Numerical Investigation on Inclined Hydraulic Transport of Large Particles for Deepsea Mining

Hydraulic transport in pipelines is the most promising conveying method for large ore particles in deepsea mining.The dynamic performances of particles during transportation in vertical,inclined and horizontal pipelines are significant for the design of hydraulic transport systems.In the present study,we focus on the statistical characteristics and flow regimes of the mixture composed of ore particles and seawater in the pipelines.Numerical simulations are conducted by using Computational Fluid Dynamics(CFD)and Discrete Element Method(DEM).The influences of inclination angle and particle diameter are evaluated through two sets of numerical tests.The regulation of the inclined transport is totally different from that of the vertical transport,whereas the dynamics of the mixtures in inclined and horizontal pipes are similar.A number of particles accumulate on the pipe wall even with a small inclination angle.Large hydraulic gradient and local concentration would occur when the inclination angle of the pipe is in the range of30°-60°.With the decrease of particle diameter,the particle flow becomes uniform,reflected by the almost uniform particle distribution in the vertical pipe and the clear interface between the suspended load and the bed-load in the inclined pipe.However,small particles will introduce larger local concentrations and hydraulic gradients in the inclined pipe,which is not conducive to particle transport.

一种模拟特定畸形波列的相位调制方法（英文）

海洋中畸形波能够给船舶与海洋结构物带来巨大危害。准确地模拟特定畸形波列是研究其与结构物相互作用的基础。文章基于商业计算流体动力学软件FLUENT建立了一个数值波浪水池。通过线性聚焦方法给定一个畸形波时历,采用傅里叶分析来求解畸形波时历中每一个组成波的波幅和相位,提出了一种相位调制方法来提高模拟精度。将数值结果与物理水槽试验进行了对比,证明该相位调制方法能够显著提高数值模拟精度,展现了研究畸形波与结构物相互作用问题的新前景。

棉秆粉碎与搂膜联合作业机关键部件设计与试验

【目的】针对新疆地区现有残膜回收机具残膜捡拾率低,立杆搂膜机具地膜自卸率低等问题,为有效解决新疆地区棉田残膜污染问题,研制了棉秆粉碎与搂膜联合作业机.【方法】首先对整机结构、工作原理、关键部件设计进行了说明,然后对试验因素运用Box-Benhnken中心组合试验方法,以刀轴转速、弹齿组数、机具前进速度进行试验与响应曲面分析,建立了响应面三维模型,并得出最优试验组合.【结果】当刀轴转速2 200 r/min、弹齿组数为12组、机具前进速度为4 km/h,残膜回收率为91.1%,棉秆粉碎合格率为91.5%;增加地膜自卸机构,卸膜率为96.7%.【结论】机具作业性能可靠,各项指标满足设计标准.

滚筒式残膜回收机田间作业性能试验分析

为了检验研制的滚筒式残膜回收机结构和工作参数的合理性。文中对滚筒式残膜回收机进行了3因素3水平正交试验,并对试验数据进行分析,通过分析得出影响残膜回收率的最优参数组合。

残膜回收机卸膜装置设计与试验

针对现有残膜回收机在作业过程中无法自动卸膜问题,研制了一种新型卸膜装置,提高了机具的作业效率。文中对卸膜装置进行了二因素三水平正交试验,并对试验数据进行优化分析,得出提高脱膜率的最佳参数。

棉秆粉碎与搂膜联合作业机田间作业性能试验分析

为了检验研制的棉秆粉碎与搂膜联合作业机的结构和工作参数的合理性。文中对棉秆粉碎与搂膜联合作业机进行了三因素三水平正交试验,并对试验数据进行分析,通过分析得出影响残膜回收率的最优参数组合。

浅吃水单柱式浮式风机动力学特性仿真研究

本文采用FAST软件对一种浅吃水单柱式浮式风机系统的动力学特性进行了研究。这一浮式风机适用于能源成本相对合理、水深为150 m的海域。本文首先讨论了这一浮式风机系统和OC3-Hywind系统在动力学特性方面的差异,然后研究了风尤其是湍流风对系统动力学特性的影响,最后对这一系统在多种载荷状况下的动力学行为进行了详尽的分析。研究结果表明:湍流风会在系统固有频率附近引起显著的激励;纵荡和纵摇运动取决于风轮推力,它们通过风轮推力和相对风速之间的联系建立起耦合关系;Spar平台的艏摇运动主要取决于平台横摇时由风轮推力引起的艏摇力矩。

Study on Nonlinear Characteristics of Freak-Wave Forces with Different Wave Steepness

The nonlinear wave forces on vertical cylinders induced by freak wave trains were experimentally investigated. A series of freak wave trains with different wave steepness were modeled in a wave flume. The corresponding wave forces on vertical cylinders of different diameters were measured. The experimental wave forces were also compared with the predicted results based on Morison formula. Particular attentions were paid to the effects of wave steepness on the dimensionless peak forces, asymmetry characteristics of the impact forces and high-frequency force components. Wavelet-based analysis methods were employed in revealing the local energy structures and quadratic phase coupling in the freak wave forces.

Motion and Dynamic Responses of A Semisubmersible in Freak Waves

The present research aims at clarifying the effects of freak wave on the motion and dynamic responses of a semisubmersible. To reveal the effects of mooring stiffness, two mooring systems were employed in the model tests and time-domain simulations. The 6-DOF motion responses and mooring tensions have been measured and the 3- DOF motions of fairleads were calculated as well. From the time series, trajectories and statistics information, the interactions between the freak wave and the semisubmersible have been demonstrated and the effects of mooring stiffness have been identified. The shortage of numerical simulations based on 3D potential flow theory is presented. Results show that the freak wave is likely to cause large horizontal motions for soft mooring system and to result in extremely large mooring tensions for tight mooring system. Therefore, the freak wave is a real threat for the marine structure, which needs to be carefully considered at design stage.

Effects of Degrees of Motion Freedom on Free-Fall of A Sphere in Fluid

Free-fall of a sphere in fluid is investigated at a Galileo number of 204 by direct numerical simulations(DNS). We mainly focus on the effects of different degrees-of-freedom(DOFs) of the sphere motion during free-fall. The characteristics of free-fall are compared with those of flow past a fixed sphere. Additional numerical tests are conducted with constraints placed on the translational or rotational DOFs of the sphere motion to analyze different DOFs of sphere motion. The transverse motion contributes significantly to the characteristics of free-fall; it results in the retardation of the vortex shedding, leading to the decrease of the Strouhal number. In addition, the transversal sphere motion exhibits the tendency to promote the sphere rotation. On the contrary, the effects of the sphere rotation and vertical oscillations during free-fall are negligible.

Research on the Effects of in-Line Oscillatory Flow on the Vortex-Induced Motions of A Deep Draft Semi-Submersible in Currents

A Deep Draft Semi-submersible （DDS） under certain flow conditions could be subjected to Vortex-Induced Motions （VIM）, which significantly influences the loads on and life fatigue of the moorings and the risers. To investigate the VIM of a DDS with four rectangular section columns in waves coupled with a uniform current, a numerical study using the computational fluid dynamics （CFD） method was conducted. The issues of the VIM of multi-column floaters can be con＇,＇eniently converted to the issues of oscillating cylinders in fluid cross flows. This paper looks into the CFD numerical simulation of infinite cylinders having rectangular sections in a two-dimensional sinusoidal time- dependent flow field coupled with a uniform current. The resulted hydrodynamic forces and motion responses in different oscillatory flows plus currents both aligned in the same direction for the incidence of 135° of the DDS relative to the flow are compared with the ones in current only cases. The results show that the VIM response of this geometric arrangement of a DDS with four rectangular columns in a current combined with oscillatory flows is more evident than that in the current only case. The oscillatory flows and waves have the significant influence on the VIM response, forces and trajectory, in-plane motions of the DDS.

瓦斯抽采系统逐级管控提升抽采浓度在余吾煤业的应用

针对余吾煤业瓦斯抽采浓度偏低的问题,提出了提升瓦斯抽采浓度的方案,对瓦斯抽采浓度低的钻孔进行排查,实施了堵漏、放水、减流等一系列措施,从抽采钻孔、管路系统、瓦斯泵站逐级管控等方面加强管理,明显提高了瓦斯抽采浓度。

A Novel Dynamics Analysis Method for Spar-Type Floating Offshore Wind Turbine

The dynamic behavior of floating offshore wind turbine (FOWT) is crucial for its design and optimization. A novel dynamics analysis method for the spar-type FOWT system is proposed in this paper based on the theorem of moment of momentum and the Newton’s second law. The full nonlinearity of the equations of motion (EOMs) and the full nonlinear coupling between external loads and the motions are preserved in this method. Compared with the conventional methods, this method is more transparent and it can be applied directly to the large-amplitude rotation cases. An in-house code is developed to implement this method. The capability of in-house code is verified by comparing its simulation results with those predicted by FAST. Based on the in-house code, the dynamic responses of a spar-type FOWT system are investigated under various conditions.

余吾煤业掘进工作面CO2气相压裂应用效果分析

2019年,余吾煤业气相压裂瓦斯治理技术在各高瓦斯掘进工作面全面推广应用,为考察气相压裂消突增透技术应用效果,选取瓦斯含量相对较高、气相压裂连续应用次数较多的S2108胶带巷、N1101胶带巷、N2103胶带巷3个地点进行分析,从压裂前后回风流瓦斯浓度变化曲线、工作面瓦斯涌出不均衡系数、月度预警次数、日平均进尺等几方面对压裂效果进行分析,得到气相压裂在提高工作面瓦斯涌出均匀性、减少瓦斯预警次数、提高掘进速度等方面有一定效果。

基于部分最大可满足性问题的动态系统中最小故障检测隔离集求解方法

选择一组能够检测并隔离所有故障的故障检测隔离集(FDIS)是动态系统基于模型故障检测与隔离(FDI)的重要步骤,该步骤通常要求FDIS的基数最小,即求解最小故障检测隔离集(MFDIS),MFDIS的求解时间随着问题规模增大呈指数级增长。BILP(Binary integer linear programming)完备方法是现行动态系统中通用和最高效的MFDIS求解方法,但该方法的求解效率有待提高。本文首次提出了基于部分最大可满足性问题(PMS)的MFDIS求解方法。提出极小超定方程集(MSO)的概念,将部分MSO集合用MSO等价集表示,以缩减问题规模。将MFDIS求解问题转化为PMS问题,进而提高求解效率。实验结果表明,本文方法将问题规模平均约简至原来的8.22%;与BILP方法相比,本文方法的求解效率提高了4.18~9.5倍。

基于集合阻塞的不确定系统中传感器选择方法

动态系统故障检测与隔离(FDI)的一个重要步骤是选择一组满足故障检测性与故障隔离性且花费最小的传感器集合。针对不确定系统,故障可诊断性量化方法被用来量化系统的故障检测性和故障隔离性。由于传感器选择问题的搜索空间随传感器规模增大呈指数增长,目前没有研究针对量化可诊断性的不确定系统提出传感器选择的完备方法。针对该问题本文提出基于集合阻塞策略的传感器选择算法:通过二进制整数优化问题(BILP)实现子集阻塞与超集阻塞;通过迭代阻塞搜索空间减小所需遍历的节点。在标准测试用例上的实验结果表明:针对实验中的绝大多数搜索空间,与深度优先遍历方法相比,本文方法效率提高了4.41~103.37倍。且在区分度计算次数相同的情况下,本文方法得到的大多数解优于现行的高效算法。