隔水管弯曲对钻柱振动影响的计算与分析

海洋油气资源钻探中隔水管的弯曲对钻柱振动以及钻进特性有特别的影响。为得到隔水管弯曲对钻柱振动的影响规律,对南海已钻深水井使用非线性有限元软件建立全井钻井数值计算模型,研究获得了不同垂深时隔水管弯曲对钻柱振动特性的影响规律。研究表明:隔水管弯曲会加剧钻柱的振动,钻柱振动加剧会导致钻井能耗上升、钻头切削能力下降并且会加快钻柱疲劳;当隔水管的弯曲达到某临界值,钻柱与隔水管间的接触力会陡增;井口的钩载越大,隔水管弯曲带来的井口钩载波动量越大;井越深,隔水管弯曲对全井钻柱最大弯矩和钻头切削能力的影响越小。     

On the derivation for the gradients of the principal invariants

In this notes, it is shown that the method carried out by Truesdell and Noll [1] for the gradients of the principal invariants is available to be used for arbitrary second-order A. Finally, some trace identities for the derivatives of invariants are given.     

On the existence of the derivative of the volume average

A general theorem on the derivative of the volume average is formulated and proved. Conditions for the existence of the derivative are presented and discussed. This is done in order to give a better base to the theory of spatial averaging.Latin Letters E ₃ three-dimensional vector space over the field of real numbers - K, K(x) averaging domain - G, G _w, G_s open sets in E ₃; components of the two-phase system - C ¹(G) the set of functions 1-times continuously differentiable in G - W1/2(G) Sobolev space - V volume of the domain K - f function defined in G, G _w - K _infi ^sup* (x), K _infi ^sup– (x) special parts of K(x) Greek Letters boundary of G, G _w, G_s; w-s interface - _ij Kronecker delta - v unit outward normal of G, G _w - _j j-dimensional Lebesgue measure Other M closure of a set M in the metric space E ₃ - f phase average of f for the w-phase - (u, v) scalar product of u, v in E ₃ - one-sided derivatives     

捷联式惯性导航系统惯性元件的设置与可靠性

本文对惯性元件的最佳冗余设置及其在飞行器上的布局与可靠性之间的关系进行了研究，建立了相应的可靠性数学模型，探讨了３／６（Ｇ）冗余惯性元件出现第三个故障时故障的检测与识别的方法。所得结果可供惯性导航系统可靠性分析及工程上应用。     

Modeling the disturbances in the lake Chebarkul caused by the fall of the meteorite in 2013

The results of numerical simulation of the possible hydrodynamic disturbances in lake Chebarkul caused by the fall of the meteorite in 2013 are presented. In the calculations the system of Navier–Stokes equations is used. The entry of the meteorite into the water at an angle of 20° is modeled. The numerical experiments are performed both with and without account for the ice cover of the lake. The dimensions of the ice cover disruption are evaluated. The dimensions of the ice-hole observable in the place of the meteorite fall are shown to be in good agreement with the theoretical predictions and the preliminary estimations.     

On the receptivity of the by-pass transition to the length scale of the outer stream turbulence

The effect of length scale on flat-plate by-pass boundary layer transition under free stream turbulence conditions has been investigated. Plane grids generated a constant value of 3 percent intensity turbulent fluctuations and five values of the dissipation length parameter in the range of 2.2 mm to 33.3 mm at 5 m/s flow velocity in the plane of the leading edge of the flat plate. The investigated boundary layer corresponds to the ERCOFTAC Test Case T3A+. Distributions of integral parameters as well as the statistical characteristics of the turbulent fluctuations were measured. They document a significant effect of turbulence length scale on the onset and the end of by-pass transition. It was found that the onset of the final stage of transition comes on later in `fine-grained' turbulence than in the case of large free stream turbulence length scale. At the same time, the extent of the transition region shortens with decreasing length scale. Nevertheless, the transition process terminates sooner in a flow with a large turbulence length scale than in a flow with a small one. An attempt has been made to describe these observations quantitatively.     

On the role of the Chezy frictional term near the shoreline

The behavior of the Chezy frictional term near the shoreline has been studied in detail. An asymptotic analysis valid for water depths going to zero clearly shows that the use of such a term implies a non-receding motion of the shoreline. This phenomenon is induced by a thin layer of water which, because of frictional forces, remains on the beach and keeps it wet seaward of the largest run-up. However, the influence of such a frictional layer of water on the global wave motion is very weak and practically negligible for most of the swash zone flow dynamics. The existence of a non-receding shoreline has led to some clarifications on the role of some ad-hoc tools used in numerical models for the prediction of the wet/dry interface.     

Reevaluation of the adhesive relationship between the tire and the soil

The author proved in an earlier article that the shear diagram is not in accord with its mechanical definition. The shear stress cannot be zero at the beginning of the initial rising portion of the curve. Shearing is not an increasing loading process, rather it is a limiting case to which a finite shear stress belongs. On the other hand the sheared surface varies under the tire. There are kinematic reasons for this. Points on the tire surface describe a looped cycloid and they slip in a backward direction (opposite to the direction of travel) while contacting the soil. Thus the driving force, which points in the direction of travel, is the product of the shear stress of finite magnitude and the sheared area. The latter increases proportionally with slip. The author describes his equation which is based on the principles discussed above. He supports his theory with a numerical example.     

地球与月球关系的研究

基于鹦鹉螺外壳生长线条数的变化是月亮绕地球运动周期随年代变化反映的假设, 采用外推 法得出两个结论: (1) 月球最初被地球俘获绕地球运动时距地球的距离为目前月地距离的0.2 倍左右; (2) 月球最初被地球俘获绕地球运动时的时间距今为7亿年左右. 这 为进一步研究地球与月球的关系提供了有益的启示.     

On the study of the initiation of the micro crack on the smooth surface of polycrystalline

Crystallographic plasticity was applied to study the initiation of micro cracks on the smooth surface of polycrystalline under uniform applied stress. Even under the uniform external stress, due to the different crystallographic orientations of the grains in the polycrystalline, there is un-uniform stress distribution and the deformation is also not uniform. Under the fatigue loading, the roughness increases with the number of fatigue, and deformation will localize in some places, where micro cracks form.     

On the criterion for the absolute stability of the control system

In this paper, firstly we give the criterion for the absolute stability of the second canonical form for the control system, including the equation of the longitudinal motions of a plane as a particular example. The corresponding result in [8], [9] is a particular example given in this paper. Secondly, we give the criteria for the absolute stability of the first canonical form in the usual case and in the critical case. Finally, we give some criteria for the absolute stability of the general form for the direct control system.All the results in this paper merely depend upon the relations between the parameters of the system itself to give an explicit algebraic discriminant.     

On the theory of the vibropump

The problem of vibratory lifting of a fluid was considered in [1] on the assumption of incompressibility of the pump tubing. In the present paper account is taken of the elasticity of the tubing materal. This leads to the consideration of forced oscillation regimes in two elastic media coupled by nonlinear conditions on one of the boundaries. In this case there is an ambiguity in the relations between the unknowns and governing quantities which leads to a hysteresis effect.     

Singularities of the boundary layer equations and the structure of the flow in the vicinity of the convergence plane on conical bodies

The singularities of the boundary layer equations and the laminar viscous gas flow structure in the vicinity of the convergence plane on sharp conical bodies at incidence are analyzed. In the outer part of the boundary layer the singularities are obtained in explicit form. It is shown that in the vicinity of a singularity a boundary domain, in which the flow is governed by the shortened Navier-Stokes equations, is formed; their regular solutions are obtained. The viscous-inviscid interaction effect predominates in a region whose extent is of the order of the square root of the boundary layer thickness, in which the flow is described by a two-layer model, namely, the Euler equations in the slender-body approximation for the outer region and the three-dimensional boundary layer equations; the pressure is determined from the interaction conditions. On the basis of an analysis of the solutions for the outer part of the boundary layer it is shown that interaction leads to attenuation of the singularities and the dependence of the nature of the flow on the longitudinal coordinate, but does not make it possible to eliminate the singularities completely.     

On the Applicability of the Relations of the Cubic Timoshenko-Type Theory of Shells to the Study of the Postcritical Behavior of Rods

The question of whether the nonlinear Timoshenko-type theory of shells can be applied to the study of the initial postcritical behavior of a rod under compression is considered. The Koiter asymptotic theory in the Budyanskii form is used. The exact solution of the problem is obtained and a formula for the coefficient of postcritical behavior allowing for the effect of lateral-shear strains is derived. It is shown that the expressions (specified to within cubic terms) for lateral-shear strains and curvature permit us to use the nonlinear theory of shells to analyze the initial supercritical behavior of rods     

Connection between the characteristics of the signal of a shadow instrument and the spectrum of the turbulence

The shadow method is one of the most widely used methods for investigating turbulence [1, 2]. Using a shadow instrument with photoelectric recording, there exists, in principal, the possibility of finding the statistical characteristics of the turbulence from the statistical characteristics of the random signal taken from the instrument. In the present work, an investigation is made of the connection between the mean value and the scattering of the signal of a shadow instrument and the energy spectrum of optical inhomogeneities in the medium.     

Hydraulic modeling of the flow in the delta of the River Neva and in the eastern part of the Gulf of Finland

In connection with the construction of Leningrad's flood defenses the flow in the mouth of River Neva has been investigated on hydraulic models of different scales both unpressurized (see, for example, [1, 2]) and pressurized (see, for example, [3]). Since the results of these investigations are being intensively debated in connection with the discussion of the effect of defensive structures on the ecology of the Leningrad region, it is important to analyze the scientific basis for the hydraulic modeling of such flows.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 5, pp. 57–65, September–October, 1990.     

A study on the period of the free lateral vibration of the beam bridge by the theory of the orthotropic rectangular plate

Conclusion The frequency of the right, simple beam bridges is discussed by the laboratory study on the model beam bridges and the field tests on existing beam bridges in this paper, but furthermore, the application to the skew beam bridge or to the continuous beam bridge and the problem of forced vibration should be studied.Even if more exact studies are necessary, it is made sure by the study in this paper that the theory of the orthotropic plate is proper to the analysis of the free lateral vibration of the beam bridge and sufficient enough for practical purpose, especially for the beam bridge of which the width is almost equal to the span.     

Contribution to the improvement of the QUICK scheme for the resolution of the convection–diffusion problems

The present paper deals with the improvement of a QUICK scheme for the resolution of convection–diffusion problems. In order to avoid any unstability problems and to increase the convergence speed a new deferred correction is suggested. Checking the required stability criteria, benefits are taken from the accuracy of the central difference scheme when it is possible. Otherwise, a upwind scheme is introduced in the deferred correction term warranting the stability of the whole scheme. Tests have been carried out on a wall driven square cavity and on a buoyancy driven cavity. Comparisons have been achieved with reference data in order to assess the accuracy of the present scheme. Further comparison with other differentiation scheme demonstrate that the present formulation is fast and accurate.     

Experimental investigation of the influence of the flow structure on the aerodynamic coefficients of the IXV vehicle

In the framework of the ESA Future Launchers Preparatory Program (FLPP) an experimental study on the aerodynamic behavior during the re-entry phase of the Intermediate eXperimental Vehicle (IXV) configuration was conducted in the DLR hypersonic wind tunnel H2K in Cologne. Tests were carried out at Mach 6.0 and 8.7 with different flap deflection angles and the angle of attack varied continuously between 20° and 55° to investigate the flow topology as well as the aerodynamic forces and moments and the surface pressure distribution. The experimental data show that depending on the combination of the flap deflection angle (δ _L/R) and angle of attack (α) the complex flow structure in the vicinity of the flaps significantly influences the vehicle’s aerodynamic coefficients. An analysis of this shock/shock and shock/boundary layer interaction causing flow separation with reattachment is performed.