Investigation of gravity influence on EOR and CO_(2) geological storage based on pore-scale simulation

Gravity assistance is a critical factor influencing CO_(2)-Oil mixing and miscible flow during EOR and CO_(2)geological storage.Based on the Navier-Stokes equation,component mass conservation equation,and fluid property-composition relationship,a mathematical model for pore-scale CO_(2) injection in oilsaturated porous media was developed in this study.The model can reflect the effects of gravity assistance,component diffusion,fluid density variation,and velocity change on EOR and CO_(2) storage.For nonhomogeneous porous media,the gravity influence and large density difference help to minimize the velocity difference between the main flow path and the surrounding area,thus improving the oil recovery and CO_(2) storage.Large CO_(2) injection angles and oil-CO_(2) density differences can increase the oil recovery by 22.6% and 4.2%,respectively,and increase CO_(2) storage by 37.9% and 4.7%,respectively.Component diffusion facilitates the transportation of the oil components from the low-velocity region to the main flow path,thereby reducing the oil/CO_(2) concentration difference within the porous media.Component diffusion can increase oil recovery and CO_(2) storage by 5.7% and 6.9%,respectively.In addition,combined with the component diffusion,a low CO_(2) injection rate creates a more uniform spatial distribution of the oil/CO_(2) component,resulting in increases of 9.5% oil recovery and 15.7% CO_(2) storage,respectively.This study provides theoretical support for improving the geological CO_(2) storage and EOR processes.

Numerical Simulation of Hydrodynamic Behaviors of Gravity Cage in Waves

This paper aims at investigation of the dynamic properties of gravity cage exposed to waves by use of a numerical model. The numerical model is developed, based on lumped mass method to set up the equations of motion of the whole cage; meanwhile the solutions of equations are solved by the Runge-Kutta-Vemer fifth-order and sixth-order method. Physical model tests have been carried out to examine the validity of the numerical model. The results by the numerical simulation agree well with the experimental data.

Preparation and characterization of a specialized lunar regolith simulant for use in lunar low gravity simulation

Lunar in-situ resource utilization(ISRU)has been put on the agenda by many countries.Due to the special material nature and low gravity environment,the lunar regolith demonstrates significantly different behavior from terrestrial geomaterials.However,the systematic understanding of its geotechnical behavior is now seriously restricted by the scarcity of lunar regolith and the difficulty in simulating lunar gravity.A new lunar regolith simulant,termed as China University of Mining and Technology Number One(CUMT-1),has been developed to recover properties of the lunar regolith and simulate the lunar gravity by adopting the recently advanced geotechnical magnetic-similitude-gravity model testing(GMMT)method.The CUMT-1 simulant was prepared by reproducing the in-situ formation and fragmentation of the lunar matrix,which plays a key role in the irregular particle morphology.The mineralogical compositions,particle morphology and gradation,specific gravity,bulk density,void ratio,shear strength,and compressibility were determined.After quantifying the magnetization and magnetic-similitude-gravity characteristics,an application of the cone penetration resistance under low gravity was further given.The obtained results are compared to the values known for lunar regolith samples and other simulants,which demonstrates promising characteristics for use in geotechnical engineering-based and scientificbased applications,especially considering the influence of lunar gravity.

Simulation of co-seismic gravity change and deformation of Wenchuan Ms8.0 earthquake

Surface co-seismic gravity changes and displacements caused by the Wenchuan Ms8.0 earthquake are calculated on the basis of the half-space dislocation theory and two fault models inversed, respectively, by Institute of Geophysics, CEA and USGS. The results show that 1 ） the dislocation consists of dip slip and rightlateral strike slip ;2 ）the co-seismic gravity change shows a four-quadrant pattern ,which is greatly controlled by the distribution of the vertical displacements, especially in the near-filed ; 3 ） the gravity change is generally less than 10 × 10^-8 ms^-2 in the far-field,but as high as several 100 × 10^-8 ms^-2 in the near-filed. These results basically agree with observational results.

Predicting bathymetry based on vertical gravity gradient anomaly and analyses for various influential factors

The prediction of bathymetry has advanced significantly with the development of satellite altimetry.However,the majority of its data originate from marine gravity anomaly.In this study,based on the expression of vertical gravity gradient(VGG)of a rectangular prism,the governing equations for determining sea depths to invert bathymetry.The governing equation is solved by linearization through an iterative process,and numerical simulations verify its algorithm and its stability.We also study the processing methods of different interference errors.The regularization method improves the stability of the inversion process for errors.A piecewise bilinear interpolation function roughly replaces the low-frequency error,and numerical simulations show that the accuracy can be improved by 41.2%after this treatment.For variable ocean crust density,simulation simulations verify that the root-mean-square(RMS)error of prediction is approximately 5 m for the sea depth of 6 km if density is chosen as the average one.Finally,two test regions in the South China Sea are predicted and compared with ship soundings data,RMS errors of predictions are 71.1 m and 91.4 m,respectively.

Simulation of Gravity Currents Using VOF Model

By the Volume of Fluid (VOF) multiphase flow model two-dimensional gravity currents with three phases including air are numerically simulated in this article. The necessity of consideration of turbulence effect for high Reynolds numbers is demonstrated quantitatively by LES (the Large Eddy Simulation) turbulence model. The gravity currents are simulated for h not equal H as well as h = H, where h is the depth of the gravity current before the release and H is the depth of the intruded fluid. Uprising of swell occurs when a current flows horizontally into another lighter one for h not equal H. The problems under what condition the uprising of swell occurs and how long it takes are considered in this article. All the simulated results are in reasonable agreement with the experimental results available.

Coseismic Effect Simulation of Yushu M_S 7.1 Earthquake and Absolute Gravity Inspection

Using the results of aftershock relocation, inversion on seismic waves and InSAR results, and surface rupture displacements obtained by geological survey after the earthquake, this paper constructs a fault model of the Yushu Ms7. 1 earthquake. Based on rectangular dislocation theory in an elastic-viscoelastic layered medium, we have simulated the co- seismic deformation and gravity change with gravitational effect considered. The pictures show that the absolute gravity measuring point is beside the extremum of coseismic gravity change, and the numerical value reaches 25.02 x 10-Sm. s-2. After a discussion about the gravity changes before the earthquake and the coherence consistency between two FG-5 absolute gravimeters, we think that the measured value 27.2 × 10^-8 m· s^-2 at Yushu station is coseismic gravity change. It＇s coincident with the simulation results based on dislocation theory. Therefore it is a good tool to test the near-field changes found by dislocation theory.

Simulation analysis of temperature control calculation of RCC gravity dam in the cold region

In this paper, regarding the actual conditions of a roller compacted concrete dam, three-dimensional finite element relocating mesh method is utilized to simulate and calculate the temperature field of the RCC dam during the construction stage and operating period. The calculation is well consistent with the actual construction process, the thin-layer pouring process the pouring temperature and all kinds of external loads involved being taken into account, By comparing and analyzing of the impact of the cold wave on the dam stress, important references are provided for the RCCD design and the temperature control during construction.

Absorbing Boundary Conditions for Simulating Water Waves Near Solid Bodies

The objective of this paper is to present a new method for designing absorbing or non-reflective boundary conditions (ABC) or (NRBC), illustrated by the case study of the modelling of a solid body in water, specifically the capillary gravity waves generated by its motion at the surface. The study analyses the flow of an inviscid, barotropic, and compressible fluid around the stationary solid body. The dynamic behaviour of the fluid is analysed using a two-dimensional coupled Neumann-Kelvin model extended with capillarity and inertia terms. For computational purposes, it is necessary to truncate the unbounded spatial domain with artificial boundaries and then introduce appropriate absorbing boundary conditions. The propagation of short wavelength waves in a convective fluid medium with significant differences in properties between the interior and the surface of the fluid presents a number of difficulties in the design of these conditions. The results are illustrated numerically and commented upon.

Numerical Simulation and Optimization of a Mid-Temperature Heat Pipe Exchanger

In this paper,we take the mid-temperature gravity heat pipe exchanger as the research object,simulate the fluid flow field,temperature field and the working state of heat pipe in the heat exchanger by Fluent software.The effects of different operating parameters and fin parameters on the heat transfer performance of heat exchangers are studied.The results show that the heat transfer performance of the mid-temperature gravity heat pipe exchanger is the best when the fin spacing is between 5 mm and 6 mm,the height of the heat pipe is between 12 mm and 13 mm,and the inlet velocity of the fluid is between 2.5 m/s to 3 m/s.

Stability analysis of gravity anchor foundation of layered argillaceous sandstone under dry-wet cycles

To investigate the stability of gravity anchors of suspension bridges,in-situ tests of the vertical bearing capacity of the bedrock,shear resistance of the anchor-rock interface,shear resistance of the bedrock were conducted in a suspension bridge project.Under dry-wet cycles,the deterioration law of the mechanical properties of argillaceous sandstone was identified in laboratory tests:the elastic modulus,cohesion and friction of the argillaceous sandstone deteriorated significantly at first few dry-wet cycles and then declined slowly after 10 cycles,ultimately these three mechanical parameters were reduced to about 1/3,1/3,2/3 of the initial value respectively.Moreover,numerical simulation was used to restore in-situ shear tests and a good agreement was obtained.Base on the results of in-situ and laboratory tests,the stability of the gravity anchor foundation under natural conditions and drywet cycles was calculated and its failure modes were analyzed.The results demonstrated that the dry-wet cycles caused uneven settlement of the anchor foundation,resulting in more serious stress concentration in the substrate.The dry-wet cycles remarkably reduced the stability coefficient of the anchor foundation,whose failure mode shifted from overturning failure under natural conditions to sliding failure.When there was weak interlayer in the rock layer,the anti-sliding stability of the anchor foundation was affected drastically.

Quantum simulations with nuclear magnetic resonance system

Thanks to the quantum simulation,more and more problems in quantum mechanics which were previously inaccessible are now open to us.Capitalizing on the state-of-the-art techniques on quantum coherent control developed in past few decades,e.g.,the high-precision quantum gate manipulating,the time-reversal harnessing,the high-fidelity state preparation and tomography,the nuclear magnetic resonance(NMR) system offers a unique platform for quantum simulation of many-body physics and high-energy physics.Here,we review the recent experimental progress and discuss the prospects for quantum simulation realized on NMR systems.

Numerical simulation on the stability of rock slope based on an improved SPH Method

The presence of random fissures has a great impact on rock slope stability.To investigate the failure modes and stability of rock slopes containing different types of pre-existing fissures,the fracture mark ξ was introduced to improve the kernel function in the traditional smoothed particle dynamics(SPH) method,and a novel numerical method,the improved kernel of smoothed particle hydrodynamics(IKSPH),was proposed to realise the microscopic damage characteristics of particles.The ‘random fissure generating method' has been proposed for random fissure generation,and the gravity increase method has been embedded into the IKSPH program,thereby realising the stability analysis of rock slopes considering crack propagation processes.A typical steep rock slope is taken as a numerical simulation example considering the random distributions of preexisting fissures,and its failure modes as well as the stability under different conditions were simulated.The results show that the failure processes of the rock slope contain propagations of microcracks and then macrocrack penetrations.When the fissure length is short,shallow collapse failure modes can be observed;when the fissure length is long,the deep layer slide occurs,and the slope stability decreases with an increase in fissure length.The micro and macrocrack surfaces are basically consistent with pre-existing fissure angles,and the safety factor is the least at a fissure angle of 30°.The greater the fissure density,the greater the number of macrocracks,and the stability decreases with an increase in the number of pre-existing fissures.The research results can provide some references for disaster protection and understanding the failure laws of rock slopes.Meanwhile,combining the geological survey results with the numerical simulations and developing a high-performance IKSPH program will be a future research direction.

On the Simulation Hypothesis and Its Implications

This paper reports on the potential use of video games as well as gaming engines in the domain of physics and artificial intelligence. Unreal Engine 4 (UE4) [1] is used to render the history of the universe back in time to the quantum gravity era and then standard cosmology is assumed for its evolution until the appearance of life that was a simplified model of human-like evolution is rendered. The results of the simulations have a potential implication on the origin of life and matter and favorite the simulation hypothesis of the universe.

Research on Suspension Gravity Compensation System of Lunar Rover with Magnetic Levitation Servo

In order to overcome the shortcomings of the traditional sling suspension method,such as complex structure of suspension truss,large running resistance,and low precision of position servo system,a gravity compensation method of lunar rover based on the combination of active suspension and active position following of magnetic levitation is proposed,and the overall design is carried out.The dynamic model of the suspension module of microgravity compensation system was established,and the decoupling control between the constant force component and the position servo component was analyzed and verified.The constant tension control was achieved by using hybrid force/position control.The position following control was realized by using fuzzy adaptive PID(proportional⁃integral⁃differential)control.The stable suspension control was realized based on the principle of force balance.The simulation results show that the compensation accuracy of constant tension could reach more than 95%,the position deviation was less than 5 mm,the position deviation angle was less than 0.025°,and the air gap recovered stability within 0.1 s.The gravity compensation system has excellent dynamic performance and can meet the requirements of microgravity simulation experiment of lunar rover.

聚结构件形式对管式油水分离器油出口含油率的影响

为了对比不同结构形式聚结构件对管式油水分离器油出口含油率的影响规律,为工程设计选型提供技术支持,通过CFD方法分析了正V形斜板、倒V形斜板、传统斜板和蛇形背向折板4种不同聚结构件作用下的浓度场和油出口含油率,并探究了正V形聚结构件在单一条件下的最适宜结构参数。结果表明,在所研究的流速(0.05~0.35 m·s^(-1))内,4种聚结构件中正V形构件具有最好的油出口含油率,蛇形背向折板与倒V形斜板位列第2、3位,传统斜板最低;随着进口流速的增大,4种聚结构件油出口含油率均相应降低,其中传统斜板下降速度最快,正V形斜板与蛇形背向折板下降最慢,相差不大,而倒V形斜板下降速度居中;利用控制变量法确定了正V形构件与壁面间距C=10 mm、水平夹角θ=60°时油出口含油率最高。

RCEP生效对国际服务贸易影响作用研究——基于增加值贸易视角

RCEP作为当前世界范围内规模最大、影响范围最广的区域自由贸易体系,在服务贸易方面做出了高水平的开放承诺,它是中国构建高标准自由贸易区网络进程中的重要抓手。以1995-2018年全球范围内66个国家服务部门的双边出口数据为样本,运用结构引力模型和泊松拟极大似然估计方法,实证研究了RCEP对服务部门增加值贸易以及福利的影响作用。反事实模拟分析结果表明,RCEP对成员国服务部门总出口和国内增加值出口均有显著的促进作用,而非成员国将在整体上受损;RCEP对一国福利的影响较小,对一国出口的影响较大;对中国而言,RCEP将大幅提高中国对日本的服务部门总出口和国内增加值出口。此外,将RCEP与CPTPP进行比较发现,RCEP对我国服务部门增加值贸易的正向影响幅度小于CPTPP。

超重力强化分离铜渣中铜的数值模拟及辅助工业设计

由于当前铜冶炼工艺产生的铜渣铜含量比较高,采用传统的电炉贫化技术分离铜液滴时间长、回收率低,因此引入超重力技术对贫化过程进行改善。采用数值模拟的方法,以卧式离心机为模型基础,选用转炉铜渣作为试验对象进行研究,借助COMSOL Multiphysics软件构建模型,模拟铜渣中铜液滴的沉降过程。根据计算结果分析重力系数(G)、温度(T)对不同粒径铜液滴沉降行为的影响。结果表明,在T=1300℃、G=1的条件下,粒径低于80μm的铜液滴无法自由沉降;在恒定温度下,重力系数以及铜液滴粒径的增加均有利于铜液滴在铜渣中的沉降;温度升高会降低铜渣和铜的黏度,促进二者分离。最后,根据铜液滴的沉降数据,对离心机半径、给料速度等工业参数提出优化建议,以提升铜的回收率,降低企业生产成本。

基于准零刚度机构与间接力控制的恒拉力系统设计与分析

现有的悬吊式微低重力模拟恒拉力系统常采用力传感器数值作为反馈直接控制系统,但实际情况下力作为反馈信号常会产生突变,影响系统控制精度。为了改进刚性控制策略下系统稳定性差与大冲击条件下力误差大的状况,文中设计了包含准零刚度机构的恒拉力系统,通过控制准零刚度机构长度间接对恒拉力系统输出拉力进行控制。对准零刚度机构进行受力分析,明确影响准零刚度机构性能的关键指标和准零刚度机构的工作行程区间,建立恒拉力系统动力学模型,设计控制系统。为了验证系统控制精度与系统抗干扰性能,进行了动力学联合仿真对设计进行验证,仿真结果表明:该恒拉力系统拉力的控制误差可控制在2%以内,且具有较好的鲁棒性。

弱引力环境四足机器人的强化学习姿态机动控制

针对四足机器人在小天体表面跳跃巡游探测过程中的空中姿态控制问题,提出了一种基于强化学习的无模型控制方案。在小天体的弱引力环境下,机器人单次跳跃的滞空时间很长,机器人需要利用这段时间修正起跳带来的姿态偏差以实现安全着陆,或改变偏航角以改变未来行进方向。提出的基于近端策略优化(PPO)算法训练的控制器以猫落反射为启发,无需引入额外的姿态控制执行器。仿真结果表明,训练得到的控制器可通过控制四足机器人摆动腿部关节实现三轴姿态机动。设计并搭建了四足机器人气浮微重力模拟试验平台,通过样机试验,控制策略模型的有效性得到了验证。