共查询到18条相似文献,搜索用时 250 毫秒
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离散元法是分析散体力学行为的数值方法。存在填隙流体时,颗粒之间或颗粒与壁之间产生的法向挤压力和切向阻力、阻力矩,是湿颗粒离散元法的理论基础。二阶流体是以微小偏离牛顿流体本构而考虑时间影响的一种流体。它具有常粘度,并且第一和第二法向应力差正比于剪切率的平方。根据Reynolds润滑理论,采用小参数法,导出了存在填隙二阶流体时,圆球沿平行于平壁缓慢移动时流体的速度场和压力方程,进而求出切向阻力和阻力矩的解析解。有趣的是在推导时所得的速度场和压力方程形式比牛顿流体要复杂得多,但最终结果表明圆球沿平行于平壁移动时因填隙二阶流体引起的切向阻力和阻力矩与牛顿流体时的结果相同。 相似文献
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本文用奇异摄动法结合正则摄动法求解了考虑毛管力因素时多孔介质中弱非牛顿流体的两相驱替问题,得到了分流函数和湿相饱和度的渐近解析解。所得结果同数值解和经典的牛顿流体两相渗流结果进行了比较,并着重讨论了非牛顿因素的影响。 相似文献
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水平地震时斜面水坝受到的非线性动水压力的全过程的解析解 总被引:1,自引:0,他引:1
本文给出在非线性Rayleigh阻尼作用下,由水平地震激发的水库内动水压力变化全过程的解析解:在激发初期其幅值较小,可用小参数法使控制方程线性化,从而求得各阶渐近控制方程的解析解;当动水压力的幅值增大到小参数展开不适用时,用van derpol法求得非线性控制方程的渐近解,从而显示了动水压力的幅值从有序变化到发生突然跳跃的多值性的非线性本质。 相似文献
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二阶流体是工业界常见的非牛顿流体,因为其本构关系简单而被广泛采用和研究.逆方法预先假定流场满足某类特定的物理的或几何的特性,从而求出流体运动方程的精确解.本文通过假定平面定常二阶非牛顿流体的涡量场与受到扰动的流函数相等这一特定形式,采用求解非线性微分方程常用的逆方法,推导并获得了平面二阶蠕流流场的精确解,由此容易进一步获得流场的压力.所获得的精确解包含了Poiseuille,简单Couette平行流动以及两相向流体的相互作用等流动.这些精确解为实验,数值以及渐进解的检验提供了借鉴和参考. 相似文献
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轴对称正交异性圆环壳的齐次完全渐近解 总被引:1,自引:0,他引:1
承受轴对称载荷的正交异性圆环壳的静力分析,归结为求解一非齐次二阶复变量方程.当所含参数μ较大时,常采用渐近解法.因方程含一阶转点,所以求全域一致有效且达到薄壳理论精度的完全渐近解较为困难.过去,齐次解只求到一级近似.本文采用广义Airy函数方法,求出了高级近似.这样,轴对称正交异性圆环壳的齐次解第一次有了达到薄壳理论精度的完全的渐近展开. 相似文献
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本文找到了溶质在孔隙介质中球向输运方程的近似解.该公式不仅结构简单、物理意义明确,而且与数值解的结果符合的较好.因此,可用于予测(计算)地下水质球向分布和传播范围. 相似文献
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本文对中心带轴匀速旋转圆盘在均布压力作用下的受力及变形问题进行了摄动分析,得到了受载条件为J^2/JH<<1时,圆盘应力及形变的渐近解。其形变渐近解为Whitaker函数形式比较表明,渐近解与Chebyshev数值解有较好的一致性。 相似文献
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《中国颗粒学报》2005,3(1-2):52-57
Interaction between two spheres with an interstitial fluid is essential in Discrete Element modeling for simulating the behaviors of ‘wet’ particulate materials. In this paper the interaction between two spheres with an interstitial Power-law fluid was approximately resolved as normal and tangential interactive models respectively, for which the governing equations were simplified on the basis of Reynolds approximation. These equations were then solved analytically together with the boundary conditions to obtain the pressure distributions for each individual model, and eventually solutions of the viscous squeeze force and the tangential viscous resistance were obtained, which provide a set of solutions for implementing into DEM code or other purposes. 相似文献
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基于两流体模型、酸性气体和钻井液状态方程,考虑酸性气体与钻井液相间虚拟质量力、粘性剪切力、相间动量交换及狭义相间阻力等条件,建立酸性气体与钻井液两相中压力波传播速度的数学模型,依据小扰动原理,对波速模型求解,得到关于波数K的波速方程。结果表明,在一定范围内,随空隙率、频率的增大,虚拟质量力对波速的影响显著增强;在高空隙率下,压强增大,虚拟质量力对波速的影响减弱;增大流体的密度或不可压缩性,均可使两相压力波速增大;延长气液交换时间或减小波动频率使相间有足够时间进行动量交换,两相压力波波速随之减小。 相似文献
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Buoyant flow is analysed for a vertical fluid saturated porous layer bounded by an isothermal plane and an isoflux plane in
the case of a fully developed flow with a parallel velocity field. The effects of viscous dissipation and pressure work are
taken into account in the framework of the Oberbeck–Boussinesq approximation scheme and of the Darcy flow model. Momentum
and energy balances are combined in a dimensionless nonlinear ordinary differential equation solved numerically by a Runge–Kutta
method. Both cases of upward pressure force (upward driven flows) and of downward pressure force (downward driven flows) are examined. The thermal behaviour for upward driven flows and downward driven flows is quite different. For upward driven
flows, the combined effects of viscous dissipation and pressure work may produce a net cooling of the fluid even in the case
of a positive heat input from the isoflux wall. For downward driven flows, viscous dissipation and pressure work yield a net
heating of the fluid. A general reflection on the roles played by the effects of viscous dissipation and pressure work with
respect to the Oberbeck–Boussinesq approximation is proposed. 相似文献
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The effect of an additional boundary condition on the plane creeping flow of a second-order fluid 总被引:2,自引:0,他引:2
Patrick Bourgin
John A. Tichy
《International Journal of Non》1989,24(6):561-569A similarity solution is obtained for the two-dimensional creeping flow of a second-order fluid with non-parallel porous walls. The resulting ordinary differential equation is fifth order. Thus, an additional velocity boundary condition is needed, the other four being due to the usual no-slip conditions. Having chosen to prescribe the rate of shear at the wall, the problem is solved by a standard numerical routine. A singular perturbation analysis is developed for small values of the Deborah number. A type of boundary layer forms for which the viscous Newtonian case is the outer solution. 相似文献
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A theoretical model based on the force balance between pressure, viscous force, and inertia force is proposed to predict the flow resistance of Newtonian and power-law non-Newtonian fluids through porous packed beds. The present model takes inertia effect into consideration, and the flow regime can be extended from Darcy flow to non-Darcy flow. It is demonstrated that the present model can predict most available experimental data well. The present results are also compared to the Ergun equation and other drag correlations. 相似文献
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An immersed smoothed point interpolation method (IS‐PIM) for fluid‐structure interaction problems 下载免费PDF全文
An immersed smoothed point interpolation method using 3‐node triangular background cells is proposed to solve 2D fluid‐structure interaction problems for solids with large deformation/displacement placed in incompressible viscous fluid. In the framework of immersed‐type method, the governing equations can be decomposed into 3 parts on the basis of the fictitious fluid assumption. The incompressible Navier‐Stokes equations are solved using the semi‐implicit characteristic‐based split scheme, and solids are simulated using the newly developed edge‐based smoothed point interpolation method. The fictitious fluid domain can be used to calculate the coupling force. The numerical results show that immersed smoothed point interpolation method can avoid remeshing for moving solid based on immersed operation and simulate the contact phenomenon without an additional treatment between the solid and the fluid boundary. The influence from information transfer between solid domain and fluid domain on fluid‐structure interaction problems has been investigated. The numerical results show that the proposed interpolation schemes will generally improve the accuracy for simulating both fluid flows and solid structures. 相似文献
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The system of Navier-Stokes equations is solved for boundary conditions corresponding to the case when an axisymmetric tangential transversal load acts at the surface of a gravity viscous incompressible fluid of infinite depth. An integral representation is obtained for the shape of the free surface under the prolonged effect of a stationary vortex load. The example of a tangential load, similar to a concentrated vortex, is examined. In this case a column is squeezed out of the fluid, the height of the column being directly proportional to the square of the moment of the transverse tangential forces and inversely proportional to the square of the product of the dynamic fluid viscosity and the area of the tangential stress distribution. The depth of the annular funnel being formed in front of the column is determined.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 4, pp. 127–132, July–August, 1978. 相似文献
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Rodolfo Repetto 《Meccanica》2006,41(1):101-117
An analytical model of the dynamics of the vitreous humour induced by saccadic movements within the eye globe is presented.
The vitreous is treated as a weakly viscous Newtonian incompressible fluid, an assumption which is appropriate when the vitreous
is liquefied or when it is replaced by aqueous humour after surgery. The thin viscous boundary layer generated during a saccadic
movement on the side wall is neglected and the flow field is assumed to be irrotational. The vitreous chamber is described
as a weakly deformed sphere and this assumption allows a linear treatment of the problem. An analytical solution is found
in the form of an expansion of spherical harmonics. Results show that the non-spherical shape of the container generates a
flow field characterised by significant velocities and strong three-dimensionality. The model allows the computation of the
dynamic pressure on the wall, which may play a role in the generation of retinal detachments. Moreover, results suggest that
the irregular shape of the globe may significantly modify tangential stresses on the boundary with respect to the case of
motion within a sphere. A simplified analytical solution, for the case of two-dimensional flow within an impulsively rotated
container, shows that boundary layer detachment is expected to occur for angles of rotation larger than a threshold value
of 15° circa. 相似文献