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Pore-scale viscous fingering as a mechanism for pattern formation – a historical overview, application, and the ways of controlling it
No full textViscous fingering instability, as one of the numerous fluid in-stabilities and mechanisms of pattern formation, is very com-mon in different fields of research. First studied experimentallyin an apparatus called a Hele-Shaw cell in 1898, it has beenwidely used, for example, as a model for porous media in lab-oratory testing. This paper provides a brief insight into themathematical model of the Saffman–Taylor instability (porescale viscous fingering) and the situations in which viscous fin-gering can be encountered. Since it is a morphogenetic insta-bility, it is usually considered a nuisance and in recent decadesmany scientists and researchers have focused on the ways toavoid its occurrence. For instance, the petroleum industry hasbeen continuously trying to discover the best solution for itscontrol since viscous fingering limits oil recovery in porousmedia. The review provides a historical overview of the phe-nomena and various methods that have been used to controlthis instability. The final part of the paper gives a summary andthe conclusions that have been drawn as the results of diversestudies.CONTACT Ivana Cvetkovic [email protected] Faculty of Mechanical Engineering, Universityof Belgrade, Belgrade 11000, Republic of Serbia© 2024 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group. This is an Open Access article distributedunder the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permitsunrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. The terms on whichthis article has been published allow the posting of the Accepted Manuscript in a repository by the author(s) or with their consent
Rarefied gas flow through annular microtube at constant and equal wall temperatures
No full textThe coaxial microtubes, which can be transparent, flexible, and biocompatible, are often part of micro-electro-mechanical systems. This paper examines the steady, subsonic rarefied gas flow through an axisymmetric microtube with an annular cross-section, induced by pressure difference. The flow is considered compressible and non-isothermal, with constant inner and outer wall temperatures. The study uses continuum approach based on continuity, momentum and energy equations together with slip and temperature jump boundary conditions. The perturbation method is used and enables including effects of inertia, convection and expansion work. Hence, analytical solutions for velocity, pressure and temperature are obtained, which allows analysis of all named effects along with annular microtube geometry. These results provide optimizing microtube designs in practical applications. Regarding solutions are analytical, they can be useful as a criterion for validating the accuracy and reliability of numerical solutions of similar problems
METHODS OF MONITORING AND APPLYING ENERGY BALANCE PARAMETERS IN THE EXPLOITATION OF MODERN MACHINE TOOLS
No full textThe digitization procedures of machine tools, which are the basis of modern industry development
strategies, are to the greatest extent based on the application of information collected during the operation of the machines. In this way, it is possible to monitor and manage production processes by applying different criteria. The paper describes the procedure for monitoring and applying energy balance parameters in drive motors of machine tools in real time and the possibility of their application in production conditions.Editor: Dr Boris Dumnić, full professor, dean
Technical treatment and design: Dr Đorđe Vukelić, full professor
Dr Milana Ilić Mićunović, assistant professor
MSc Aleksandar Milošević, assistan
Challenges with Waste Material Obtained by 3D Printing
No full textToday, the waste material obtained by 3D printing operations presents significant challenges due to the increasing global adoption of this technology, leading to serious environmental implications. The generation of plastic waste from unsuccessful prints and end-of-life products is a growing concern, impacting the circular economy. With a 26% annual growth rate in additive manufacturing, the amount of waste is rapidly increasing, necessitating effective waste management strategies. However, 3D printing offers advantages in waste reduction compared to
traditional manufacturing methods, with only 40% waste generation compared to subtractive technologies and much of the waste being recyclable. The challenges of waste material obtained by 3D printing are numerous and require a comprehensive approach to waste management and recycling. Moreover, leveraging the abundant opportunities for reusing materials and developing sustainable composite filaments, 3D printing can contribute to environmental sustainability and the principles of circular economy
Specijalni alat za interni transport strukturnih elemenata šinskih vozila - SPECIAL TOOL FOR INTERNAL TRANSPORT OF STRUCTURAL ELEMENTS OF RAIL VEHICLES
Get PDFPronalazak u širem smislu pripada uređajima za rukovanje i transport, a u užem smislu pronalazak se odnosi na uređaje za prihvatanje tereta koji se koriste na uređajima za rukovanje, podizanje i interni transport aluminijumskih elemenata, podsklopova i sklopova nosećih struktura različitih vrsta šinskih vozila, koji se koriste u industriji šinskih vozila
ADDITIVE TECHNOLOGIES AND APPLICATION OF THE STEP-NC PROTOCOL
Get PDFU radu je predstavljen pristup za primenu STEP-NC protokola u aditivnoj proizvodnji. Koristi se sta-ndard ISO 10303 AP238 koji omogućava implementaciju geometrijskih informacija o slojevima do-davanja materijala kao ulaznih podataka za generisanje STEP-NC programa. Prikazana je i me-todologija za primenu STEP-NC protokola u aditivnoj proizvodnji. Za potrebe verifikacije i simulacije generisanih programa za aditivnu proizvodnju koristi se okruženje STEP-NC Machine i sopstvene konfigurisane mašine za dodavanje materijala u okviru ovog softveraThe paper presents an approach for applying the STEP-NC protocol in additive manufacturing. The ISO 10303 AP238 standard is used, which enables the implementation of geometrical information about material addition layers as input data for the generation of STEP-NC programs. The methodology for applying the STEP-NC protocol in additive manufacturing is also given. For verification and simulation of the generated programs for additive manufacturing, the STEP-NC Machine environment and us own configured machines for additive manufacturing within this software are use
Comparative Studies of the Structural and Physicochemical Properties of the First Fullerene Derivative FD-C60 (Fullerenol) and Second Fullerene Derivate SD-C60 (3HFWC)
Get PDFIn order to maximally reduce the toxicity of fullerenol (the first derivative of C60, FD-C60), and increase its biomedical efficiency, the second derivative SD-C60 (3HFWC, Hyper-Harmonized Hydroxylated Fullerene Water Complex) was created. Several different methods were applied in the comparative characterization of FD-C60 and SD-C60 with the same OH groups in their core. FD-C60 as an individual structure was about 1.3 nm in size, while SD-C60 as an individual structure was 10–30 nm in size. Based on ten physicochemical methods and techniques, FD-C60 and SD-C60 were found to be two different substances in terms of size, structure, and physicochemical properties; FD-C60, at 100 °C, had endothermic characteristics, while SD-C60, at 133 °C, had exothermic characteristics; FD-C60 did not have water layers, while SD-C60 had water layers; the zeta potential of FD-C60 was −25.85 mV, while it was −43.29 mV for SD-C60. SD-C60 is a promising substance for use in cosmetics and pharmaceuticals
Computation of pairs of related Gauss-type quadrature rules
No full textThe evaluation of Gauss-type quadrature rules is an important topic in scientific computing. To determine estimates or bounds for the quadrature error of a Gauss rule often another related quadrature rule is evaluated, such as an associated Gauss-Radau or Gauss-Lobatto rule, an anti-Gauss rule, an averaged rule, an optimal averaged rule, or a Gauss-Kronrod rule when the latter exists. We discuss how pairs of a Gauss rule and a related Gauss-type quadrature rule can be computed efficiently by a divide-and-conquer method
Reconfigurable open architecture control system with integrated digital twin for 3-axis woodworking milling machine
No full textThis study proposes a reconfigurable open architecture control system for the Computer Numerical
Control (CNC) woodworking educational machine tool called “EMCO F1 CNC”. On this machine
physical hardware reconfiguration (spindle position can be vertical and horizontal) is possible. The
idea was to develop a control system that would follow the configuration changes of the machine
tool. The educational character of the machine and its reconfigurability demand possibilities for
machining programme simulations in order to determine optimal workpiece position in the
workspace and programme verification. Those are the reasons for developing a virtual machine tool integrated with the control system as a digital twin. The study presents a novel methodology for the development of control systems, merging the concept of “virtual commissioning” with iterative errordriven processes. The objective was to develop a dynamic control system capable of promptly adjusting to kinematics changes in real time. In a wood machining experiment, a test workpiece for machine tools for both machine configurations verified the operation of the developed control system
Neizotermska stišljiva strujanja gasa u mikrokanalima
No full textОвладавање технологијом серијскe производње микро-електро-
механичких-система (МЕМС-а) крајем прошлог века, довело je до тога да
минијатурни уређаји данас буду широко распрострањени и примењиви у
свим областима људског деловања. Интензивна употреба микроуређаја у
најразличитије сврхе утицала је на снажан развој многих области науке.
Струјања флуида настала услед разлике притисака или кретања зидова
канала, као и феномени транспорта одвијају се у микромоторима,
микролежајима, микропумпама, микротурбинама, микромлазницима,
микровентилима и микрофилтерима који су саставни део МЕМС-a. Таква
струјања могу да обезбеде погон микромотора, омогуће убризгавање
лекова, хлађење електронских уређаја, одговарајућу носивост
микролежаја и могу имати разне друге примене. Све то намеће потребу за
изучавањем струјања флуида у микроканалима, а добијени резултати
имају директну примену приликом планирања, конструисања и
експлоатације МЕМС-a.
У монографији се анализирају проблеми неизотермског,
дводимензијског, стационарног, стишљивог, дозвучног струјања гаса у
микроканалима променљивог попречног пресека (конвергентном,
дивергентном и каналу константне висине). Како су у питању
микрострујања ефекат разређености гаса узима се у обзир. Дају се
оригинална аналитичка решења за неизотермска струјања гаса која се
одвијају услед разлике притисaка на улазу и излазу микроканала.
Процедура решавања изложена у монографији се може применити и код
микрострујања која се остварују смицањем, тј. кретањем зидова
микроканала: код микро-Куетовог и струјања гаса у микролежајима.
Струјање гаса третира се макроскопски, решавањем система
једначина континуума: једначине континуитета, Навије-Стоксове
једначине и једначине енергије. Користе се гранични услови Максвел-
Смолуковског првог реда за брзину клизања и температурски скок гаса на
зиду, тако да добијена решења покривају области континуума и струјања
гаса са клизањем. Претпоставља се да је струјање потпуно развијено и да
се све величине споро мењају у подужном правцу. Узима се у обзир
зависност динамичке вискозности и топлотне проводљивости од
температуре према молекуларном моделу чврстих сфера. Наведене
претпоставке, уз познату везу Маховог, Кнудсеновог и Рејнолдсовог броја
омогућавају прецизну процену реда величине сваког члана система
основних једначина и граничних услова понаособ. С обзиром на величину
Рејнолдсовог броја издвајају се два карактеристична случаја која се одвојено решавају: струјање при малим и струјање при умерено великим
вредностима Рејнолдсовог броја. Аналитичка решења се претпостављају у
облику пертурбационих редова по Кнудсеновом броју и добијају
решавањем одговарајућих система основних једначина и граничних
услова. У монографији се добијају решења за прве две апроксимације
притиска, брзине и температуре за сваки од наведених услова струјања
гаса. Прва апроксимација одговара струјању гаса у условима континуума,
док друга укључује ефекат разређености и остале ефекте другог реда
зависно од случаја који се разматра.
Резултати приказани у монографији се слажу са експерименталним
резултатима из доступне литературе. Добијени аналитички резултати су
експлицитни и једноставни за употребу, па могу служити као релевантни у
истраживањима везаним за неизотермска микрострујања гасова.Mastering the production technology of micro-electro-mechanical-systems
(MEMS) and especially their serial production at the end of the last century,
has given rise to a wide adoption and ubiquitous applicability of miniature
devices in all areas of human activity. The intensive use of microdevices for
various purposes has influenced development of many scientific fields.
Pressure-driven or shear-driven fluid flows, as well as transport phenomena,
take place in micromotors, microbearings, micropumps, microturbines,
microjets, microvalves and microfilters, which are integral parts of MEMS.
Such flows can drive micromotors, inject drugs, cool electronic devices, ensure
the appropriate load capacity of microbearings and can have various other
applications. Тhis calls for a research of fluid flow in microchannels, while the
achieved results may have a direct application in design, construction and
exploitation of MEMS.
This monograph analyzes the problems of nonisothermal, twodimensional,
steady, compressible, subsonic gas flow in microchannels of
variable cross-section (convergent, divergent and channel of constant height).
The microflows are analised, so the effect of gas rarefaction has to be
considered. The original analytical solutions are given for nonisothermal,
pressure-driven gas microflows that take place due to the pressure difference at
the entrance and the exit of the microchannel. The solution procedure presented
in the monograph can also be applied to shear-driven microflows, e.g. in micro
Couette gas flow and gas flow in micro bearings.
The gas flow is treated macroscopically, using the system of continuum
equations: the continuity, Navier-Stokes and energy equation. First-order
Maxwell-Smoluchowski boundary conditions are used for the slip velocity and
gas temperature jump at the wall, so that the obtained solutions cover the
continuum and slip gas flow regions. It is assumed that the flow is fully
developed and that all quantities change slowly in the streamwise direction.
The dependence of dynamic viscosity and thermal conductivity on temperature
is considered according to the molecular model of solid spheres. The mentioned
assumptions, along with the known relation of Mach, Knudsen and Reynolds
numbers, enable a precise estimation of the order of magnitude of each term of
the system of equations and boundary conditions. Considering the value of the
Reynolds number there are two characteristic cases which are solved
separately: flow at low and flow at moderately high values of the Reynolds
number. Analytical solutions are assumed in the form of perturbation series
according to the Knudsen number and are obtained by solving the
corresponding systems of equations and boundary conditions. The monograph provides the solutions for the first two approximations of pressure, velocity and
temperature for each of the specified gas flow conditions. The first
approximation corresponds to the gas flow in continuum conditions, while the
second one includes the rarefaction effect and other second-order effects
depending on the case under consideration.
The results presented in the monograph are in a good agreement with the
experimental results from the available literature. The obtained analytical
results are explicit and easy to reproduce, so they can serve as benchmarks in
research related to non-isothermal gas microflows