Transient Simulation of the Electrolyte Flow in a Closed Device for Precise Electrochemical Machining - new
M. Hackert-Oschätzchen, M. Penzel, M. Kowalick, G. Meichsner, A. Schubert[1,2]
Professorship Micromanufacturing Technology, Technische Universität Chemnitz, Chemnitz, Germany
Fraunhofer Institute for Machine Tools and Forming Technology, Chemnitz, Germany
Precise electrochemical machining (PEM) is an innovative machining technology which results from further development of the electrochemical sinking. PEM works with pulsed low frequency direct current and oscillation of the tool electrode. As part of the project ‘Electrochemical machining of internal precision and micro-geometries with high aspect ratios by process-state-dependent electrolyte ...
基于 Level-Set 界面跟踪方法建立了激光熔覆过程的三维瞬态数值模型，研究了瞬态熔化和凝固过程中传热传质的演化规律。该模型使用 Level-Set 方法跟踪熔池气/液界面，采用焓－多孔度（enthalpy-porosity）方法得到了固/液界面之间的糊状区，并考虑了质量添加、材料熔化/凝固、热毛细效应（Marangoni效应）、浮力效应、活性元素质量传输等对熔池流动和界面的影响。通过该模型，具体分析了质量添加、力和界面平衡条件对熔池气/液界面的影响，以及由熔池温度/浓度分布引起的热毛细效应、金属材料的熔/凝过程和熔池流动形式对熔池固/液界面的影响。结果表明：熔池的气/液界面主要由力平衡条件决定，截面近似为圆弧型，其尺寸与单位时间的质量添加量相关。熔池的固/液形态由于熔池的表面温度梯度和表面活性元素含量共同引起的熔池流动方向和速度的变化，出现三种不同的类型，分别为下凹型（熔池内流） ...
赵旭山 , 郝雷 , 蒋利军 , 米菁 , 杨海龄 ,
随着能源紧张、油价攀升，环境污染严重，利用可再生绿色能源又成为不懈努力的方向。槽式太阳能热发电技术具有兼容性强、对电网冲击小、性价比高、发电成本低、可存储可调度等特点，近年来得到了迅猛发展，其核心部件为高温太阳能真空集热管，如图1所示。本研究利用 COMSOL Multiphysics® 针对真空集热管真实工况下的动态过程开展研究，并在此基础上开展集热管结构的优化设计。 由图1可知：集热管在电站中服役工况下，槽面会聚的太阳光主要集中于集热管下半面，上半面接收的会聚太阳光较少；导热工质自吸收管一端进入，接收会聚太阳光辐照能量，从吸收管另一端流出，流入→流出过程中，导热工质被加热；集热管外表面与外部环境通过热辐射和对流两种方式换热；吸收管与玻璃罩管间形成的环形密闭高真空区域各内表面通过热辐射换热，不考虑对流；集热管两端支撑固定于聚光器上，由于本身自重和热应力 ...
S. Pramanik, G. L. Kulukuru, M. Mishra
Indian Institute of Technology Ropar, Rupnagar, Punjab, India
When a less viscous fluid displaces a more viscous one in a porous medium or Hele-Shaw cell, the interface between the two miscible fluids does not remain flat and deforms into fingers growing in time . It occurs due to the faster movement of less viscous fluid than the more viscous one, for a given pressure gradient. Fingering affects in aquifers, in packed bed reactors, and detrimental to ...
Dipartimento di Ingegneria Industriale, Università degli Studi di Parma, Parma, Italy
The work is focused on the numerical analysis of forced convection in curved tubes investigating the correlation between the heat transfer and friction factor enhancement and the effects of the wall curvature. The analysis was performed by integrating the continuity, momentum and energy equations within COMSOL Multiphysics. The local Nusselt number reaches values higher than the ones expected ...
D. C. Raharja , R. E. Hincapie , M. Be , C. L. Gaol , L. Ganzer ,
 Clausthal University of Technology, Clausthal-Zellerfeld, Germany
Aqueous polymers used for enhanced oil recovery (EOR) application is considered a complex fluid. It can exhibit Newtonian and Non-Newtonian behavior depending on the velocity or the stresses that it is submitted during the flooding process. Therefore, the polymer flooding project requires a detailed understanding of chemical and physical process occurred in the porous subsurface reservoir, ...
I .F. Melikhov , A. S. Amosov , S. A. Chivilikhin ,
 Corning Scientific Center, Saint Petersburg, Russia
 ITMO University, Saint Petersburg, Russia
Ultrasonic levitation is a novel technology for contactless handing of various objects. It is already used in various manufacturing processes where it is important to keep untouched surface. In this paper we introduce a model of so-called near-field ultrasonic levitation which allows flying heights of the hundred-micron order. Our model computes air flow in the gap between a vibration source and ...
Control the Poly-Dispersed Droplet Breakup Mode in a Droplet-based Microfluidic Device by External Electric Field
Y. Li , K. Nandakumar , M. Jain ,
 Cain Department of Chemical Engineering, Louisiana State University, Baton Rouge, LA, USA
Droplet–based microfluidics has received special research attentions in last two decades due to its superior control over fluid flow as well as other unique advantages. By introducing two immiscible fluids into microfluidic systems, the reagent fluid is encapsulated inside discrete droplets or slugs of nanoliter volume . Interestingly, two breakup modes, termed as “mono-dispersed” and ...
A. Giaccherini , A. Lavacchi ,
 INSTM, Firenze, Italy
 ICCOM - CNR, Firenze, Italy
In this work we report a numerical model of a Rotating Disk Electrode (RDE) voltammetry in a finite size domain. Thus, explaining the discrepancy of the diffusion coefficient obtained from the experimental rotating speed, with respect to the literature data. We achieved a very good agreement at the limiting current and at the unexpected peak for the RDE voltammetry at 2000 rpm and different ...
A. Kumar , C. Kaur , S. S. Padhee ,
 PEC University of Technology, Chandigarh, India
 IIT Ropar, Punjab, India
This paper explores the complexities of a dragonfly's flapping wing motion. It includes the literature as well as analytical results using simulations done in COMSOL Multiphysics® software. The study depicts the Fluid-Structure Interaction of the 2D wing (airfoil) with air, governed by Naiver-Stokes equations. The wing follows mathematical functions and is given motion similar to dragonfly's ...