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结合表征体元尺度的通用渗流模型,提出离散统一动理学格式(DUGKS)渗流方法,分别用均匀网格和非均匀网格计算二维Poiseuille、Couette、方腔流等经典渗流问题,检验DUGKS渗流方法的有效性和非均匀网格应用的优势,将DUGKS渗流方法应用到裂缝系统中. 相似文献
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《工程热物理学报》2016,(1)
流体在临界点附近参数区域,其黏性系数、比热容、导热系数、密度等热物理性质都会发生剧烈变化,因此超临界流体在多孔介质中的渗流特性较为复杂,常规流体多孔渗流压降特性规律能否适用有待于验证。以超临界水煤气化技术为代表的一系列高新技术的发展对多孔介质中超临流体的渗流特性的认识提出了更高的要求。本文考察了典型操作参数(温度300~450℃,压力22.7~25 MPa,流量0.8~3 kg.h~(-1))对多孔介质中超临界水渗流压降特性的影响。研究结果表明:Ergun公式在估算多孔介质中超临界水渗流压降的过程,黏性项被高估,惯性项被低估。本工作有望为超临界水煤气化技术中超临界水流化床的设计提供依据。 相似文献
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以空心玻璃微球为研究对象,利用高压充气系统充气,测量了不同条件下玻璃微球对氘气在室温条件下的气体渗透系数。研究结果表明:微球的壁厚对气体渗透系数影响较大,2 mm以上厚壁球的气体渗透系数约5.0×10-22 mol·m-1·s-1·Pa-1,而壁厚小于1 mm时,渗透系数约1.56×10-20 mol·m-1·s-1·Pa-1,两者相差30倍。预充气挑选工艺对微球的气体渗透系数也产生一定影响,对于薄壁空心玻璃微球一次充放气气体渗透系数增加约50%,两次充放气则增大一倍左右。对上述影响因素进行了初步的探讨,气体渗透系数改变的主要原因是玻璃微球表面的结构裂纹、空位和缺陷。 相似文献
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孔隙渗流是多孔介质渗流的微观基础。本文对孔隙中的两相流应用分相模型,结合达西渗流定律,提出了适用于油水两相的相对渗透率模型,得到相对渗透率与孔隙度无关、相对渗透率只是微孔隙中相态分布的几何尺度以及流体饱和度的函数等结论。设计了微流动实验装置,以去离子水和白油的乳化液为两相流体,在不同含油率下研究了微孔隙中油水两相的渗流特性,并与相应条件下的模型计算结果进行对比。结果表明,对于低渗透尺度等级的微孔隙,实验与计算结果吻合较好,对于高渗透尺度等级的微孔隙,实验与计算结果存在偏差。在某些条件下,油与水的相对渗透率之和存在大于1的情形。 相似文献
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纵向受迫振荡圆柱绕流问题的数值模拟 总被引:2,自引:0,他引:2
用有限体积法对平行于均匀来流方向受迫振荡的圆柱绕流问题进行了二维数值模拟.雷诺数选取Re=200、855、4000等几种亚临界雷诺数情况.通过研究不同振幅和振动频率下的流场结构和一些重要流动参数如升阻力系数、Strouhal数等随Re数、KC数、Stokes数的变化关系,验证了实验中观察到的一定条件下发生的"频率锁定"现象,并将涡脱落方式划分为三种主要模态.文中引入网格速度,对常用的处理速度与压力耦合的SIMPLE算法作了适当的补充和修改,以适应随时间变化的网格坐标. 相似文献
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The flow field around a rotationally oscillating circular cylinder in a uniform flow is studied by using a particle image
velocimetry to understand the mechanism of drag reduction and the corresponding suppression of vortex shedding in the cylinder
wake at low Reynolds number. Experiments are conducted on the flow around the circular cylinder under rotational oscillation
at forcing Strouhal number 1, rotational amplitude 2 and Reynolds number 2,000. It is found from the flow measurement by PIV
that the width of the wake is narrowed and the velocity fluctuations are reduced by the rotational oscillation of the cylinder,
which results in the drag reduction rate of 30%. The mechanism of drag reduction is studied by phase-averaged PIV measurement,
which indicates the formation of periodic small-scale vortices from both sides of the cylinder. It is found from the cross-correlation
measurement between the velocity fluctuations that the large-scale structure of vortex shedding is almost removed in the cylinder
wake, when the small-scale vortices are generated at the unstable frequency of shear layer by the influence of rotational
oscillation. 相似文献
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圆柱面上微小后向台阶层流绕流场的数值研究 总被引:2,自引:0,他引:2
1前言钩体绕流是燃烧、传热领域基本的流动现象,具有流动分离、流态转被、旋涡脱落、涡致振动等复杂特性。降低钩体绕流阻力一直是人们关心的问题。自从Prandtl圆球绊线实验以来,Stuper,Roshko,Zukausks,Achenbach,Klebanoff等[‘一列从不同角度研究了钝体绕流阻力的构成因素及降低钝体绕流阻力的若干方法。一致的观点是:因绕流钝体必然伴随着流动分离,流动阻力可分为与粘性有关的摩擦阻力及与流动分离有关的压差阻力两部分,其中,压差阻力约占总阻力的90N95%,其大小与流动分离点的位置密切相关。若流动分离时边界层内为层流… 相似文献
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基于高阶的间断有限元方法, 数值模拟低马赫数下并列圆柱的可压缩层流流动, 捕捉并列圆柱流场中的漩涡结构, 以便分析并列圆柱尾流的流动特性. 针对二维圆柱的边界形式, 采用曲边三角形单元构造二维圆柱的曲面边界, 以适应高阶离散格式的精度. 在验证方法合理性的基础上, 分析圆柱间距及雷诺数对漩涡脱落及受力特性的影响规律. 研究结果表明: 并列圆柱的间距是影响流场流动特性的一个主要因素, 它会改变圆柱漩涡脱落的形式. 随着圆柱间距的增加, 上下圆柱的平均阻力系数及平均升力系数的绝对值随之显著下降. 雷诺数对于平均阻力系数的影响相对较小. 但随着雷诺数的增加, 上下圆柱的平均升力系数会随之降低, 而漩涡的脱落频率会随之增大. 相似文献
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In the flow around a circular cylinder, a sudden decrease in the drag force occurs at a high Reynolds number, but the same
phenomenon occurs at a lower Reynolds number in the case where there exist grooves or roughness on the circular cylinder surface.
In this paper, in order to make clear the flow characteristics around a circular cylinder in the case of changing the shapes
of grooves, the drag coefficient, pressure distribution, velocity distribution and turbulent distribution were measured. Moreover
the flow around the cylinder was analyzed by applying the RNGk · ∈ turbulent model, and the surface flow pattern was investigated using the oil-film technique. From these results, it is clear
that the drag coefficient of a circular cylinder with triangular grooves decreases by about 15% compared with that of a circular
cylinder with arc grooves. 相似文献
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在本文中,我们提出了一个稳定的求解扩散——对流方程的Саульев型格式,并提出了它的单调性和自调性。最后将其应用于二维粘性不可压缩圆柱绕流的计算,与已发表的数值结果和实验结果相比较表明我们的计算结果是好的。 相似文献
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In a circular cylinder with uniform flow, a sudden decrease in the drag force occurs at a high Reynolds numbers; however,
it is known that the same phenomenon occurs at a lower Reynolds number in the case where there exist grooves or roughness
on the circular cylinder surface. To clarify the flow characteristics around a circular cylinder in the case of changing the
shape of grooves we analyzed the drag coefficient, lift coefficient, turbulent kinetic energy, vorticity and pressure by applying
the RNGk-ε turbulent model. The shapes of the grooves were arced, triangulated and curved. The results showed that the separation
point for a circular cylinder with curved sectional grooves shifts to the most downstream side and the drag coefficient becomes
the smallest among circular cylinders with grooves. 相似文献
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Heating effects of air flows past a two-dimensional circular cylinder at low Reynolds numbers and low Mach numbers are investigated by numerical simulation. The cylinder wall is heated partially rather than heated on the whole surface as with previous researches. The heating effects are completely different for various heating locations on the cylinder surface. Heating either windward or leeward side stabilizes the flow and reduces or completely suppresses vortex shedding from the cylinder at supercritical Reynolds numbers, which is consistent with previous results of heating on the whole surface of the cylinder. However, as the lateral sides of the cylinder (perpendicular to the stream-wise direction) are heated, an adverse effect is found for the first time in that the flow is destabilized and vortex shedding can be excited at subcritical Reynolds numbers. As the lateral sides of the cylinder are cooled, the flow is stabilized. 相似文献