旋转对流下铜在微沟道中的电沉积

将刻有微沟道的芯片固定在旋转圆盘电极上,在旋转对流条件下于微沟道中电沉积铜.微沟道深度为1μm,宽度分别为0.35μm,0.50μm,0.70μm.研究了芯片的旋转、电流密度以及Cu2+浓度等对微沟道中铜沉积的影响.实验表明,在旋转对流传质下,铜在微沟道中的沉积速率比静止芯片时的约快2～3倍.较低的Cu2+浓度和适中的沉积电流密度更有利于超等厚沉积的形成.

Adomian decomposition method simulation of von Kármán swrling bioconvection nanofluid flow

The study reveals analytically on the 3-dimensional viscous time-dependent gyrotactic bioconvection in swirling nanofluid flow past from a rotating disk.It is known that the deformation of the disk is along the radial direction.In addition to that Stefan blowing is considered.The Buongiorno nanofluid model is taken care of assuming the fluid to be dilute and we find Brownian motion and thermophoresis have dominant role on nanoscale unit.The primitive mass conservation equation,radial,tangential and axial momentum,heat,nano-particle concentration and micro-organism density function are developed in a cylindrical polar coordinate system with appropriate wall(disk surface)and free stream boundary conditions.This highly nonlinear,strongly coupled system of unsteady partial differential equations is normalized with the classical von Kármán and other transformations to render the boundary value problem into an ordinary differential system.The emerging 11th order system features an extensive range of dimensionless flow parameters,i.e.,disk stretching rate,Brownian motion,thermophoresis,bioconvection Lewis number,unsteadiness parameter,ordinary Lewis number,Prandtl number,mass convective Biot number,Péclet number and Stefan blowing parameter.Solutions of the system are obtained with developed semi-analytical technique,i.e.,Adomian decomposition method.Validation of the said problem is also conducted with earlier literature computed by Runge-Kutta shooting technique.

Series Solution for Rotating Flow of an Upper Convected Maxwell Fluid over a Stretching Sheet

The equations for two-dimensional flow of an upper convected Maxwell （UCM） fluid in a rotating frame are modeled. The resulting equations are first simplified by a boundary layer approach and then solved by a homotopy analysis method （HAM）. Convergence of series solution is discussed through residual error curves. The results of the influence of viscoelastic and rotation parameters are plotted and discussed.

尘卷风的形成、结构和卷起沙尘过程的数值研究

文中应用数值算法对尘卷风的发展过程进行了模拟计算与分析。通过模拟计算得到了尘卷风的内部详细结构和运动过程。研究表明尘卷风是由于地面局部增热不均匀而形成的一种特殊的旋转对流运动。在尘卷风形成的过程中 ,外围空气通过贴近地面的薄层被地面加热后流向中心部位 ,外围空气的旋转能量在中心部位得到加强形成尘卷风 ,其旋转能量是热泡原来具有的旋转能量的局部集中和一部分势能转化而形成的 ,其旋转方向是由热对流泡的初始旋转方向所决定。尘卷风是一种类兰金涡 ,旋转速度和压力的分布具有兰金组合涡的特点 ;在成熟阶段 ,尘卷风的详细结构可以粗略地分为 4个区域———地面附近的气流汇聚区域、柱状的涡核区域、旋风与地面作用形成的转角风区域以及涡核外部的外围气流区域。转角区域可以细分为两个子区域———外围的方位角风区域(在该区域 ,上升气流运动方向与轴线之间有一定的夹角 ,称为方位角 )和中心的下沉停滞气流区域。尘卷风中心的低压和急速的上升气流可使大量沙尘扬起 ,不同直径的沙尘颗粒在尘卷风的作用下运动轨迹不同 ,因此卷起不同大小沙尘的尘卷风的外形也是不同的。

CONVEXITY AND SYMMETRY OF TRANSLATING SOLITONS IN MEAN CURVATURE FLOWS

This paper proves that any rotationally symmetric translating soliton of mean curvature flow in R3 is strictly convex if it is not a plane and it intersects its symmetric axis at one point. The authors also study the symmetry of any translating soliton of mean curvature flow in Rn.

The Inverse Mean Curvature Flow in Rotationally Symmetric Spaces

In this paper,the motion of inverse mean curvature flow which starts from a closed star-sharped hypersurface in special rotationally symmetric spaces is studied.It is proved that the flow converges to a unique geodesic sphere,i.e.,every principle curvature of the hypersurfaces converges to a same constant under the flow.

Turbulent Convective Heat Transfer of Methane at Supercritical Pressure in a Helical Coiled Tube

The heat transfer of methane at supercritical pressure in a helically coiled tube was numerically investigated using the Reynolds Stress Model under constant wall temperature. The effects of mass flux （G）, inlet pressure （Pin） and buoyancy force on the heat transfer behaviors were discussed in detail. Results show that the light fluid with higher temperature appears near the inner wall of the helically coiled tube. When the bulk temperature is less than or approach to the pscudocritical temperature （Tpc）, the combined effects of buoyancy force and centrifugal force make heavy fluid with lower temperature appear near the outer-right of the helically coiled tube. Beyond the Tpc, the heavy fluid with lower temperature moves from the outer-right region to the outer region owing to the centrifugal force. The buoyancy force caused by density variation, which can be characterized by Gr/Re3 and Gr/Re2.7, enhances the heat transfer coefficient （h） when the bulk temperature is less than or near the T~, and the h expe- riences oscillation due to the buoyancy force. The oscillation is reduced progressively with the increase of G. Moreover, h reaches its peak value near the Tpv. Higher G could improve the heat transfer performance in the whole temperature range. The peak value ofh depends on Pin. A new correlation was proposed for methane at su- percritical pressure convective heat transfer in the helical tube, which shows a good agreement with the present simulated results.

Experimental and Numerical Investigation of Centrifugal Pumps with Asymmetric Inflow Conditions

Most of the times pumps operate off best point states.Reasons are changes of operating conditions,modifications,pollution and wearout or erosion.As consequences non-rotational symmetric flows,transient operational conditions,increased risk of cavitation,decrease of efficiency and unpredictable wearout can appear.Especially construction components of centrifugal pumps,in particular intake elbows,contribute to this matter.Intake elbows causes additional losses and secondary flows,hence non-rotational velocity distributions as intake profile to the centrifugal pump.As a result the impeller vanes experience permanent changes of the intake flow angle and with it transient flow conditions in the blade channels.This paper presents the first results of a project,experimentally and numerically investigating the consequences of non-rotational inflow to leading edge flow conditions of a centrifugal pump.Therefore two pumpintake-elbow systems are compared,by only altering the intake elbow geometry:a common single bended 90°elbow and a numerically optimized elbow(improved regarding rotational symmetric inflow conditions and friction coefficient).The experiments are carried out,using time resolved stereoscopic PIV on a full acrylic pump with refractions index matched(RIM)working fluid.This allows transient investigations of the flow field simultaneously for all blade leading edges.Additional CFD results are validated and used to further support the investigation i.e.for comparing an analog pump system with ideal inflow conditions.

Theory and experimental verification of valveless piezoelectric pump with rotatable unsymmetrical slopes

A valveless piezoelectric pump with rotatable unsymmetrical slopes is developed in this research.It has the following features:The pump integrates driving and transporting,and it can mix different fluids while transporting them.In this paper,firstly,the design of the valveless piezoelectric pump with rotatable unsymmetrical slopes was proposed,and the single-direction flow principle was explained.Then,the fluid mechanics model of the valveless piezoelectric pump with rotatable unsymmetrical slopes was established.Meanwhile,the numerical simulation of the pump was performed.Finally,the experiments on relationship between the rotation angles of the slope and the flow rates were conducted.The experimental results showed that the maximum flow was 32.32 mL min 1.The maximum relative error between the theoretical results and the experimental ones was 14.59%.For the relationship between rotation angles and flow ratio of two inlets,the relative error between the experimental and theoretical maxima was 3.75%.Thus,the experiments proved the feasibility of the pump design and verified the theory.

Phase Space Analysis and Anisotropic Universe Model in f(T) Gravity

In this paper, we study the stability of locally rotationally symmetric （LRS） Bianchi I universe model in f（T） gravity through phase space analysis. We assume that the f（T） gravity can be treated as effective dark energy behaving like perfect fluid, and suggest that there are interactions between pressureless matter as well as dark energy. We construct the corresponding autonomous system of equations to check the stability of the model for non phantom, vacuum and phantom phases. It is concluded that critical points remain more stable in phantom phase as compared to non phantom and vacuum cases. Finaily, we discuss the cosmological behavior of the model through some cosmological parameters.

Laminar Forced Convection from a Rotating Horizontal Cylinder in Cross Flow

The influence of non-dimensional rotational velocity, flow Reynolds number and Prandtl number of the fluid on laminar forced convection from a rotating horizontal cylinder subject to constant heat flux boundary condition is numerically investigated. The numerical simulations have been conducted using commercial Computational Fluid Dynamics package CFX available in ANSYS Workbench 14. Results are presented for the non-dimensional rotational velocity α ranging from 0 to 4, flow Reynolds number from 25 to 40 and Prandtl number of the fluid from 0.7 to 5.4. The rotational effects results in reduction in heat transfer compared to heat transfer from stationary heated cylinder due to thickening of boundary layer as consequence of the rotation of the cylinder. Heat transfer rate increases with increase in Prandtl number of the fluid.

Area-preserving mean curvature flow of rotationally symmetric hypersurfaces with free boundaries

We consider the area-preserving mean curvature flow with free Neumann boundaries. We show that a rotationally symmetric n-dimensional hypersurface in R^(n+1)between two parallel hyperplanes will converge to a cylinder with the same area under this flow. We use the geometric properties and the maximal principle to obtain gradient and curvature estimates, leading to long-time existence of the flow and convergence to a constant mean curvature surface.

Effects of f(R) Model on Dynamics of Axial Shear-Free Dissipative Fluids

We present a general analysis on non-static axial system with dissipative shear-free anisotropic fluid using polynomial inflationary f(R) model.We study the effects of dissipation on the dynamics of geodesic matter distribution.This leads the system either to rotation-free or expansion-free but not both simultaneously under geodesic condition.It is found that the system preserves its symmetry in both cases.For the rotation-free case,when there is no dissipation and Ricci scalar is constant,the axial system reduces to FRW universe model.This is exactly the same result obtained in general relativity.