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51.
Extrudate swell through an orifice die 总被引:2,自引:0,他引:2
The extrudate swell of a viscoelastic fluid through an orifice die is investigated by using a mixed finite element and a streamline integration method (FESIM), using a version of the K-BKZ model. The free surface calculation is based on a local mass conservation scheme and an approximate numerical treatment for the contact point movement of the free surface. The numerical results show a vortex growth and an increasing swelling ratio with the Weissenberg number. Convergence with mesh refinement is demonstrated, even at a high Weissenberg number of O(587), where the swelling ratio reaches a value of about 360%. In addition, it is found that the effective flow channel at the entrance region next to the orifice die is reduced due to the enhanced vortex growth, which may be a source of flow instability. 相似文献
52.
Slip effects on streamline topologies and their bifurcations for peristaltic flows of a viscous fluid
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We discuss the effects of the surface slip on streamline patterns and their bifurcations for the peristaltic transport of a Newtonian fluid. The flow is in a two-dimensional symmetric channel or an axisymmetric tube. An exact expression for the stream function is obtained in the wave frame under the assumptions of long wavelength and low Reynolds number for both cases. For the discussion of the particle path in the wave frame, a system of nonlinear autonomous differential equations is established and the methods of dynamical systems are used to discuss the local bifurcations and their topological changes. Moreover, all types of bifurcations and their topological changes are discussed graphically. Finally, the global bifurcation diagram is used to summarize the bifurcations. 相似文献
53.
Guo‐Dong Zhang Yinnian He Yan Zhang 《Numerical Methods for Partial Differential Equations》2014,30(6):1877-1901
In this article, a streamline diffusion finite element method is proposed and analyzed for stationary incompressible magnetohydrodynamics (MHD) equations. This method is stable for any combinations of velocity, pressure, and magnet finite element spaces, without requiring Ladyzenskaja‐Babu?ka‐Brezzi (LBB) condition. The well‐posedness and convergence (at optimal error rate) of this scheme are proved in terms of some conditions. Two numerical experiments are illustrated to validate our theoretical analysis and show the streamline diffusion finite element approach is effective for solving the MHD problems. © 2014 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 30: 1877–1901, 2014 相似文献
54.
《Particuology》2022
A 90° elbow equipped with guide vanes was developed with the intent of reducing elbow erosion. Numerical models were formed to predict the maximum erosion rate of elbow and Face-1, and the response surface methodology was used to study the relationship between the erosion rate and structural parameters of guide vane. A second-order response surface model was established to determine the relationship between R1 and variables, and a reduced cubic (RC) polynomial model was obtained to reveal the relationship between R2 and the three factors. The numerical results show that the low-speed region is expended and the maximum discrete particle matter (DPM) concentration is reduced after installing the guide vane. This internal component provides a shelter for the elbow from the direct impact of high-speed solids. 相似文献
55.
We consider streamline diffusion finite element methods applied to a singularly perturbed convection–diffusion two‐point boundary
value problem whose solution has a single boundary layer. To analyse the convergence of these methods, we rewrite them as
finite difference schemes. We first consider arbitrary meshes, then, in analysing the scheme on a Shishkin mesh, we consider
two formulations on the fine part of the mesh: the usual streamline diffusion upwinding and the standard Galerkin method.
The error estimates are given in the discrete L
∞ norm; in particular we give the first analysis that shows precisely how the error depends on the user-chosen parameter τ0 specifying the mesh. When τ0 is too small, the error becomes O(1), but for τ0 above a certain threshold value, the error is small and increases either linearly or quadratically as a function of . Numerical
tests support our theoretical results.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
56.
57.
Lyu Fuyan Qu Yuanyuan Zhang Ningxiao Gao Jie Hao Xuedi Wu Miao 《Journal of Dispersion Science and Technology》2016,37(11):1563-1569
Yield stress is a key rheological parameter of dense paste. Considering practical utility and to estimate the possible slipping flow, yield stress measurements were carried out using the curve extrapolation method and vane method with rheometer in both controlled shear stress (CSS) and controlled shear rate (CSR) model. All measured yield stresses show to increase exponentially with concentration in different scale. The vane method yield stresses are both higher than the extrapolation curve yield stress. For the coal slurry used in this paper, the extrapolation curve yield stress is lower by 17–30% than the dynamic yield stress that obtained under test model CSR. It indicates that wall slip exists in pipeline transportation; meanwhile wall slip can reduce transportation resistance of dense paste to some extent. 相似文献
58.
为了对金属约束条件下的定常非理想爆轰进行理论研究,对未反应炸药和爆轰产物采用JWL形
式状态方程,对金属采用p(,T)形式状态方程。采用过爆轰前导冲击波的流线偏转角在影响域内沿高度线
性变化的假设,并且由未反应炸药和金属的冲击波极曲线的交点确定爆轰冲击边缘角,则可从未反应炸药斜
冲击波极曲线关系式求出爆轰前导冲击波阵面的形状。采用爆轰前导冲击波阵面之后的流线是直线的假设,
则爆轰流动控制方程由偏微分方程变为沿流线的常微分方程,沿着所有流线求解便给出爆轰化学反应区内
声速线与化学反应结束线的位置。理论分析同时给出约束金属折射冲击波后面的流体的流动状态。理论结
果给出的爆轰化学反应区结构特征和约束金属内的流动状态特征与高精度数值模拟的结果符合良好,说明
本文中给出的理论方法具有良好的合理性和适用性。 相似文献
59.
60.
A nonconforming finite element method of finite difference streamline diffusion type is proposed to solve the time-dependent linearized Navier-Stokes equations. The backward Euler scheme is used for time discretization. Crouzeix-Raviart nonconforming finite element approximation, namely, nonconforming (P1)2 - P0 element, is used for the velocity and pressure fields with the streamline diffusion technique to cope with usual instabilities caused by the convection and time terms. Stability and error estimates are derived with suitable norms. 相似文献