ON THE STABILITY OF A LIQUID-FILLED ROTOR

The dynamic stability of a high-spinning liquid-filled rotor with both internal and external damping effects involved in is investigated in this paper. First, in the case of the rotor subjected to a transverse harmonic motion, the dynamic pressure of the liquid acting on the rotor is extracted throuhg a planar flow analysis. Then the equation of perturbed motion for the liquid-filled rotor is derived. The analytical stability criteria as well as the stability boundaries are given. The results are extensions of those given by previous literature.     

INFLUENCE OF OCEAN INTERNAL WAVE ON PROPAGATION OF UNDERWATER RADIATION NOISE

The underwater acoustic field influenced by a selected ocean internal wave was computed using the Parabolic Equation (PE) method and split-step difference algorithm in this paper. Acoustic field is formed by sound source with different frequency covering the range of radiation noise of ships and submarines. Owing to the adoption of complex variables,sparse matrix, Gaussian source and analysis on the grid size.numerical results are achieved smoothly. The results show that internal wave‘s influence on underwater sound can‘t be neglected, especially for higher sound frequency. So it‘s necessary to take internal wave into account in identifying radiation noise of ships and submarines, namely for sound intensity, transmission loss and spectra shape.     

A NEW METHOD FOR PREDICTION OF PRODUCTIVITY OF FRACTURED HORIZONTAL WELLS BASED ON NON-STEADY FLOW

Hydraulic fracturing technologies of horizontal well are important ways to develop oil-gas field with low permeability. Productivity forecast of fractured horizontal wells is a difficult problem of hydraulic fracturing technologies. Basing on non-steady flow of fractures fluid during production, applying potential function principles, superposition principle and mathematical method for solving, coupling of seepage flow in the formation and pipe flow in the well bore, a new model on multi-fracture interference productivity forecast of fractured horizontal well is established in this article. The results indicate the coincidence rate between this model and practice is high. The pressure loss in the horizontal well bore has definite influence on the production status of fractured horizontal wells. The productions of different fractures in horizontal well bore are unequal, the productions of outer fractures are higher than middle fractures; the pressure in the well bore shows an uneven distribution, the pressure declines gradually from finger tip to heel end. Asymmetry of fractures may make productivity of fractured horizontal wells decline. The conclusions are instructive in designing fractured horizontal well for low permeability reservoir.     

NUMERICAL PREDICTION OF BLADE FREQUENCY NOISE OF CAVITA- TING PROPELLER

The blade frequency noise of a cavitating propeller in a uniform flow is analyzed in the time domain. The unsteady loading (of a dipole source) and the sheet cavity volume (of a monopole source) on the propeller surface are calculated by a potential-based surface panel method. Then the time-dependent pressure and the cavity volume data are used as the input for the Fowcs Williams-Hawkings formulation to predict the acoustics pressure. The integration of the noise source is performed over the true blade surface rather than the ideal blade surface without thickness. The noise characteristics of the cavitating propeller are discussed. With the sheet cavitation, the thickness (cavitation) noise is larger than the loading noise and is the dominant noise source.The noise directivity is not as clear as that of the noise under a non-cavitation condition. The cavitation noise is attenuated mores lowly than the non-cavitation noise.     

翼型体广谱声的频域预报方法

本文提出了一种广谱声预报的频域方法，并通过与试验数据的比较证明了方法的有效性，尽管文中以平板翼为例，进行了实例计算，但方法本身适用于任意形体在介质中以亚音速作惯性运动时的广谱声预报。相对于时域方法而言，由于省去了将频域数据转化为时域数据的中间过程，因此该方法较时域方法(Casper and Farassat，2002)更为有效。本文的关键在于具有平均流效果的格林函数的成功应用，由此格林函数所表达的积分算式将在后续文中进一步拓展应用于具有非惯性运动的螺旋桨广谱噪声的预报。     

基于新原理的光电遥测垂线坐标仪

介绍一种基于新原理的光电遥测垂线坐标仪的工作原理、技术性能及网络构成。     

NUMERICAL PREDICTION OF PROPELLER EXCITED ACOUSTIC RESPONSE OF SUBMARINE STRUCTURE BASED ON CFD,FEM AND BEM

A mesh-less Refined Integral Algorithm (RIA) of Boundary Element Method (BEM) is proposed to accurately solve the Helmholtz Integral Equation (HIE).The convergence behavior and the practicability of the method are validated.Computational Fluid Dynamics (CFD),Finite Element Method (FEM) and RIA are used to predict the propeller excited underwater noise of the submarine hull structure.Firstly the propeller and submarine’s flows are independently validated,then the self propulsion of the "submarine+propeller" system is simulated via CFD and the balanced point of the system is determined as well as the self propulsion factors.Secondly,the transient response of the "submarine+ propeller" system is analyzed at the balanced point,and the propeller thrust and torque excitations are calculated.Thirdly the thrust and the torque excitations of the propeller are loaded on the submarine,respectively,to calculate the acoustic response,and the sound power and the main peak frequencies are obtained.Results show that:(1) the thrust mainly excites the submarine axial mode and the high frequency area appears at the two conical-type ends,while the torque mainly excites the circumferential mode and the high frequency area appears at the broadside of the cylindrical section,but with rather smaller sound power and radiation efficiency than the former,(2) the main sound source appears at BPF and 2BPF and comes from the harmonic propeller excitations.So,the main attention should be paid on the thrust excitation control for the sound reduction of the propeller excited submarine structure.     

A FIELD TEST DATA RESEARCH BASED ON A NEW HYDRAULIC PARAMETERS QUICK TEST TECHNOLOGY

The hydraulic parameter quick test system in accordance with the oscillation principle can overcome the shortcomings of traditional methods in determining hydraulic parameters which, besides having complex hydrogeological restrictions and needing complex equipment in the field, are often both time and energy consuming, and high cost. Based on the hydrogeological conditions in the north anchorage of Taizhou Yangtze River Highway Bridge, a quick hierarchical test is carried out for different depths of single-hole drilling to verify the function of the system in this case. Meanwhile, with a purification of the raw data gathered in the test by wavelet denoising, the hydraulic parameters are worked out by adopting the Kipp model. A comparison between the Kipp model results and stratigraphic data as well as pumping test results justifies the reliability and accuracy of the new method. The study finds other advantages of the method like high efficiency in operation, flexibility in stratified test, as well as environmental-friendliness. Therefore, the technology is of significant practical value and application prospect.     

UNSTEADY PROPELLER SURFACE PRESSURE PREDICTION WITH A POTENTIAL BASED PANEL METHOD

ＵＮＳＴＥＡＤＹＰＲＯＰＥＬＬＥＲＳＵＲＦＡＣＥＰＲＥＤＩＣＴＩＯＮＷＩＴＨＡＰＯＴＥＮＴＩＡＬＢＡＳＥＤＰＡＮＥＬＭＥＴＨＯＤ￥ＣｈｅｎＪｉａ－ｄｏｎｇ（ＣｈｉｎａＳｈｉｐＳｃｉｅｎｔｉｆｉｃＲｅｓｅａｒｃｈＣｅｎｔｅｒ，Ｂｏｘ１１６，Ｗｕｘｉ２１...     

A NEW METHOD OF CHANNEL FRICTION INVERSION BASED ON KALMAN FILTER WITH UNKNOWN PARAMETER VECTOR

1.INTRODUCTION Floodhydrauliccalculationhasbecomeanec essarytechnologyinengineeringdesignsandflood disastercontrolprogramming.Eventhoughthe theoryoffloodhydraulicsimulationhasbeenfully developedsince1970s,andalotofcommercialor freesoftwarehasappeared,suchasMike11and HEC RAS,therearesomeobstaclesinengineering applications.E.g.,therationalityofmodelpa rametersisthebaseofreliabilityofsimulation.Es pecially,thechannelfrictionisstilldependenton engineer’sexperience,althoughitcanbeobtained …     

A RIVER FLOW ROUTING MODEL BASED ON DIGITAL DRAINAGE NETWORK

On the basis of Digital Elevation Model （DEM） data, watershed delineation and spatial topological relationship were proposed by the Digital Elevation Drainage Network Model （DEDNM） for the area upstream of the Hanzhong Hydrological Station in the Hanjiang River in China. Then, the Muskingum-Cunge method considering lateral flow into the river was applied to flood routing on the platform of digital basin derived from DEDNM. Because of considering lateral flow into the river, the Muskingum-Cunge method performs better than the Muskingum method in terms of the Nash-Sutcliffe model efficiency coefficient and the relative error of flood discharge peak value. With a routing-after-superposition algorithm, the Muskingum-Cunge method performs better than the Muskingum method in terms of the Nash-Sutcliffe model efficiency coefficient and the relative error of flood discharge peak value. As a result, the digital basin coupled with the Muskingum-Cunge method provides a better platform for water resources management and flood control.     

EXPERIMENTAL STUDY ON A NEW KIND OF OPEN TYPE BREAKWATERS

A new kind of open type breakwaters was proposed based on the concept of wave energy conversion. The excellent feature of the structure is that it can absorb and utilize the wave energy to dissipate waves. The effects of some factors, such as the configuration insides, the geometrical parameters and the relative width (the ratio of the width to the wave length), on the performance of the breakwater were discussed based on a series of regular wave tests in the wave flume. The hydrodynamic characteristics of the new open type breakwater were analyzed in detail, and the structure was optimized to improve the performance of the breakwater to effectively dissipate the waves with long period. The variation of the coefficients of wave transmission and reflection along with attenuation with respect to relative width was examined. The results of the physical model tests indicate that the transmission coefficient significantly decreases by about twenty percent at the range of relative width from 0. 1 to 0.2, compared with the traditional open type breakwaters.     

基于背景网格的混凝土细观力学预处理方法

为了提高混凝土细观力学预处理的效率与骨料投放密实度，以适应不同体积、不同骨料含量混凝土的细观模拟要求，本文提出了一种新的预处理方法。该方法在骨料投放阶段，首先形成投放区域的背景网格以及对应网格点的状态矩阵，用以进行骨料的投放定位以及骨料间相互侵入的判定，提高了投放的效率和密实度；其次，在细观有限元剖分阶段，利用已有的背景网格状态矩阵完成混凝土细观三相介质的坐标生成，简化了预处理过程。此外，采用分级配随机投放的方式，可保证投放的随机性以及级配分布的合理性。实例证明，该方法实现的二维骨料投放密实度可超过80%，三维可超过60%，为细观混凝土数值模拟的预处理提供了一种有力的工具。     

ASSESSMENT OF BED-LOAD PREDICTORS BASED ON SAMPLING IN A GRAVEL BED RIVER

Bedload transport in alluvial channels has been extensively studied and different equations based on field and/or experimental data have been proposed.Prediction of bed-load transport rate using different equations results in wide ranges which are not always reliable.In this study,some of the universal bedload predictors were evaluated with measured load by a Helley-Smith sampler in the Node River,a gravel bed river in the northeast part of Iran.From 19 sets of data,14 series of data were used to evaluate the bed-load transport equations.The results show that the equations presented by Van Rijn,Meyer-Peter and Mueller,and Ackers and White may adequately predict bedload transport in the range of field data.     

RESEARCH OF INNER FLOW IN A DOUBLE BLADES PUMP BASED ON OPENFOAM

The inner flow analysis of centrifugal pumps has gradually become an important issue for the hydraulic design and performance improvement.Nowadays,CFD simulation toolbox of pump inner flow mainly contains commercial tools and open source tools.There are some defects for commercial CFD software for the numerical simulation of 3-D turbulent internal flow in pump,especially in capturing the flow characteristics under the off-design operating conditions.Additionally,it is difficult for researchers to do further investigation because of the undeclared source.Therefore,an open source software like Open Field Operation and Manipulation (OpenFOAM) is increasingly popular with researchers from all over the world.In this paper,a new computational study was implemented based on the original solver and was used to directly simulate the steady-state inner flow in a double blades pump,with the specific speed is 111.In order to disclose the characteristics deeply,three research schemes were conducted.The ratios () of the flow rate are 0.8,1.0 and 1.2,respectively.The simulation results were verified with the Particle Imaging Velocimetry (PIV) experimental results,and the numerical calculation results agree well with the experimental data.Meanwhile,the phenomena of flow separation under the off-design operating conditions are well captured by OpenFOAM.The results indicate that OpenFOAM possesses obvious strong predominance in computing the internal flow field of pump.The analysis results can also be used as the basis for the further research and the improvement of centrifugal pump.     

一种新的水面蒸发计算模型的研究

依据水面蒸发过程的物理机制,选用饱和水汽压差、风速、相对湿度、水汽温差4个因子,建立一个以各因子单函数连乘积的形式为基本结构的水面蒸发计算模型．并利用不同气候区多站水面蒸发实验资料,确定模型参数．经全国各地33个蒸发实验站资料检验,此模型的拟合误差较小,移用误差也较小．     

HIGH-SPEED FLOW EROSION ON A NEW ROLLER COMPACTED CONCRETE DAM DURING CONSTRUCTION

A new roller compacted concrete dam of Fengman Hydropower Station is to be built in the toe of the old dam,which was identified as a dangerous dam.The new dam during construction would be influenced by the high-speed flow discharged from the old dam,which is an important problem to be considered for the first time in China,and which would affect the construction of the whole project.Therefore,a series of erosion experiments were conducted in this article.A high-speed flow erosion test apparatus was developed for the erosion experiments of the new dam materials.The maximum jet velocity goes up to 40 m/s and the section area of the nozzle is 0.0025 m2.In the process of experiments,the equipment shows a good performance.Erosive wear tests for two types of materials used in the new dam,a roller compacted concrete and a distorted concrete with four kinds of ages were carried out with the flow velocity in the range of 30 m/s-35 m/s.Erosion parameters and erosion laws for the two types of concretes with different ages were determined,and a general relationship between the erosion rate and the flow velocity is obtained as:,with the velocity exponent between 3.33 and 3.93.It is concluded that the erosion resistance of the distorted concrete is better than that of the roller compacted concrete and the mechanical properties of the concretes of over 14 d age are influenced slightly by the water impact.The test results might serve as a practical technique guide for the safety of this project during its construction in the flood season.     

FLOW AROUND A CIRCULAR CYLINDER USING A FINITE-VOLUME TVD SCHEME BASED ON A VECTOR TRANSFORMATION APPROACH

Flows around a circular cylinder displaying an unsteady vortex shedding process at the Reynolds numbers of 1000,3900 and 1×104 are studied using a finite-volume Total Variation Diminishing(TVD) scheme for solving the Unsteady Reynolds-Averaged Navier-Stokes(URANS) equations.An Elemental Velocity Vector Transformation(EVVT) approach is proposed for the local normal and tangential velocity transformation at the interfaces of main and satellite elements.The presented method is validated by comparing with the available experimental data and numerical results.It is shown that the two-dimensional TVD finite volume method with the Renormalization Group(RNG) turbulence model can be used to determine hydrodynamic forces and captures vortex shedding characteristics very well.     

A STUDY OF DRAG COEFFICIENT RELATED WITH VEGETATION BASED ON THE FLUME EXPERIMENT

This study is focused on the effects of ecological factors (diameter and flexibility) and vegetation community composition on the drag coefficient related with vegetation. The single leafy shrub and three mixed communities (including shrub-grass, shrub-reed and reed-grass community) were studied. The flow velocity and water level were measured and used to calculate the drag coefficient based on the Bernoulli's equation, Darcy drag formula and the expression for the drag coefficient related with Darcy drag factor. The trend of the drag coefficient in the vertical direction was analyzed against flow depth, diameter, diameter Reynolds number, flow depth Reynolds number and relative roughness height in different discharges. The results show that beside the dense leafy shrubs community, the vertical trend of the drag coefficient among other cases against flow depth, diameter, diameter Reynolds number, flow depth Reynolds number and relative roughness height can be approximately expressed by power law functions under different flow discharges. Moreover, in a mixed community with two plants with distinctly different ecological factors, the one with the most distinct variations of ecological factors determines the vertical trend of the drag coefficient; the other one only affects the magnitude of the drag coefficient. Furthermore, if the ecological factors of the vegetation in the vertical direction are kept almost not changed, the drag coefficient can be approximately regarded as a constant.     

STUDY ON A NEW APPROACH OF CAVITATION EROSION TEST FOR NONMETALLIC MATERIALS

１．　ＩＮＴＲＯＤＵＣＴＩＯＮＣａｖｉｔａｔｉｏｎｄａｍａｇｅｏｆｍａｔｅｒｉａｌｓｉｎｖｏｌｖｅｓｍａｎｙｆａｃｔｏｒｓ，ｓｕｃｈａｓｔｈｅｍｅｃｈａｎｉｃａｌｐｒｏｐｅｒｔｉｅｓｏｆｍａｔｅｒｉａｌ，ｔｈｅｐｒｏｐｅｒｔｉｅｓｏｆｌｉｑｕｉｄｍｅｄｉａ，ｔｈｅｆｌｏｗｆｉｅｌｄｃｈａｒａｃｔｅｒｉｓｔｉｃｓ，ｅｔｃ．Ｉｔｉｓｗｅｌｌｋｎｏｗｎｔｈａｔｔｈｅｍｅｃｈａｎｉｓｍｏｆｃａｖｉｔａｔｉｏｎｅｒｏｓｉｏｎｉｓｖｅｒｙｃｏｍｐｌｉｃａｔｅｄ．Ｕｐｔｏｎｏｗ，ｔｈｅｃａｐａｂｉｌｉｔｙｏ…