共查询到20条相似文献,搜索用时 734 毫秒
1.
FENE-P流体混合层中拟序结构的研究 总被引:1,自引:0,他引:1
采用FENE-P模型对高雷诺数下二维粘弹性混合过程中拟序结构的演变进行了数值研究.由于对聚合物应力场采用了适当的滤波措施,得到了较AH更宽参数范围内FENE-P流体混合层流场中拟序结构的运动特性,计算结果表明:在流场中加入聚合物,基波和次谐波的发展受到抑制,涡量扩散加强,减慢了配对时两涡核的旋转运动,这种影响随Weissenberg数的增大而减小,但却随参数b的增大而加强.另外,与相同溶液粘度下的牛顿流体相比,配对过程中涡量完全合并的时刻延迟了. 相似文献
2.
3.
4.
5.
本对三维涡度方程单向周期初边值问题建立了一种Fourier拟谱-有限差分格式,分析了其广义稳定性和收敛性,数值结果显示了这种方法的特点。 相似文献
6.
7.
用拟小波方法数值求解Burgers方程 总被引:8,自引:1,他引:7
引进了一种拟小波方法数值求解Burgers方程,空间导数用拟小波数值格式离散,时间导数用四阶Runge-Kutta方法离散,计算的雷诺数变化从10到无穷大,拟小波数值方法能很好描述函数的局部快速变化特性,这一点通过对Burgers方程的数值求解以及与共相应解析解的比较中得到证实。 相似文献
8.
本文对三维涡度方程单向周期初边值问题建立了一种Fourier拟谱-有限差分格式,分析了其广义稳定性和收敛性,数值结果显示了这种方法的优点。 相似文献
9.
在文献「1」、「2」的启发下,本文建立一个零压梯度下,考虑局部产生以及外来扰动涡旋的壁湍流边界层大涡拟序结构的统计及动力学模型,在此基础上对充分发展的宽明渠流动中壁面附近的热扩散进行了数值模拟,建立了边界层拟序脉动速度和温度的数据库,发现了与速度快慢条相对应的高低温流条及其随时间的展向的摆动,数值模拟结果与前人的计算和实验结果吻合很好。 相似文献
10.
11.
A similarity solution is used to analyse the flow of the Oldroyd fluid B, which includes the Newtonian and Maxwell fluids, in a curved channel modelled by the narrow annular region between two circular concentric cylinders of large radius. The solution is exact, including inertial forces. It is found that the non-Netonian kinematics are very similar to the Newtonian ones, although some stress components can become very large. At high Reynolds number a boundary layer is developed at the inner cylinder. The structure of this boundary layer is asymptotically analysed for the Newtonian fluid. Non-Newtonian stress boundary layers are also developed at the inner cylinder at large Reynolds numbers. 相似文献
12.
13.
Influence of power-law index on transitional Reynolds numbers for flow over a semi-circular cylinder
In this work, the governing partial differential equations (continuity and Cauchy’s momentum equations) describing the flow of power-law type non-Newtonian fluids across a semi-circular cylinder (oriented with its curved surface in the upstream direction) have been solved numerically. In particular, consideration has been given to the delineation of the critical Reynolds numbers denoting the onset of flow separation from the surface of the cylinder and the onset of the laminar vortex shedding regime. This information is germane to establish the scaling of the macroscopic characteristics like drag coefficient and Strouhal number on the governing parameters, namely, Reynolds number and power-law index. The present results clearly suggest that the transitional Reynolds numbers show a strong dependence on the type (shear-thinning and shear-thickening) of fluid behavior as well as on the severity of the shear-dependence of the viscosity. With reference to the behavior seen in Newtonian fluids, the flow remains not only attached to the surface up to higher Reynolds numbers, but shear-thinning behavior also delays the onset of the laminar vortex shedding regime. As expected, shear-thickening fluids, of course, display the opposite characteristics. 相似文献
14.
Stefan Kopecz Mathias Krebs Andreas Meister Olaf Wünsch 《Zeitschrift für Angewandte Mathematik und Physik (ZAMP)》2010,61(4):673-684
This paper deals with the efficient simulation of polymer melts, as an example of highly viscous non-isothermal non-Newtonian fluids. In flow fields of our interest, which are characterized by small Reynolds numbers and large Prandtl numbers, steep gradients occur in thin boundary layers of the temperature distribution, whereas the boundary layers associated with the velocity field possess a considerable different length scale. In order to benefit from these properties, we introduce a physically motivated multigrid approach by computing velocity and temperature fields on different meshes. This new development is achieved by the modification of a discrete projection method. Numerical experiments are presented which confirm that the method decreases the computational effort considerably, while preserving the numerical accuracy. 相似文献
15.
Viscoelastic non-Newtonian fluids can be achieved by adding a small amount of polymer additives to a Newtonian fluid. In this paper, numerical simulations are used to investigate the influence of such polymer additives on the behavior of flow past a circular cylinder. A numerical method is proposed that discretizes the non-linear viscoelastic system on a uniform Cartesian grid, with a penalization method to model the presence of the cylinder. The drag of the cylinder and the flow behavior under the effect of different Reynolds numbers (), Weissenberg numbers (Wi) and polymer viscosity ratios (ε) are studied. Numerical results show that different flow characteristics are exhibited in different parameter zones. The polymer viscosity ratio plays an important role at low Weissenberg and Reynolds numbers, but as the Reynolds and Weissenberg numbers increase, the influence of ε weakens. The drag force of the cylinder is mostly affected by the Reynolds and Weissenberg numbers. At low Reynolds numbers, the drag of the cylinder and the flow fields are only affected by a large value of Wi when the elastic forces are strong. Non-trivial drag reduction occurs only when there is vortex shedding in the wake flow, whereas drag enhancement happens when the vortex shedding is inhibited. 相似文献
16.
High Accuracy Numerical Simulation of Non-Isothermal Viscoelastic Polymer Fluid Past a Cylinder北大核心CSCD
下载免费PDF全文
![点击此处可从《应用数学和力学》网站下载免费的PDF全文](/ch/ext_images/free.gif)
采用同位网格有限体积(coupled and linked equations algorithm revised,CLEAR)方法求解黏性和XPP (eXtended Pom-Pom)黏弹性流动的控制方程,基于延时修正方法构造了动量和本构方程对流项的高精度AVLsmart格式。首先,为了验证该文方法的有效性,对不同Reynolds数下不可压黏性流体圆柱绕流问题进行了模拟。随后,对等温及非等温不可压XPP黏弹性流体圆柱绕流问题进行了有效模拟,给出了速度矢量、应力分量、拉升量以及温度的分布规律,分析了We数对水平速度、法向应力及拉升量的影响。该文研究成果能为精确预测复杂型腔纤维增强黏弹性聚合物熔体动态充填过程提供理论基础。 相似文献
17.
Computational Mathematics and Mathematical Physics - Boundary layer theory is used to show that, at large Reynolds numbers, the three-dimensional Navier–Stokes equations can be rewritten in a... 相似文献
18.
Baltasar Mena Ernest Levinson Bruce Cawwell 《Zeitschrift für Angewandte Mathematik und Physik (ZAMP)》1972,23(2):173-181
Summary The couple on a sphere in the centre of a finite rotating circular cylinder is measured over a wide range of Reynolds numbers for both Newtonian and non-Newtonian fluids. Wall effects are calculated. Experimental results are compared with Collins' analysis. Secondary flow is made visible. For non-Newtonian fluids the apparatus determines accurately the zero shear rate viscosity.
Résumé Le couple sur une sphère dans un cylindre circulaire rotatoire est mesuré pour des divers nombres de Reynolds et pour des fluides Newtoniens et non-Newtoniens. L'effet des parois sur le couple est calculé. Les resultats obtenus sont comparés avec l'analyse de Collins. Pour les fluides non-Newtoniens l'appareil determine la viscosité de zéro cisaillement.相似文献
19.
We construct anisotropoviscous two- and three-layer models of the effect of reduction of hydrodynamic resistance through the
addition of polymers. The three-layer model can be used to compute the hydrodynamic resistance of turbulent flows with polymer
additives in the entire region of variation of the Reynolds numbers, and the two-dimensional model can be used with large
Reynolds numbers. Two figures. Bibliography: 3 titles.
Translated fromTeoreticheskaya i Prikladnaya Mekhanika, No. 26, 1996, pp. 135–141 相似文献
20.
S.Ø. Wille 《Applied Mathematical Modelling》1980,4(5):351-356
The finite element method has been used to solve the Navier-Strokes equations for steady flow conditions in bifurcations. The results are presented as pressure, velocity and streamline plots at different Reynolds number. The three bifurcations considered have rigid walls and bifurcation angles of 0°, 20° and 180°. For the bifurcation with branch angles 0° and 20° there is flow separation along the inner wall of the outlet branches and large spatial pressure variations, these phenomena being more pronounced at the higher Reynolds numbers. For the bifurcation with a branch angle of 180° the high pressure gradients occured at the outer corner and for the high Reynolds number a vortex formation developed downstream of this corner. 相似文献