Simulating the evolution of focused waves by a two-layer Boussinesq-type model

Accurate simulation of the evolution of freak waves by the wave phase focusing method requires accurate linear and nonlinear properties,especially in deep-water conditions.In this paper,we analyze the ability to simulate deep-water focused waves of a two-layer Boussinesq-type(BT)model,which has been shown to have excellent linear and nonlinear performance.To further improve the numerical accuracy and stability,the internal wavegenerated method is introduced into the two-layer Boussinesq-type model.Firstly,the sensitivity of the numerical results to the grid resolution is analyzed to verify the convergence of the model;secondly,the focused wave propagating in two opposite directions is simulated to prove the symmetry of the numerical results and the feasibility of the internal wave-generated method;thirdly,the limiting focused wave condition is simulated to compare and analyze the wave surface and the horizontal velocity of the profile at the focusing position,which is in good agreement with the measured values.Meanwhile the simulation of focused waves in very deep waters agrees well with the measured values,which further demonstrates the capability of the two-layer BT model in simulating focused waves in deep waters.

A new model simulating the development of gas condensate reservoirs

A new simulation model for the development of gas condensate reservoirs is introduced based on the influence that phase change,non-Darcy flow,and capillary pressure have on the production of gas condensates.The model predicts well performance,including bottom-hole pressure,oil/gas production rate,oil/gas recovery,gaseoil ratio,and the change in produced fluid composition.It also calculates dynamic characters,such as the change of pressure field and oil/gas saturation field during the development of gas condensate reservoirs.The model is applicable to different boundary conditions(both constant-pressure and sealed boundary)and different production modes(both constant-pressure and constant-volume production modes).Model validation attempted using numerical simulation results for sealed boundary conditions with constant-pressure production mode has shown a relatively good match,proving its validity.For constant-pressure boundary conditions with constant-volume production mode,four stages are defined according to the dynamic behavior of production performance in the development of gas condensate reservoirs.

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.

An approach for simulating the air brake system of long freight trains based on fluid dynamics

Air brake systems are critical equipment for railway trains, which affects the running safety of the trains significantly. To study air braking characteristics of long freight trains, an approach for simulating air brake systems based on fuid dynamics theory was proposed. The structures and working mechanisms of locomotive and wagon air brakes are introduced, and mathematical models of the pipes, brake valves, reservoirs or chambers, cylinders, etc., are presented.Besides, the dynamic motions of parts in the main valve are considered. The simulation model of the whole air brake system is then formulated, and the solving method based on the finite-difference method is used. New efficient pipe boundary conditions without iterations are developed for brake pipes and branch pipes, which can achieve higher computational efficiency. The proposed approach for simulating the air brake system is validated by comparing with published measured data. Simulation results of different train formations indicate that models that consider the dynamic behavior of brake pipes are recommended for predicting the characteristics of long trains under service braking conditions.

Simulating the strong ground motion of the 2022 MS6.8 Luding,Sichuan,China Earthquake

Stochastic finite-fault simulations are effective for simulating ground motions and are widely used in engineering to determine the impacts of ground motion and develop relevant predictive equations.In this study,the source,path,and site amplification coefficient of western Sichuan Province,China,and stochastic finite-fault simulations were used to simulate the acceleration time series,Fourier amplitude spectra,and 5%damped response spectra of 28 strong-motion stations with rupture distances within 300 km of the 2022 MS6.8 Luding earthquake.The simulation results of 14 stations at rupture distances of 45-185 km match the observation.However,the simulation results of 3 near-and 6 far-field stations at rupture distances of 12-36 km and 222-286 km,respectively,were obviously deviated from the observations.Simulation results of the near-field stations are larger than the observations at high frequencies(>6 Hz).The discrepancy likely comes from the nonlinear site effect of near-field stations,which reduced the site amplification at high frequencies.Simulation result of the far-field stations is smaller than the observation at frequencies above 1 Hz.As these stations are located close to the Longmenshan Fault Zone(LFZ),thus,we obtained a new quality factor(Q)from data of historical events and stations located around LFZ.Using the new Q value,the discrepancies of the high-frequency simulation results of the far-field stations were corrected.This result indicated that the laterally varying Q values can be used to address the impact of strong crustal lateral heterogeneity on simulation.

Evaluation of Performance of Polar WRF Model in Simulating Precipitation over Qinghai-Tibet Plateau

Considering the complex topographic forcing and large cryosphere concentration,the present study utilized the polar-optimized WRF model(Polar WRF)to conduct downscaling simulations over the Qinghai-Tibet Plateau(TP)and its surrounding regions.Multi-group experiments with the 10 km horizontal resolution are used to evaluate the modeling of precipitation.Firstly,on the basis of the model ground surface properties upgrade and the optimized Noah-MP,the“better-performing”configuration suite for modeling precipitation is comprehensively examined.Various model parameters such as nudging options,five cumulus parameterization schemes,two planetary boundary layer schemes,and six microphysics schemes are investigated to further refine the Polar WRF configuration.Moreover,the precipitation simulation for a full calendar year is compared with multiple reanalyses and observations.The simulations demonstrate that the Polar WRF model successfully captures the general features of precipitation over this region and is sensitive to model parameters.Based on the results,it is recommended to use grid nudging with q intensity coefficient of 0.0002,the multi-scale kain-fritsch cumulus parameterization,the Yonsei University boundary layer scheme,and the Morrison 2-mom microphysics with reduced default droplet concentration value of 100 cm-3.Overall,the model performance is better than the ERA-interim and TRMM 3b42.It is comparable to,and in some cases slightly better than,the CRA-Land,especially in the prediction for the western part of the plateau where in situ observations are limited,and the cryosphere-atmosphere interaction is more pronounced.

Ballistic response of skin simulant against fragment simulating projectiles

The response of biological phantoms against high velocity impact is actively sought for applications in defense,space,soft robotics and sensing.Towards this end,we study the ballistic response of silicone based skin simulant against fragment impact.Using a pneumatic gas gun setup,six chisel-nosed and three regular shaped(sphere,cylinder,and cube)fragments were impacted on the skin simulant.The resulting skin simulant response was studied in terms of ballistic limit velocities,energy densities,failure pattern,and the mechanics of interaction.The results indicate that the shape of the fragment affects the ballistic limit velocities.The ballistic limit velocities,energy densities of the chisel-nosed fragment simulating projectiles were relatively insensitive to the size(mass),except for the smallest(0.16 g)and largest(2.79 g)chisel-nosed fragment.For the same size(1 g),ballistic limit velocities and failure are dependent on the shape of the fragment.The skin simulant failed by combined plugging and elastic hole enlargement.Failure in the spherical fragment was dominated by the elastic hole enlargement,whereas plugging failure was dominant in all other fragments.The spherical,cylindrical,and chisel-nosed fragments created circular cavities,and the cubical fragment created a square cavity.In the case of the spherical fragment,slipping of the fragment within the skin simulant was seen.Cubical fragments created lateral cracks emanating from the corners of the square cavity.Interestingly,for all the fragments,the maximum deformation corresponding to the perforation was lower than the non-perforation indicating rate dependent,stress driven failure.The maximum deformation was also dependent on the shape of the fragment.Overall,these results provide unique insights into the mechanical response of a soft simulant against ballistic impact.Results have utility in the calibration and validation of computational models,design of personal protective equipment,and antipersonnel systems.

Method of simulating hybrid STT-MTJ/CMOS circuits based on MATLAB/Simulink

The spin-transfer-torque(STT)magnetic tunneling junction(MTJ)device is one of the prominent candidates for spintronic logic circuit and neuromorphic computing.Therefore,building a simulation framework of hybrid STT-MTJ/CMOS(complementary metal-oxide-semiconductor)circuits is of great value for designing a new kind of computing paradigm based on the spintronic devices.In this work,we develop a simulation framework of hybrid STT-MTJ/CMOS circuits based on MATLAB/Simulink,which is mainly composed of a physics-based STT-MTJ model,a controlled resistor,and a current sensor.In the proposed framework,the STT-MTJ model,based on the Landau-Lifshitz-Gilbert-Slonczewsk(LLGS)equation,is implemented using the MATLAB script.The proposed simulation framework is modularized design,with the advantage of simple-to-use and easy-to-expand.To prove the effectiveness of the proposed framework,the STT-MTJ model is benchmarked with experimental results.Furthermore,the pre-charge sense amplifier(PCSA)circuit consisting of two STT-MTJ devices is validated and the electrical coupling of two spin-torque oscillators is simulated.The results demonstrate the effectiveness of our simulation framework.

The Assessment of the Application of the CFD Package OpenFOAM to Simulating Flow around the Propeller

During the design process of the ship,a lot of attention is given to tune-up parameters of the propeller,which is one of the most important part of the propulsion system.Designing new generation,more effective and efficient propellers require knowledge of hydrodynamic phenomena occurring in the propeller area.For this reason,a lot of time and funds is spent on the propeller research and development.Usually these are experimental tests in cavitation tunnels and towing tanks.However,more and more research is carried out by CFD simulation.OpenFOAM software is open source CFD package,which becomes popular alternative to commercial codes.This paper attempts to answer the question:if OpenFOAM is suitable for such specific applications like accurate simulation of flow around the propeller?The paper presents the results of a CFD simulation of marine propeller created with OpenFOAM software.The obtained results were compared with the of the commercial CFD codes simulations and the experimental research.

自动化生产线工业机器人的装调工艺仿真

在自动化生产线安装调试工作中,工业机器人的装调费时费力且难以迅速满足生产线工艺要求,提出了使用Process Simulate软件对自动化生产线中的工业机器人进行工艺仿真的解决方案。文章介绍了使用Process Simulate软件对自动化生产线中的工业机器人进行工艺仿真的基本方法和过程,从而实现工业机器人装调效率和自动化生产线生产效率的提高。

菠菜播种收割一体机结构设计与有限元分析

针对现有菠菜收割机留根、铲根深浅不一以及播种机撒播效率低、线绳播种成本高等问题,通过理论计算和SolidWorks建模分析,设计了一种犁地深度可调、整株收割、定量等距播种的菠菜播种收割一体机。采用Simulation模块对优化的机架和犁进行有限元分析发现,机架的大部分最大应力点位于机架前端的输料口处,在制造时需提高此处的焊接质量;犁须选用耐腐蚀性好的材料以减少其在腐蚀性土壤环境中的损坏。通过综合比较和有限元分析发现,机架所受最大应力均小于玻璃钢屈服极限,若通过合理成型设计弥补玻璃钢的成形性差等问题,有望使其成为未来农机具中犁制造的优选材料。研究结果可为菠菜播种收割一体机设计和关键部件优化提供一定理论参考。

仿真技术在船舶舱室单元生产线设计中的应用

采用流水线模式生产船舶预制舱室单元正越来越受到关注,但目前针对其生产线设计方法的研究较少,为了改进流水生产线设计方案,提高生产力,本文开展仿真技术在舱室单元流水生产线设计不同阶段中的应用研究。首先在工序规划阶段运用遗传算法模块优化生产工序,其次在布局设计阶段基于仿真试验模块求解最佳库容,最后在方案比选阶段通过模拟复杂生产系统运行输出关键指标。研究结果表明,仿真技术在能为流水线工艺和布局设计提供有力支撑,对工程设计具有应用价值。

无开挖电缆保护管道支护装置设计与仿真

针对地下管道放置要求,设计了一种无开挖电缆保护管道支护装置,可以实现多变地质中管道的自动安装。运用SOLIDWORKS软件进行建模,运用Simulation对重要零部件进行有限元分析,对强度进行校核,选择相应的材料,通过ADAMS软件对四杆机构进行运动仿真及分析,得到托板在质心处的运动情况,使整机结构和运动参数得到了优化,为样机制造奠定了基础。

虚实结合的驾驶人风险感知能力评测教学实验设计与实践

驾驶人风险感知能力评测教学实验立足于我国高质量人才培养课程这一核心要素,充分考虑不同道路交通因素对驾驶人安全驾驶的影响,致力于打造虚实结合的线上线下混合式一流教学实验课程。该教学实验基于交通仿真技术,通过线上实验与线下仿真模拟实验相结合的方式,在任课教师的指导下,由学生自主完成课程学习、场景设计、线上或线下实验和实验报告等实验流程。培养学生在课程学习与实验中的创新性与主观能动性,提升学生综合素质与团队协作能力,综合考量学生对道路交通多项学科专业课的掌握情况,并基于现阶段的教学情况对未来提出展望。

MW级大储能量飞轮轴系结构力学及动力学研究

当前,对于高功率大储能量飞轮储能系统的仿真和实验研究还不够充分,本工作主要针对MW/100 MJ级飞轮储能样机展开。比较分析了内置式和表贴式两种结构飞轮电机转子的结构力学,比较了不同动平衡块材质对应力及形变的影响,并开展了轴系的动力学特性分析。对飞轮样机开展了实验测试,验证了系统的稳定性。数值计算结果表明,表贴式结构形式可以使电机硅钢片应力显著降低,但是通常这种结构需要在硅钢片外缠绕碳纤维加强层,以确保运行时磁钢不会因为离心力与硅钢片发生分离。动平衡块材质为不锈钢时的应力值相较于动平衡块为铝合金时提高了45%以上。对轴系进行了动力学特性分析,在工作转速下存在着1300 r/min和4200 r/min两个刚性振型,分别为平动和锥动。测试运行中,飞轮轴系在1300 r/min出现振动峰值,证明了数值仿真计算的准确性。但是数值仿真中的4200 r/min临界转速(锥动)在实际运行中并未出现明显峰值,在本工作的轴系结构中,相较于锥动,平动振型更容易被激发。

基于DEM-MBD耦合的液压挖掘机动力学仿真分析

在实际工况下,液压挖掘机工作装置受到的载荷较大且具有强时变性,因此工作装置各组成杆件及液压缸较易出现各种形式的失效。针对以上问题,选取某型号液压挖掘机作为研究对象,根据液压挖掘机工作装置实际挖掘物料工况,利用多体动力学软件ADAMS建立液压挖掘机虚拟样机模型并利用离散元软件EDEM建立物料模型。通过DEM-MBD耦合仿真分析方法,对液压挖掘机工作装置进行动力学仿真分析,主要获取挖掘物料过程中铲斗受力变化曲线、不同时刻铲斗受力云图,通过对其分析,能够获取铲斗在挖掘作业过程中受力变化情况,为铲斗的有限元分析、优化设计提供理论依据。

结构化网格快速生成工具的开发及其在冶金模拟仿真中的应用

结构化网格在模拟计算高精度、复杂问题时具有更高的计算准确度和更好的收敛性,但其划分难度大且耗时较长,如何快速生成高质量结构化网格是进行CFD(Computational fluid dynamics)等模拟计算领域的前沿问题.根据冶金容器的几何结构特征,引入了参数一体化建模+网格划分的理念,利用Python脚本快速批处理数据和开源CFD软件OpenFOAM的优势,成功开发了适用于冶金反应器的网格快速生成工具.以钢包–中间包–结晶器及其附属连接装置为例,进行了案例分析测试.结果表明,该工具软件生成的结构化网格在扭曲度和正交性等方面质量较高,可以满足各类模拟仿真的需求.该工具在解决冶金容器几何结构更新和网格分布调整方面相比于传统前处理方法可以在几十秒内快速生成高质量结构化网格.此外,开发了便于用户使用的图形用户界面,界面中仅需输入关键的几何结构和网格参数,即可对冶金容器快速便捷地生成相应的结构化网格,有效提升了前处理的简易度和效率.这一工具软件有望应用于冶金数字化和智能化转型发展的多种场景,并为其提供有效的软件支撑.

注重基础、立足工程、强化实践、融入模拟、激励创新——材料力学教学改革探索

材料力学是机械类、土木类和力学类等工科类专业的核心课程,课程秉承“强基础、重实践、融模拟、促创新”的理念;构建“融工程、融前沿、融思政”的教学资源与内容,夯实学生的力学理论知识,培养学生利用力学理论解决实际工程问题的能力,同时帮助学生塑造正确的世界观、人生观、价值观和职业观;将抽象的力学概念与三阶递进的课程实践融会贯通,培养学生的动手实践能力、探索精神和创新能力;将数值模拟技术引入课堂,初步培养学生利用数值模拟软件解决力学问题的能力。建立以传授知识为中心,以解决工程问题为导向,以创新实践为特点,以数值模拟软件为工具,以立德树人为根本的课堂。

合作尝试法联合仿真模拟人在妇产科见习中的应用研究

目的分析合作尝试教学法联合仿真模拟人在妇产科主动融通见习中的应用效果。方法2022年10月,选择在中南大学湘雅三医院妇产科见习的五年制学生,共131名,随机分2组:研究组66名学生采用合作尝试教学法联合仿真模拟人进行教学,对照组65名学生采用以案例为导向的教学法(case-based learning,CBL),教学评估内容为产后出血的模拟训练,通过理论测试、迷你临床演练评估(mini-clinical evaluation exercise,Mini-CEX)、学生评教表、课后调查问卷表等多方面评估教学效果。结果研究组的理论测试成绩、Mini-CEX评分表中的各项成绩、课后问卷调查的满意度均高于对照组,差异有统计学意义(P<0.001)。学生评教表中研究组学生对带教老师的教学基本功、教学内容、教学方法、教学效果的评分远高于对照组,差异有统计学意义(P<0.001)。在师德、教学管理方面的评分一致,差异无统计学意义(P>0.05)。结论在妇产科主动融通见习教学中,应用合作尝试教学法联合仿真模拟人的教学形式,可以有效促进理论知识的学习、提高体格检查及操作技能水平、调动学生学习的主动性、积极性,能够真正做到“主动、融通”,并能够使学生更准确地做出临床判断、更好地做到人文关怀、改善其在临床工作中的整体表现,显著提高临床见习教学效果,并能够改善学生对教师的主观评价,更好的体现教师的教学能力及价值,值得在医学生本科教学中应用。

乡村数字治理的驱动机制:模型构建与仿真模拟

乡村数字治理是技术赋能驱动、组织协同推动、环境牵引拉动的结果。理清各驱动要素的相互关系并以此构建驱动机制,对于提升乡村数字治理效能至关重要。基于TOE框架分析乡村数字治理的驱动要素及相互关系,以长沙县为例,构建其系统动力学模型,并进行仿真模拟分析。研究发现,在整个仿真中组织维度影响最明显,环境维度影响次之,技术维度影响相对较弱,而三个维度中影响最大的因素分别为党的领导、村民数字素养、应用场景创新。为此,应进一步加强党的全面领导,提升村民数字素养,创新数字应用场景,建立健全组织、技术与环境“三位一体”的乡村数字治理驱动机制。