共查询到20条相似文献,搜索用时 18 毫秒
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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。 相似文献
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试论静力学在流体力学课程中的地位 总被引:1,自引:0,他引:1
从材料的本构方程和基本运动方程出发, 比较了静力学在弹性力学和流体力学中的
地位. 与弹性静力学在弹性力学中占有重要地位不同, 流体静力学在流体力学中仅处
于次要地位, 它不是流体动力学的基础, 而只是一个特例. 确立这种观点有助于提高对流体
力学学科特点的认识, 提高流体力学教学质量. 相似文献
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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. 相似文献
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Jiří Mls 《Transport in Porous Media》1987,2(6):615-621
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
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G, G
w, Gs
open sets in E
3; components of the two-phase system
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C
1(G)
the set of functions 1-times continuously differentiable in G
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W1/2(G)
Sobolev space
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V
volume of the domain K
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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, Gs; w-s interface
-
ij
Kronecker delta
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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 相似文献
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进气道入口形状对冲压发动机性能影响数值研究 总被引:1,自引:0,他引:1
进气道是冲压发动机设计中非常重要的环节,其入口设计会直接影响冲压发动机的总压恢复系数σ和流量系数φ等重要性能。本文采用二阶迎风隐式TVD格式,内外流分区耦合求解可压缩N-S方程,数值模拟了掺混段出口压力与来流压力比为P/P∞=4.2超临界状态下,二元方形截面“X”型布局进气道、弹体和掺混段一体化通气模型复杂流场。计算比较了两种不同二元进气道入口形状流场和冲压发动机总压恢复系数σ、流量系数φ的结果,对其产生的原因进行了分析。 相似文献
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表面织构对刀具切削性能及前刀面摩擦特性的影响 总被引:2,自引:1,他引:1
为了研究刀具表面织构对切削性能的影响,通过控制前刀面上微凹坑的直径、深度和面积占有率等参数制备了两组表面高度算术平均值Sa相同的织构刀具.使用Talysurf CCI Lite非接触式三维光学轮廓仪对织构表面进行测量,采用ISO25178参数对测量表面进行表征;通过SL200KS接触角测量仪测量织构刀具前刀面湿润性的变化;随后在CA6140车床上进行45钢切削试验,研究不同织构对切削力、前刀面摩擦特性、工件表面粗糙度和切屑形变的影响.结果表明:合理的表面织构能够改善刀具的切削性能;切削液在前刀面铺展较快的织构刀具获得了较好的切削性能;凹坑直径、深度和面积占有率的协同作用对改善刀具切削性能至关重要,为了协调这三个织构参数,进一步研究三维表征参数Sku、Ssk、Sv、Vvv、Vvc、Sdv、Sda、Spd与刀具切削性能的关联性,为刀具表面设计提供了基础. 相似文献
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Experimental Mechanics - The Hole-Drilling method is a semi-destructive technique useful for obtaining residual stress distributions by drilling and measuring relieved strains. The standard for... 相似文献
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廖晓昕 《应用数学和力学(英文版)》1982,3(2):267-279
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. 相似文献
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《Wave Motion》1987,9(1):107-110
The caustics of high-frequency wave propagation may be classified using catastrophe theory. The wavefield in the vicinity of any caustic is described by the corresponding diffraction catastrophe. The singularity index, β, is a measure of the rate at which such a wavefield diverges as ω→∞ at the point where all control parameters and moduli are set equal to zero. It is shown that away from this point β also describes a balance between two different measures of the unfolding of the wavefield in each control direction, β = σnϱn. The indices σn and ϱn describe, respectively, the rate at which individual ray arrivals separate in time and decay as a function of control parameter. 相似文献
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O. E. Tsynkova 《Fluid Dynamics》1966,1(1):123-125
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. 相似文献
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捷联式惯性导航系统惯性元件的设置与可靠性 总被引:4,自引:1,他引:4
王珍熙 《中国惯性技术学报》1996,(1)
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。 相似文献
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George Komndi 《Journal of Terramechanics》1993,30(2)
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. 相似文献
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岳珠峰 《应用数学和力学(英文版)》2004,25(8):887-893
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. 相似文献
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《European Journal of Mechanics - B/Fluids》2000,19(5):707-722
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. 相似文献