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08 October 2010, Volume 32 Issue 5
Application study
2010, 32(5):  10-13.  doi:10.6052/1000-0879-lxysj2009-406
Abstract ( 1421 )   PDF (690KB) ( 548 )
Considering the non-uniformity of the flow velocity distribution in a fluid-conveying pipe caused by the viscosity of real fluid, the centrifugal-force term in the equation of motion of the pipe is modified in the cases of laminar flow and two modes of turbulent flow. The modification factors are found to be 1.333, 1.020 and 1.037$\sim$1.055 for laminar flow in circular pipe, turbulent flow in smooth circular pipe and turbulent flow in rough circular pipe, respectively. The critical flow velocities for divergence in the above-mentioned three cases are found to be 13.4{\%}, 1.0{\%} and 1.8\%$\sim$2.6{\%}, respectively, lower than those for ideal fluid flow. The effects of fluid viscosity on the equation of motion and the critical flow velocity of fluid-conveying pipe are explicitly related to the flow mode only. The viscosity coefficient plays an implicit role via Reynolds number, which determines the flow mode.
Education Study
2010, 32(5):  96-97.  doi:10.6052/1000-0879-lxysj2009-422
Abstract ( 1221 )   PDF (432KB) ( 506 )
2010, 32(5):  77-80.  doi:10.6052/1000-0879-lxysj2009-432
Abstract ( 1640 )   PDF (276KB) ( 446 )
This paper discusses the equilibrium and stability of floating body, and introduced the definition of metacentre, then gives three different methods of calculating the height of metacentre through examples, and finally explains the reason why we can determine the stability of an equilibrium of floating body by height of metacetre.
High-quality talents training in Engineering Mechanics
傅衣铭,陈昌萍 and 饶燕妮
2010, 32(5):  92-93.  doi:10.6052/1000-0879-lxysj2009-443
Abstract ( 1277 )   PDF (438KB) ( 353 )
According to the basic features of the engineering mechanics and its widely practical characteristics, and in order to meet the growing demands of society to the graduates of the mechanics, this essay, aiming at the disadvantages of traditional engineering mechanics education, which, to a certain extent, restrict to cultivate the high-quality talents with both theory and application, states some suggestions about how to educate the high-quality engineering mechanics talents and about reforms of current mechanics education in relevant colleges.
2010, 32(5):  87-88.  doi:10.6052/1000-0879-lxysj2009-489
Abstract ( 1400 )   PDF (300KB) ( 500 )
In order to obtain the center of gravity which not easy to be obtained by the theory or the experiment to certain complex rigid body, according to the rotation inertia parallel axis theorem, the relational expressions asking the center of gravity were deduced by the known axis rotation inertia and certain geometry relations, and theoretically two possibility centers of mass were got, which May be Selected after the actual judgment. So long as surveys the rigid body first with the instrument to three parallel axis rotation inertias, may obtain the center of gravity position by that relational expressions. Sometimes this method is simple compared to the direct survey the center of gravity.
Application study
2010, 32(5):  41-44.  doi:10.6052/1000-0879-lxysj2010-019
Abstract ( 1205 )   PDF (667KB) ( 492 )
Based on the sedimentation calculation of foundation and the practical observation of basic sedimentation, the analyses are made of the influence of precipitation of river construction on the adjacent buildings. The result shows that the subsidence of the buildings and cracks are due to the precipitation water in the construction; the foundation settlement of adjacent buildings decreases from near region to far region of the construction site of precipitation; an effective way is to combine the water curtain with the recharge well to control the decrease of the groundwater level.
Education Study
2010, 32(5):  83-86.  doi:10.6052/1000-0879-lxysj2010-020
Abstract ( 1197 )   PDF (796KB) ( 1529 )
How to determine the friction force of a rolling rigid-body often confused the students who are learning engineering mechanics. The reason that results in the friction force was analyzed, and thenthe equation to determine the static friction force was ascertained. By means of the work-energy principle, the effect of friction force was discovered. It was concluded that the total work of the static friction force of a rolling rigid-body is zero and the total work of the sliding friction force of a rolling rigid-body is negative. The role of the friction force is to realize the conversion between the rotation kinetic and the stable motion kinetic energy. The direction of the static friction force is to prevent the trend of motion due to force, and the direction of the sliding friction force is negative to the direction of sliding movement.
Application study
2010, 32(5):  45-49.  doi:10.6052/1000-0879-lxysj2010-031
Abstract ( 1470 )   PDF (901KB) ( 497 )
Based on the theory of Euler-Bernoulli beams, the bending, buckling and free vibration of functionally graded material (FGM) beams were analyzed. By comparing the governing equations of functionally graded material beams and uniform beams, an analogous transform relation between the solution of FGM beam and that of uniform beam were obtained. If the material properties of FGM beam can be expressed in power functions in the lateral direction, the transformation factors between the solutions of the two kinds of beams were derived in analytical forms, which reflect the non-uniform properties of the functionally graded material beams. Therefore, the solution of static and dynamic problems of FGM beams can be transformed to that of a uniform beam and the calculation of the transformation factors under the same loadings and boundary conditions. This method can provide a simple and convenient approach in analysis of non-uniform beams and find applications in engineering.
2010, 32(5):  31-35.  doi:10.6052/1000-0879-lxysj2010-033
Abstract ( 1044 )   PDF (1449KB) ( 469 )
The seismic responses of the piles in a wave-current field are studied by theoretical analysis and finite element simulation. Besides the wave-current force and hydrodynamic pressure on the piles in the wave-current field, the results of the model test show that the vortex-induced lateral force should also be considered. The finite element simulation of a platform with four piles in the wave-current field under seismic action is carried out. It is shown that the seismic responses of the piles are magnified by water. Except for the acceleration along piles, the relative displacement and shear force and moment are increased significantly under the combined action of the wave-current force and the vortex-induced lateral force. And it is also indicated that the failure at the bottom of piles occurs easily under the seismic action.
2010, 32(5):  55-61.  doi:10.6052/1000-0879-lxysj2010-034
Abstract ( 1105 )   PDF (2112KB) ( 438 )
The important parameters for the concrete composite target to simulate the monolithic target include the number of matrix layers and thicknesses of adhesive layers of the concrete composite target. The influence of the two parameters on the penetration deceleration is studied by using AUTODYN2D hydrocode. The calibration and validation for the initial simulation model and material parameters are done through a comparison of numerical simulation results with the experimental results and the analytical model in literature. Multi-group simulation models of the concrete composite targets subjected to projectile impact are configured based on the number of matrix layers and thicknesses of adhesive layers of composite targets. The results of penetration velocity and deceleration-time histories show that the composite target can simulate the monolithic target in the deceleration penetration experiments, but the thicknesses of adhesive layers should not be more than half of the projectile nose length, the deviation between them increases as the number of matrix layers of composite target increases when the thicknesses of adhesive layers are more than half of the projectile nose length. The simulation results provide references for the configuration of concrete composite targets in trials.
Interesting mechanics story
2010, 32(5):  109-112.  doi:10.6052/1000-0879-lxysj2010-044
Abstract ( 1318 )   PDF (1850KB) ( 542 )
Shadow play is studied with our professional dynamics in order to find out a new method for simulating the real shadow play motion. The content of this work is as follows. First, found a dynamics model of several rigid, which respect to the geometric of shadow. Second, found dynamics equation for generating motion of every part of a shadow and make value with numerical value method. Third, generate shadow play animations by FLASH action-scrip. In a short, action-scrip could generate the real shadow play animations.
Application study
2010, 32(5):  14-17.  doi:10.6052/1000-0879-lxysj2010-050
Abstract ( 1299 )   PDF (1402KB) ( 461 )
Sediment particles in natural rock with a large number of connected cracks and faults, have some impact on the transport of groundwater and the variable permeability by creating micro-cracks and damage zones around faults. In this paper, an experiment about seepage on the rock electro-hydraulic servo test system of MTS815.02, together with electron micrograph of sandstone pore, is designed and used to investigate the relationship between the variable permeability and the filling silt in creating cracks. Results show that the permeability in cracked rock decreases distinctly under the silt-induced effect. The permeability, along with the sediment particles in macro-fissures in the cracked rock to achieve re-balancing of transport, gradually increases over time and eventually stabilizes.
Education Study
2010, 32(5):  89-91.  doi:10.6052/1000-0879-lxysj2010-061
Abstract ( 1449 )   PDF (405KB) ( 527 )
The kinetic energy loss calculated mode of collision for the two-rigid-body system with sliding friction is derived.
Application study
2010, 32(5):  72-75.  doi:10.6052/1000-0879-lxysj2010-072
Abstract ( 1198 )   PDF (688KB) ( 531 )
In this paper, taking the prolate cycloid-three-wire as a model of physical dynamics, we consider the damping's influence on computation of workpiece's moment of inertia by using the second kind Lagrange's equation. It is difficult to calculate the value of amplitude of swing accurately by the amplitude measuring method. So, an equal arc length- time ratio method is proposed to improve the precision for a workpiece of large size. The damping ratio $\zeta$ is obtained by calculating the time ratio of hanging dish which swings beyond the equal arc length in the same location with different periods.
2010, 32(5):  27-30.  doi:10.6052/1000-0879-lxysj2010-078
Abstract ( 1303 )   PDF (1087KB) ( 581 )
Considering that the viscosity of the hydraulic oil will change accordingly when the temperature and pressure vary, the flow rate equation and leakage rate equation of the annular spiral flow in Hydraulic Rotary Actuator are derived based on continuity equation, N-S equation and energy equation. Using the CFD simulation software Fluent'', the flow field and the leakage law of the internal annular spiral flow are simulated. Comparing the simulation results with the theoretical calculation of the flowing annular spiral flow, the theoretical analysis is verified, which may provide a theoretical basis for studies of internal leakage and volume depletion in Hydraulic Rotary Actuator.
2010, 32(5):  22-26.  doi:10.6052/1000-0879-lxysj2010-187
Abstract ( 1328 )   PDF (804KB) ( 425 )
In this paper, the nonlinear stability of double-diffusive convection with cross-diffusion in a thermohaline system is analyzed. By using a simple expression, the nonlinear equations are solved. By expressing two cross-diffusive coefficients by two parameters, a more general $R_T$-$R_S$ relation and expressions of steady finite amplitude are obtained. These expressions can be reduced to those previously-derived ones when both cross-diffusive coefficients are equal to zero.
Review
2010, 32(5):  1-9.  doi:10.6052/1000-0879-lxysj2010-348
Abstract ( 1883 )   PDF (2676KB) ( 1111 )
Magnetoconfined fusion is discussed with focus on its fluid mechanics and heat transfer problems relevant to fusion blanket and first wall. Experimental and numerical MHD is reviewed.
Application study
ANALYSIS OF LATERAL BEARING CAPACITY OF RIGID ROOT-FOUNDATION
龚维民,殷永高,童小东 and 单建
2010, 32(5):  67-71.  doi:10.6052/1000-0879-lxysj2008-458
Abstract ( 1022 )   PDF (737KB) ( 462 )
Based on the Winkler beam theory, the working mechanism and the bearing capacity of a lateral-loaded root-foundation are investigated, with a model of calculation. The elastic solution of the lateral-loaded root-foundation is obtained by using the load transfer method. The lateral bearing capacity is calculated, and the distributions of the lateral displacement, flexural moment, shear force and soil resistance of the root-foundation are obtained. The results show that the lateral bearing capacity of the root-foundation is better than the traditional caisson foundation, with the top lateral displacement being reduced by 35%~45% and the lateral bearing capacity being increased by 45%~55%. The calculated results are in good agreement with the test results in the elastic range, therefore, the load transfer method can be applied in the engineering calculation of root-foundations.
2010, 32(5):  18-21.  doi:10.6052/1000-0879-lxysj2009-233
Abstract ( 1514 )   PDF (611KB) ( 627 )
The physical property and rheological behavior parameters of the flow in the wellbore are sensible functions of temperature. It is of fundamental importance to calculate the temperature field for the optimization design of an oil/gas production scheme. Based on the thermal conduction theory, a mathematical model is formulated for the temperature calculation of the wellbore for mechanical recovery wells. The influences of such factors as the well yield, water content, well depth, pipe radius, ambient temperature and geothermal gradient, on the wellhead temperature are investigated.
Around the mechanics
2010, 32(5):  113-115.  doi:10.6052/1000-0879-lxysj2009-339
Abstract ( 1582 )   PDF (975KB) ( 1049 )
Interesting mechanics story
2010, 32(5):  107-108.  doi:10.6052/1000-0879-lxysj2009-343
Abstract ( 1311 )   PDF (791KB) ( 490 )