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08 February 2013, Volume 35 Issue 1
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    2013, 35(1):  67-68.  doi:10.6052/1000-0879-12-003
    Abstract ( 1108 )   PDF (394KB) ( 2000 )  
    The optimal angle for the shot-put is obtained through elementary mathematics. The envelope of the parabola family is used to determine the parameters for putting shots on a slope. It is shown in the general case that the velocity of the shot in the initial putting-direction is just zero at the given height or distance when it is put in the optimal angle.
    2013, 35(1):  1-7.  doi:10.6052/1000-0879-12-218
    Abstract ( 1506 )   PDF (710KB) ( 1117 )  

    There are two independent fundamental differential operators (called the "fundamental differential operator pair") on curved surfaces. This paper focuses on the topic: Among all fundamental differential operator pairs, [[▽,]], formed by the classical gradient ▽(···) and the shape gradient (···), is the optimal one. The following conclusions are included: (1) The paths for constructing the fundamental differential operator pairs are not unique. (2) The commutative nature of the inner-product of [[▽,]] is the basis of its optimality and advantage over all other fundamental differential operator pairs. (3) Based on the inner-product of [[▽,]], all higher order scalar differential operators for physics and mechanics on curved surfaces can be constructed optimally. In other words, [[▽,]]is the optimal "fundamental brick" for establishing the differential equations of physics and mechanics on curved surfaces. (4) [[▽,]] exists universally in physics and mechanics on soft matter curved surfaces.

    NUMERICAL AERODYNAMIC ANALYSIS OF MARS SCIENCE LABORATORY
    LÜ Junming, CHENG Xiaoli, WANG Qiang
    2013, 35(1):  31-35,54.  doi:10.6052/1000-0879-12-041
    Abstract ( 1021 )   PDF (6842KB) ( 1267 )  

    Based on the hypersonic entry in the entry-descending-landing procedure,the three-dimensional Navier-Stokes equations are solved by a parallel code to analyze the flow field structures, the aerodynamic characteristics and their variation patterns of the Mars Science Laboratory entering the Martian atmosphere with and without the chemical reaction models. The analysis shows that a large number of CO2 is dissociated behind the shock and much energy is consumed, with the chemical non-equilibrium effect, the shock layer is strongly compressed. The comparisons between the real gas and the perfect gas show that the vortex in the wake flow is reduced, the positions of the separation lines and the singularity are distinctly different; under the chemical non-equilibrium condition, the lift coefficient almost keeps the same, the drag coefficient increases, the lift-to-drag ratio and the pitch moment are smaller than those of the perfect gas.

    BHA MECHANICAL ANALYSIS FOR ROTARY STEERING DRILLING SYSTEM
    TANG Xueping, SU Yinao, GE Yunhua, SHENG Limin, LI Tiejun
    2013, 35(1):  55-59.  doi:10.6052/1000-0879-12-281
    Abstract ( 1157 )   PDF (1759KB) ( 1289 )  
    the rotary steering drilling system represents the advanced level of the directional drilling, and the development direction of the well-path control technology. In order to solve the problem of the well-path control for a rotary steering drilling, the rotary steering bottom hole assembly (RS-BHA) analysis is made in this paper. Applying the beam-column theory, a three-dimensional mechanical model for a typical RS-BHA is established. The relation between the bit side force and the steering parameter is derived, and based on the limiting curvature method, the building capability of the rotary steering tool can be predicted, and the steering parameter for the planned well-path is calculated. The RS-BHA can be optimized through a mechanical analysis, and the rules of the well-path control are obtained, which can provide a theoretical basis for the design of the rotary steering drilling tool and the automatic control in the directional drilling.
    A VIBRATION TESTING METHOD FOR DETERMINING THE STIFFNESS OF BADMINTON ROD
    WANG Meng, ZHENG Meisheng, TIAN Lianjun, LIN Qing
    2013, 35(1):  69-71.  doi:10.6052/1000-0879-12-304
    Abstract ( 1278 )   PDF (636KB) ( 1376 )  

    In this paper, a vibration testing method to determine the stiffness of the badminton rod is presented. The badminton rod is simplified as a mass-spring system of a single degree of freedom, the natural frequency of which is measured by the vibration testing method. Then the stiffness parameter of the rod can be calculated by the frequency formula. The suggested vibration testing method is more convenient and accurate than the current flexible test method, and can be used as a standard method of judging the soft and hard degree of a badminton rod.

    2013, 35(1):  8-14,19.  doi:10.6052/1000-0879-12-269
    Abstract ( 1705 )   PDF (2994KB) ( 2372 )  
    The basic theory and the current development of the discrete element method are reviewed in this paper, as well as those of the coupling algorithms of the discrete element method with the finite element method, the boundary element method, and the interface element method. The future development of the discrete element method is also discussed.
    INFLUENCE OF THE UNSTEADY TURBULENCE IN FIELD GUST ON SAND SALTATION
    YANG Bin, GAO Kai, LIU Jiang, WANG Yuan
    2013, 35(1):  15-19.  doi:10.6052/1000-0879-12-404
    Abstract ( 1008 )   PDF (1191KB) ( 1111 )  
    In the study of the aeolian sand saltation, the interactions between the wind and the sand particles are the key. Both the macro-sized unsteady feature and the micro-sized high frequent turbulence prevalent simultaneously in the field gust would lead to the fluctuant sand-transport rate and the intermittent saltation process in the wind-sand flow. While the time-averaged wind velocity is used to analyze the natural wind-sand flow, the high unsteady feature and the turbulent intensity in the flow would cause huge errors. It may be the reason why the results derived from the field observation, the wind-tunnel experiment and the numerical simulation have great deviations. The sand saltation within the wild gust field is an important research issue. Unfortunately, there are few reliable instantaneous measurements on the whole flow field to validate the related mathematical model. The development of the whole field measurement with high frequency in the wind-sand flow and the simulation technique of the field gust in the wind tunnel would solve this problem.
    WIND TUNNEL STUDY OF VERTICAL PROFILE OF DRIFTING SNOW
    LÜ Xiaohui, HUANG Ning, GUO Lei, LI Guang
    2013, 35(1):  20-25.  doi:10.6052/1000-0879-12-420
    Abstract ( 918 )   PDF (2653KB) ( 1020 )  
    In previous wind tunnel experiments on drifting snow, the artificial or compacted snow is usually used as a substitute for the natural snow. But there is a big difference between the natural snow and its substitutes in their physical and mechanical properties. In this paper, the movement of the fresh snow is studied by the particle image velocimetry, including the distributions of the snow size with the height, and the vertical profile of the mean particle size and the snow particle number flux. The results show that the snow transport rate can be expressed as an exponential function at the high friction velocity (u* > 0:5 m/s), and a power function at the low friction velocity (u* < 0:5 m/s). In overall, the transport rate linearly increases with the friction velocity.
    2013, 35(1):  26-30.  doi:10.6052/1000-0879-12-401
    Abstract ( 821 )   PDF (1100KB) ( 1385 )  
    The degradation of the Rhodamine B and the sewage is investigated based on the hydrodynamic cavitation in this paper, including the factors affecting the degradation, such as the cavatation number, the sewage initial concentration, and the cyclic and inlet pressures. It is shown that the degradation of the pollutant water increases with the increase of the inlet pressure, the best degradation of the Rhodamine B occurs in the range of 4 mg/L~10 mg/L, and the TP (total phosphorus) degradation is better than NH4+ by zoo percent.
    2013, 35(1):  36-40,30.  doi:10.6052/1000-0879-12-257
    Abstract ( 912 )   PDF (1849KB) ( 788 )  
    In order to study the structural response of geometrically large displacement in a cantilever beam, based fully on utilizing the linear finite element method (FEM) principle and procedure, the "accumulated linearization" is proposed to construct the structural model and to search the solving strategy for this kind of problem. The process of the numerical calculation shows that the proposed method is easy to realize in the widely available FEM software. Meanwhile, the "one time linearization" and the "non-linearization solving" in the numerical calculation are compared with this method. For the above problem, the proposed method is not only rational and feasible, but also can check the results of "one time linearization" to some extent. And the numerical simulation results of the two approaches are distinctly different, in which the former's results approach those of the "non-linearization solving".
    THE COMPARISON OF SEVERAL METHODS FOR THE LAYERED PLATE PROBLEM
    ZHU Bingqi, TANG Peijun, CHEN Xuehong
    2013, 35(1):  41-45.  doi:10.6052/1000-0879-12-344
    Abstract ( 1002 )   PDF (337KB) ( 571 )  
    In order to compare the merits and demerits of the finite element methods in the Lagrange system and the Hamilton system for the problem of layered plates and to choose appropriate numerical methods, several finite element methods are applied for the layered plates. With the use of MATLAB, an example is calculated and analyzed. Numerical results show that the conventional FEM (finite element method) and the improved FEM in the Hamilton System and the rational FEM in the Lagrange system all have their advantages, while the accuracy of the conventional FEM in the Lagrange system is poor.
    ANALYTICAL MODEL OF INTERACTION OF LONG ROD WITH MOVING PLATE
    TENG Taoju, LIU Hongwei, FENG Yan
    2013, 35(1):  46-48,93.  doi:10.6052/1000-0879-11-173
    Abstract ( 677 )   PDF (1326KB) ( 524 )  
    Through the physical process analysis of the interaction of long rod with moving plate, based on the theoretical model of the long rod penetration into a semi-infinite target, the theoretical model of the long rod penetration into a moving plate target is established. This model can give a quantitative description of the disturbance of the moving plate by the diameter loss of the long rod. The results of the theoretical model are both verified by experiments and numerical simulations, and the model can used to study the long rod interaction with moving plates.
    DEBONDING ALONG A SOFTENING FRP-CONCRETE INTERFACE OF PLATED BEAMS
    QU Hongchang, LI Yuanxin, ZHANG Peng
    2013, 35(1):  49-54.  doi:10.6052/1000-0879-12-275
    Abstract ( 1011 )   PDF (1438KB) ( 722 )  
    In order to investigate the debonding process of the interface between the FRP(fiber reinforced poly- mer) and the concrete for the FRP strenthening structure, both the strengthened beam and the strengthening FRP are modeled as two linearly elastic Euler-Bernoulli beams bonded together through a thin adhesive layer. For the FRP-concrete structure, there are two types of debonding failures: The plate end debonding and the intermediate crack (IC) induced debonding. For the second type debonding failures in the FRP-concrete bonded joint model where the FRP plate is subject to tension at both ends, the debonding process of the FRP-concrete interface is discussed in detail, and the closed-form solutions of the bond slip, the interface shear stress, and the axial force of the FRP in different stages are obtained. The results of theoretical analyses are confirmed by experiments. Parametric studies are further carried out to investigate the effect of the thickness of the adhesive layer and the bond length on the bond behavior of the FRP-concrete interface.
    2013, 35(1):  60-66.  doi:10.6052/1000-0879-11-207
    Abstract ( 958 )   PDF (2844KB) ( 1132 )  
    The scattering of SH-wave with arbitrary incident angle by a circular lining in a right-angle plane is studied together with its influence on the seismic ground motion. The problem in a right-angle plane is transformed into the scattering of SH-wave in half-space by using the complex function method, the multi-polar coordinate transformation and the image method. According to the boundary conditions , the solution of the problem can be reduced to a series of algebraic equations. The numerical examples show that the concentration of the dynamic stress and the ground motion are related with the different wave numbers, the angle, the geometrical location and the thickness of the circular cavity.