Numerical Analysis of the Mixed Flow of a Non-Newtonian Fluid over a Stretching Sheet with Thermal Radiation

A mathematical model is elaborated for the laminar flow of an Eyring-Powell fluid over a stretching sheet.The considered non-Newtonian fluid has Prandtl number larger than one.The effects of variable fluid properties and heat generation/absorption are also discussed.The balance equations for fluid flow are reduced to a set of ordinary differential equations through a similarity transformation and solved numerically using a Chebyshev spectral scheme.The effect of various parameters on the rate of heat transfer in the thermal boundary regime is investigated,i.e.,thermal conductivity,the heat generation/absorption ratio and the mixed convection parameter.Good agreement appears to exist between theoretical predictions and the existing published results.

MHD Effects on Mixed Convective Nanofluid Flow with Viscous Dissipation in Surrounding Porous Medium

In existence of concerning magnetic field, heat together with mass transfer features on mixed convective copper-water nanofluid flow through inclined plate is investigated in surrounding porous medium together with viscous dissipation. A proper set of useful similarity transforms is considered as to transform the desired governing equations into a system as ordinary differential equations which are nonlinear. The transformed equations for nanofluid flow include interrelated boundary conditions which are resolved numerically applying Runge-Kutta integration process of sixth-order together with Nachtsheim and Swigert technique. The numerical consequences are compared together with literature which was published previously and acceptable comparisons are found. The influence of significant parameters like as magnetic parameter, angle for inclination, Eckert number, fluid suction parameter, nanoparticles volume fraction, Schmidt number and permeability parameter on concerning velocity, temperature along with concentration boundary layers remains examined and calculated. Numerical consequences are presented graphically. Moreover, the impact regarding these physical parameters for engineering significance in expressions of local skin friction coefficient in addition to local Nusselt together with Sherwood numbers is correspondingly examined.

Efect of double dispersion on non-Darcy mixed convective flow over vertical surface embedded in porous medium

A numerical study of a non-Darcy mixed convective heat and mass transfer flow over a vertical surface embedded in a dispersion, melting, and thermal radiation is porous medium under the effects of double investigated. The set of governing boundary layer equations and the boundary conditions is transformed into a set of coupled nonlinear ordinary differential equations with the relevant boundary conditions. The transformed equations are solved numerically by using the Chebyshev pseudospectral method. Comparisons of the present results with the existing results in the literature are made, and good agreement is found. Numerical results for the velocity, temperature, concentration profiles, and local Nusselt and Sherwood numbers are discussed for various values of physical parameters.

A Mixed Convection Boundary Layer Flow over a Vertical Wall in a Porous Medium, with Exponentially Varying Fluid Viscosity

This study investigates a mixed convection boundary layer flow over a vertical wall embedded in a highly porous medium. The fluid viscosity is assumed to decrease exponentially with temperature. The boundary layer equations are transformed into a non-similar form using an appropriate non-similar variable ξ and a pseudo-similar variable η. The non-similar equations are solved using an efficient local non-similarity method. The effect of viscosity variation parameter on the heat transfer, skin friction and the velocity and temperature distribution within the boundary layer is investigated. The viscosity variation parameter, the viscous dissipation parameter and non-simi-larity variable are shown to have a significant effect on velocity and thermal boundary layer and also on the skin friction coefficient and heat transfer at the wall.

Unsteady Mixed Convection Slip Flow around a Stretching Sheet in Porous Medium

The heat and mass transfer of unsteady MHD two-dimensional mixed convection boundary layer flow over an exponentially porous stretching sheet is presented in this paper. Multiple slip conditions, radiation, suction or blowing, heat generation or absorption along with magnetism and porous medium are incorporated. We reduce the leading equations which are partial differential equations into a family of ordinary differential equations that are non-linear using a set of similarity transformations. The resulting equations with coupled boundary conditions are solved numerically with the aid of bvp4c solver with MATLAB package. The impacts of several non-dimensional governing parameters on the flow fields such as velocity, temperature and concentration profiles along with friction coefficient, temperature gradient and concentration gradient are portrayed graphically and discussed in detail. The result indicates that the magnetic parameter decreases the skin friction coefficient. Thermal boundary layer thickness reduces with increasing radiation parameters and enhances with increasing Prandtl number. It is also observed that the thermal slip parameter depreciates the heat transfer rate and the mass slip parameter diminishes the mass transfer rate. A comparison has been made between the current results and the numerical results of previous studies and observed a very close good agreement.

Rheological properties of warm mix asphalt binder by DSR test at medium temperature

The rheological properties including the complex modulus G＊ and the phase angle δof matrix and warm mix asphalt （WMA）binders were measured by using the dynamic shear rheometer （DSR ） test at the medium temperature ranging from 16 to 40 ℃,and the relationships between the fatigue factor G＊ sinδand the matrix binder property,WMA additive and test temperature were established.It is found that G＊ decreases with the increasing temperature while δincreases inversely,and G＊ of the asphalt binder with high WMA additive dosage is large,and δis small.G＊sinδexponentially decreases with the increasing temperature and linearly increases with the increase in additive dosage,and the amplitudes of variation are large at low temperatures and high additive dosages.The effect of WMA additive on the rheological property is more remarkable for the matrix asphalt binder with low G＊.Besides,aging has a great effect on the property of matrix asphalt binder,and a slight effect on the interaction between asphalt and additive.The high additive dosage can increase the fatigue cracking potential of the asphalt binder.

A New Method for Hydrocarbon Detection Based on Multi-phase Theory

The hydrocarbon detection techniques used currently are generally based on the theory of single-phase medium, but hydrocarbon reservoir mostly is multi-phase medium, therefore, multisolutions and uncertainties are existed in the result of hydrocarbon detection. This paper presents a fast way to detect hydrocarbon in accordance with BOIT theory and laboratory data. The technique called DHAF technique has been applied to several survey area and obtained good result where the coincidence rate for hydrocarbon detection is higher than other similar techniques. The method shows a good prospect of the application in hydrocarbon detecting at exploration stage and in reservoir monitoring at production stage.

Large-eddy simulation of fluid mixing in tee with sintered porous medium

Mixing processes of hot and cold fluids in a tee with and without sin- tered copper spheres are simulated by FLUENT using the large-eddy simulation （LES） turbulent flow model and the sub-grid scale （SGS） Smagorinsky-Lilly （SL） model with buoyancy. Comparisons of numerical results of the two cases with and without sintered copper spheres show that the porous medium significantly reduces velocity and temper- ature fluctuations because the porous medium can effectively restrict the fluid flow and enhance heat transfer. The porous medium obviously increases the pressure drop in the main duct. The porous medium reduces the power spectrum density （PSD） of tempera- ture fluctuations in the frequency range from 1 Hz to 10 Hz.

Mixed graphite cast iron for automotive exhaust component applications

Both spheroidal graphite iron and compacted graphite iron are used in the automotive industry. A recently proposed mixed graphite iron exhibits a microstructure between the conventional spheroidal graphite iron and compacted graphite iron. Evaluation results clearly indicate the suitability and benefits of mixed graphite iron for exhaust component applications with respect to casting, machining, mechanical, thermophysical, oxidation, and thermal fatigue properties. A new ASTM standard specification(A1095) has been created for compacted, mixed, and spheroidal graphite silicon-molybdenum iron castings. This paper attempts to outline the latest progress in mixed graphite iron published.

A MIXED ELECTRIC BOUNDARY VALUE PROBLEM FOR AN ANTI-PLANE PIEZOELECTRIC CRACK

The analytical continuation method is adopted to solve a mixed electric boundary value problem for a piezoelectric medium under anti-plane deformation.The crack face is partly conductive and partly impermeable.The results show that the stress intensity factor is identical with the mode Ⅲ stress intensity factor independent of the conducting length.But the electric field and the electric displacement are dependent on the electric boundary conditions on the crack faces and are singular not only at the crack tips but also at the junctures between the impermeable part and conducting portions.

MHD Effect on an Oscillatory Mixed Convective Flow Past an Infinite Vertical Porous Plate with Radiation

A parametric study to investigate the effects of magnetic field and radiation on a mixed convective flow past an infinite vertical porous plate with constant suction velocity when the free stream varies periodically with time about a steady mean is presented. A uniform magnetic field is applied normal to the plate. The Rosseland approximation is used to describe the radiative heat flux in the energy equation and the resultant set of non-dimensional equations are solved analytically by adopting regular perturbation technique. The profiles of velocity, temperature, skin-friction and nusselt number are demonstrated graphically for various values of the parameters involved in the problem and the results are physically interpreted.

Hydrodynamic Anisotropy Effects on Radiation-Mixed Convection Interaction in a Vertical Porous Channel

The effects of hydrodynamic anisotropy on the mixed-convection in a vertical porous channel heated on its plates with a thermal radiation are investigated analytically for fully developed flow regime. The porous medium is anisotropic in permeability whose principal axes are oriented in a direction that is oblique to the gravity. The generalized Brinkman-extended Darcy model which allows the no-slip boundary-condition on solid wall is used in the formulation of the problem. The flow reversal, the thermal radiation influence for natural, and forced convection are considered in the limiting cases for low and high porosity media. It was found that the anisotropic permeability ratio, the orientation angle of the principal axes of permeability and the radiation parameter affected significantly the flow regime and the heat transfer.

深冷轧制变形对新型Ni-W-Co-Ta高密度合金显微组织与性能的影响

采用熔炼-浇铸-锻造流程制备新型Ni-W-Co-Ta高强度合金,并对Ni-W-Co-Ta合金经深冷轧制变形后的显微组织及力学性能演变规律进行表征。结果表明:随着变形量的增加,新型Ni-W-Co-Ta高密度合金中等轴晶粒沿轧制方向不断被拉长,同时产生大量的滑移带以协调剧烈的塑性变形,并最终形成纤维组织。变形量的增大导致位错密度急剧增大,位错交互作用显著加强,进而使晶粒尺寸细化至纳米量级;合金强度、硬度随着变形量的增加而显著提高,伸长率则急剧下降。断口形貌则由韧性断裂(未变形)向准解理-韧性混合型断裂转变(90%变形量)。

等离子射流在模拟液体发射药中扩展特性的数值模拟

为了深入认识液体工质电热化学炮中等离子射流的点火过程,开展了等离子射流在液体发射药LP1846模拟工质中扩展特性的研究,建立了等离子射流在液体中扩展的二维轴对称非稳态数学模型,并基于液体工质为水的文献实验进行模型验证。在此基础上对等离子射流在LP1846液体发射药模拟工质中的扩展过程进行数值模拟,分析等离子射流在扩展过程中形态的变化以及射流场压力、速度和温度的分布特性。结果表明,扩展过程中由于Taylor-Helmholtz不稳定性,等离子射流和液体发射药模拟工质两相间存在湍流掺混现象,并随着扩展逐渐加剧,表现为射流头部凸出并逐渐轴向拉长形成尖头,同时射流卷吸液体发射药模拟工质在Taylor空腔中产生液滴,且数量逐渐增多。此外,等离子射流扩展过程中近喷孔处由于液体发射药模拟工质回流而出现颈缩现象。射流场由于膨胀波-压缩波交替作用而存在波动现象,且在近喷孔处尤为剧烈,表现为压力场呈现高低压相间分布,速度场也呈类似分布。

磁场强化非均相分离技术的工业应用进展

概述了磁场分离技术在分离多相混合介质中的研究和应用进展,对磁场分离技术的应用原理和分离优势进行了分析。根据混合相内的介质类别,分别针对固、液、气不同应用领域,介绍了磁场分离工艺在矿物精选、污水处理、气体除杂中的典型应用,并分析了相应运行工况下的磁场排布规律和介质分离特性。从组合工艺的研究视角出发,总结了磁场分离技术与气浮分离技术、膜分离技术、旋流分离技术的耦合应用现状,并分析了上述组合工艺的技术特点、运行成效。为拓宽磁场分离技术的适用范围,讨论了磁种在磁场分离工艺中的辅助应用,以强化该技术对无磁性介质的分离。

中温温拌再生沥青性能研究

本文对中温再生沥青制备工艺以及性能进行研究,通过试验研究了制备温度、剪切时间、中温再生剂掺量对中温再生沥青性能的影响。研究结果表明,(1)制备中温再生沥青的工艺条件为:70#基质沥青加热温度为120℃,中温再生剂加热温度为80℃,中温再生剂在沥青中的剪切时间为90min;(2)中温再生剂提高了沥青的低温延展性,降低了沥青的黏度,提高了施工和易性;(3)老化沥青的针入度随着中温再生剂掺量的增加而增加,软化点随着中温再生剂掺量的增加而降低,对于70#基质沥青而言,中温再生剂的最佳掺量为沥青质量的4%。

中锰低温钢富氩混合气体保护焊工艺研究

较高的锰含量给中锰低温钢焊接带来了挑战,这在一定程度上限制了中锰低温钢在工业生产中的应用。采用富氩混合气体保护焊对中锰低温钢进行焊接试验,研究不同焊接热输入条件下,焊接接头显微组织和力学性能的变化规律。结果表明:除焊缝及母材外,焊接接头各区域均为局部硬化区,且硬化程度随热输入的增加而增大;当热输入由12 kJ/cm增加到22 kJ/cm时,焊接接头的屈服强度由820 MPa降至775 MPa,抗拉强度由983 MPa降至925 MPa;当热输入为12 kJ/cm和16.8 kJ/cm时,其焊接接头在-40℃条件下均有着良好的冲击韧性,且后者焊接接头各区域冲击吸收功较为均匀,在45 J左右;焊缝区细小的夹杂物及针状铁素体提供了高密度的大角度晶界,减缓了裂纹扩展速率。热影响区稳定性较低的残余奥氏体在受到冲击载荷作用时发生相变诱导塑性(TRIP)效应,提高了焊接接头的低温冲击韧性。

大掺量中温再生沥青混合料性能研究

采用中温再生剂制备了中温再生沥青,研究了中温再生沥青混合料的拌和成型温度以及其路用性能。通过绘制中温沥青的黏温曲线并联合中温再生沥青混合料的马歇尔试验结果,确定了中温再生沥青混合料的制备成型温度。通过马歇尔指标参数确定了中温再生沥青混合料的最佳配合比,并将中温再生沥青混合料和热拌再生沥青混合料的路用性能进行对比。研究结果显示:(1)中温再生沥青混合料的最佳拌和温度为135℃,最佳压实温度为125℃,比热拌再生沥青混合料低40℃;(2)中温再生沥青混合料的高温性能、水稳定性和低温性能均优于热拌再生沥青混合料;(3)随着RAP掺量的增加,中温再生沥青混合料的高温稳定性逐渐升高,但RAP掺量的增加会降低水稳定性和低温性能。

立式螺旋搅拌磨机磨矿介质动力学研究

针对传统单相模拟法在模拟立式螺旋搅拌磨机(以下简称“立磨机”)过程中的局限性,如可视化反映特征少、未考虑流体对介质的作用导致仿真精度低等问题。采用一种基于CFD-DEM固液耦合仿真的新方法,用于模拟立磨机湿磨的磨矿过程,该方法能有效提高湿磨仿真的精度。首先建立立磨机的三维模型,以及完成参数标定的流体与介质颗粒,而后利用固液耦合仿真新方法对湿磨条件下磨筒内介质球的运动进行可视化仿真分析。结合室内试验,以主轴扭矩作为仿真精度的评价指标,并定义了一种区域介质球运动速度算法,描述了磨筒内介质球的运动规律,最后对比分析了磨矿过程中介质的法向作用力与切向作用力。研究结果表明:耦合模拟法仿真的轴向扭矩值与试验扭矩值的平均相对误差为6.98%;结果显示,介质运动的平均速度最大值和最小值分别为0.1646m/s与0.0112m/s,且速度梯度较大的位置位于螺旋搅拌叶片周围区域;介质接触时法向力是切向力的5倍。由此可知,耦合模拟法相比传统单相模拟法能有效提高仿真精度。螺旋搅拌叶片周围区域因速度梯度大,是矿物能被有效研磨的前提,研磨物质主要受到介质的挤压破碎作用。

BCJ-4I型混装炸药车在石碌铁矿中深孔爆破的应用

针对石碌铁矿上向中深孔人工装药过程中,存在安全隐患大、工人劳动强度大、返粉率高、作业环境恶劣、作业效率低等缺点,引进先进的混装炸药车,应用专用乳胶基质及敏化剂溶液、闭环比例控制、无线遥控寻孔和自动送、退管等关键技术,实现装药作业机械化、自动化、智能化,降低了炸药成本,改善了爆破效果,同时减小了工人劳动强度,提高了作业安全性。