. Evaluation of subgrid-scale models in large-eddy simulations of turbulent flow in a centrifugal pump impeller [J].Chinese Journal of Mechanical Engineering, 2012, 25(5): 911-918.

    [14] Yang Z., Wang F. A dynamic mixed nonlinear subgridscale model for large-eddy simulation [J].Engineering Computations, 2012, 29(7): 778-791.

    [15] Smagorinsky J. General circulation experiments with the primitive equations [J].Monthly Weather Review, 1963, 91(3): 99-164.

    [16] Ryu S., Iaccarino G. A subgrid-scale eddy-viscosity model based on the volumetric strain-stretching [J].Physics of Fluids, 2014, 26(6): 065107.

    [17] Vollant A, Balarac G., Corre C. A dynamic regularized gradient model of the subgrid-scale stress tensor for largeeddy simulation [J].Physics of Fluids, 2016, 28(2): 025114.

    [18] Singh S., You D. A dynamic global-coefficient mixed subgrid-scale model for large-eddy simulation of turbulent flows [J].International Journal of Heat and Fluid Flow, 2013, 42: 94-104.

    [19] Yang Z., Cui G., Xu C. et al. Large eddy simulation of rotating turbulent channel flow with a new dynamic globalcoefficient nonlinear subgrid stress model [J].Journal of Turbulence, 2012, 13(48):1-20.

    [20] Pedersen N., Larsen P. S., Jacobsen C. B. Flow in a centrifugal pump impeller at design and off-design conditions?Part I: Particle image velocimetry (PIV) and laser doppler velocimetry (LDV) measurements [J].Journal of Fluids Engineering, 2003, 125(1): 61-72.

    (Received December 30, 2014, Revised June 30, 2015)

    * Project supported by the National Nature Science Foundation of China (Grant Nos. 51139007, 51321001), the Natural Science Foundation of Zhejiang Province (Grant No. LQ17E090005) and the National Science and Technology

    Support Program of China (Grant No. 2015BAD20B01).

    Biography: Pei-jian Zhou (1986-), Male, Ph. D.

    Fu-jun Wang,

    E-mail:wangfj@cau.edu.cn

    猜你喜歡
    佩劍
    江蘇青年女子佩劍運(yùn)動(dòng)員主動(dòng)進(jìn)攻技術(shù)分析
    我國(guó)女子佩劍技戰(zhàn)術(shù)打法特征及發(fā)展趨勢(shì)探究
    2019年全國(guó)擊劍錦標(biāo)賽佩劍冠軍傅穎技戰(zhàn)術(shù)的運(yùn)用
    Unsteady flow structures in centrifugal pump under two types of stall conditions *
    從戎贊
    放飛歷史思維創(chuàng)新課堂教學(xué)
    考試周刊(2018年31期)2018-03-22 12:21:08
    淺析中國(guó)佩劍文化及刀劍的文化意象
    我國(guó)男子佩劍運(yùn)動(dòng)員比賽中進(jìn)攻技術(shù)統(tǒng)計(jì)分析
    擊劍體驗(yàn)課
    孔子佩劍考
    卷宗(2014年12期)2014-04-02 18:30:57
    亚洲,欧美精品.| 中文天堂在线官网| 国产亚洲av片在线观看秒播厂| 五月天丁香电影| 亚洲 欧美一区二区三区| 国产极品粉嫩免费观看在线| 亚洲精品aⅴ在线观看| 啦啦啦 在线观看视频| 日韩视频在线欧美| 亚洲国产精品成人久久小说| 91老司机精品| 一本色道久久久久久精品综合| 香蕉国产在线看| 久久人妻熟女aⅴ| 久久av网站| 成年动漫av网址| 精品人妻一区二区三区麻豆| 久久久久网色| 在线观看免费高清a一片| 久久热在线av| 国产极品粉嫩免费观看在线| 永久免费av网站大全| 精品一品国产午夜福利视频| 国产爽快片一区二区三区| 最近的中文字幕免费完整| 9191精品国产免费久久| 国产一区二区 视频在线| 久久午夜综合久久蜜桃| 免费不卡黄色视频| 成人黄色视频免费在线看| 美女大奶头黄色视频| 国产高清不卡午夜福利| 欧美变态另类bdsm刘玥| 久久国产精品男人的天堂亚洲| 亚洲国产成人一精品久久久| 久久久精品区二区三区| www日本在线高清视频| 久久97久久精品| 在线观看国产h片| 欧美国产精品一级二级三级| 99香蕉大伊视频| 日韩大码丰满熟妇| 天堂中文最新版在线下载| 老司机影院毛片| 国产一卡二卡三卡精品 | 成年av动漫网址| 纯流量卡能插随身wifi吗| 日韩制服丝袜自拍偷拍| 如何舔出高潮| 一区二区三区乱码不卡18| 日韩免费高清中文字幕av| 制服人妻中文乱码| 中文字幕最新亚洲高清| 国产精品三级大全| 久久久久精品国产欧美久久久 | 免费在线观看视频国产中文字幕亚洲 | 亚洲四区av| av国产久精品久网站免费入址| 亚洲自偷自拍图片 自拍| 男男h啪啪无遮挡| xxxhd国产人妻xxx| 啦啦啦中文免费视频观看日本| av在线播放精品| 国产av国产精品国产| 日日爽夜夜爽网站| 最近中文字幕高清免费大全6| 日本爱情动作片www.在线观看| 91老司机精品| 高清不卡的av网站| 久久久久人妻精品一区果冻| 女人精品久久久久毛片| 可以免费在线观看a视频的电影网站 | 丰满乱子伦码专区| 欧美国产精品一级二级三级| 欧美日韩视频高清一区二区三区二| 日韩中文字幕视频在线看片| 成人国语在线视频| av片东京热男人的天堂| 大香蕉久久成人网| 亚洲精品日韩在线中文字幕| 日韩av在线免费看完整版不卡| 国产成人精品久久久久久| 人成视频在线观看免费观看| 男的添女的下面高潮视频| 电影成人av| 高清黄色对白视频在线免费看| 男女免费视频国产| 你懂的网址亚洲精品在线观看| 国产有黄有色有爽视频| 色网站视频免费| 精品国产一区二区三区久久久樱花| 日韩熟女老妇一区二区性免费视频| 19禁男女啪啪无遮挡网站| 女性生殖器流出的白浆| 亚洲成色77777| 成年美女黄网站色视频大全免费| 国产成人精品无人区| 男女高潮啪啪啪动态图| 可以免费在线观看a视频的电影网站 | 国产精品一区二区在线不卡| 两个人看的免费小视频| 精品午夜福利在线看| 成人影院久久| av天堂久久9| 国产片内射在线| 久久午夜综合久久蜜桃| 免费观看性生交大片5| 午夜福利影视在线免费观看| 午夜福利影视在线免费观看| 一二三四在线观看免费中文在| 精品国产超薄肉色丝袜足j| 如何舔出高潮| 老汉色∧v一级毛片| 亚洲精品一区蜜桃| 午夜福利乱码中文字幕| 在线精品无人区一区二区三| 久久久国产精品麻豆| 老鸭窝网址在线观看| 在线观看免费日韩欧美大片| 欧美激情高清一区二区三区 | 美女福利国产在线| 亚洲综合精品二区| 女性被躁到高潮视频| 99久国产av精品国产电影| 久久精品亚洲熟妇少妇任你| 亚洲欧美精品综合一区二区三区| 久久人人爽人人片av| 国产深夜福利视频在线观看| 日本欧美视频一区| 宅男免费午夜| 女性生殖器流出的白浆| 大话2 男鬼变身卡| 国产精品无大码| 国产97色在线日韩免费| 男女边吃奶边做爰视频| 亚洲精品久久午夜乱码| 婷婷色综合www| 欧美成人午夜精品| 久久久久久人人人人人| 另类精品久久| videos熟女内射| 日韩欧美一区视频在线观看| 亚洲国产精品999| 精品国产乱码久久久久久男人| 国产成人精品无人区| 菩萨蛮人人尽说江南好唐韦庄| 激情五月婷婷亚洲| 两个人看的免费小视频| 久久精品国产综合久久久| 在线 av 中文字幕| 国产无遮挡羞羞视频在线观看| 午夜精品国产一区二区电影| 乱人伦中国视频| 精品人妻在线不人妻| 日韩熟女老妇一区二区性免费视频| 大话2 男鬼变身卡| 成人黄色视频免费在线看| 国产成人欧美在线观看 | 香蕉丝袜av| av在线观看视频网站免费| 欧美人与性动交α欧美精品济南到| 亚洲一级一片aⅴ在线观看| www.熟女人妻精品国产| 国产成人a∨麻豆精品| 欧美国产精品va在线观看不卡| 麻豆乱淫一区二区| 成年av动漫网址| 午夜福利乱码中文字幕| 十八禁网站网址无遮挡| 香蕉丝袜av| 欧美亚洲 丝袜 人妻 在线| 日本vs欧美在线观看视频| 亚洲国产中文字幕在线视频| 黄色怎么调成土黄色| 一区二区三区乱码不卡18| 国产亚洲一区二区精品| 久久国产精品男人的天堂亚洲| 久久鲁丝午夜福利片| 国产av码专区亚洲av| 亚洲av国产av综合av卡| 汤姆久久久久久久影院中文字幕| 街头女战士在线观看网站| 亚洲精品乱久久久久久| 欧美日韩视频高清一区二区三区二| av国产久精品久网站免费入址| 下体分泌物呈黄色| 国产乱来视频区| 亚洲成人免费av在线播放| 亚洲精品美女久久av网站| 久久免费观看电影| 亚洲av成人精品一二三区| 国产一区亚洲一区在线观看| 欧美精品av麻豆av| 日日摸夜夜添夜夜爱| 国产精品熟女久久久久浪| 免费黄色在线免费观看| 9热在线视频观看99| 男女下面插进去视频免费观看| 亚洲人成电影观看| 日韩制服骚丝袜av| av天堂久久9| 国产精品一二三区在线看| 中文字幕制服av| 美女午夜性视频免费| 赤兔流量卡办理| 国产有黄有色有爽视频| 亚洲国产欧美一区二区综合| 如日韩欧美国产精品一区二区三区| 色综合欧美亚洲国产小说| 最新在线观看一区二区三区 | 日韩熟女老妇一区二区性免费视频| 国产伦人伦偷精品视频| 亚洲精品久久久久久婷婷小说| 操出白浆在线播放| 中文字幕色久视频| 亚洲av电影在线观看一区二区三区| 亚洲国产欧美网| 国产乱来视频区| 国产av一区二区精品久久| 国产av精品麻豆| 男女边摸边吃奶| 亚洲av成人精品一二三区| 国产亚洲最大av| 国产免费视频播放在线视频| 9191精品国产免费久久| 侵犯人妻中文字幕一二三四区| 国产深夜福利视频在线观看| 人人妻人人爽人人添夜夜欢视频| 在线天堂最新版资源| 大香蕉久久成人网| 一本色道久久久久久精品综合| 丰满迷人的少妇在线观看| 无限看片的www在线观看| 亚洲熟女毛片儿| 嫩草影视91久久| 男女无遮挡免费网站观看| 天天添夜夜摸| 精品国产乱码久久久久久小说| 亚洲综合色网址| 卡戴珊不雅视频在线播放| 国产日韩欧美视频二区| 自线自在国产av| 在线精品无人区一区二区三| 母亲3免费完整高清在线观看| 日本一区二区免费在线视频| 成人三级做爰电影| 中文字幕精品免费在线观看视频| 国产精品久久久久久精品古装| 日本91视频免费播放| 波野结衣二区三区在线| 婷婷色综合大香蕉| 久久影院123| 99九九在线精品视频| 女人被躁到高潮嗷嗷叫费观| 亚洲视频免费观看视频| 亚洲国产精品一区二区三区在线| 久久这里只有精品19| 一二三四中文在线观看免费高清| 99热全是精品| 欧美在线黄色| 色网站视频免费| 街头女战士在线观看网站| 久久久久人妻精品一区果冻| 高清欧美精品videossex| 18禁观看日本| 国产成人系列免费观看| 夫妻性生交免费视频一级片| 久久免费观看电影| 久久久久视频综合| 中文字幕高清在线视频| 欧美亚洲日本最大视频资源| 80岁老熟妇乱子伦牲交| 精品国产一区二区三区久久久樱花| 国产 一区精品| 国产激情久久老熟女| 女人爽到高潮嗷嗷叫在线视频| 女的被弄到高潮叫床怎么办| 亚洲国产精品999| 十八禁人妻一区二区| av网站在线播放免费| 大片免费播放器 马上看| 母亲3免费完整高清在线观看| 99热国产这里只有精品6| 午夜免费鲁丝| 午夜福利影视在线免费观看| 久久人人97超碰香蕉20202| 亚洲视频免费观看视频| 久久99一区二区三区| 亚洲av成人精品一二三区| 日韩成人av中文字幕在线观看| a级毛片黄视频| 91成人精品电影| 性高湖久久久久久久久免费观看| av在线观看视频网站免费| 日韩av免费高清视频| 大片免费播放器 马上看| 999久久久国产精品视频| 看免费成人av毛片| 男人操女人黄网站| 久久青草综合色| 麻豆精品久久久久久蜜桃| 男女无遮挡免费网站观看| 老鸭窝网址在线观看| 久久久久国产一级毛片高清牌| 亚洲婷婷狠狠爱综合网| 水蜜桃什么品种好| 精品少妇一区二区三区视频日本电影 | 亚洲精品国产区一区二| 岛国毛片在线播放| 亚洲成人手机| 一级毛片我不卡| 国产亚洲一区二区精品| 国产av一区二区精品久久| 少妇被粗大的猛进出69影院| 丝袜美腿诱惑在线| 欧美日韩视频精品一区| 午夜久久久在线观看| 亚洲精品日本国产第一区| 久久婷婷青草| 午夜日本视频在线| 国产片内射在线| 丰满饥渴人妻一区二区三| 久久精品aⅴ一区二区三区四区| 亚洲精品美女久久av网站| 超色免费av| 久久99热这里只频精品6学生| 亚洲精品第二区| 国产深夜福利视频在线观看| 欧美激情极品国产一区二区三区| 久久精品亚洲av国产电影网| 丰满乱子伦码专区| 水蜜桃什么品种好| 久久婷婷青草| 电影成人av| 夫妻午夜视频| 精品少妇一区二区三区视频日本电影 | 亚洲三区欧美一区| 亚洲视频免费观看视频| 精品免费久久久久久久清纯 | 另类亚洲欧美激情| 欧美日韩成人在线一区二区| 国产一区二区 视频在线| 亚洲精品在线美女| 国产成人一区二区在线| 亚洲美女黄色视频免费看| 亚洲 欧美一区二区三区| 晚上一个人看的免费电影| 一级毛片黄色毛片免费观看视频| 色婷婷av一区二区三区视频| 亚洲成人手机| 男女午夜视频在线观看| 香蕉丝袜av| 中文字幕色久视频| 久久精品亚洲熟妇少妇任你| 日韩电影二区| 国产成人精品久久久久久| 中文精品一卡2卡3卡4更新| 丰满少妇做爰视频| 免费少妇av软件| 日韩人妻精品一区2区三区| 各种免费的搞黄视频| 五月天丁香电影| 亚洲第一青青草原| 亚洲色图 男人天堂 中文字幕| 欧美日韩国产mv在线观看视频| avwww免费| 亚洲av日韩在线播放| 亚洲精品国产色婷婷电影| 麻豆乱淫一区二区| 欧美黑人精品巨大| 在线观看免费日韩欧美大片| 亚洲婷婷狠狠爱综合网| 亚洲成人免费av在线播放| 欧美精品人与动牲交sv欧美| 久久久精品94久久精品| 在线免费观看不下载黄p国产| 欧美人与善性xxx| 亚洲欧美成人综合另类久久久| 2021少妇久久久久久久久久久| 国产精品国产av在线观看| 成人黄色视频免费在线看| 好男人视频免费观看在线| av在线老鸭窝| 又大又爽又粗| 亚洲成人手机| 欧美激情 高清一区二区三区| 久久久久精品久久久久真实原创| 中文字幕精品免费在线观看视频| 日韩欧美一区视频在线观看| 在线观看免费日韩欧美大片| 亚洲 欧美一区二区三区| 亚洲伊人色综图| 高清黄色对白视频在线免费看| 色综合欧美亚洲国产小说| 建设人人有责人人尽责人人享有的| 久久久久精品人妻al黑| 亚洲一级一片aⅴ在线观看| 丝袜脚勾引网站| 国产一区二区三区综合在线观看| 午夜老司机福利片| 欧美日韩av久久| www.av在线官网国产| 中国三级夫妇交换| 9热在线视频观看99| 宅男免费午夜| 久久精品久久久久久噜噜老黄| 人妻人人澡人人爽人人| 久久久精品免费免费高清| 国产极品天堂在线| 综合色丁香网| 伊人久久国产一区二区| 国产福利在线免费观看视频| 国产一区二区 视频在线| 18禁动态无遮挡网站| 男女免费视频国产| 亚洲情色 制服丝袜| av在线老鸭窝| 久久久亚洲精品成人影院| 一区二区三区四区激情视频| 亚洲欧美色中文字幕在线| 又大又爽又粗| 日韩欧美精品免费久久| avwww免费| 黄片无遮挡物在线观看| netflix在线观看网站| 亚洲精品久久成人aⅴ小说| 精品国产乱码久久久久久小说| 一区二区三区乱码不卡18| 少妇被粗大的猛进出69影院| 亚洲一卡2卡3卡4卡5卡精品中文| 国产精品嫩草影院av在线观看| 精品人妻熟女毛片av久久网站| 国产男人的电影天堂91| 黄网站色视频无遮挡免费观看| 免费高清在线观看日韩| 亚洲国产精品一区三区| 国产成人系列免费观看| 十八禁人妻一区二区| 男女国产视频网站| 久久久久久久大尺度免费视频| 高清黄色对白视频在线免费看| 黑人欧美特级aaaaaa片| 精品国产一区二区三区四区第35| 波多野结衣一区麻豆| 无限看片的www在线观看| 1024香蕉在线观看| 国产成人91sexporn| 日韩一区二区三区影片| 日韩熟女老妇一区二区性免费视频| 一级毛片 在线播放| 亚洲精品久久成人aⅴ小说| 老汉色av国产亚洲站长工具| 中文精品一卡2卡3卡4更新| 悠悠久久av| 视频在线观看一区二区三区| av电影中文网址| 大香蕉久久网| 国产精品欧美亚洲77777| 丁香六月天网| 别揉我奶头~嗯~啊~动态视频 | 日韩一本色道免费dvd| netflix在线观看网站| 久久久久精品人妻al黑| www.精华液| 天天躁狠狠躁夜夜躁狠狠躁| 日韩一卡2卡3卡4卡2021年| 国产精品蜜桃在线观看| 欧美精品一区二区免费开放| 国产精品一区二区精品视频观看| 国产熟女欧美一区二区| 亚洲av电影在线观看一区二区三区| 国产又爽黄色视频| 久久久久精品久久久久真实原创| 性色av一级| 国产精品久久久久久人妻精品电影 | 国产精品亚洲av一区麻豆 | 91aial.com中文字幕在线观看| 一级a爱视频在线免费观看| 欧美精品一区二区大全| 亚洲综合精品二区| 成年人免费黄色播放视频| 亚洲精品国产一区二区精华液| 精品亚洲成a人片在线观看| 伊人亚洲综合成人网| 国产片内射在线| 久久狼人影院| 超色免费av| 看免费av毛片| 国产不卡av网站在线观看| 高清av免费在线| 人人妻,人人澡人人爽秒播 | 啦啦啦 在线观看视频| 美女扒开内裤让男人捅视频| 亚洲少妇的诱惑av| 亚洲欧洲国产日韩| 亚洲精品中文字幕在线视频| 纵有疾风起免费观看全集完整版| 大片免费播放器 马上看| av有码第一页| 日本爱情动作片www.在线观看| 久久久欧美国产精品| svipshipincom国产片| 少妇精品久久久久久久| 中文字幕人妻熟女乱码| 热re99久久精品国产66热6| 日韩一本色道免费dvd| 在现免费观看毛片| 90打野战视频偷拍视频| 亚洲 欧美一区二区三区| 免费在线观看完整版高清| 国产精品欧美亚洲77777| 国产免费又黄又爽又色| 精品一区二区免费观看| 女的被弄到高潮叫床怎么办| 大香蕉久久成人网| 国产精品免费视频内射| 国产成人精品无人区| 无限看片的www在线观看| 欧美日韩综合久久久久久| 黄色毛片三级朝国网站| 国产伦理片在线播放av一区| 欧美少妇被猛烈插入视频| 久久久精品免费免费高清| 国产精品欧美亚洲77777| 国产色婷婷99| 国产成人欧美在线观看 | 日日爽夜夜爽网站| 亚洲精品一二三| 欧美少妇被猛烈插入视频| 搡老岳熟女国产| 可以免费在线观看a视频的电影网站 | 99精国产麻豆久久婷婷| 欧美乱码精品一区二区三区| 成人亚洲欧美一区二区av| 一区二区三区乱码不卡18| 国产av精品麻豆| 国产在视频线精品| 黄频高清免费视频| 不卡av一区二区三区| 高清黄色对白视频在线免费看| 中文乱码字字幕精品一区二区三区| 亚洲第一区二区三区不卡| 午夜福利影视在线免费观看| 欧美日韩一区二区视频在线观看视频在线| 精品少妇内射三级| 90打野战视频偷拍视频| 国产免费一区二区三区四区乱码| 你懂的网址亚洲精品在线观看| 亚洲综合精品二区| 香蕉丝袜av| 国产精品熟女久久久久浪| 满18在线观看网站| 老司机影院成人| 欧美精品一区二区大全| 国产精品一区二区精品视频观看| 在线看a的网站| av女优亚洲男人天堂| 亚洲一区二区三区欧美精品| 国产精品一二三区在线看| 亚洲精品,欧美精品| 蜜桃国产av成人99| 别揉我奶头~嗯~啊~动态视频 | 狂野欧美激情性xxxx| 巨乳人妻的诱惑在线观看| 黑人猛操日本美女一级片| 久热这里只有精品99| 伦理电影免费视频| 亚洲,欧美精品.| 久久青草综合色| 中文字幕人妻丝袜一区二区 | 国产伦理片在线播放av一区| 国产精品女同一区二区软件| 捣出白浆h1v1| 一二三四中文在线观看免费高清| av有码第一页| 亚洲欧美一区二区三区久久| 国产av精品麻豆| 色婷婷久久久亚洲欧美| 人成视频在线观看免费观看| 国产精品一区二区精品视频观看| 亚洲人成电影观看| 悠悠久久av| 少妇人妻久久综合中文| 在线观看一区二区三区激情| xxx大片免费视频| 久久精品熟女亚洲av麻豆精品| 激情五月婷婷亚洲| 欧美黄色片欧美黄色片| 啦啦啦中文免费视频观看日本| 久久精品人人爽人人爽视色| 王馨瑶露胸无遮挡在线观看| 免费观看人在逋| 欧美日韩av久久| 街头女战士在线观看网站| 亚洲精品国产av蜜桃| 国产成人免费观看mmmm| 午夜影院在线不卡| 欧美少妇被猛烈插入视频| 人妻一区二区av| 一二三四中文在线观看免费高清| 最近中文字幕2019免费版| 亚洲精品日本国产第一区| 亚洲一区二区三区欧美精品| 另类精品久久| 黑人欧美特级aaaaaa片| 亚洲国产欧美日韩在线播放| 亚洲天堂av无毛| 黑人巨大精品欧美一区二区蜜桃| 久久久精品国产亚洲av高清涩受| 极品少妇高潮喷水抽搐| av又黄又爽大尺度在线免费看| 日韩欧美一区视频在线观看| 综合色丁香网| 国产高清不卡午夜福利| 中文乱码字字幕精品一区二区三区|