气藏型储气库井注采动态不稳定流分析方法

随着时代的发展,当前中国正处在经济体制改革的关键时期,能源是中国工业生产、人民生活的重要保障,在强非均质气藏型储气库中,采用分析方式对其进行配产是非常重要的,也是解决城市季节性调峰、平抑供气峰值波动的有效路径。文章通过对相关文献进行查阅,首先对储气库注采运行特点进行了简要的分析与阐述,结合相关科学理论知识,进一步提出了注采动态不稳定流分析数学模型与求解方法、注采动态不稳定流分析模型图版及分析流程,最终引进了气藏型储气库井实践案例,对其进行了深度分析。

气藏型储气库井注采动态不稳定流分析方法

针对现有不稳定流分析方法的局限性,结合强非均质气藏型储气库注采运行特点,建立了考虑储气库多周期注采历史动态等复杂因素的动态不稳定流分析方法,并绘制了相关理论图版。提出了适合储气库井交变工况的“三点两段”式注采动态不稳定流分析新模式,“三点”指循环注采的3个时间点,即建库注气起始点、注采分析段起始点和结束点,“两段”指历史流动段和注采分析段。研究发现:储气库井注采过程中无因次拟压力和无因次拟压力积分曲线前期下掉;无因次拟压力积分导数曲线中间过渡区存在采气期曲线上凸、注气期曲线下凹的现象,不同流动历史下的曲线具有非典型性。新方法实现了储气库注采动态不稳定流分析,呼图壁储气库典型井的实际应用表明,新方法压力历史拟合精度高,解释参数关联性强,应用结果可靠。

水泵水轮机转动部分——非转动部分联合作用的不稳定流分析与试验研究

用ＬＤＶ和ＰＩＶ方法及一只专门设计的不稳定流５探头探针对ｎｑ＝６６水泵水轮机转轮和导叶之间的流场和压力场进行了试验研究。对不同的设计工况和非设计工况的测量值进行了理论分析。本文介绍了一次数字近似结果。分析结果表明，当水流入射角与导叶进口不相匹配时，进行转动部分－非转动部分联合作用计算是必要的。

Fluid–solid coupling analysis of rock pillar stability for concealed karst cave ahead of a roadway based on catastrophic theory

In order to study the mechanism of water inrush from a concealed, confined karst cave, we established a fluid–solid coupling model of water inrush from a concealed karst cave ahead of a roadway and a strength reduction method in a rock pillar for preventing water inrush based on catastrophic theory. Fluid–solid coupling effects and safety margins in a rock pillar were studied. Analysis shows that rock pillar instability, exerted by disturbance stress and seepage stress, is the process of rock pillar catastrophic destabilization induced by nonlinear extension of plastic zones in the rock pillar. Seepage flow emerges in the rock pillar for preventing water inrush, accompanied by mechanical instability of the rock pillar. Taking the accident of a confined karst cave water-inrush of Qiyi Mine as an example, by studying the safety factor of the rock pillar and the relationship between karst cave water pressure and thickness of the rock pillar,it is proposed that rock pillar thickness with a safety factor equal to 1.5 is regarded as the calculated safety thickness of the rock pillar, which should be equal to the sum of the blasthole depth, blasting disturbance depth and the calculated safety thickness of the rock pillar. The cause of the karst water inrush at Qiyi Mine is that the rock pillar was so small that it did not possess a safety margin. Combining fluid–solid coupling theory, catastrophic theory and strength reduction method to study the nonlinear mechanical response of complicated rock engineering, new avenues for quantitative analysis of rock engineering stability evaluation should be forthcoming.

Theoretical and Numerical Stability Analysis of the Liquid Metal Pinch Using the Shallow Water Approximation

The pinch instability for a cylindrical jet of liquid metal passed through by an axial electrical current is investigated. Besides the pinch effect originating from surface tension, the Lorentz force, created by the axial current density and the corresponding azimuthal magnetic field, causes an electromagnetic pinch effect. This effect has drawn attention in electrical engineering, because it can be used in the construction of liquid metal current limit- ers with self-healing properties. In this paper a simple model is derived using the shallow water approximation： the equations describing the full system are reduced to two one-dimensional evolution equations for the axial velocity and the radius of the jet. A stability analysis for this reduced system is carried out yielding critical current density and the growth rate for the instability. To investigate the nonlinear behaviour of the pinch instability for finite perturbations simulations, the shallow water model are performed.

Analysis of the secondary instability of the incompressible flows over a swept wing

The crossflow instability of a three-dimensional (3-D) boundary layer is an important factor which affects the transition over a swept-wing.In this report,the primary instability of the incompressible flow over a swept wing is investigated by solving nonlinear parabolized stability equations (NPSE).The Floquet theory is applied to study the dependence of the secondary and high-frequency instabilities on curvature,Reynolds number and angle of swept (AOS).The computational results show that the curvature in the present case has no significant effect on the secondary instabilities.It is generally believed that the secondary instability growth rate increases with the magnitude of the nonlinear mode of crossflow vortex.But,at a certain state,when the Reynolds number is 3.2 million,we find that the secondary instability growth rate becomes smaller even when the magnitude of the nonlinear mode of the crossflow vortex is larger.The effect of the angle of swept at 35,45 and 55 degrees,respectively,is also studied in the framework of the secondary linear stability theory.Larger angles of swept tend to decrease the spanwise spacing of the crossflow vortices,which correspondingly helps the stimulation of 'z' mode.

Instability of thermocapillary flow in liquid layers under microgravity

The instability of the thermocapillary flow in liquid layers is studied in the present paper using the linear stability analysis.Based on the two-dimensional steady flow state,the three-dimensional disturbance with a wave number in the spanwise direction is considered.The effects of the aspect ratio and free surface shape of the liquid layer on the flow instability are studied,and the results are compared with the case with the two-dimensional disturbance.

Heteroclinic bifurcations in attitude maneuver of coupled slosh-spacecraft with flexible appendage

In this paper, the chaotic dynamics in an attitude transition maneuver of a slosh-spacecraft coupled with flexible appendage in going from minor axis to major axis spin under the influence of dissipative effects due to fuel slosh and a small flexible appendage constrained to only torsional vibration is investigated. The slosh-spacecraft coupled with flexible appendage in attitude maneuver carrying a sloshing liquid is considered as multi-body system with the sloshing motion modeled as a spherical pendulum. The focus in this paper is that the dynamics of the liquid and flexible appendage vibration are coupled. The equations of motion are derived and transformed into a form suitable for the application of Melnikov’s method. Melnikov’s integral is used to predict the transversal intersections of the stable and unstable manifolds for the perturbed system. An analytical criterion for chaotic motion is derived in terms of system parameters. This criterion is evaluated for its significance to the design of spacecraft. The dependence of the onset of chaos on quantities such as body shape and magnitude of damping values, fuel fraction and torsional vibration frequency of flexible appendage are investigated. In addition, we show that a spacecraft carrying a sloshing liquid, after passive reorientation maneuver, will end up with periodic limit motion other than a final major axis spin because of the intrinsic non-linearity of fuel slosh. Furthermore, an extensive numerical simulation is carried out to validate the Melnikov’s analytical result.

Analytic approach on geometric structure of invariant manifolds of the collinear Lagrange points

An analytical method is proposed to find geometric structures of stable,unstable and center manifolds of the collinear Lagrange points.In a transformed space,where the linearized equations are in Jordan canonical form,these invariant manifolds can be approximated arbitrarily closely as Taylor series around Lagrange points.These invariant manifolds are represented by algebraic equations containing the state variables only without the help of time.Thus the so-called geometric structure of these invariant manifolds is obtained.The stable,unstable and center manifolds are tangent to the stable,unstable and center eigenspaces,respectively.As an example of applicability,the invariant manifolds of L 1 point of the Sun-Earth system are considered.The stable and unstable manifolds are symmetric about the line from the Sun to the Earth,and they both reach near the Earth,so that the low energy transfer trajectory can be found based on the stable and unstable manifolds.The periodic or quasi-periodic orbits,which are chosen as nominal arrival orbits,can be obtained based on the center manifold.