Now being English, with a passion for aircraft and history, I cannot help but think of the work of Sir Barnes Wallis as I walk and skip stones over the waves. The story goes that prior to the 1943 Dambusters Raid, Sir Barnes Wallis spent weeks and months experimenting with marbles. His goal: to understand the complex physics involved in skipping objects off water before committing to flight tests and scale prototypes. And that got me to thinking, could you simulate a stone skipping on the water? It’s a very simple problem to describe in words, but one that’s very complicated to solve as it involves the modelling of motion dynamics, aerodynamics and hydrodynamics.! p% d' v* q+ t0 V9 w+ r! p a
作者想起了著名的巴恩斯沃利斯教授的跳跳炸弹摧毁水坝的历史事件，作者在想，怎么样模拟石头在水面跳跃的过程呢，用语言来描述很简单，但解决起来却很复杂，因为它涉及到运动动力学，空气动力学和流体力学等等。, Q: I2 | U( P. \
; ]; C/ L, G3 y6 l" @/ F8 g& fOnce I returned to the office I gave a call to my good friends at SSA to bounce (pun intended) a few ideas off them. In a strange alignment of happenstance, SSA had given their intern the task of recreating the work of Sir Barnes Wallis using Abaqus from SIMULIA. SSA are masters of FEA, and Abaqus in particular, and they were using the Coupled Eulerian Lagrangian (CEL) method in Abaqus to model the fluid structural interaction of a marble skipping over water.
/ o# G! N" N1 i( W# q. ~于是作者找来他的朋友，用abaqus来模拟这一过程，使用Abaqus中耦合欧拉拉格朗日（CEL）方法来模拟一个石头跳过水流结构的相互作用。
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. p2 ^2 B9 O W# SPut very simply the CEL method allows engineers and analysts to simulate time dependent processes that involve extreme deformation, or the calculation of the interaction of fluids and structural components amongst other capabilities.
. H0 c/ j2 F5 `; L, b9 E$ i" v, [% b/ E提出很简单的CEL方法使工程师和分析模拟涉及到极限形变，和流体和结构部件其中包括功能的相互作用的运算时间附属进程。
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5 Q' u3 t, _/ Q+ `In this model, the guys at SSA ‘threw’ a 10cm diameter steel ball with an initial velocity, Vx=10m/s, Vy=1m/s and an angle of attack 5.71° at a 5m long, 2m wide, 0.5m deep strip of water. Gravity was enabled together with the multi-physics response of the ball and water. CEL technology provided the tools for SSA to capture the time dependent aspect of the ball/water interaction in a single dynamic analysis.
& f5 O4 g9 D- M5 @! k( D在这个模型中，投手在SSA'扔'一个直径10厘米的不锈钢球，其初速度 Vx=10米/秒，Vy速度=1米/秒，投掷角度5.71° ，在5米长，2米宽，0.5米水深的条状水区域。重力作一起用于球和水的多物理响应。 CEL技术提供的工具对于SSA捕捉球/水相互作用的时间依赖性方面中，单一的动态分析。
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0 S. b: b9 K& m/ T. KThe results SSA were able to generate were amazing. What took Sir Barnes Wallis weeks and months of physical testing SSA recreated in days. I will let the images speak from themselves, but you can clearly see the impact areas, the wash created by each impact, and the number of bounces for each ‘throw’.
" u3 ?% C% T' x% b, r让图像自己说话，但你可以清楚地看到影响的领域，每个冲击造成的冲洗，和每个'扔'的数量的反弹 \/ f; k( ^( y M# c2 S
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The analysis allows us to see the rapidly shortening ‘skips’ as the ball loses energy before it finally sinks.. o4 K2 w9 r3 P) q* n: e6 N
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The great thing about simulation is that now SSA have a ‘working’ simulation model it is a relatively simple step to throw other objects of varying the initial conditions of the ball to achieve the perfect ‘throw’.. W7 o- ?# Z7 N0 t V H
Now I don’t claim to be an expert in the application CEL technology, but if you have a problem where you want to capture time varying results, include multi-physics interactions and large displacements/deformations are involved, then CEL technology is the way to go. I am constantly amazed at the power that today’s engineers have available to them. If you can dream it then with SOLIDWORKS and Dassault Systems you can design, test, and validate manufacturing and assembly processes before a single part has been produced.4 ]1 l4 a( f/ |8 Q
现在，我不声称在应用CEL技术方面的专家，但如果你有，你想捕捉时间变化结果的问题，包括多物理场相互作用和大位移/变形参与，那么CEL技术的方式去。我经常惊讶于当今的工程师们提供给他们的权力。如果你可以想像到，那就用solidworks来设计，用abaqus来验证你的设计。
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发表于 2015-6-5 14:01:10
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