Water flooding optimization with adjoint model under control constraints简

The oil recovery enhancement is a major technical issue in the development of oil and gas fields. The smart oil field is an effective way to deal with the issue. It can achieve the maximum profits in the oil production at a minimum cost, and represents the future direction of oil fields. This paper discusses the core of the smart field theory, mainly the real-time optimization method of the injection-production rate of water-oil wells in a complex oil-gas filtration system. Computing speed is considered as the primary prerequisite because this research depends very much on reservoir numerical simulations and each simulation may take several hours or even days. An adjoint gradient method of the maximum theory is chosen for the solution of the optimal control variables. Conven-tional solving method of the maximum principle requires two solutions of time series： the forward reservoir simulation and the backward adjoint gradient calculation. In this paper, the two processes are combined together and a fully implicit reservoir simulator is developed. The matrixes of the adjoint equation are directly obtained from the fully implicit reservoir simulation, which accelera-tes the optimization solution and enhances the efficiency of the solving model. Meanwhile, a gradient projection algorithm combined with the maximum theory is used to constrain the parameters in the oil field development, which make it possible for the method to be applied to the water flooding optimization in a real oil field. The above theory is tested in several reservoir cases and it is shown that a better development effect of the oil field can be achieved.     

Numerical prediction of hydrodynamic forces on a ship passing through a lock with different configurations简

A CFD method is used to numerically predict the hydrodynamic forces and moments acting on a ship passing through a lock with a constant speed. By solving the RANS equations in combination with the RNG k-e turbulence model, the unsteady viscous flow around the ship is simulated and the hydrodynamic forces and moments acting on the ship are calculated. UDF is com-piled to define the ship motion. Meanwhile, grid regeneration is dealt with by using the dynamic mesh method and sliding interface technique. Under the assumption of low ship speed, the effects of free surface elevation are neglected in the numerical simulation. A bulk carrier ship model is taken as an example for the numerical study. The numerical results are presented and compared with the available experimental results. By analyzing the numerical results obtained for locks with different configurations, the influences of approach wall configuration, lock configuration symmetry and lock chamber breadth on the hydrodynamic forces and moments are demonstrated. The numerical method applied in this paper can qualitatively predict the ship-lock hydrodynamic interaction and pro-vide certain guidance on lock design.     

Water level updating model for flow calculation of river networks简

Complex water movement and insufficient observation stations are the unfavorable factors in improving the accuracy of flow calculation of river networks. A water level updating model for river networks was set up based on a three-step method at key nodes, and model correction values were collected from gauge stations. To improve the accuracy of water level and discharge forecasts for the entire network, the discrete coefficients of the Saint-Venant equations for river sections were regarded as the media carrying the correction values from observation locations to other cross-sections of the river network system. To examine the applicability, the updating model was applied to flow calculation of an ideal river network and the Chengtong section of the Yangtze River. Comparison of the forecast results with the observed data demonstrates that this updating model can improve the forecast accuracy in both ideal and real river networks.     

A hybrid DEM/CFD approach for solid-liquid flows简

A hybrid scheme coupling the discrete element method(DEM)with the computational fluid dynamics(CFD)is developed to model solid-liquid flows.Instead of solving the pressure Poisson equation,we use the compressible volume-averaged continuity and momentum equations with an isothermal stiff equation of state for the liquid phase in our CFD scheme.The motion of the solid phase is obtained by using the DEM,in which the particle-particle and particle-wall interactions are modelled by using the theoretical contact mechanics.The two phases are coupled through the Newton’s third law of motion.To verify the proposed method,the sedimentation of a single spherical particle is simulated in water,and the results are compared with experimental results reported in the literature.In addition,the drafting,kissing,and tumbling(DKT)phenomenon between two particles in a liquid is modelled and reasonable results are obtained.Finally,the numerical simulation of the density-driven segregation of a binary particulate suspension involving 10 000 particles in a closed container is conducted to show that the presented method is potentially powerful to simulate real particulate flows with large number of moving particles.     

Numerical simulation of hull/propeller interaction of submarine in submergence and near surface conditions简

Hull/propeller interaction is of great importance for powering performance prediction. The features of hull/propeller interaction of a submarine model with a high-skew five blade propeller in submergence and near surface conditions are numerically simulated. The effect of propeller rotation is simulated by the sliding mesh technique. Free surface is captured by the volume of fluid （VOF） method. Computed results including resistance, thrust, torque and self-propulsion factor are compared with experimental data. It shows fairly good agreement. The resistance and wave pattern of the model at different depths of submergence are computed. And the thrust, torque and self-propulsion factor of the model in submergence and near surface condition are compared to analyze the effect of free surface on self-propulsion performance. The results indicate that free surface has more influence on resistance than that on self-propulsion factors.     

Phenomenological model for torsional galloping of an elastic flat plate due to hydrodynamic loads简

This study investigates the torsional galloping phenomenon, an instability type flow-induced oscillation, in an elastic stru-cture due to hydrodynamic loads into the water current. The structure applied here is a rectangular flat plate with an elastic axis in its mid-chord length. The elasticity is provided by torsion spring. The flat plate has only one degree of freedom which is rotation in pure yaw about its axis. It is observed that as the current speed is higher than a critical velocity, the flat plate becomes unstable. The instability leads to torsional galloping occurrence, as a result of which the flat plate begins to yaw about the elastic axis. By testing two different chord lengths each with several torsion spring rates, the flat plate behavior is investigated and three different responses are recognized. Then, a phenomenological model is developed with the original kernel in the form of the van der Pol-Duffing equa-tion. The model explains these three responses observed experimentally.     

A time fractional model to represent rainfall process简

This paper deals with a stochastic representation of the rainfall process.The analysis of a rainfall time series shows that cumulative representation of a rainfall time series can be modeled as a non-Gaussian random walk with a log-normal jump distribution and a time-waiting distribution following a tempered α-stable probability law.Based on the random walk model,a fractional Fokker-Planck equation(FFPE) with tempered α-stable waiting times was obtained.Through the comparison of observed data and simulated results from the random walk model and FFPE model with tempered α-stable waiting times,it can be concluded that the behavior of the rainfall process is globally reproduced,and the FFPE model with tempered α-stable waiting times is more efficient in reproducing the observed behavior.     

小清河分洪区洪水影响的二维模拟研究简

在收集地形及水文资料的基础上,对小清河分洪区的水流运动进行了二维数值计算,分析了分洪区洪水的运动特性、淹没情况及涿州市防洪圈建设对分洪区蓄滞洪的影响。     

Simulation of buoyancy-induced turbulent flow from a hot horizontal jet简

Experimental visualizations and numerical simulations of a horizontal hot water jet entering cold water into a rectangular storage tank are described. Three different temperature differences and their corresponding Reynolds numbers are considered. Both experimental visualization and numerical computations are carried out for the same flow and thermal conditions. The realizable k-e model is used for modeling the turbulent flow while the buoyancy is modeled using the Boussinesq approximation. Polynomial approximations of the water properties are used to compare with the Boussinesq approximation. Numerical solutions are obtained for unsteady flow while pressure, velocity, temperature and turbulence distributions inside the water tank as well as the Froude number are analyzed. The experimental visualizations are performed at intervals of five seconds for all different cases. The simulated results are compared with the visualized results, and both of them show the stratification phenomena and buoyancy force effects due to temperature difference and density variation. After certain times, depending on the case condition, the flow tends to reach a steady state.     

Numerical simulation unsteady cloud cavitating flow with a filter-based density correction model简

In this paper, various turbulence closure models for unsteady cavitating flows are investigated. The filter-based model （FBM） and the density correction model （DCM） were proposed to reduce the turbulent eddy viscosities in a turbulent cavitating flow based on the local meshing resolution and the local fluid density, respectively. The effects of the resolution control parameters in the FBM and DCM models are discussed. It is shown that the eddy viscosity near the cavity closure region can significantly influence the cavity shapes and the unsteady shedding pattern of the cavitating flows. To improve the predictions, a Filter-Based Density Cor-rection model （FBDCM） is proposed, which blends the FBM and DCM models according to the local fluid density. The new FBDCM model can effectively represent the eddy viscosity, according to the multi-phase characteristics of the unsteady cavitating flows. The experimental validations regarding the force analysis and the unsteady cavity visualization show that good agreements with experimental visualizations and measurements are obtained by the FBDCM model. For the FBDCM model, the attached cavity length and the resulting hydrodynamic characteristics are subsequently affected by the detail turbulence modeling parameters, and the model is shown to be effective in improving the overall predictive capability.     

基于离散元方法与水动力学耦合的河冰动力学模型

流凌和冰坝是我国北方冬季比较常见的河冰现象,尤其冰坝,可导致严重的凌洪灾害,是河冰研究中的重要部分。本文将离散单元方法与二维水动力学相耦合,建立河冰的动力学数值模型,以模拟河冰输移、聚集、堆积,以及冰坝形成的动力过程。针对河道中大量密集且几何形状随机的流冰现象,采用扩展多面体单元对冰块进行构造,并通过离散元接触模型表征河冰输移和冰坝形成过程中冰块间的相互作用。河流水动力部分则采用考虑河冰影响的二维非定常浅水方程进行描述,并采用有限元方法进行数值计算。冰水耦合中的计算参数由河冰离散单元与其所在水动力学有限元网格节点的位置插值计算得到。通过对冰盖封河造成水位抬高过程的数值模拟,并将计算结果与理论分析结果以及DynaRICE河冰模型的模拟结果进行对比,以验证模型的有效性。在此基础上,对规则河道中河冰输移、堆积和形成冰坝的过程进行数值模拟和结果分析。通过以上河冰离散元与水动力学的耦合方法及其对河冰动力过程的数值模拟,对河冰动力过程从细观角度进行新的认识并为河冰动力过程研究提供一种有效的数值方法。     

黄河流凌量地电测试模拟方法研究

以黄河济南段冰凌研究为例,采用电测深方法时黄河凌汛期典型断面进行了地电测试,并与无冰情况下的测深曲线进行了时比。得出如下结论：有冰和无冰时电测深曲线有明显差异。河道流冰增加．则电阻率的阻值增大。测深曲线的面积与河道流凌量成正比关系。     

基于遥感数据的河冰过程解译及分析

鉴于河冰的野外观测受观测技术、条件及方法的限制而无法获得大尺度、长序列的河冰过程数据,而遥感技术可有效完成复杂时空尺度海量信息的收集处理,以Landsat8遥感影像为数据源,通过单波段信息量比较及相关系数、信息熵和最佳指数的联合分析,得到最佳波段组合;采用监督分类的最大似然法对黄河内蒙古段三湖河口河段2013—2014年冬季不同时期遥感卫片数据进行解译,并对解译结果进行分析,从而获得该河段不同时期河冰的生消演变过程及特性。结果表明:应用7、4、3波段组合获得了较高的河冰解译精度,解译影像可以反映大尺度下冬季河冰的生消演变及输移过程,结合气象、水文等数据可以解释典型河冰现象,为河冰的理论分析及机理研究提供数据支撑。     

基于深度学习和信号分解的北方寒区河流开河日期预报

中国北方寒区河流春季开河时易产生冰凌现象,威胁涉河水工建筑物的安全。准确地预测寒区河流开河日期可为防凌指挥、调度决策提供重要参考依据。本文基于中国北方典型寒区-黑龙江省的5个代表水文站近60年的历史开河日期序列,采用完全自适应集合经验模态分解(CEEMDAN)技术和深度学习长短期记忆模型(LSTM)方法构建河流开河日期预报的耦合模型,以期提高河流开河日期预报的精度。结果表明：本研究构建的开河日期预报耦合模型(CEEMDAN-LSTM)预测精度明显优于单一深度学习方法(LSTM)计算结果;与LSTM相比,CEEMDAN-LSTM可将开河日期预报的平均绝对误差从2.51 d降低至1.20 d,合格率从91.59%提高至100%。验证期平均绝对误差从3.85 d降低至1.65 d,合格率从88%提高至96%。因此,所构建的开河日期预报耦合模型具有较高的预报精度,可为我国北方寒区春季防凌指挥和调度提供技术支持。     

基于GASS-BPEE交叉训练算法的河道冰情预报组合模型

在文章的河道冰情预报的组合模型中,首先在成因分析的基础上,采用逐步回归算法对预报因子进行有效的筛选,然后采用GASS-BPEE交叉训练算法对冰情要素进行预报.利用该组合模型对凌汛灾害多发的松花江依兰、佳木斯江段开河日期进行了预报,结果表明所建立的河道冰情预报组合模型结构简单、预报精度较高,具有实用价值.     

感潮河段平面二维非恒定水流模型深化研究

建立了基于非结构网格的感潮河段平面二维非恒定流模型,探讨了时间步长和非结构网格无序性对计算误差的影响,并和结构网格上的研究成果进行了对比。计算结果表明:(1)当采用隐式算法求解非恒定流时,时间步长会对流速和水位计算结果产生影响,当时间步长小于一定值时,计算所得的水位过程和流速分布才和实测值比较吻合,当时间步长增加时计算值与实测值之间误差将逐渐增加;(2)时间步长较小时,网格布置的无序性不会对非恒定流模拟产生明显不利的影响,但是随着时间步长的增加非结构网格的无序性会导致计算误差快速增加。     

基于数字图像相关方法的黄河冰断裂性能研究

河冰的断裂性能是衡量河冰承载力、模拟和预测开河的重要参数。为明晰黄河冰的断裂性能,基于数字图像测量技术(Digital Image Correlation,DIC)开展了黄河冰的三点弯曲梁试验,分析了不同条件下试样的断裂形态,研究了温度和加载速率对黄河冰断裂韧度的影响。研究结果表明:DIC方法适用于黄河冰断裂试验的研究;黄河冰试样的断裂形态主要受到晶体形态的影响,试样的破坏形式以Ⅰ型断裂为主;黄河冰断裂韧度随着加载速率的增加而降低,随着温度的升高而减小,但在试验给定温度范围内降幅较小;提出了黄河冰断裂韧度与温度、加载速率的关系式,为极限荷载作用下河冰断裂过程的分析及冰荷载断裂参数的选用提供了依据。     

无粘沙质床面上冲积性河湾形成和演变规律自然模型试验研究

基于雷诺方程和有限体积法建立了描述弯道水流运动的三维数学模型,并利用室内物理模型试验进行验证,验证结果表明,数学模型能够较好地模拟弯道内水流的流速分布以及湍流特征。以验证后的模型为工具,对具有不同平面形态和床面形态的弯道中的水流运动进行了模拟,模拟结果表明：弯道中浅滩和深槽相间的地形起伏加剧了断面流速分布的不均匀性,同时使得水流动力轴线更加偏向凹岸,流速的沿程变化也较平整床面更为复杂;另外,与对称型河弯（正弦派生曲线型）相比,非对称河弯（Kinoshita派生曲线型）中在两弯顶中间存在较多的低流速区,有利于泥沙的落淤,而对岸流速一般较大,形成河岸的快速崩退,这能够从一个侧面解释非对称河弯向下游方向整体的快速迁移。     

闸控感潮河段重金属迁移转化规律研究

以长江感潮江段的某入江河道为典型案例,根据闸控条件下的水文特征、污染物迁移转化特性分别建立了由入江河道及长江相关河段构成的动态二维水动力及重金属数学模型,模拟分析了闸门控制下入江河道的水流运动规律、点源连续排放的重金属浓度随时间变化及二维平面分布特征。模拟结果表明:在长江潮汐、水闸控制影响下,入江河道内重金属浓度在一定范围内呈现周期性波动的现象,重金属浓度整体呈增大趋势,随着污水排放时间的推移,河道内各断面处重金属浓度最大值和波动区间均趋于稳定;典型超周期内,河道内落潮流污染带长度大于涨潮流。重金属在潮汐河道内的变化是一个非常复杂的过程,对这一过程的模拟,可以为河道水质治理和污染防治提供技术依据。     

河流自然模型试验时效的研究

在概述河流自然模型试验定义和前人众多试验研究的基础上,讨论了试验时间的确定对河流自然模型试验的意义。结合对概化水槽试验的分析,论述了河流自然模型试验时效的定义、实质及其影响因素,初步得出试验时效与河床组成、河谷比降以及流量的关系,并提出时效的判定指标。通过相似理论以及河段裁弯概化模型试验与天然河流的对比,对其合理性进行了初步验证。最后,引入“空代时”假说,分析了该假说在时效验证中的可行性。