共查询到19条相似文献,搜索用时 140 毫秒
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发展了一种基于MOF(Moment of Fluid)界面重构的二维中心型MMALE(Multi-Material Arbitrary Lagrangian-Eulerian)方法.其中,流体力学方程组采用中心型拉氏方法进行离散求解.混合网格的热力学封闭采用Tipton压力松弛模型.混合网格内的界面重构采用MOF方法,并对MOF方法作了简化和改进.重映步采用一种基于多边形剪裁算法的精确积分守恒重映方法.计算了若干数值例子,包括二维漩涡发展问题、Sedov问题、激波与氦气泡相互作用问题、水中强激波与空气泡相互作用问题、二维RT不稳定性问题等.数值算例表明,该方法具有二阶精度,能够计算界面两侧密度比和压力比很大的问题,并且其健壮性优于交错型MMALE方法,适合计算多介质复杂流体动力学问题. 相似文献
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研制了二维多介质流体程序,主要包括单介质内高精度流体力学计算,多介质混合网格内各种介质输运过程和压力驰豫平衡过程计算、实际状态方程的黎曼解计算。流体计算分别采用高分辨两步PPM(Parabolic Piecewise Method)算法、TVD(Total Variation Diminishing)算法和FCT(Flux Corrected—Transport)算法,流体界面追踪采用VOF(Volume-of-Fluid)。数值求解可压缩多流体方程组和可压缩VOF方程。二维界面追踪分别采用一阶精度Youngs方法和二阶精度Elivira方法,三维界面追踪采用一阶精度Youngs方法, 相似文献
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为满足分层掺杂点火内爆靶辐射驱动不对称性全过程物理分析的需求,在激光聚变二维总体程序LARED集成上发展了辐射输运建模下的多介质ALE方法-RTALE(Radiative Transfer Arbitrary-Lagrangian-Eulerian)。为提高多介质ALE方法的健壮性,发展了驰豫网格重构算法,该重构算法生成的新网格能自适应流场的变化。数值模拟了激波与气柱相互作用的RM不稳定性实验,模拟的气泡变形程度与试验结果基本一致,其中驰豫网格重构算法中的驰豫因子能够很好地反映流场密度梯度。基于辐射多群输运建模的LARED集成程序能够完整模拟辐射驱动不对称性条件下掺杂点火靶二维内爆过程,克服了传统ALE方法计算不下去和算不好的困难,界面变形程度也符合物理分析。 相似文献
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基于MOF界面重构的多物质ALE方法 总被引:2,自引:0,他引:2
提出一种基于MOF(Moment-of-Fluid)界面重构的多物质ALE(Arbitrary Lagrangian-Eulerian)方法.流体力学方程组采用相容有限元方法进行空间离散.提出一种新的二维子网格力学模型,用来计算混合网格中的物理量经过一个拉氏步后发生的变化,混合网格内的界面重构采用MOF方法.提出一种精确积分守恒重映方法.给出数值算例,如空气和水的Riemann问题,Dukowicz问题,水中强激波与空气泡相互作用问题等.结果表明,方法具有较高的精度,能够处理物质界面和网格的大变形问题. 相似文献
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在采用Youngs界面重构技术的基础上,对三维欧拉方法混合网格的计算格式进行了研究。运用Youngs技术确定界面后,混合网格内每一部分物质一般不再是正规的六面体结构,可能是非规则的四面体、五面体、六面体或七面体。本文采用对非规则网格适应性很强的有限体积法对每一部分分别进行计算,给出了混合网格内每种物质的压力、速度、能量等的计算公式,比较有效地解决了混合网格的计算问题。 相似文献
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王丽丽 《工程物理研究院科技年报》2004,(1):352-352
用TVD格式结合VOF界面处理方法编制了二维多介质高分辨欧拉程序,以解决冲击波和多介质界面处理。程序包括单介质网格高精度流体力学计算、多介质网格内界面重构、各种介质输运和压力驰豫平衡过程。其中单介质网格的计算采用Harten二阶TVD格式结合MacCormark方法计算含有源项的非齐次守恒定律方程组,通过4节点限制函数保证格式单调。多介质网格采用Youngs方法构造界面,采用x,y方向分裂格式计算体积份额输运,再根据体积份额输运计算质量、动量和能量的输运,最后利用等熵条件计算各种介质的压力驰豫平衡过程。 相似文献
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Stefano Carli Wouter Dekeyser Reinart Coosemans Renaud Dejarnac Michael Komm Miglena Dimitrova Jiří Adámek Petra Bílková Petr Böhm 《等离子体物理论文集》2020,60(5-6):e201900155
Mean-field plasma edge transport codes such as SOLPS-ITER heavily rely on ad-hoc radial diffusion coefficients to approximately model anomalous transport. Such coefficients are experimentally determined and vary between different machines, and also depend on the operational regime and plasma location within the same device. Therefore, to match experimental data the modeller is required to manually tune several free parameters in expensive simulations, and the code's predictive capabilities are significantly downgraded. As a solution, a new model has been developed for SOLPS-ITER, solving an additional transport equation for the turbulent kinetic energy k, derived by consistently time-averaging the Braginskii equations, and including a diffusive closure for the anomalous particle flux. This closure model relates the anomalous diffusion coefficient to the local k value. The resulting equation structure and its closure are inspired by TOKAM2D isothermal interchange turbulence simulation results. Within this model, fewer and hopefully more universal free parameters are retained, thus improving the code's predictive capabilities. The new model has been tested on a COMPASS case for which upstream plasma profiles were available. Experimental data and a reference solution, obtained by matching the profiles through manual tuning of radial diffusivities, have been used to estimate the parameters of our new transport model. A ballooned particle diffusivity profile is retrieved by the new radial transport model, thanks to the proposed interchange drive. The obtained upstream profiles qualitatively agree with the experiment and prove the new model is a promising first attempt to be further refined. 相似文献
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S. Chudzik 《Infrared Physics & Technology》2012,55(1):73-83
The article presents results of research developing methods for determining thermal parameters of a thermal insulating material. This method applies periodic heating as an excitation and an infrared camera is used to measure the temperature distribution on the surface of the tested material. The usefulness of known analytical solution of the inverse problem was examined in simulation study, using a three-dimensional model of the heat diffusion phenomenon in the sample of the material under test. To solve the coefficient inverse problem an approach using an artificial neural network is proposed. The measurements were performed on an experimental setup equipped with a ThermaCAM PM 595 infrared camera and a frame grabber. The experiment allowed verification of the chosen 3-D model of the heat diffusion phenomenon and proved suitability of the proposed test method. 相似文献
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S. Chudzik 《Opto-Electronics Review》2012,20(1):40-46
The article presents the results of research developing methods for determining the coefficient of thermal diffusivity of
thermal insulating material. This method applies a periodic heating as an excitation and an infrared camera is used to measure
the temperature distribution on the surface of tested material. In simulation study, the usefulness of known analytical solution
of the inverse problem was examined using a three-dimensional model of the phenomenon of heat diffusion in the sample of tested
material. To solve the coefficient inverse problem, an approach using artificial neural network is proposed. The measurements
were performed on an experimental setup equipped with a ThermaCAM PM 595 infrared camera and frame grabber. The experiment
allowed to verify the chosen 3D model of heat diffusion phenomenon and to determine suitability of the proposed test method. 相似文献
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惯性约束聚变研究中,热辐射光子在介质中的输运以及热辐射光子与介质的相互作用是重要研究课题,蒙特卡罗方法是该类问题的重要研究手段之一.隐式蒙特卡罗方法虽然能正确地模拟热辐射在介质中的输运过程,但当模拟重介质(材料的吸收系数大)问题时,该方法花费的计算时间将变得很长,导致模拟效率很低.本文以离散扩散蒙特卡罗方法为基础,开发了"离散扩散蒙特卡罗方法辐射输运模拟程序",可以较好地解决重介质区的计算效率问题,但是离散扩散蒙卡罗方法在模拟轻介质区时精度不够高.辐射输运问题中通常既有轻介质也有重介质,为了能同时解决蒙特卡罗方法模拟的效率和精度问题,本文研究了离散扩散蒙特卡罗方法与隐式蒙特卡罗方法相结合的模拟方法,并提出了新的扩散区与输运区界面处理方法,研制了混合蒙特卡罗方法的辐射输运模拟程序.典型辐射输运问题模拟显示:在模拟重介质问题时,该程序能大幅缩短模拟时间,且能取得与隐式蒙特卡罗方法一致的结果;在模拟轻重介质均存在的问题时,与隐式蒙特卡罗方法相比,混合蒙特卡罗方法的模拟精度与其相当且计算效率同样能够得到显著提升. 相似文献
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主动中子多重性计数测量方法是常用的核材料质量无损测量方法,已广泛应用于核材料衡算、核安保测量与军控核查等领域。我们通过对JMCT中子-光子输运程序的二次开发,实现了对经典点模型铀样品质量估算实验的数值模拟,并提出了改进的铀样品质量计算公式。该算法可以显著降低本实验中源-样品耦合与源中子反照等作用对铀样品质量估算精度的影响。建立了主动中子多重性计数测量探测系统模型和32个铀样品半球壳模型,模拟得到了与铀样品距离不同的DT源和AmLi源主动中子多重性计数,利用数值模拟手段检验了质量估算算法的有效性。数值模拟结果表明,改进的铀质量估算算法可以使质量估算的平均偏差率降低到10%以下。 相似文献
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Gordon L. Olson 《Journal of Quantitative Spectroscopy & Radiative Transfer》2012,113(5):325-334
Current theories for approximating the effects of stochastic media on radiation transport assume very limited physics such as one dimension, constant grey opacities, and no material energy balance equation. When applied to more complex physical problems, the standard theory fails to match the results from direct numerical simulations. This work presents the first direct numerical simulations of multigroup radiation transport coupled to a material temperature equation in a 2D stochastic medium that are compared to closures proposed by various authors. After extending it from grey to multigroup physics, one closure that is not commonly used successfully models the results in dilute systems where one material comprises less than 5% of the total. This closure is more accurate for related grey transport problems than it is for the multigroup problem. When the specific heats are material- and temperature-dependent, it is much more difficult to fit the direct numerical solutions with an approximate closure. 相似文献