共查询到19条相似文献,搜索用时 203 毫秒
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聚变堆液态金属包层矩形管道中的氚输运过程与磁流体动力学(MHD)流动传热过程耦合在一起,形成了复杂的载氚热磁流体输运特性。基于开发的MHD流动与传热数值模拟程序对矩形管道中液态金属MHD流动传热特性及其氚输运的影响进行了数值模拟。该程序首先求解了动量守恒方程,并与理论解进行了对比验证,然后与能量守恒方程耦合求解,得到了温度影响下矩形管道中的液态金属流场分布,在此基础上对强磁场高核热梯度影响下的氚浓度分布进行了数值模拟,得到了氚浓度在管道中的分布特性。结果显示,液态金属在矩形管道中的流动传热对氚输运过程产生了显著影响。 相似文献
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液态金属磁流体动力学(MHD)效应是聚变堆液态包层需要解决的关键问题之一。通过实验与数值模拟相结合的方法,研究了高特征参数下绝缘圆管内液态金属MHD效应,获得了强磁场下绝缘圆管内压降变化和流速分布的规律。研究结果表明,绝缘圆管内液态金属MHD压降随外加磁场强度的增加而线性增大,随管道内平均流速的增加也呈线性增长的关系,且压降实验结果与数值模拟及理论结果吻合较好;流速分布的特点为哈特曼层内流速变化剧烈,速度梯度大。基于压降的实验数据分析可得,强磁场环境下绝缘圆管中层流湍流的转换分界点约为Re/Ha=45。 相似文献
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运用零维模型分析了液态锂作为包层流动液帘与堆芯等离子体的兼容性,得到了液态锂工作温度对堆芯有效平均等离子体电荷Zeff、燃料稀释以及聚变功率之间的关系。结果表明在正常工作情况下,液态锂的蒸发对Zeff的影响不是很严重,但对燃料稀释和聚变功率的影响却较为敏感。在具有较高功率密度的反剪切位形聚变实验增殖堆FEB E设计方案Ⅱ的条件下,计算了液态锂的流速与它表面最大温升的关系,结果表明,即便对0.5m·s-1的低速流动液态锂,其蒸发对聚变等离子体的影响甚微。最后对氢同位素饱和状态下液态锂包层表面的溅射作了初步的讨论。 相似文献
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分支管道引起的磁流体动力学(MHD)效应是磁约束聚变堆液体金属包层或自冷包层的关键问题之一。然而,由于磁流体的复杂性和实验条件的限制,尤其2维(2D)和3维(3D)效应的实验数据还很少,分支管道的MHD效应实验结果尚未见报道,而且MHD压降理论值与实验值相差10%-25%,何种原因尚未深究。继开展流出分支管道引起的磁流体动力学(MHD)效应研究之后,我们利用国际合作渠道提供的仪器和国内唯一专门研究磁流体动力学效应液态金属回路,开展了3维和3维磁流体动力学效应实验研究。 相似文献
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采用三维计算流体动力学(CFD)方法对聚变堆液态包层增殖区高温液态铅锂与结构内高压氦气耦合换热进行数值模拟。建立了充放式高压氦气回路和换热实验段,开展了包层典型工况下液态铅锂与氦气多流场耦合换热对比实验验证。研究了氦气压力和增殖区铅锂入口温度、核热功率密度变化时的流动与传热特性及其影响规律,获得了氦气与RAFM钢壁面、液态铅锂与RAFM钢壁面之间的换热系数和换热关联式,为液态包层的设计研发提供了参考依据。 相似文献
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《中国科学:物理学 力学 天文学(英文版)》2010,(10)
Direct numerical simulation (DNS) of incompressible magnetohydrodynamic (MHD) turbulent channel flow has been performed under the low magnetic Reynolds number assumption.The velocity-electric field and electric-electric field correlations were studied in the present work for different magnetic field orientations.The Kenjeres-Hanjalic (K-H) model was validated with the DNS data in a term by term manner.The numerical results showed that the K-H model makes good predictions for most components of the velocity-electric field correlations.The mechanisms of turbulence suppression were also analyzed for different magnetic field orientations utilizing the DNS data and the K-H model.The results revealed that the dissipative MHD source term is responsible for the turbulence suppression for the case of streamwise and spanwise magnetic orientation,while the Lorentz force which speeds up the near-wall fluid and decreases the production term is responsible for the turbulence suppression for the case of the wall normal magnetic orientation. 相似文献
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A one-equation turbulence model which relies on the turbulent kinetic energy transport equation has been developed to predict the flow properties of the recirculating flows. The turbulent eddy-viscosity coefficient is computed from a recalibrated Bradshaw’s assumption that the constant a1 = 0.31 is recalibrated to a function based on a set of direct numerical simulation (DNS) data. The values of dissipation of turbulent kinetic energy consist of the near-wall part and isotropic part, and the isotropic part involves the von Karman length scale as the turbulent length scale. The performance of the new model is evaluated by the results from DNS for fully developed turbulence channel flow with a wide range of Reynolds numbers. However, the computed result of the recirculating flow at the separated bubble of NACA4412 demonstrates that an increase is needed on the turbulent dissipation, and this leads to an advanced tuning on the self-adjusted function. The improved model predicts better results in both the non-equilibrium and equilibrium flows, e.g. channel flows, backward-facing step flow and hump in a channel. 相似文献
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Direct numerical simulation of elastic turbulence and its mixing-enhancement effect in a straight channel flow 下载免费PDF全文
In this paper,we present a direct numerical simulation(DNS) of elastic turbulence of viscoelastic fluid at vanishingly low Reynolds number(Re = 1) in a three-dimensional straight channel flow for the first time,using the Giesekus constitutive model for the fluid.In order to generate and maintain the turbulent fluid motion in the straight channel,a sinusoidal force term is added to the momentum equation,and then the elastic turbulence is numerically realized with an initialized chaotic velocity field and a stretched conformation field.Statistical and structural characteristics of the elastic turbulence therein are analyzed based on the detailed information obtained from the DNS.The fluid mixing enhancement effect of elastic turbulence is also demonstrated for the potential applications of this phenomenon. 相似文献
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采用FLUENT软件分别对外加均匀横向磁场的等截面三维充分发展液态金属管流的层流模型和低雷诺数湍流Lam/Bremhost(LB)模型进行了数值模拟,分析了外加磁场对普通方管LB模型速度分布和压降的影响。比较在相同哈特曼数下,层流和湍流模型方管截面上速度分布和管道中MHD压降。其中,对电流的计算采用磁感应方程来求得。数值模拟结果证明了用低雷诺数LB湍流模型解决方管磁流体流动的可行性。通过层流模型和湍流模型的对比可知,层流模型有较短的入口长度,但管内流体的压降却很大;而湍流模型管内速度更加平均化,管内压降较小,但管内入口长度较长。 相似文献
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为研究引流条对磁流体湍流的影响,采用自主开发的低磁雷诺数流固耦合磁流体相干结构模型大涡模拟求解器,对均匀磁场作用下平行层内带引流条导电矩形管和标准导电矩形管中液态金属湍流进行了数值模拟研究。结果表明,外加垂直流动方向的均匀磁场与流动的导电流体相互作用产生与流动方向相反的洛伦兹力,能够抑制磁流体的湍流脉动,这种抑制作用随着哈特曼数增大而增强。在弱导电率条件下,当Re=16350、Ha=212 时,两种管道中的流动均转换为层流流动状态。管道内壁面摩擦系数随着哈特曼数的增大而增大。引流条能在其近壁局部区域增强横向速度,有效激发湍流,但在弱壁面导电率条件下,带引流条导电矩形管壁面摩擦系数较标准矩形管大。 相似文献
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《中国科学:物理学 力学 天文学(英文版)》2010,(9)
A theoretical model of turbulent fiber suspension is developed by deriving the equations of Reynolds averaged Navier-Stokes,turbulence kinetic energy and turbulence dissipation rate with the additional term of fibers.In order to close the above equations,the equation of probability distribution function for mean fiber orientation is also derived.The theoretical model is applied to the turbulent channel flow and the corresponding equations are solved numerically.The numerical results are verified by comparisons with the experimental ones.The effects of Reynolds number,fiber concentration and fiber aspect-ratio on the velocity profile,turbulent kinetic energy and turbulent dissipation rate are analyzed.Based on the numerical data,the expression for the velocity profile in the turbulent fiber suspension channel flow,which includes the effect of Reynolds number,fiber concentration and aspect-ratio,is proposed. 相似文献
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采用理论分析和数值模拟相结合的方法,系统研究了尺度自适应模拟(scale-adaptive simulation,SAS)和大涡模拟(large-eddy simulation,LES)的关联性问题.在理论分析方面,对比分析了系综平均和滤波的定义、Spalart-Allmaras(SA)湍流模型和动态亚格子(subgrid-scale,SGS)模型关于湍流黏性系数的求解方式.理论分析结果表明,系综平均等价于盒式直接滤波,SAS和LES的控制方程在数学形式上具有一致性;SAS存在过多的湍流耗散,主要来自于SA输运方程中的扩散项.在数值模拟方面,选取来流Mach数0.55,Reynolds数2×105的圆柱可压缩绕流为分析算例.计算结果表明,SAS和LES预测的大尺度平均流场信息几乎一致,SAS预测的湍流脉动信息略低于LES.SAS在圆柱近尾迹区的湍流耗散过大,而在稍远的尾迹区几乎能够完全等效于LES. 相似文献
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LIU Nansheng LU Xiyun & ZHUANG Lixian Department of Mechanics Mechanical Engineering University of Science Technology of China Hefei China 《中国科学G辑(英文版)》2004,47(4):463-476
Rotating turbulence occurs extensively in nature and engineering circumstances. Meanwhile, understanding physical mechanisms of the rotating turbulence is important to the fundamental research of turbulence. The turbulent flow in rotating frames undergoes two kinds of Coriolis force effects. First, a secondary flow is induced in the case that there is a mean vorticity component perpendicular to the rotating axis. Second, there are augmenting or suppressing effects on the turbulence if there i… 相似文献
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采用直接数值模拟方法,对槽道湍流中确定分布的Lorentz力的流动控制与减阻问题进行研究.讨论了Lorentz力作用于槽道湍流后,流场的特性和涡结构的特性,并对此类Lorentz力对槽道湍流的控制与减阻机理进行了讨论.研究发现:1)Lorentz力诱导的层流流场壁面附近存在梯度极大的展向速度剪切层,该剪切层容易形成流向涡结构;2)在给定合适参数的确定分布的Lorentz力作用下,湍流流场仅剩周期分布的准流向涡;3)与未控制流场相比,控制后的流场中,准流向涡的抬升高度大大降低,从而减小猝发强度,使壁面阻力下降. 相似文献