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液氮大炮英文作文The nuclear weapon effect clearance explosion is one of the most destructive weapons of mass destruction. To make this clear, one only needs to recall the picture of Hiroshima or the international disturbance caused by the accidental but huge radiation release at the Chernobyl nuclear power station. The pollution of Chernobyl nuclear power station is much greater than expected, which can be expected from the nuclear explosion of about KT on the ground, but to a certain extent Similar to the result of a large-scale nuclear war, in which more than ten kinds of weapons of nominal equivalent are exploded at a height designed to maximize the damage to the explosion.The nuclear explosion produces a harsh environment including explosion, thermal pulse and neutron, X-ray and gamma ray, radiation, electromagnetic pulse (EMP and ionization of upper atmosphere, depending on the environment of nuclear device initiation, explosion effect) For example, ground impact, water impact, void, crater, a lot of dust and radioactive fallout will bring problems to the survivalof friendly forces system, and may lead to the destruction or failure of enemy weapons. However, the EMP generated by detonating a single nuclear weapon at high altitude poses a threat to the military system thousands of miles away. This threat may be exploited by the third world countries.It can carry a rocket carrying a high-yield device (about one million tons or more) into the upper atmosphere hundreds of kilometers away, thousands of kilometers away from the atmosphere (to avoid destroying its own territory) Self system.。
装备环境工程第20卷第8期·90·EQUIPMENT ENVIRONMENTAL ENGINEERING2023年8月重大工程装备气流清扫的超音速喷管气动设计及其性能的对比分析赵宏星1，卢耀辉1，王北昆1，唐波1，罗银生2，陈德君2，毛荣生2（1.西南交通大学 机械工程学院，成都 610031；2.唐山百川智能机器股份有限公司，河北 唐山 063000）摘要：目的提出使用拉瓦尔喷管产生高速气流清扫固体表面附着的水膜。
方法设计中心轴对称锥形喷管（Taper-A）、中心轴对称Sivell法喷管（Sivell-A）、中心轴对称短化喷管（MLN-A）和二维锥形型线喷管（Taper-2D），建立包括外流场的LES数值仿真模型，并进行仿真，分析研究外流场结构，并基于韦伯数判据，分析超音速喷管的清扫性能。
结果喷管短化设计方法可以将喷管长度缩短50%。
外流场速度呈波动衰减趋势，特征线法喷管的气流膨胀更充分。
缩短喷管长度会减小内流场的附面层厚度，因此MLN-A在速度波动中的能量耗散较少；喷管过长也会降低清扫性能，MLN-A和Taper-2D在x L>2区域的最大等效水膜厚度小于0.2 μm，但MLN-A有效清扫面积比Taper-A的喷管提高15%以上，清扫性能最优。
结论喷管短化设计方法可以有效缩短喷管。
喷管结构对清扫性能影响较大。
MLN-A喷管的清扫性能最优。
关键词：超音速喷管；气动设计；大涡模拟；外流场；清扫性能中图分类号：U270.1+1 文献标识码：A 文章编号：1672-9242(2023)08-0090-08DOI：10.7643/ issn.1672-9242.2023.08.012Aerodynamic Design and Performance Comparison of SupersonicNozzle Using Airflow SweepingZHAO Hong-xing1, LU Yao-hui1, WANG Bei-kun1, TANG Bo1, LUO Yin-sheng2, CHEN De-jun2, MAO Rong-sheng2(1. School of Mechanical Engineering, Southwest Jiaotong University, Chengdu 610031, China;2. Tangshan Baichuan Intelligent Machine Co., Ltd., Hebei Tangshan 063000, Chin)ABSTRACT: It is proposed to use a Laval nozzle to generate high-speed airflow to clean the water film attached to the solid surface. A central axisymmetric conical nozzle (Taper-A), a central axisymmetric Sivell nozzle (Sivell-A), a central axisymmet-ric minimum length nozzle (MLN-A), and a two-dimensional conical nozzle (Taper-2D) were designed. An LES numerical收稿日期：2023-03-27；修订日期：2023-05-09Received：2023-03-27；Revised：2023-05-09基金项目：四川省科技计划项目（2022YFG0251）Fund：Sichuan Science and Technology Programme (2022YFG0251)作者简介：赵宏星（1998—），男，硕士研究生，主要研究方向为空气动力学。
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大模型diffusion原理英文回答：Diffusion is a fundamental principle in large-scale modeling that describes the process of how substances or information spread through a system. It is commonly used in various fields such as physics, chemistry, biology, and social sciences to understand how different entities interact and propagate.In physics and chemistry, diffusion refers to the movement of particles from an area of high concentration to an area of low concentration. This is driven by the random motion of particles, which leads to a net flow of particles down the concentration gradient. For example, if you open a bottle of perfume in one corner of a room, the scent molecules will diffuse and spread throughout the entire room over time.In biology, diffusion is essential for variousbiological processes. For instance, oxygen and carbondioxide are exchanged in the lungs through the process of diffusion. Oxygen molecules move from the air sacs in the lungs to the bloodstream, where they are transported to different parts of the body. Similarly, carbon dioxide molecules produced as waste in cells diffuse from the bloodstream to the lungs, where they are exhaled.In social sciences, diffusion is used to study the spread of ideas, innovations, or behaviors within a population. It is often referred to as "cultural diffusion" or "social diffusion." For example, the adoption of new technologies, such as smartphones or social media platforms, can spread rapidly through a population through social networks and word-of-mouth. The diffusion of these innovations can be influenced by factors such as social influence, communication channels, and individual characteristics.Large-scale modeling of diffusion involves representing the system as a network of interconnected nodes. Each node represents a location, individual, or entity, and theconnections between nodes represent the pathways through which diffusion occurs. Mathematical models, such as the diffusion equation or network models, are used to simulate and analyze the spread of substances or information in the system.In conclusion, diffusion is a fundamental principle in large-scale modeling that describes how substances or information spread through a system. It is a universal phenomenon that can be observed in various fields, from physics and chemistry to biology and social sciences. Understanding diffusion is crucial for predicting and managing the spread of substances, ideas, or behaviors in complex systems.中文回答：扩散是大规模建模中的一个基本原理，描述了物质或信息在系统中的传播过程。
No1Feb第1期(总第224期)2021年2月机 械 工 程 与 自 动 化MECHANICAL ENGINEERING & AUTOMATION文章编号= 1672-6413(2021)01-0076-03底排弹动态特性及发射强度有限元分析贾晓玲(武警工程大学装备管理与保障学院，陕西西安710086)摘要：为有效规避底排弹发射过程中的安全隐患，运用ANSYS 仿真软件建立了某型底排弹的有限元模型,并进行了动态特性和发射强度仿真分析，得到弹丸前3阶固有频率、关键部位应力及应变云图，以此判断底 排弹整体是否满足设计初期的发射安全稳定性要求。
仿真数据与实验数据对比误差较小，验证了仿真结果的准确性。
关键词：底排弹；动态特性；发射强度；有限元中图分类号：TP391.7：TG413 文献标识码：A0引言底排弹发射时，由于弹丸在膛内运动受到各种载 荷的作用，各零部件会发生不同程度的变形，当变形超 过一定允许程度时会影响底排弹沿炮膛正确的运动, 严重时会使底排弹在膛内受阻，或底排弹零件发生破 裂甚至炸药被引爆等而发生膛炸事故。
为了预防这些 情况发生,有必要对底排弹进行发射强度分析。
底排 弹出炮口后，其固有频率与其飞行环境中的载荷频率 接近时，将威胁弹丸的弹道安全性和飞行稳定性，严重 情况下底排弹将碎裂。
因此底排弹固有频率的研究分 析十分必要⑴，这些参数可用于(重)设计过程,优化弹 丸系统的动态特性。
有限元分析方法作为一种强有力 的数值计算方法，具有数据运算速度快、分析成本低、 计算精度高、模型修改较方便等优点，广泛应用于国防 工业领域［6。
本文运用ANSYS 有限元分析软件对 某底排弹进行了动态特性和发射强度计算，以校核弹 丸的整体性能。
1底排弹动态特性分析1. 1 底排弹有限元模型建立某型号底排弹整体结构如图1所示，主要包括底 排装药、底排壳体、弹带、主装药、弹体、引信等部件。
1 —挡板；一底排装药；一底排壳体；一弹带;5 —主装药；6—弹体；一引信图1底排弹整体结构在底排弹的动态特性有限元分析中，主装药和底 排装药相对于弹体和底排壳体来说属于柔性体，且挡板相对于底排壳体来说体积较小，故可以作合理简化。
BZ反应||Belousov-Zhabotinski reaction, BZ reactionFPU问题||Fermi-Pasta-Ulam problem, FPU problemKBM方法||KBM method, Krylov-Bogoliubov-Mitropolskii method KS[动态]熵||Kolmogorov-Sinai entropy, KS entropyKdV 方程||KdV equationU形管||U-tubeWKB方法||WKB method, Wentzel-Kramers-Brillouin method[彻]体力||body force[单]元||element[第二类]拉格朗日方程||Lagrange equation [of the second kind] [叠栅]云纹||moiré fringe; 物理学称“叠栅条纹”。
[叠栅]云纹法||moiré method[抗]剪切角||angle of shear resistance[可]变形体||deformable body[钱]币状裂纹||penny-shape crack[映]象||image[圆]筒||cylinder[圆]柱壳||cylindrical shell[转]轴||shaft[转动]瞬心||instantaneous center [of rotation][转动]瞬轴||instantaneous axis [of rotation][状]态变量||state variable[状]态空间||state space[自]适应网格||[self-]adaptive meshＣ0连续问题||C0-continuous problemＣ1连续问题||C1-continuous problemＣＦＬ条件||Courant-Friedrichs-Lewy condition, CFL condition ＨＲＲ场||Hutchinson-Rice-Rosengren fieldＪ积分||J-integralＪ阻力曲线||J-resistance curveＫＡＭ定理||Kolgomorov-Arnol'd-Moser theorem, KAM theoremＫＡＭ环面||KAM torusｈ收敛||h-convergenceｐ收敛||p-convergenceπ定理||Buckingham theorem, pi theorem阿尔曼西应变||Almansis strain阿尔文波||Alfven wave阿基米德原理||Archimedes principle阿诺德舌[头]||Arnol'd tongue阿佩尔方程||Appel equation阿特伍德机||Atwood machine埃克曼边界层||Ekman boundary layer埃克曼流||Ekman flow埃克曼数||Ekman number埃克特数||Eckert number埃农吸引子||Henon attractor艾里应力函数||Airy stress function鞍点||saddle [point]鞍结分岔||saddle-node bifurcation安定[性]理论||shake-down theory安全寿命||safe life安全系数||safety factor安全裕度||safety margin暗条纹||dark fringe奥尔-索末菲方程||Orr-Sommerfeld equation奥辛流||Oseen flow奥伊洛特模型||Oldroyd model八面体剪应变||octohedral shear strain八面体剪应力||octohedral shear stress八面体剪应力理论||octohedral shear stress theory巴塞特力||Basset force白光散斑法||white-light speckle method摆||pendulum摆振||shimmy板||plate板块法||panel method板元||plate element半导体应变计||semiconductor strain gage半峰宽度||half-peak width半解析法||semi-analytical method半逆解法||semi-inverse method半频进动||half frequency precession半向同性张量||hemitropic tensor半隐格式||semi-implicit scheme薄壁杆||thin-walled bar薄壁梁||thin-walled beam薄壁筒||thin-walled cylinder薄膜比拟||membrane analogy薄翼理论||thin-airfoil theory保单调差分格式||monotonicity preserving difference scheme 保守力||conservative force保守系||conservative system爆发||blow up爆高||height of burst爆轰||detonation; 又称“爆震”。
索尼探梦之旅
时间：2019-05-15 10:27:50 | 作者：干旭栋
今天，妈妈带我和琦琦一家人一起去朝阳公园的索尼探梦科技馆玩。
一到公园买了票，我们就直奔索尼探梦科技馆，进了馆里，我就被各种各样的科技吸引了。
这里有叔叔、阿姨的讲解，我和琦琦玩的很开心，妈妈说我们俩都快要玩疯了。
最让我感兴趣的是叔叔做的三个实验。
第一个实验是静电水母，首先，叔叔拿出一个长条形气球和一块毛皮，他先拿气球磨擦毛皮，然后就产生静电，工作人员拿出道具，叔叔让我们猜是什么东西，小朋友们猜什么的都有，我也没猜对，叔叔说：“你们猜不?缋春苷?常，这是我养的一只宠物叫水母，它在睡觉，现在把它唤醒，工作人员一甩，叔叔用气球在它下面移动控制水母，好神奇啊！叔叔说：“这是因为气球和水母是同一种静电，它们相互排斥，所以叔叔就可以控制水母。
第二个是静电泡泡，它是由水、洗洁精和糖做成的，把泡泡吹破就像彩色的雪花一样，特别漂亮。
第三个实验是静电杯，它是由两个塑料杯和锡纸做的，在两个杯子上分别包上锡纸，两个杯子中间放上条条的锡纸，这个静电杯就做好了，在用皮毛磨擦就产生了静电，我和妈妈还上台体验了静电杯的实验，我的手被电了一下，太神奇了。
我们玩的很开心，也学到了许多知识。
可以变大变小的机器人作文English Answer:In the realm of innovation and technological advancement, the concept of a shape-shifting robot has captivated the imaginations of scientists, engineers, and science fiction enthusiasts alike. The prospect of creating a robotic entity with the ability to seamlessly alter its size and form holds immense potential for a wide range of applications, from medical interventions to industrial manufacturing.While the complete realization of such a marvel remains a subject of ongoing research, significant progress has been made in developing robotic systems capable of limited shape-shifting capabilities. Inspired by the extraordinary adaptations found in the natural world, researchers have explored various approaches to mimic the flexibility and versatility of biological organisms.One promising avenue involves the use of soft robotics, which utilizes flexible materials and actuators to create robots that can conform to complex surfaces and navigate challenging environments. By incorporating shape-memory materials or hydraulic systems, these robots can undergo reversible size changes, enabling them to squeeze through narrow passages or adapt their morphology to specific tasks.Another approach explores the potential ofreconfigurable modular robotics. These systems consist of individual robotic modules that can connect and disconnect, allowing them to assemble into different configurations. By varying the number and arrangement of modules, these robots can achieve a range of sizes and shapes, adapting todifferent functional requirements.Beyond physical shape-shifting, researchers are also investigating cognitive shape-shifting, where robots can adapt their internal representations and capabilities to match changing task demands. This involves developing algorithms and machine learning techniques that enable robots to learn and adapt to different scenarios, modifyingtheir behaviors and strategies accordingly.The potential applications of a fully functional size-changing robot are vast and far-reaching. In the medical field, such a robot could navigate the intricate anatomy of the human body, performing minimally invasive procedures or delivering targeted therapies. In manufacturing, it could optimize assembly processes, adapting its size and shape to fit precisely within production lines.Furthermore, size-changing robots could revolutionize exploration and disaster response. By altering their dimensions, they could access remote and inaccessible areas, gather vital information, or provide assistance in hazardous environments. The ability to adjust their size would allow them to traverse narrow spaces, scale obstacles, or operate in confined spaces.However, the development of fully autonomous size-changing robots presents several challenges. Ensuring stability and control during size changes, coordinating complex movements, and addressing power requirements areamong the technical hurdles that need to be overcome. Additionally, ethical considerations must be addressed to ensure that such technology is used responsibly and without malicious intent.Despite the challenges, the pursuit of size-changing robots holds immense promise for advancing robotics technology and unlocking unprecedented possibilities in various fields. As research continues and innovative solutions emerge, we can anticipate the advent of robotsthat can seamlessly adapt their size and shape, revolutionizing our interactions with technology andshaping the future of industry and human endeavors.中文回答：变大变小的机器人。
Introduction:This tutorial demonstrates how to model the2D turbu-lentflow across a circular cylinder using LES(Large Eddy Simula-tion),and computeflow-induced noise(aero-noise)using FLUENT’s acoustics model.In this tutorial you will learn how to:•Perform2D Large Eddy Simulation(LES)•Set parameters for an aero-noise calculation•Save surface pressure data for an aero-noise calculation•Calculate aero-noise quantities•Postprocess an aero-noise solutionPrerequisites:This tutorial assumes that you are familiar with the menu structure in FLUENT,and that you have solved or read Tu-torial1.Some steps in the setup and solution procedure will not be shown explicitly.Problem Description:The problem considers turbulent airflow over a2D circular cylinder at a free stream velocity U of69.19m/s.The cylinder diameter D is1.9cm.The Reynolds number based on theflow parameters is about90000.The computational do-main(Figure3.0.1)extends5D upstream and20D downstream of the cylinder,and5D on both sides of it.If the computational domain is not taken wide enough on the downstream side,so that no reversedflow occurs,the accuracy of the aero-noise prediction may be affected.The rule of thumb is to take at least20D on the downstream side of the obstacle.c Fluent Inc.June20,20023-1Aero-Noise Prediction of Flow Across a Circular CylinderAero-Noise Prediction of Flow Across a Circular Cylindernoise.msh.File−→Read−→Case...As FLUENT reads the gridfile,it will report its progress in the console window.2.Check the grid.Grid−→CheckFLUENT will perform various checks on the mesh and will report the progress in the console window.Pay particular attention to the reported minimum volume.Make sure this is a positive number.3.Scale the grid.Grid−→Scale...(a)Under Units Conversion,select cm in the Grid Was Created indrop-down list.(b)Click on Scale.4.Display the grid.Display−→Grid...(a)Display the grid with the default settings(Figure3.0.2).(b)Use the middle mouse button to zoom in on the image so youcan see the mesh near the cylinder(Figure3.0.3).Quadrilateral cells are used for this LES simulation becausethey generate less numerical diffusion than triangular cells.Cell size should also be small enough to make numerical dif-fusion much smaller than subgrid scale turbulence viscosity.Extra:You can use the right mouse button to check which zone number corresponds to each boundary.If you clickthe right mouse button on one of the boundaries in thegraphics window,its zone number,name,and type will beprinted in the FLUENT console window.This feature is c Fluent Inc.June20,20023-3Aero-Noise Prediction of Flow Across a Circular CylinderAero-Noise Prediction of Flow Across a Circular CylinderAero-Noise Prediction of Flow Across a Circular CylinderAero-Noise Prediction of Flow Across a Circular CylinderAero-Noise Prediction of Flow Across a Circular CylinderAero-Noise Prediction of Flow Across a Circular CylinderAero-Noise Prediction of Flow Across a Circular CylinderAero-Noise Prediction of Flow Across a Circular CylinderAero-Noise Prediction of Flow Across a Circular CylinderAero-Noise Prediction of Flow Across a Circular CylinderAero-Noise Prediction of Flow Across a Circular Cylindernoise1.cas/dat).File−→Write−→Case&data...You can skip items9-12to avoid the time-consuming calculationsnecessary to get the“dynamically steady state”flowfield.Instead,you can read the corresponding case and datafiles(cylnoise1.cas/dat).See Chapter28of the User’s Guide for more information on using3-14c Fluent Inc.June20,2002Aero-Noise Prediction of Flow Across a Circular CylinderAero-Noise Prediction of Flow Across a Circular Cylindernoise2.cas/dat).File−→Write−→Case&Data...Step7:Aero-Noise Calculation1.Save surface pressure variation data.(a)Set up the schemefile and user-defined functions(UDFs)foraero-noise calculation.i.Read the schemefile,normally located in the lib directory,to create the Acoustic-Parameters panel.File−→Read−→Scheme...ii.Select acousticAero-Noise Prediction of Flow Across a Circular CylinderAero-Noise Prediction of Flow Across a Circular Cylindernoisenoise noisenoisenoise whole for the File Name to Read Surface Pressure.FLUENT’s aero-noise calculation module operates on asinglefile of surface pressure data at a time.If the surfacepressure data is saved in separatefiles,you may want toconcatenate them into one singlefile.3-18c Fluent Inc.June20,2002Aero-Noise Prediction of Flow Across a Circular Cylinderacousticpowerpower db.xy for the File Name to Power Spectrum in dB Unit.(c)Changefile name for the surface monitor.Solve−→Monitor−→Surface...i.Click on Define next to monitor-1ii.In the Define Surface Monitor panel,change the name of the monitor from monitor-point-behind-pres1-1.outto monitor-point-behind-pres4-1.out.(d)Save case and datafiles(cylnoise4.cas/dat).File−→Write−→Case&Data...(g)Exit FLUENTFile−→ExitIt is necessary to exit parallel FLUENT because the followingaero-noise calculation is performed with an Execute On De-mand UDF,which can only be used in the serial version ofthe solver.2.Calculate aero-noise(a)Start the serial version of FLUENT.c Fluent Inc.June20,20023-19Aero-Noise Prediction of Flow Across a Circular Cylinderpar.scm).File−→Read−→Scheme...(c)Read case and datafiles(cylnoise noise noise noise noise noisenoise whole.If you did not perform the calculation to write thefiles thatwill be used in this step,you can continue by using the corre-spondingfiles provided in the documentation CD.(e)Use the Execute On Demand UDF to perform the aero-noisecalculation.Define−→User-Defined−→Execute On Demand...(f)Select the cal-sound UDF and click Execute.Note:There is a limit to the minimum number of time steps ac-cording to the sound calculation scheme.The minimum num-ber of time steps needs to be larger than n=T/dt,where Tis the propagation time through a distance L,roughly equalto the length scale of the sound generating wall,and dt is thetime step size applied in the unsteady calculation.If the givennumber of time steps for cal-sound is smaller than the requiredminimum number,a warning will be printed on FLUENT’sconsole window,along with the indication of the minimumnumber<n>of time steps requiredWarning:Number of Time Steps of The Input Surface Data Must be Larger Than:<n>.3-20c Fluent Inc.June20,2002Aero-Noise Prediction of Flow Across a Circular Cylinder1.69e+021.52e+021.35e+021.19e+021.02e+028.49e+016.80e+015.12e+013.43e+011.75e+016.49e-01Figure3.0.7:Velocity Vectors2.Display contours of static pressure at the current time step(Fig-ure3.0.8).Display−→Contours...3.Inspect the Sound Pressure Level(SPL)value.The the value ofsound intensity in units of W/m2and its alternative expression in dB are printed in the FLUENT console window after the execution of the cal-sound UDF,and areIntensity=4.060634e+00(W/m2)SPL=1.261719e+02(dB)c Fluent Inc.June20,20023-21Aero-Noise Prediction of Flow Across a Circular Cylinder3.91e+031.78e+03-3.56e+02-2.49e+03-4.62e+03-6.75e+03-8.89e+03-1.10e+04-1.32e+04-1.53e+04-1.74e+04Figure3.0.8:Static Pressure Contours4.Plot Acoustic Pressure variation(Figure3.0.9).Plot−→File...(a)Click on Add.(b)Select thefile cyl pres.xy and click OK.Remember to delete thefiles you do not want to display from theFiles list.5.Plot Power Spectrum of sound pressure(Figure3.0.10).(a)Power Spectrum in units of P a2.Plot−→File...i.Click on Add.ii.Select thefile cyl spectrum.xy and click OK.Figure3.0.10shows a frequency range of0−2000Hz,withmajor and minor rules turned on.From thisfigure it can be 3-22c Fluent Inc.June20,2002Aero-Noise Prediction of Flow Across a Circular CylinderAero-Noise Prediction of Flow Across a Circular Cylinderpower db.xy and click OK .Frequency (Hz)5.00e+016.00e+017.00e+018.00e+019.00e+011.00e+021.10e+021.20e+0201e+032e+033e+034e+035e+036e+037e+038e+039e+031e+04Power Spectrum (dB)Figure 3.0.11:Plot of Power Spectrum of Sound Pressure.Figure 3.0.11shows a frequency range of 0−10kHz .6.Inspect Surface Dipole Strength.(a)Display contours of Surface Dipole Strength on surface cylin-der (Figure 3.0.12).Display −→Contours...i.In the Contours Of drop-down lists,select User-DefinedMemory and udm-0.ii.Turn offNode Values .3-24cFluent Inc.June 20,2002Aero-Noise Prediction of Flow Across a Circular Cylinder4.13e+053.72e+053.31e+052.89e+052.48e+052.07e+051.65e+051.24e+058.25e+044.12e+04-1.94e+02Figure3.0.12:Contour of Surface Dipole Strengthiii.Click on Display.The value of Surface Dipole Strength for each cell face is storedfor the center of the face on the cylinder wall.Surface DipoleStrength is the distribution of unit area contribution on thesound generating surface to the intensity of sound measuredat the observer’s location.(b)Plot Surface Dipole Strength(udm-0)on surface cylinder(Fig-ure3.0.13).Plot−→XY Plot...Figure3.0.13shows Surface Dipole Strength distribution onboth the upper and lower half cylinder faces.Extra:Once theflow simulation reaches a“dynamically steady state”, the accuracy for predicting Sound Pressure Level(SPL)and Power Spectrum is usually dependent on the number of time steps used.LES requires a mesh size as small as the length scale of eddies in the inertial sub-range.The corresponding time step size is calcu-c Fluent Inc.June20,20023-25Aero-Noise Prediction of Flow Across a Circular CylindercylinderFigure3.0.13:Plot of Surface Dipole Strengthlated by dt=Cdx/U,where C is the Courant number,and thus isvery small compared with the period T of the dominating acousticwave component(i.e.that corresponding to the frequency of thehighest peak in the power spectrum).For an accurate aero-noiseprediction,at least10periods of the dominating wave componentare required for sampling.The number of time steps for this re-quirement can be roughly estimated for theflow over the cylinder.In a certain Reynolds number range(roughly Re<50000),theStrouhal number(St=fD/U)for the dominating frequency f isabout0.2.Therefore,the period is T=D/0.2/U.From the aboveequations,the number of time steps for each period can be calcu-lated as N=T/dt=5/CD/dx.In LES,the ratio between thedomain scale D and the typical cell size dx can easily be50-100.As an example,if C is taken as order of1,N can be as high as250-500for each period.For40periods,10000-20000time stepsmay be required.Summary:This tutorial demonstrated how to set up and calculate an aero-noise problem for theflow around a cylinder,using the2D LES 3-26c Fluent Inc.June20,2002Aero-Noise Prediction of Flow Across a Circular CylinderAero-Noise Prediction of Flow Across a Circular Cylinder。
超大机器人作文英语Title: The Advent of Giant Robots: A Technological Marvel。
In the realm of science fiction and speculative technology, the concept of giant robots has always captured the imagination of humanity. From towering mechs to colossal humanoid machines, the idea of these massive constructs dominating the landscape has been a recurring theme in literature, movies, and popular culture. However, what was once confined to the realms of fantasy and imagination is now edging closer to reality, thanks to remarkable advancements in robotics and engineering. Inthis essay, we delve into the realm of super-sized robots, exploring their potential applications, technological challenges, and societal implications.The emergence of super-sized robots represents a significant milestone in the field of robotics. These colossal machines, often several stories tall, possessimmense strength, agility, and versatility, capable of performing a wide range of tasks previously deemed impossible for conventional robots. Whether it's industrial applications such as construction, mining, and manufacturing, or more specialized tasks like disaster response, space exploration, and defense, giant robotsoffer unparalleled capabilities and efficiency.One of the most promising applications of giant robots lies in the field of disaster response and recovery. In the aftermath of natural disasters such as earthquakes, hurricanes, or tsunamis, traditional rescue efforts are often hindered by the presence of debris, unstable structures, and hazardous conditions. Giant robots equipped with advanced sensors, manipulators, and mobility systems can navigate through treacherous terrain, clear debris, and locate survivors with greater speed and precision than human rescuers alone. Moreover, these robots can perform tasks such as building temporary shelters, repairing infrastructure, and delivering essential supplies, thereby expediting the recovery process and saving lives.Furthermore, giant robots hold immense potential in the realm of space exploration. With ambitions of establishing permanent settlements on the Moon, Mars, and beyond, the need for robust and adaptable robotic systems has never been greater. Giant robots can assist in the construction of habitats, extraction of resources, maintenance of infrastructure, and even the exploration of hostile environments such as lava tubes or polar regions. By leveraging the strength and dexterity of these colossal machines, space agencies can significantly reduce the cost, complexity, and risk associated with human missions to distant celestial bodies.However, the development and deployment of giant robots are not without challenges. One of the primary concerns is ensuring the safety and reliability of these massive machines, especially in dynamic and unpredictable environments. Engineering robust control systems, implementing redundant safety measures, and conducting rigorous testing are essential steps in mitigating therisks associated with operating giant robots in real-world scenarios. Moreover, the sheer scale and complexity ofthese machines pose logistical challenges in terms of transportation, maintenance, and power supply,necessitating innovative solutions and infrastructure support.Another critical consideration is the ethical and societal implications of integrating giant robots into various aspects of human life. As these machines become increasingly autonomous and capable of making complex decisions, questions regarding accountability, transparency, and job displacement arise. It is imperative to establish clear guidelines and regulations governing the use of giant robots, ensuring that they operate in accordance withethical principles and respect human dignity. Additionally, efforts must be made to mitigate any adverse effects on employment and livelihoods, perhaps through retraining programs, job diversification, or universal basic income initiatives.In conclusion, the emergence of giant robots represents a monumental leap forward in the field of robotics and technology. With their unparalleled strength, agility, andversatility, these colossal machines have the potential to revolutionize industries, advance scientific exploration, and enhance disaster response capabilities. However, realizing this potential requires overcoming significant technical, logistical, and ethical challenges. By addressing these challenges proactively and responsibly, we can harness the transformative power of giant robots for the betterment of humanity, ushering in a new era of innovation and progress.。
