Applied sciences

Bulletin of the Polish Academy of Sciences: Technical Sciences

Content

Bulletin of the Polish Academy of Sciences: Technical Sciences | 2005 | vol. 53 | No 4 |

Download PDF Download RIS Download Bibtex

Abstract

Traditional fluid mechanics edifies the indifference between liquid and gas flows as long as certain similarity parameters – most prominently the Reynolds number – are matched. This may or may not be the case for flows in nano- or microdevices. The customary continuum, Navier-Stokes modelling is ordinarily applicable for both air and water flowing in macrodevices. Even for common fluids such as air or water, such modelling bound to fail at sufficiently small scales, but the onset for such failure is different for the two forms of matter. Moreover, when the no-slip, quasi-equilibrium Navier – Stokes system is no longer applicable, the alternative modelling schemes are different for gases and liquids. For dilute gases, statistical methods are applied and the Boltzmann equation is the cornerstone of such approaches. For liquid flows, the dense nature of the matter precludes the use of the kinetic theory of gases, and numerically intensive molecular dynamics simulations are the only alternative rooted in first principles. The present article discusses the above issues, emphasizing the differences between liquid and gas transport at the microscale and the physical phenomena unique to liquid flows in minute devices.

Go to article

Authors and Affiliations

M. Gad-El-Hak
Download PDF Download RIS Download Bibtex

Abstract

A review is given on a number of colloidal phenomena with special reference to their applicability to nanoparticles. Phenomena addressed include preparation, electric double layers and their characterization, electrokinetics, van der Waals and Lifshits forces, electric and steric particle interaction.

Go to article

Authors and Affiliations

J. Lyklema
Download PDF Download RIS Download Bibtex

Abstract

In this paper we present the numerical simulation-based design of a new microfluidic device concept for electrophoretic mobility and (relative) concentration measurements of dilute mixtures. The device enables stationary focusing points for each species, where the locally applied pressure driven flow (PDF) counter balances the species’ electrokinetic velocity. The axial location of the focusing point, along with the PDF flowrate and applied electric field reveals the electrokinetic mobility of each species. Simultaneous measurement of the electroosmotic mobility of an electrically neutral specie can be utilized to calculate the electrophoretic mobility of charged species. The proposed device utilizes constant sample feeding, and results in time-steady measurements. Hence, the results are independent of the initial sample distribution and flow dynamics. In addition, the results are insensitive to the species diffusion for large Peclet number flows (Pe > 400), enabling relative concentration measurement of each specie in the dilute mixture.

Go to article

Authors and Affiliations

J. Hahm
A. Beskok
Download PDF Download RIS Download Bibtex

Abstract

We discuss recent progress in hybrid atomistic-continuum methods with particular emphasis on developments in boundary condition imposition in molecular simulations, an essential ingredient of hybrid methods. Both Dirichlet (state variable) and flux boundary conditions are discussed. We also briefly review various coupling approaches and discuss the effects of compressibility and molecular fluctuations on the choice of coupling method. Common elements between hybrid methods and related multiscale simulation approaches are also briefly discussed.

Go to article

Authors and Affiliations

N.G. Hadjiconstantinou
Download PDF Download RIS Download Bibtex

Abstract

The topic of incompressible fluid flow in rough channels is of practical interest in many diverse applications. It also forms the basis of our understanding of fluid-wall interactions, turbulent eddy generation, and their effect on the frictional pressure losses. Although this topic is also of fundamental interest, the work in this area is entirely guided by the experimental work of earlier investigators [1–6]. The works by Nikuradse [4] and Colebrook [5] constitute a major milestone from which useful empirical models are derived. As we approach the microscale, Nikuradse’s experimental work again is brought to focus, perhaps this time to gain an insight into the mechanisms affecting fluid-wall interaction in rough channels. In this paper, Nikuradse’s work is revisited in light of the recent experimental work on roughness effects in microscale flow geometries.

Go to article

Authors and Affiliations

S.G. Kandlikar
Download PDF Download RIS Download Bibtex

Abstract

The paper presents the results of a numerical study devoted to the hydraulic properties of a network of parallel triangular microchannels (hydraulic diameter Dh = 110 um). Previous experimental investigations had revealed that pressure drop through the microchannels system dramatically increases for the Reynolds number exceeding value of 10. The disagreement of the experimental findings with the estimations of flow resistance based on the assumption of fully developed flow were suspected to result from the so-called scale effect. Numerical simulations were performed by using the classical system of flow equations (continuity and Navier-Stokes equations) in order to explain the observed discrepancies. The calculations showed a very good agreement with the experimental results proving that there is no scale effect for the microchannels considered, i.e. the relevance of the constitutive flow model applied was confirmed. It was also clearly indicated that the excessive pressure losses in the high Reynolds number range are due to the secondary flows and separations appearing in several regions of the microchannel system.

Go to article

Authors and Affiliations

M. Niklas
M. Favre-Marinet
D. Asendrych
Download PDF Download RIS Download Bibtex

Abstract

This mini-review reports the recent advances in the hydrodynamic techniques for formation of bubbles of gas in liquid in microfluidic systems. Systems comprising ducts that have widths of the order of 100 micrometers produce suspensions of bubbles with narrow size distributions. Certain of these systems have the ability to tune the volume fraction of the gaseous phase – over the whole range from zero to one. The rate of flow of the liquids through the devices determines the mechanism of formation of the bubbles – from break-up controlled by the rate of flow of the liquid (at low capillary numbers, and in the presence of strong confinement by the walls of the microchannels), to dynamics dominated by inertial effects (at high Weber numbers). The region of transition between these two regimes exhibits nonlinear behaviours, with period doubling cascades and irregular bubbling as prominent examples. Microfluidic systems provide new and uniquely controlled methods for generation of bubbles, and offer potential applications in micro-flow chemical processing, synthesis of materials, and fluidic optics.

Go to article

Authors and Affiliations

P. Garstecki
A.M. Gańán-Calvo
G.M. Whitesides
Download PDF Download RIS Download Bibtex

Abstract

A systematic approach for analyzing the static and dynamic electromechanical response of electrostatic actuators is presented. The analysis is based on energy methods. An analysis approach for extracting dynamic response parameters of electrostatic actuators, while only considering static states of the system, is presented. This is an efficient method for extracting the dynamic pull-in parameters because it does not require time integration of momentum equations.

Go to article

Authors and Affiliations

D. Elata
Download PDF Download RIS Download Bibtex

Abstract

Very thin liquid jets can be obtained using electric field, whereas an electrically-driven bending instability occurs that enormously increases the jet path and effectively leads to its thinning by very large ratios, enabling the production of nanometre size fibres. This mechanism, although it was discovered almost one century ago, is not yet fully understood. In the following study, experimental data are collected, with the dual goal of characterizing the electro-spinning of different liquids and evaluating the pertinence of a theoretical model.

Go to article

Authors and Affiliations

T.A. Kowalewski
S. Błoński
S. Barral
Download PDF Download RIS Download Bibtex

Abstract

Dissipative Particle Dynamics (DPD) is a simulation method at mesoscopic scales that bridges the gap between molecular dynamics and continuum hydrodynamics. It can simulate efficiently complex liquids and dense suspensions using only a few thousands of virtual particles and at speed-up factors of more than one hundred thousands compared to Molecular Dynamics. Lowe’s approach provides a powerful alternative to the usual DPD integrating schemes. Here, we demonstrate the details and potential of Lowe’s scheme. We compute viscosity, diffusivity and Schmidt number values and we present comparison of wormlike chain models under shear with experimental and Brownian Dynamics results for ll-phage DNA.

Go to article

Authors and Affiliations

V. Symeonidis
G.E. Karniadakis
B. Caswell
Download PDF Download RIS Download Bibtex

Abstract

Molecular motors are nature’s nanomachines, and are the essential agents of movement that are an integral part of many living organisms. The supramolecular machine, called the nuclear pore complex (NPC), controls the transport of all cellular material between the cytoplasm and the nucleus that occurs naturally in all biological cells. In the presence of appropriate chemical stimuli, the NPC opens or closes, like a gating mechanism, and permits the flow of material into and out of the nucleus. As a first step in understanding the design characteristics of the NPC, nanoscale studies were conducted to understand the transport characteristics of an idealized NPC model using CFD analysis, discrete element transport and coupled fluid-solid analysis. Results of pressure and velocity profiles obtained from the models indicate that the fluid density, flexibility of walls and the geometry of the flow passage are important in the design of NPC based nano- and micro-motors.

Go to article

Authors and Affiliations

R.M. Pidaparti
P.W. Longest
A.T. Hsu
H.U. Akay
Download PDF Download RIS Download Bibtex

Abstract

The paper gives an introduction to nanostructuring techniques used for industrial fabrication of bulk nanocrystalline metals – basic

materials utilized in shaping nanoscale structures. Nanostructured metals, called nanometals, can be produced by severe plastic deformation (SPD). We give an expert coverage of current achievements in all important SPD methods and present future industry developments and research directions including both batch and continuous processes. In the laboratories of both WUT and UOS we have developed industry standard equipment and machinery for nanometals processing. Utilizing the latest examples from our research, we provide a concise introduction to the field of mass production of nanometals for nanotechnology.

Go to article

Authors and Affiliations

L. Olejnik
A. Rosochowski
Download PDF Download RIS Download Bibtex

Abstract

A short literature survey which justifies coating of ceramic cutting inserts is presented. The results reported are on selected nitride

coatings, in particular nanoscale multilayer, with layers of type Ti-Zr-N, TiN, ZrN and (TiAl)N, deposited by the arc PVD method on oxidecarbide ceramic cutting inserts of type TACN and TW2 produced at the Institute of Advanced Manufacturing Technology. Measurements and quality assessments were made, including of thickness of the coatings and of their constituent micro and nanolayers, microhardness of the coating and of the substrate, surface roughness of the inserts and of the cylindrical workpieces turned with these tools. Lifetimes of the coated and uncoated inserts were compared in turning an alloy tool steel. A significant increase in lifetime of the coated TW2 cutting tools was shown.

Go to article

Authors and Affiliations

K. Czechowski
I. Pofelska-Filip
B. Królicka
P. Szlosek
B. Smuk
J. Wszołek
A. Kurleto
J. Kasina
Download PDF Download RIS Download Bibtex

Abstract

The techniques of micro and nano structurization of surfaces of various materials are utilized in electronics and medicine. Such procedure as wet and dry etching allows to fabricate protruded or recessed micro and nanostructures on the surface. In the paper some examples of utilization of a surface structurization, known from literature, are described. Some structurization methods and experimental results for fabrication of the arrays of sharp microtips are presented. Wet and/or dry etching, and thermal oxidation process were used to form the arrays of sharp gated and non-gated, protruded or recessed silicon microtips on silicon wafer. For the first time, the arrays of silicon carbide (SiC) microtips on glass wafer have been produced by use of the transfer mold technique. Arrays of sharp microtips are used as field electron emission cathodes for vacuum microelectronics devices. Some electron emission measurements for these cathodes have been carried out. New application of silicon microtips array in biochemistry has been tested with satisfactory results.

Go to article

Authors and Affiliations

A. Górecka-Drzazga

Editorial office

Editorial Board 2020-2022

Editor-in-Chief:

M.P. Kazmierkowski, Warsaw University of Technology

Honorary (Past) Editor-in Chief:

T. Kaczorek, Warsaw University of Technology

Deputy Editor-in-Chief:

A. Rogalski, Division IV Technical Sciences PAN

B. Błachowski, Institute of Fundamental Technological Research PAN

Board of Topical Co-editors:

Artificial and Computational Intelligence

S. Osowski and B. Sawicki, Warsaw University of Technology

Biomedical Engineering and Biotechnology

A. Liebert, Institute of Biocybernetics and Biomedical Engineering PAN

Civil Engineering

L. Czarnecki, Building Research Institute, ITB, Warsaw

Control, Robotics and Informatics

J. Klamka and A. Babiarz, Silesian Technical University

A. Borkowski, Institute of Fundamental Technological Research PAN

Electronics, Telecommunication and Optoelectronics

M. Mrozowski and A. Lamęcki, Gdansk University of Technology

Mechanical and Aeronautical Engineering, Thermodynamics

B. Błachowski and P. Korczyk, Institute of Fundamental Technological Research PAN

A. Tylikowski, Lukasiewicz Research Network - Institute of Mechanised Construction and Rock Mining, Warsaw

Materials Science and Nanotechnology

B. Major and P. Czaja, Institute of Metallurgy and Materials Science PAN

Power Systems and Power Electronics

M.P. Kazmierkowski, Warsaw University of Technology

International Editorial Advisory Board

R. Asthana, University of Wisconsin-Stout, Menomonie, USA

Xu Binshi, China Association of Plant Engineering, Beijing, P.R. China

F. Blaabjerg, Aalborg University, Denmark

C. Cecati, University of L’Aquila, Italy

A. Cichocki, RIKEN Institute, Tokyo, Japan

M. David, National Polytechnique de Toulouse, France

R. Ebner, Materials Centre Leoben, Leoben, Austria

E. Fornasini, University of Padova, Padova, Italy

L.G. Franquelo, University of Sevilla, Spain

M. Gad-el-Hak, Virginia Commonwealth University, Richmond, USA

M. Giersig, Free University of Berlin, Germany

D. van Gemert, Catholic University Leuven, KU Leuven, Belgium

L. Keviczky, Hungarian Academy of Sciences, Budapest, Hungary

V. Kučera, Czech Technical University in Prague, Prague, Czech Republic

R. Kennel, Technical University Munich, Germany

T.A. Kowalewski, Institute of Fundamental Technological Research PAN

E. Levi, Liverpool John Moore University, UK

G. Maier, Technical University of Milan, Milan, Italy

K.F. Man, City University of Hong Kong,

R. Maniewski, Institute of Biocybernetics and Biomedical Engineering PAN

H.A. Mang, Austrian Academy of Sciences, Vienna, Austria

H. Mihashi, Tohoku University, Aoba-ku, Sendai, Japan

S. Mindess, University of British Columbia, Vancouver, Canada

D.A. Mlynski, University of Karlsruhe, Karlsruhe, Germany

A.S. Nowak, University of Michigan, Ann Arbor, USA

K. Ohnishi, Keio University, Yokohama, Japan

A. Öberg, Linköping University, Linköping, Sweden

W. Pedrycz, University of Alberta, Canada

S. Przemieniecki, University of South Florida, Tampa, USA

M. Razeghi, Northwestern University, Evanston, USA

J. Rodriguez, University of Andres Bello, Santiago, Chile

J.V. Sloten, Catholic University Leuven, Leuven, Belgium

B.M. Wilamowski, University of Auburn, Alabama, USA

W. Włosiński , Warsaw University of Technology, Warsaw, Poland

A.L. Yarin, University of Illinois at Chicago, USA

Du Xiangwan, Chinese Academy of Engineering, China

J. Żurada, Department of Computer Engineering, University of Louisville, USA

Contact

Editorial Office:

Pałac Kultury i Nauki

Wydział IV Nauk Technicznych PAN

Pl. Defilad 1

PL 00-901 Warszawa

Copy Editor:

Renata Podraza, e-mail: renata.podraza@pan.pl

Finance:

Ewa Trojanowska, ewa.trojanowska@pan.pl

Instructions for authors

Open Access policy

Bulletin of the Polish Academy of Sciences: Technical Sciences jest czasopismem wydawanym w wolnym dostępie na licencji CC BY-NC-ND 4.0.

Bulletin of the Polish Academy of Sciences: Technical Sciences is an open access journal with all content available with no charge in full text version. The journal content is available under the licencse CC BY-NC-ND 4.0.

This page uses 'cookies'. Learn more