Influence of Thermophoresis and Brownian Motion of Nanoparticles on Radiative Chemically-Reacting MHD Hiemenz Flow over a Nonlinear Stretching Sheet with Heat Generation

In this study,a radiative MHD stagnation point flow over a nonlinear stretching sheet incorporating thermophoresis and Brownian motion is considered.Using a similarity method to reshape the underlying Partial differential equations into a set of ordinary differential equations(ODEs),the implications of heat generation,and chemical reaction on the flow field are described in detail.Moreover a Homotopy analysis method(HAM)is used to interpret the related mechanisms.It is found that an increase in the magnetic and velocity exponent parameters can damp the fluid velocity,while thermophoresis and Brownian motion promote specific thermal effects.The results also demonstrate that as the Brownian motion parameter is increased,the concentration values become smaller.

Partial slip effects in flow over nonlinear stretching surface

The two-dimensional flow of a viscous nanofluid is investigated. The flow is caused by a nonlinear stretching surface with the slip effects of the velocity, the temperature, and the concentration. The fluid is electrically conducted in the presence of an applied magnetic field. Appropriate transformations reduce the nonlinear partial differential system to an ordinary differential system. The convergent solutions of the governing nonlinear problems are computed. The results of the velocity, the temperature, and the concentration fields are calculated in series forms. The effects of the different parameters on the velocity, the temperature, and the concentration profiles are shown and analyzed. The skin friction coefficient, the Nusselt number, and the Sherwood number are also com-puted and investigated for different embedded parameters in the problem statements.

Impact of Melting Heat Transfer and Variable Characteristics on an MHD Non-Newtonian Shear-Thinning Fluid Flow with Gyrotactic Microorganisms over a Nonlinear Stretched Surface

The objective of this work is to examine how temperature-dependent thermal conductivity and concentration-dependent molecular diffusion affect Reiner-Philippoff nanofluid flow past a nonlinear stretching sheet. At the interface of the elongated surface zero-mass flux and melting heat condition are incorporated. The formulated mathematical problem is simplified by implementing suitable similarity transformations. For the numerical solution bvp4c is utilized. The parameters emerging in the model are discussed versus allied profiles through graphical illustrations. It is perceived that the velocity of the fluid decays on incrementing the Bingham number. The gyrotactic microorganism profile declines on amplifying the Peclet number. The validation of the proposed model is also added to this study. .

Thermal Radiation, Heat Source/Sink and Work Done by Deformation Impacts on MHD Viscoelastic Fluid over a Nonlinear Stretching Sheet

This work is focused on the effects of heat source/sink, viscous dissipation, radiation and work done by deformation on flow and heat transfer of a viscoelastic fluid over a nonlinear stretching sheet. The similarity transformations have been used to convert the governing partial differential equations into a set of nonlinear ordinary differential equations. These equations are then solved numerically using a very efficient implicit finite difference method. Favorable comparison with previously published work is performed and it is found to be in excellent agreement. The results of this parametric study are shown in several plots and tables and the physical aspects of the problem are highlighted and discussed.

Effects of Radiations and Heat Source/Sink on a Casson Fluid Flow over Nonlinear Stretching Sheet

The present study deals with the flow over a nonlinearly stretching sheet of Casson fluid with the effects of radiation and heat source/sink. The Casson fluid model is used to characterize the non-Newtonian fluid behaviour. With the help of justified similarity transformations the governing equations were reduced to couple nonlinear ordinary differential equations. The effective numerical technique Keller Box method is used to solve these equations. The variations in velocity, temperature profiles were presented with the various values of nonlinear stretching parameter n and Casson parameter β. The nature of Skinfriction and Local nusselt number has presented. Effects of radiation and heat source/sink on temperature profiles have been discussed.

Effect of Nonlinear Thermal Radiation on Boundary Layer Flow of Viscous Fluid over Nonlinear Stretching Sheet with Injection/Suction

The present study reveals the effect of nonlinear thermal radiation and magnetic field on a boundary layer flow of a viscous fluid over a nonlinear stretching sheet with suction or an injection. Using suitable similarity transformations, governing partial differential equations were reduced to higher order ordinary differential equations and further these are solved numerically using of Keller-Box method. Effect of flow controlling parameter on velocity, temperature and nanoparticle fluid concentration, local skin friction coefficient, local Nusselt number and local Sherwood numbers are discussed. It is found that the dimensionless velocity decreases and temperature, concentration are increased with the increasing of magnetic parameter. The temperature profile is an increasing function of thermal radiation when it is increasing.

Darcy–Forchheimer Three-Dimensional Flow of Williamson Nanofluid over a Convectively Heated Nonlinear Stretching Surface

The present study elaborates three-dimensional flow of Williamson nanoliquid over a nonlinear stretchable surface. Fluid flow obeys Darcy–Forchheimer porous medium. A bidirectional nonlinear stretching surface generates the flow. Convective surface condition of heat transfer is taken into consideration. Further the zero nanoparticles mass flux condition is imposed at the boundary. Effects of thermophoresis and Brownian diffusion are considered. Assumption of boundary layer has been employed in the problem formulation. Convergent series solutions for the nonlinear governing system are established through the optimal homotopy analysis method(OHAM). Graphs have been sketched in order to analyze that how the velocity, temperature and concentration distributions are affected by distinct emerging flow parameters. Skin friction coefficients and local Nusselt number are also computed and discussed.

Casson fluid flow and heat transfer over a nonlinearly stretching surface

A boundary layer analysis is presented for non-Newtonian fluid flow and heat transfer over a nonlinearly stretching surface. The Casson fluid model is used to characterize the non-Newtonian fluid behavior. By using suitable transformations, the governing partial differential equations corresponding to the momentum and energy equations are converted into non-linear ordinary differential equations. Numerical solutions of these equations are obtained with the shooting method. The effect of increasing Casson parameter is to suppress the velocity field. However the temperature is enhanced with the increasing Casson parameter.

Finite element solution of nonlinear convective flow of Oldroyd-B fluid with Cattaneo-Christov heat flux model over nonlinear stretching sheet with heat generation or absorption

In this study,a two-dimensional boundary layer flow of steady incompressible nonlinear convective flow of Oldroyd-B fluid over a nonlinearly stretching sheet with Cattaneo-Christov heat flux model and heat generation or absorption is examined.The governing equations of the boundary layer flow which are highly nonlinear partial differential equations are converted to the ordinary differential equations using similarity transformations and then the Galerkin finite element method(GFEM)is used to solve the proposed problem.The effect of local Deborah numbers 0,and ft.local buoyancy parameter z,Prandtl number Pr,Deborah number y,and heat generation/absorption parameter<5 on the temperature and the velocity as well as heat transfer rate and shear stress are discussed both in graphical and tabular forms.The result shows the enlargement in the local buoyancy parameter A will improve the velocity field and the heat transfer rate of the boundary layer flow.Moreover,our present work evinced both local skin friction coefficient and heat transfer rate step up if we add the values of non-linear stretching sheet parameter and local heat generation/absorption parameter has quite the opposite effect.The numerically computed values of local skin friction coefficient and local Nusselt number are validated with available literature and evinced excellent agreement.

MHD Stagnation Point Flow of a Casson Fluid over a Nonlinearly Stretching Sheet with Viscous Dissipation

Study to analyze the MHD stagnation point flow of a Casson fluid over a nonlinearly stretching sheet with viscous dissipation was carried out. The partial differential equations governing this phenomenon were transformed into coupled nonlinear ordinary differential equations with suitable similarity transformations. These equations were then solved by finite difference technique known as Keller Box method. The various parameters such as Prandtl number (Pr), Eckert number (Ec), Magnetic parameter (M), Casson parameter (β) and non linear stretching parameter (n) determining the velocity and temperature distributions, the local Skin friction coefficient and the local Nusselt number governing such a flow were also analyzed. On analysis it was found that the Casson fluid parameter (β) decreased both the fluid velocity and temperature whereas an increase in (β) increased both the heat transfer rate and wall skin-friction coefficient.

Mixed Convection MHD Flow of a Casson Nanofluid over a Nonlinear Permeable Stretching Sheet with Viscous Dissipation

The present study deals with the mixed convection MHD flow of a Casson nanofluid over a nonlinear permeable stretching sheet with viscous dissipation. The governing partial differential equations are transformed into nonlinear coupled ordinary differential equations with the help of suitable similarity transformations. These equations were then solved numerically by using an implicit finite difference method known as Keller-Box method. The effects of various parameters such as magnetic parameter (M), Casson parameter (β), local Grashoff number (Gr), local modified Grashoff number (Gc), nonlinear parameter (n), Eckert number (Ec) on velocity, temperature and concentration were discussed and presented graphically. It is found that a larger value of Casson parameter leads to decrease the velocity and temperature. Increase in the local Grashoff number reduces the temperature. Nanoparticle concentration is decreased for the larger values of local Modified Grashoff number. The numerical values of skin friction, Nusselt number and Sherwood number are presented in tables.

MHD Flow, and Heat Transfer with Effects of Buoyancy, Viscous and Joules Dissipation over a Nonlinear Vertical Stretching Porous Sheet with Partial Slip

In this paper, the problem of steady laminar two-dimensional boundary layer MHD flow and heat transfer of an incompressible viscous fluid with the presence of buoyancy force and viscous dissipation over an vertical nonlinear stretching sheet with partial slip is investigated numerically. Numerical solutions of the resulting nonlinear boundary value problem in the case when the sheet stretches with a velocity varying nonlinearly with the distance is carried out. The effects of for various values of suction parameter, magnetic parameter, Prandtl number, Eckert number, buoyancy parameter, nonlinear stretching parameter and slip parameter on flow and heat transfer characteristics is investigated.

Stretch Forming Simulation of Woven Composites Based on an Orthotropic Non-Linear Material Model

Characterisation experiments have been conducted on a woven self-reinforced polypropylene composite (SRPP) including uniaxial and bias extension tests. Outcomes of these experiments were employed to develop a non-linear orthotropic material model within an incremental deformation framework. The material model of the woven composite was implemented into a finite element simulation to predict stretch forming behaviour of SRPP specimens. The predicted strain paths at the pole of specimens were verified against experimental outcomes. It was shown that specimens possessing different aspect ratios deform under a wide range of deformation modes from uniaxial extension to biaxial stretch modes. Finally, the effect of different forming parameters on the strain path evolution of the woven composite was elucidated through numerical simulations. It was shown that the aspect ratio of the samples plays an important role in forming behaviour of woven composites. Development of a reliable and accurate numerical model for predicting forming behaviour of woven composites and understanding their main forming mechanisms promote and encourage the extensive application of these materials systems in a wide range of mass producing industries. Adopting woven composites in manufacturing industrial components facilitates addressing environmental concerns such as recyclability and sustainability issues.

Heat transfer characteristics of thin power-law liquid films over horizontal stretching sheet with internal heating and variable thermal coefficient

The effect of internal heating source on the film momentum and thermal transport characteristic of thin finite power-law liquids over an accelerating unsteady horizontal stretched interface is studied. Unlike most classical works in this field, a general surface temperature distribution of the liquid film and the generalized Fourier＇s law for varying thermal conductivity are taken into consideration. Appropriate similarity transformations are used to convert the strongly nonlinear governing partial differential equations （PDEs） into a boundary value problem with a group of two-point ordinary differential equations （ODEs）. The correspondence between the liquid film thickness and the unsteadiness parameter is derived with the BVP4C program in MATLAB. Numerical solutions to the self-similarity ODEs are obtained using the shooting technique combined with a Runge-Kutta iteration program and Newton＇s scheme. The effects of the involved physical parameters on the fluid＇s horizontal velocity and temperature distribution are presented and discussed.

非线性拉伸对层流燃烧速度提取的影响

基于理论模型推导出一种非线性NLC层流燃烧速度外推方程,并采用定容燃烧弹获取甲烷/空气、正丁烷/空气和氢气/空气的火焰发展历程。基于文献常用和本文提出的4种线性和非线性外推方程研究4种典型火焰中非线性拉伸对层流燃烧速度提取的影响。研究结果表明:随着马克斯坦长度的增加,非线性拉伸的影响增加,不同方程测量的层流燃烧速度差异增加。其中,本文提出的非线性NLC模型得到的结果与实验结果吻合最好,测量层流燃烧速度精度最高;非线性LC和NLS模型表现居中,而线性LS模型明显高估层流燃烧速度。另外,可以采用高精度非线性模型并适当增加初始火焰半径的策略减小非线性拉伸的影响,从而提高层流燃烧速度的测量精度。

压电晶体谐振器非线性厚度拉伸振动研究

基于压电理论的三维运动方程和边界条件,能够精确得到描述压电晶体板的振动。由于压电特性、各向异性及非线性,方程非常复杂,解析求解几乎不可能。考虑压电谐振器晶体板的结构特点,以一维无限大压电晶体板为研究对象,分析压电晶体谐振器非线性厚度拉伸振动。针对边界短路的非线性厚度拉伸振动,通过伽辽金法求解微分方程,得到振动振幅、晶体材料高阶弹性常数与非线性频率漂移之间的关系。并且利用解耦方法,通过振动幅值建立恒定电流与频率漂移之间的联系。

夜间车道线检测的研究

夜间环境下的车道线检测是汽车智能辅助安全驾驶系统在夜间正常工作的前提和基础。由于夜间环境下存在图像整体较暗、光照不均匀、车道线不易检测的特点,使当前在日间环境下应用良好的算法难以适用。针对此问题,该文提出一种夜间车道线检测的方法。通过从摄像机获取的图像中提取感兴趣区域,采用双边滤波去除感兴趣区域中的噪点,并使用暗光增强算法提高对比度,最后通过边缘检测算法提取出边缘并应用霍夫变换得出直线。应用该文算法对夜间环境下的车道图像进行测试,实验结果表明,该文算法较常规的车道检测算法更能准确地检测出车道线。

弹性曲梁在机械和热载荷共同作用下的几何非线性模型及其数值解

基于Euler-Bernoulli梁的几何非线性理论,建立了弹性曲梁在任意分布机械载荷和热载荷共同作用下的几何非线性静平衡控制方程。该模型不仅计及了轴线伸长,同时也精确地考虑了梁的初始曲率对变形的影响以及轴向变形与弯曲变形之间的相互耦合效应。应用打靶法数值求解了半圆形曲梁在横向均匀升温作用下的非线性弯曲问题,数值比较了轴向伸长对曲梁变形的影响。

穿支血管蒂螺旋桨皮瓣蒂部血管扭转的非线性有限元模拟研究

目的研究牵张力、伴行静脉数量和动静脉间距对穿支血管蒂螺旋桨皮瓣蒂部血管扭转的影响。方法应用LSDYNA软件建立穿支血管蒂三维非线性数字化模型,分3组进行实验:(1)等长和等张扭转;(2)血管蒂为1支和2支伴行静脉;(3)穿支动静脉间距分别在0、2、4、6 mm的情况下扭转。3组实验均从0°扭转至180°,通过血管最窄处横截面积变化,反映血管的通畅性。结果 (1)等张扭转组血管蒂通畅程度明显大于等长扭转组;(2)1支管腔通畅程度大于2支,但2支静脉的管腔截面积之和仍大于1支;(3)穿支动静脉间距加大,管腔的狭窄程度也逐渐增加。结论 (1)在血管蒂扭转的同时施加牵张力,将使血管的通畅性明显降低;(2)在穿支血管蒂螺旋桨皮瓣中,2支伴行静脉的通畅性仍较1支为好;(3)穿支动静脉间距越大,扭转后绞窄越明显,甚至发生管腔闭塞。

低阈值展宽脉冲锁模掺Er^(3+)光纤环形激光器的实验研究(英文)

将正色散值较小的掺铒光纤引入传统的环形腔构成了低阈值的展宽脉冲锁模激光器.通过使用这种掺铒光纤,激光器的锁模阈值大大降低,激光器的自起振泵浦功率仅为90mW,而且在29mW的低泵浦功率时仍然可维持稳定的锁模状态.实验中获得了脉冲宽度为175fs,光谱半高宽为40nm,重复频率为33MHz的锁模脉冲输出.激光器工作稳定,光谱干净光滑.