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15 February 2011, Volume 33 Issue 1
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    2011, 33(1):  66-69.  doi:10.6052/1000-0879-lxysj2010-069
    Abstract ( 1129 )   PDF (654KB) ( 368 )  
    According to flow characteristics of different flow areas of fractured horizontal wells in low permeability oil reservoirs, the vadose region of fractured horizontal wells can be divided into three districts, the non-Darcy flow district with a high speed controlled by cracks, the ellipse flow district and the matrix non-Darcy flow district. Two-phase porous flow mathematical models of matrix non-Darcy flow with start-up pressure gradient are built. The results indicate that the production goes with the increase of fracture conductivity; the incremental scope of production decreases with the increase of production time; initial production of fractured horizontal decreases progressively with the increase of fracture length, the incremental scope of production decreases with the increase of fracture length; the production of fractured horizontal wells is the maximum in the situation with a long median crack and a short two-way crack.
    Around the mechanics
    2011, 33(1):  43-47.  doi:10.6052/1000-0879-lxysj2010-134
    Abstract ( 1556 )   PDF (882KB) ( 807 )  
    In order to reduce the negative impact of the environment due to shallow tunnel construction, the ground movement and deformation are estimated through simulating the entire process of the shallow tunnel construction, and the surrounding rock stress and strain in different situations are obtained. On this basis, the non-linear regression method for consideration of time factors is used to obtain the space-time deformation law of ground surface. This work provides a new way of estimating the effect of shallow tunnel construction on ground surface.
    2011, 33(1):  48-52.  doi:10.6052/1000-0879-lxysj2010-239
    Abstract ( 1444 )   PDF (826KB) ( 494 )  
    Dynamic shear modulus and damping ratio are two main parameters when dynamic performance of aeolian soil in west Liaoning province is researched. This paper analyses the influence of confining pressure, consolidation ratio and frequency of vibration on dynamic shear modulus and damping ratio of aeolian soil though a series of dynamic triaxial tests. Experimental results show that the dynamic shear modulus of aeolian soil increases with the confining pressure and the consolidation ratio up, just the opposite, the damping ratio decreases; the dynamic shear modulus and the consolidation ratio decreases with the frequency of vibration up, but unlike the two factors above, the influence is small.
    2011, 33(1):  29-34.  doi:10.6052/1000-0879-lxysj2010-255
    Abstract ( 1035 )   PDF (987KB) ( 430 )  
    Based on the initial parameter method, this paper studies the deformation and stress distributions of elastic foundation frame subjected to uniform pressure and with two nodes simply supported. Firstly, the calculation formula for deflections of a finite-length elastic foundation beam with elastic support at both ends is derived. Based on the boundary conditions and the symmetry of the structure, a local structure is considered without taking account of the displacement boundary conditions at the two simply supported nodes. The initial parameter of the local structure is obtained according to the boundary conditions of the displacement and the internal force, then, the distribution of stresses of the whole structure is obtained based on the symmetry. The calculation formulas of the real deflection for the frame are obtained, modified by the foregoing displacement distribution according to the displacement boundary conditions.
    2011, 33(1):  70-73.  doi:10.6052/1000-0879-lxysj2010-256
    Abstract ( 1073 )   PDF (1210KB) ( 386 )  
    In pipe flow visualization experiments in the rack, compressed air and spray liquid are used as test media, with liquid in a continuous simulation and testing of experimental parameters; high-speed video camera is used to capture the actual shape of the droplet gas stream --- ellipsoid. It was found that: that sphere model and elliptical sphere model give, respectively, a deviation of 10{\%} and 58.3{\%} compared with experiment. This paper analyzes the stress state in ellipsoid and the experimental data are used to build a new mathematical ellipsoid model, and the new model gives results in agreement with water production line of seven wells.In40 plexiglass tube rack visualization the self-development of high 16m, experiment, using compressed air and water as the experimental medium (gas-liquid ratio "10000), to simulate different pressure, gas and other gas well under the conditions of carrying a continuous fluid, high-speed High-speed video cameras to capture the actual flow in the droplet shape --- similar to the sphere ellipsoid, test wellhead pressure, temperature, gas and other parameters. It was found that Turner spherical model calculated and experimental results deviation of 10%, spe70016 ellipsoid model and the experimental results deviation of 58.3%. Article analyzes the ellipsoid stress state, the application of experimental data fitting drag coefficient has been derived, consistent with the experimental wells to bring the new ellipsoid fluid mathematical model. This paper selects seven western Sichuan gas field production data, for example with water wells, according to derived ellipsoid model of the new formula, the results in line with the production wells. The experimental research for the research and teaching and guiding both the importance of field applications.
    2011, 33(1):  94-96.  doi:10.6052/1000-0879-lxysj2010-282
    Abstract ( 1196 )   PDF (501KB) ( 524 )  
    Not only it is important to impart knowledge, it is more important to improve students' creativity and comprehensive quality during fluid dynamics teaching.In this paper four "unity" is discussed,which includes the unity of hydrostatics and hydrodynamics teaching,the unity of fluid pressure on the plane and the surface, the unity of theory and practice and the unity of this course and specialty. The following view is put forward.To make students establish philosophical thought, to improve their abilities of solving practical problem by computer, to teach some relevant prospective professional knowledge are very important.
    2011, 33(1):  86-88.  doi:10.6052/1000-0879-lxysj2010-295
    Abstract ( 1975 )   PDF (506KB) ( 857 )  
    The direction of the friction force is determined when a homogeneous circle rolls without slipping on horizontal plane under the action of the couple or the horizontal force. Only by the couple made pure rolling circle, fraction is the only force causing the linear acceleration and has a moment about the mass center whose direction is reversed to of the couple. Then, the fraction force also decreasing the angular acceleration. When the circle is acted only upon by a horizontal force, using rigid planar differential equations of motion and theorem of kinetic energy, the direction of fraction force is determined by the acting location, the radius of the cylinder and radius of gyration.
    Around the mechanics
    2011, 33(1):  1-9.  doi:10.6052/1000-0879-lxysj2010-524
    Abstract ( 1734 )   PDF (2545KB) ( 1014 )  
    This paper briefly summarizes the strategic value of the near space and the fierce competition in developing hypersonic vehicles over the world, and focuses on the development of the thermal protection system of hypersonic vehicles as well as related fundamental scientific problems, including the thermal protection principle, technique and thermo-mechanical coupling analysis.
    2011, 33(1):  10-16.  doi:10.6052/1000-0879-lxysj2010-116
    Abstract ( 1135 )   PDF (3684KB) ( 573 )  
    A localized small force provides a unique non invasive probe based on both the structure of the force chain network and the response of granular matter. In this work, quasistatic packings of 30\,000 spherical particles confined within a 2m*1m*0.01m container are simulated by using discrete element method. The sizes of particles are 0.01m, 0.008m and 0.006m, respectively, and the number of particles of each size is 10 000. A localized force is exerted on one of the top layer particles with a small magnitude of 5.2*10$^{ - 2}$N, which is 100 times of the weight of the largest particle with the size of 0.01\,m in order to ensure that the granular material keeps still. The results show strong heterogeneous pathways of force propagation and the fluctuations of force are evident. With the increase of the distance from the exerted particle, the force fluctuations are reduced. The calculated stress values agree with the Flamant solutions of stress as the distance is more than 5 times the size of the largest particle. The effect of surface friction of particles is discussed. The preliminary results indicate that a larger friction coefficient leads to more uniform stress distributions.
    2011, 33(1):  17-20.  doi:10.6052/1000-0879-lxysj2010-333
    Abstract ( 1597 )   PDF (1167KB) ( 531 )  
    It is extremely important to accurately determine the ship mooring collision load in considering ship and offshore platform's strength. This paper proposes a method to determine the ship mooring collision load with energy principle and the finite element method. In collision, the impact kinetic energy and the deformation energy are considered in the energy conservation law. The kinetic energy refers to the ship's kinetic energy including the additional water mass. It is transformed into the deformation energy when collision occurs. That collision load can be calculated by the relationship between the deformation energy and the load. The theoretical solution of abeam is used to validate the method. The method can be used to determine the impact force of the fender in practical cases.
    2011, 33(1):  21-23.  doi:10.6052/1000-0879-lxysj2010-294
    Abstract ( 1335 )   PDF (719KB) ( 655 )  
    The high-mass (400\,kg) drop weight impact tests for no ignition Comp.B were numerically simulated by using the Johnson-Cook constitutive model, to investigate the mechanical response characteristics of Comp.B in inertial impact. $\sigma $-$t$ curves of numerical simulation with EOS and without EOS were obtained at different charge conditions. The main mechanical parameters are compared, such as peak stress, stress rise time, etc., The results of Johnson-Cook constitutive model with EOS agree better with experiments. This model can be used to simulate the mechanical response characteristics of explosive in inertial impact.
    2011, 33(1):  24-28.  doi:10.6052/1000-0879-lxysj2010-414
    Abstract ( 1490 )   PDF (873KB) ( 385 )  
    In this paper, a delamination identification strategy based on vibration signatures by using artificial neural networks is presented Through different nodes with same coordinates, a finite element model for internal delamination is established.The global vibration identification factors of damaged and damage free laminates are obtained by numerical simulation. In the studies, the identification capability for the quantitative prediction of delamination in composites laminates is focused. The results show that the strategy based on the vibration signal measurement and artificial neural networks is efficient to detect delamination defects and there is a good possiblity to apply the proposed method to the helth monitoring of a practical composite structure.
    2011, 33(1):  35-38.  doi:10.6052/1000-0879-lxysj2010-420
    Abstract ( 1226 )   PDF (939KB) ( 366 )  
    This paper discusses how to locate damage in beam structures. Damage is related with changes of local stiffness or local mass. Based on the equivalent element concept, this paper proposes new methods of damage localization for continuous beam and simply supported beams, respectively, by using support reaction and mid-span displacement as damage indicators. The damage location results are expressed in small regions intervals. The feasibility and effectiveness of the methods are demonstrated by numerical simulations and model experiments.
    Around the mechanics
    2011, 33(1):  39-42.  doi:10.6052/1000-0879-lxysj2010-262
    Abstract ( 1002 )   PDF (698KB) ( 726 )  
    In order to compare the truss model and the frame model, a simple experimental structure is adopted in this paper. For several special sections of the experimental truss and frame, test data are obtained, including the internal force on those sections and the middle node displacements. At the same time, the finite element simulation for the two kinds of models is performed by using ANSYS software. By comparing experimental results with theoretical calculation results the models are verified and mechanical characteristics of the two structures are obtained. The difference between the actual truss and the ideal truss and that between experimental value and theoretical value are analyzed through finite element simulation. Some conclusions are drawn for structure design and teaching.
    2011, 33(1):  53-55.  doi:10.6052/1000-0879-lxysj2010-375
    Abstract ( 1162 )   PDF (642KB) ( 631 )  
    In this paper, the impact of the pushing force on the release angle of the shot-put sportsman is studied, and the optimal value of the release angle is calculated numerically using the MATLAB. Some influencing factors on the optimal release angle, such as the height, pushing force, attenuation coefficient of angle and shot's mass are discussed.
    2011, 33(1):  56-59.  doi:10.6052/1000-0879-lxysj2010-313
    Abstract ( 926 )   PDF (613KB) ( 484 )  
    The loading of the hydraulic modularized combined trailer of any axis is studied in this paper, which concerns the design of vehicles and the safely of loading. The relationship between the loading mass and loading span, and the loading calculation formula are obtained, and the typical vehicle loading cases are calculated to obtain related loading pictures.
    2011, 33(1):  60-63.  doi:10.6052/1000-0879-lxysj2010-340
    Abstract ( 1071 )   PDF (590KB) ( 336 )  
    The method of lines is used to deal with torsion problems of prismatic bars with sector cross-section. Firstly, ordinary differential equations are obtained from partial differential equations of the torsion problem of prismatic bars with sector cross-sections, and are solved analytically. Secondly, the torsion stress function is derived semi-analytically. Finally, the torsion stiffness of the sector cross-section is obtained. The special solution of the ordinary differential equations is obtained by means of the double sweep method, and the eigenvalues and eigenvectors of the tridiagonal matrix are solved, without using the inverse matrix, based on a theorem that eigenvectors of a real symmetric matrix are orthogonal. The torsion stiffness is solved by a compound trapezoid formula. The numerical results are in good agreement with the existing results, which show the correctness of the algorithm. This method is a kind of semi-analytical method, and can be applied in design of prismatic bars with sectorial cross-section in engineering.
    2011, 33(1):  64-65.  doi:10.6052/1000-0879-lxysj2010-179
    Abstract ( 1432 )   PDF (344KB) ( 717 )  
    A trolly wire with insulators in electric transmissions is investigated in this paper. Based on longitudinal-transversal bending theory, the deflection curve equations of aluminum cable steel reinforced is derived. The sag and the horizontal tension of the trolly wire are obtained based on a insulator's simplified model under dead weight and temperature loads. The results show that the method in this paper is simple and effective. The main influencing factors of the sags are temperature and span of trolly wire. The average variation rate of the sag to temperature is 2.55mm/$^{\circ}$C; the sag will be almost increased by 60% when the span of trolly wire decreases 1%.
    2011, 33(1):  74-77.  doi:10.6052/1000-0879-lxysj2010-115
    Abstract ( 1766 )   PDF (788KB) ( 627 )  
    The traditional model of beams and the Cosserat model of elastic rods are compared in this paper as two different modeling approaches for one-dimensional elastic body. The three-dimensional motion of a beam is analyzed considering all influence factors, such as the tensile or compressed deformation of the centerline, the shear deformation and the inertia of rotation of the cross section, and the loads on the ends. The stability conditions and free frequency of lateral vibration of a beam are derived on the basis of exact Cosserat model. The Bernoulli beam, Timoshenko beam, and Kirchhoff rod are simplifications of exact Cosserat model under different conditions.
    2011, 33(1):  84-85.  doi:10.6052/1000-0879-lxysj2010-105
    Abstract ( 1261 )   PDF (628KB) ( 336 )  
    2011, 33(1):  89-91.  doi:10.6052/1000-0879-lxysj2010-097
    Abstract ( 1239 )   PDF (1216KB) ( 551 )  
    With the developing of technique and the achievement of research project, the real three dimensional numerical modeling method has been applied the rock mechanics teaching practice. The potential of teaching resource were promoted, and the numerical test of rock mechanics, deformation and failure of rock. Many mechanical phenomenon which can not observed in physical experiment were modeled, for example, the rocks three dimensional structure, rock failure process, and blocks slip etac. It is useful to improve the students’ ability in practice and interesting in science, encouraging student to make good understanding of subject, and increase the quality of rock mechanical experiment.