The jet over a stretching wall with suction or injection

The steady laminar wall jet over a stretching surface in the presence of lateral suction or injection is considered. Similarity solutions absent in previous publications are found in some new ranges of parameters in the governing equation. The accuracy and reliability of the solutions have been checked through detailed convergence study and compared with the solutions from the numerical method and analytic method, and excellent agreement has been found. This gives the strongest evidence that those solutions...     

具有正负系数的时滞微分方程解的振动性与渐近性

考虑具正负系数的时滞微分方程 x'(t)+p(t)x(t-)-q(t)x(t-r)=0,(1)其中p,q∈C([t_0,∞),R~+),τ,r∈R~+=[0,∞).我们获得了(1)的所有解振动的充分条件.也研究了(1)的所有非振动解的渐近性.     

Decay estimates for oscillatory integrals with polynomial phase

We obtain estimates for certain oscillatory integrals with polynomial phase. These estimates are stated in terms of roots of various derivatives of the phase polynomial.     

南京下蜀黄土的非均匀性研究

下蜀黄土分布在不同高程的多种地貌单元, 如山顶、阶地、山麓及盆地, 由黄土层和红土层两部分组成, 具有成分和结构差异, 尤其是水稳定性。它是-种非均匀性土层。当其位于地下水位以上或开放性状态时, 土层出现非饱和状态和负孔隙水压力, 产生较大的基质吸力。工程施工中, 可利用这-特性, 但必须控制各种向下净流量, 以抑制土体饱和度增大的趋势。     

Marangoni flow and mass transfer of power-law non-Newtonian fluids over a disk with suction and injection

We scrutinize the approximate analytical solutions by the optimal homotopy analysis method (OHAM) for the flow and mass transfer within the Marangoni boundary layer of power-law fluids over a disk with suction and injection in the present paper. Concentration distribution on the surface of a disk varies in a power-law form. The non-Newtonian fluid flow is due to the surface concentration gradient without considering gravity and buoyancy. According to the conservation of mass, momentum and concentration, the governing partial differential equations are established, and the appropriate generalized Kármán transformation is found to reduce them to the nonlinear ordinary differential equations. OHAM is used to access the approximate analytical solution. The influences of Marangoni the number, suction/injection parameters and power-law exponent on the flow and mass transfer are examined.     

Drag reduction by flow separation control on a car after body

New development constraints prompted by new pollutant emissions and fuel consumption standards (Corporate Average Economy Fuel) require that automobile manufacturers develop new flow control devices capable of reducing the aerodynamic drag of motor vehicles. The solutions envisaged must have a negligible impact on the vehicle geometry. In this context, flow control by continuous suction is seen as a promising alternative. The control configurations identified during a previous 2D numerical analysis are adapted for this purpose and are tested on a 3D geometry. A local suction system located on the upper part of the rear window is capable of eliminating the rear window separation on simplified fastback car geometry. Aerodynamic drag reductions close to 17% have been obtained. Copyright © 2008 John Wiley & Sons, Ltd.     

非饱和土吸力的温度性质

根据热力学理论，讨论非饱和土中的土吸力随温度变化的情况，得到在一般情况下非饱和土中的土吸力随着温度增加而线性减小的规律．     

On the reversed flow and oscillating wake in an asymmetrically heated channel

The detailed processes of flow reversal in a buoyancy-induced flow through a one-side-heated vertical channel of finite height were simulated numerically. It is of interest to note that the wake above the heated plate is oscillatory at high Rayleigh number and there exists a minimum in the transient variation of the average Nusselt number. Additionally, the predicted steady average Nusselt number and induced flow rate are correlated by empirical equations.     

Numerical simulation of the horizontal Bridgman growth. Part III: Calculation of the interface

We study the transient motion of the solidification front during the growth of semiconductor crystals in the horizontal Bridgman geometry. The calculation is based on a two-dimensional flow. We use finite elements which deform with the motion of the interface. The energy equation is coupled with the isothermal constraint of the interface in an implicit transient algorithm. Several examples show the oscillatory motion of the interface caused by the periodic flow of the melt, and they reveal the importance of the growth rate on the shape of the interface.     

Numerical modeling of the turbulent viscous-gas flow past a cylinder with a circular vortex cell in the presence of suction from the central body surface

The compressibility effect on the cylinder drag reduction due to air suction through the surface of a central body in a circular vortex cell is estimated on the basis of the solution of the steady Reynolds equations closed by the shear stress transfer model, together with the continuity, energy, and state equations.