MEASUREMENT OF HYDRODYNAMIC FORCES ACTING ON A CIRCULAR CYLINDER NEAR A PLANE BOUNDARY IN STEADY FLOW

In this paper,the characteristics of hydrodyna(?) forces on a circular cylindernear a plane boundary have been studied experimentally in w(?) tunnels.The drag coefficientC_D,mean lift coefficient C_(L0),T.m.s.lift coefficient C_(L Tms),maximum lift coefficient C_(L max) andfluctuating lift coefficients C'_(L Tms),C'_(L max),and lift(vortex shedding)frequency have been mea-sured on condition that the thickness of plane boundary layer,δ,was 0.1D(D is the diameter ofthe cylinder)at the station of the centre of the cylinder,and Reynolds number,Re,varied from4.5×10~3 to 1.76×10~5.The regularity of the change of these coefficients with Re and gap ratioG/D is found.The measurement of the lift frequency shows that a strong non-linear coupling ac-tion appears when the gap ratio between the circular cylinder and plane,G/D,reaches 0.5,andthe shedding of regular vortex is suppressed when G/D=0.2.     

NUMERICAL STUDY ON THE VORTEX STRUCTURES IN THE WAKE OF AN OSCILLATING CIRCULAR CYLINDER IN A UNIFORM FLOW

ＮＵＭＥＲＩＣＡＬＳＴＵＤＹＯＮＴＨＥＶＯＲＴＥＸＳＴＲＵＣＴＵＲＥＳＩＮＴＨＥＷＡＫＥＯＦＡＮＯＳＣＩＬＬＡＴＩＮＧＣＩＲＣＵＬＡＲＣＹＬＩＮＤＥＲＩＮＡＵＮＩＦＯＲＭＦＬＯＷＬｕＸｉ－ｙｕｎ；ＴｏｎｇＢｉｎｇ－ｇａｎｇ；ＺｈｕａｎｇＬｉ－ｘｉａｎ...     

WAVE FORCES ON INCLINED CYLINDER IN REGULAR WAVES

Through a series of model tests,the wave forces on horizontal and inclined circularcylinders are measured and analyzed.Based on Morison Equation and Stokes second order wavetheory,the relationship between the hydrodynamic force coefficients with KC number and sub-merged water depth as well for horizontal cylinders are analyzed,also the relationship betweenthe hydrodynamic force coefficients with KC number,inclined angle and the effect of water freesurface as well for the inclined cylinders are investigated.     

不同雷诺数下水平桩柱的水动力待征

本文介绍了均匀振荡流中光滑水平桩柱上水动力特征的试验研究.试验中,雷诺数Re=20000～260000(该区域为亚临界区与临界区),Kc=5～40.分析中,利用最小二乘法来确定Morison方程中的速度力系数C_(?)及惯性力系数C_M;还利用最大值法及均方根值法对合力系数C_F与升力系数C_L进行分析,所有的正向力与升力系数都作为Re及Kc数的函数给出,并且各系数相对于其平均值的均方差值也在图中示出.其主要研究成果如下:当Re≥80000时,所有的水动力系数(包括C_D、C_M,C_F与C_L),几乎与雷诺数Re无关,且各系数均随Kc数的逐渐增加而趋向于不同的常数;当Re<80000时,速度力系数C_D随Re数的增大而减小,而惯性力系数C_M随Re数的增大而增大.     

ANALYSIS OF OSCILLATORY BLOOD FLOW IN VARYING-AREA ELASTIC VESSEL

In this paper, by solving the fundamental e-quations of periodically oscillatory blood flow, the distributions of pressure gradient and blood velocity in varying-area e-lastic vessel were obtained, and then the wall shear stress and its gradient were calculated. As an example, the pulsatile blood flow in human carotid was analyzed and the effects of vessel taper angle on the distribution of wall shear stress and its gradient were discussed in detail. Numercial results show that the wall shear stress will enlarge when the taper angle increases. Meantime, no matter whether the vessel is converging or diverging, with the increase of the absolute value of taper angle, the amplitude of wall shear stress gradient will enlarge significantly.     

SLOW DRIFT DAMPING FORCE ACTING ON A CYLINDER IN WAVES

ＳＬＯＷＤＲＩＦＴＤＡＭＰＩＮＧＦＯＲＣＥＡＣＴＩＮＧＯＮＡＣＹＬＩＮＤＥＲＩＮＷＡＶＥＳ￥ＨｕＣｈａｎｇ－ｈｏｎｇ（ＫｙｕｓｈｕＵｎｉｖｅｒｓｉｔｙ，ｋａｓｕｇａ，Ｊａｐａｎ）ＬｉｕＹｉｎ－ｚｈｏｎｇ（ＳｈａｎｇｈａｉＪｉａｏＴｏｎｇＵｎｉｖｅｒｓ...     

COMPUTATION OF SHIP MANOEUVRING RELATED VISCOUS FLOW AND HYDRODYNAMIC FORCES

An efficient multi block incompressible viscous flow solver based on solving the Reynolds Averaged Navier Stokes (RANS) equations numerically has been developed that can be applied to simulation of a variety of ship maneuvering related flows and calculation of hydrodynamic forces. Valida tion and verification of the solution procedure were carried out on several model problems with good agreement to experimental and numerical results.     

STUDY OF VORTEX CHARACTERISTICS OF THE FLOW AROUND A HORIZONTAL CIRCULAR CYLINDER AT VARIOUS GAP-RATIOS IN THE CROSS-FLOW

1. INTRODUCTION The flow around a horizontal circular cylinder near a plane boundary (fixed wall) is of great significance in Hydrodynamics. For instance, sewagepipelines in water body of rivers in environmental engineering, conveying pipelines and optica…     

HAGEN POISEUILLE FLOW OF A GRANULAR MATERIAL IN A CYLINDER

1 .　ＩＮＴＲＯＤＵＣＴＩＯＮＩｎｒｅｃｅｎｔｙｅａｒｓ ,ｓｔｕｄｙｉｎｇｔｈｅｍｏｔｉｏｎｏｆｆｉｎｅｇｒａｎｕ ｌａｒｍａｔｅｒｉａｌｓｉｓａｎｅｗｔｏｐｉｃｉｎｆｌｕｉｄｍｅｃｈａｎｉｃｓ.Ａｌｔｈｏｕｇｈｇｒａｎｕｌａｒｍａｔｅｒｉａｌｓｄｏｅｓｎｏｔｂｅｌｏｎｇｔｏｒｅａｌｆｌｕｉｄ ,ｔｈｅｍｅｔｈｏｄｓｏｆｓｔｕｄｙｉｎｇ ｇｒａｎｕｌａｒｍａｔｅｒｉａｌｓａｒｅｓｉｍｉｌａｒｔｏｔｈｏｓｅｏｆｆｌｕｉｄ ｓｔｕｄｙｉｎｇ .Ｓｏｍａｎｙｍｅｔｈｏｄｓｏｆｆｌｕｉｄ ｓｔｕｄｙｉｎｇｈａｖｅ…     

EFFECTS OF WATER-DEPTH ON HYDRODYNAMIC FORCE OF ARTIFICIAL REEF

The effects of water-depth on the hydrodynamic force of the artificial reef were studied by simulating regular and irregular waves. The computational results show that the water-depth has a substantial effect on hydrodynamic force. The hydrodynamic force increases with the decrease of water-depth in shallow. Especially, in the ultra-shallow water these loads increase very evidently with the decrease of water-depth. The long-term values of hydrodynamic force increase with the decrease of the ratio of water-depth to reef height, and are about 10% larger than those of deep water when the ratio of water-depth to reef height is 4.0. However water-depth hardly affects the long term values of hydrodynamic force when the ratio of water-depth to reef height is larger than 6.0.     

FORCE REDUCTION OF FLOW AROUND A SINUSOIDAL WAVY CYLINDER

A large eddy simulation of cross-flow around a sinusoidal wavy cylinder at Re=3000 was performed and the load cell measurement was introduced for the validation test. The mean flow field and the near wake flow structures were presented and compared with those for a circular cylinder at the same Reynolds number. The mean drag coefficient for the wavy cylinder is smaller than that for a corresponding circular cylinder due to the formation of a longer wake vortex generated by the wavy cylinder. The fluctuating lift coefficient of the wavy cylinder is also greatly reduced. This kind of wavy surface leads to the formation of 3-D free shear layers which are more stable than purely 2-D free shear layers. Such free shear layers only roll up into mature vortices at further downstream position and significantly modify the near wake structures and the pressure distributions around the wavy cylinder. Moreover, the simulations in laminar flow condition were also performed to investigate the effect of Reynolds number on force reduction control.     

CALCULATION OF VISCOUS FLOW AROUND CIRCULAR CYLINDER WITH THREE-DIMENSIONAL NUMERICAL SIMULATION

1 .　ＩＮＴＲＯＤＵＣＴＩＯＮＴｈｅｆｌｏｗａｒｏｕｎｄａｃｉｒｃｕｌａｒｃｙｌｉｎｄｅｒｉｓｖａｌｕａｂｌｅｉｎｏｉｌｃｏｍｐａｎｉｅｓｏｒｏｆｆｓｈｏｒｅｉｎｄｕｓｔｒｙｔｈａｔｒｅｌｙｉｎｍｏｓｔｃａｓｅｓｏｎｓｕｂｓｅａｐｉｐｅｌｉｎｅｏｒｒｉｓｅｒｓｔｏｔｒａｎｓｐｏｒｔｇａｓａｎｄｏｉｌｆｒｏｍｏｃｅａｎｇｒｏｕｎｄｓｔｏｌａｎｄｏｒｓｕｒｆａｃｅｐｌａｔｆｏｒｍ .Ｗｅｓｈｏｕｌｄｅｎｓｕｒｅｔｈａｔｔｈｅｓｅｏｆｆｓｈｏｒｅｓｔｒｕｃｔｕｒｅｓａｒｅｒｅｓｉｓ ｔａｎｔａｎｄｓｔａｂ…     

EXPERIMENTAL INVESTIGATION OF HYDRODYNAMIC CHARACTERISTICS OF OVERLAND FLOW WITH GEOCELL

The hydrodynamic characteristics of the overland flow with a geocell slope are different from those of traditional flows because of its special structure. In this paper,a hydraulic flume with different slope gradients is used to study the hydrodynamic characteristics of the overland flow with geocell. The differences of flow characteristics between the overland flow with the geocell slope and the traditional flows are studied, and the hydrodynamic characteristics are obtained, including the flow pattern, the flow velocity and the hydraulic friction factor for the slope flow with geocell under different flow rates and slope gradients. The results show that there is a positive power function relationship between the rill depth of the slope surface (h) and the drag coefficient of the Darcy Weisbach (f).There is a positive logarithmic function relationship between the drag coefficient f and the Reynolds number Red,and there is a negative power function relationship between the drag coefficient f and the Froude number Fr.     

EXPERIMENTAL STUDY ON THE SECOND-ORDER DIFFRACTION WAVE PRESSURE AND FORCE ON A CIRCULAR CYLINDER UNDER STOKES WAVE ACTION

This paper presents the model test to measure the second-order wave pressureand forces on a circular cylinder fixed in Stokes wave with a given draught.The distributions ofsecond-order oscillating and steady wave pressure on the wet surface of the cylinder and secondorder oscillating wave forces were obtained in this test,but the second-order steady wave forcewas not able to be measured due to its very small magnitude.The test results also show thatthird-order wave force may be greater than the second-order force when wave frequencies arehigh.The experimental results were compared with the corresponding calculation results of Ref-erence[3].     

A STUDY ON TRANSIENT FLUID FLOW OF HORIZONTAL WELLS IN DUAL-PERMEABILITY MEDIA

To adopt horizontal wells in dual media reservoirs,a good understanding of the related fluid flows is necessary.Most of the recent studies focus on dual porosity media instead of dual permeability media.In this article,through both integral transformation and sink-source superposition,a new Laplace-domain solution is obtained for the slightly-compressible fluid flow in the 3-D dual-permeability media in which the horizontal well is operating in a constant rate of production.Major asymptotic characteristics of diagnosis curves of dimensionless downhole pressure are analyzed by the limited analysis.Effects of parameters of dual-permeability media including mobility ratio κ,storativity ratio ω and inter-porosity flow parameter κ on the downhole pressure are studied by using the Laplace numerical inversion.The new solution obtained in this article includes and improves the previous results and then can be used as a basis for either pressure transient analysis or formation behavior evaluation for the typical reservoir with horizontal wells.     

THE RADIATION AND DIFFRACTION OF WATER WAVES BY A BOTTOM-MOUNTED CIRCULAR CYLINDER IN A TWO-LAYER FLUID

An analytical method was proposed to analyze the radiation and diffraction of water waves by a bottom-mounted circular cylinder in a two-layer fluid. Analytical expressions for added mass and damping coefficients, as well as the wave excitation forces of the circular cylinder were obtained by an eigenfunction expansion method. The hydrodynamic forces on the bottom-mounted circular cylinder in a two-layer fluid include not only the added mass and damping coefficients, but also the wave forces of the surface and internal-wave modes. This is different from the case of a homogenous fluid. Some examples were given, showing that density stratification can have a relative large effect on these hydrodynamic forces over a wide range of frequencies.     

PRELIMINARY STUDY ON CIRCULATION HEIGHT OF CIRCULATION FLOW WITH THE HORIZONTAL AXIS

1.　INTRODUCTIONCirculationflowisoneofcommonflowpatternsinnaturalrivers.Astherotationaxisishorizontal,andismainlyperpendiculartothemainstream,thiskindofcirculationflowisusuallycalledthehorizontalaxiscirculationflow(Zhang,1996).Itusuallyappearsinlocalareaswherebedboundarieschangesuddenly.Forexample,itexistsincross-riverchanneldugforsunkingpipe,anddownstreamofanapronextension,andsoon.Thehorizontalaxiscirculationareaisalwaystheimportantplacewheresedimentdepositsorerodesandtheerodingordeposi…     

HE SPATIO-TEMPORAL STRUCTURE OF BINARY FLUID CONVECTION WITH HORIZONTAL FLOW

1 .　INTRODUCTIONDuringthepastfew yearstheinvestigationofconvectioninahorizontalfluidlayerheatedfrombelowhasevolvedtooneofthemostintensivelystudiedbranchesofhydrodynamics .Thisisbecauseitisofsignificanceinboththeoryandapplication .Fromapracticalviewpointmanyinteresting pro cessesinvolvethermallydrivenflows ,amongwhicharesuchdiversephenomenaasconvectioninstars,theocean ,andtheatmosphrere .Fromatheoreticalviewpointconvectiveflowsprovideex perimentallyrealizablesystemsforvery precisestudieso…     

INTERACTION OF A FLOATING ELLIPTIC CYLINDER WITH A VIBRATING CIRCULAR CYLINDER

1. INTRODUCTION The hydrodynamic interaction between two submerged “non-circular’ bodies is of significant importance from both practical and theoretical points of view. In general, a detailed study of this problem is very difficult. Even in an ideal fl…     

ON HYDRODYNAMIC INTERACTION UPON THE WAVE FORCES ON VERTICAL PILE ARRAY

A systematic study is carried out on the hydrodynamic interaction of sin-gle-row vertical pile array with a large number of piles by using the method of wave sourcedistribution.Some new properties for the hydrodynamic interaction among piles are firstreported in this paper.The Present study shows the importance and necessity of reassess-ing the hydrodynamic interaction among multiple objects of large number to reach a com-plete understanding on that subject.