夹套冰温库内流场的数值模拟

随着计算机技术的飞速发展,计算流体力学(CFD)越来越广泛地应用于各个领域。通过CFD对复杂流动问题进行研究,能够较精确地反映流场的流动情况。利用CFD技术对夹套冰温库内的流场进行了稳态数值模拟,分析了夹套冰温库内流场的分布情况,讨论了该库体结构下不同送风速度对库内流场均匀性的影响。研究表明,具有夹套结构的冰温库,库内流场分布均匀,采用顶部静压箱送风,底部四周回风的送回风方式,能够使库内形成自上而下的均匀活塞流,不同送风速度对冰温库内流场的影响很小。研究结果证明数值模拟能较好地反映现实情况。     

基于有限体积虚拟区域方法的两相流动直接模拟

为提高计算效率，提出有限体积法离散下的虚拟区域颗粒两相流动直接模拟方法.在控制方程中加入相应的虚拟区域源项，保证了颗粒内部的刚体运动特性.该源项中含有颗粒信息部分及流体信息部分.在每次迭代后，对源项中的流体信息部分进行更新，从而更好地保证颗粒内速度的刚体分布.计算静止颗粒圆柱绕流及单个颗粒的沉降过程，验证了算法的准确性.     

A remark on similarity analysis of boundary layer equations of a class of non-Newtonian fluids

A similarity analysis of three-dimensional boundary layer equations of a class of non-Newtonian fluid in which the stress, an arbitrary function of rates of strain, is studied. It is shown that under any group of transformation, for an arbitrary stress function, not all non-Newtonian fluids possess a similarity solution for the flow past a wedge inclined at arbitrary angle except Ostwald-de-Waele power-law fluid. Further it is observed, for non-Newtonian fluids of any model only $90°$ of wedge flow leads to similarity solutions. Our results contain a correction to some flaws in Pakdemirli׳s [14] (1994) paper on similarity analysis of boundary layer equations of a class of non-Newtonian fluids.     

On wave families in a two-layer falling film

Using an approximate method, families of non-linear steady-traveling periodic waves in a two-layer falling film have been found for the first time. Computed waves have qualitatively similar behavior as that of those found in homogeneous films but the quantitative characteristics of the waves strongly depend on additional similarity parameters in the two-layer films. In particular, the average location of the interface affects the bifurcation scheme of the waves.     

幂律流体在多孔介质中径向渗流的分形模型

基于分形理论及毛细管模型,本文研究了非牛顿幂律流体在各向同性多孔介质中径向流动问题,推导了幂律流体径向有效渗透率的分形解析表达式．研究结果表明,幂律流体径向有效无量纲渗透率模型和Chang and Yortsos’s模型吻合很好;同时还得出幂律流体径向有效渗透率随孔隙率、幂指数的增加而增加,随迂曲度分形维数的增加而减少．     

Stability of Poiseuille flow in the presence of a longitudinal magnetic field

The stability of the plane flow of an electrically conducting fluid with respect to small perturbations was studied at large Reynolds numbers in the presence of a longitudinal magnetic field. The dependence of the critical Reynolds number on the electrical conductivity is investigated. At large Reynolds numbers, a new branch of instability and a sudden change in the critical Reynolds numbers is found. __________ Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 49, No. 3, pp. 45–53, May–June, 2008.     

Effect of rotation in generalized thermoelastic solid under the influence of gravity with an overlying infinite thermoelastic fluid

The present problem is concerned with the study of deformation of a rotating generalized thermoelastic solid with an overlying infinite thermoelastic fluid due to different forces acting along the interface under the influence of gravity.The components of displacement,force stress,and temperature distribution are first obtained in Laplace and Fourier domains by applying integral transforms,and then obtained in the physical domain by applying a numerical inversion method.Some particular cases are also discussed in the context of the problem.The results are also presented graphically to show the effect of rotation and gravity in the medium.     

Magnetohydrodynamic stagnation-point flow of a power-law fluid towards a stretching surface

Steady two-dimensional stagnation-point flow of an electrically conducting power-law fluid over a stretching surface is investigated when the surface is stretched in its own plane with a velocity proportional to the distance from the stagnation-point. We have discussed the uniqueness of the solution except when the ratio of free stream velocity and stretching velocity is equal to 1. The effect of magnetic field on the flow characteristic is explored numerically and it is concluded that the velocity at a point decreases/increases with increase in the magnetic field when the free stream velocity is less/greater than the stretching velocity. It is further observed that for a given value of magnetic parameter M, the dimensionless shear stress coefficient |F^″(0)| increases with increase in power-law index n when the value of the ratio of free stream velocity and stretching velocity is close to 1 but not equal to 1. But when the value of this ratio further differs from 1, the variation of |F^″(0)| with n is non-monotonic.     

Some unsteady exact pseudo-plane solutions for the Navier-Stokes equations

Unsteady pseudo-plane and plane motions for Navier-Stokes equations have been studied, which are generalized Beltrami flows, related to separable stream functions. All the pseudo-plane motions of the first kind of such a type, a wide class of plane universal solutions, which seems to be new, and a class of pseudo-plane motions of the second kind, dependent on an arbitrary function of time, with a primitive steady plane solution which is the celebrated Kelvin's cat's eye vortices are formed.

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Sommario Si studiano moti non stazionari pseudopiani e piani dell'equazioni di Navier Stokes. Questi moti sono flussi generalizzati di Beltrami con una particolare dipendenza della funzioni di corrente dalle coordinate spaziali in modo separato. Nell'ambito di questa famiglia di flussi vengono esplicitamente trovati tutti i moti pseudopiani di primo tipo e vengono anche individuate un'ampia classe di soluzioni universali piane e una classe di moti pseudopiani del secondo tipo che possiedono come flussoprimitivo i famosi vortici adocchi di gatto di Kelvin.