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2. Numerical simulations of nozzles with gas and liquid focusing for production of micro-jets : dissertationGrega Belšak, 2022, doktorska disertacija Ključne besede: numerical simulations, OpenFOAM, liquid sheets, micro-jets, multiphase flow, converging nozzles, double flow focusing nozzle, gas compressibility, vacuum conditions, atmospheric conditions, operational parameters, liquid properties, dissertations Objavljeno v RUNG: 07.12.2022; Ogledov: 1357; Prenosov: 39 Celotno besedilo (21,26 MB) |
3. Development of prototype of electronic speckle interferometry based spirometerMohanachandran Nair Sindhu Swapna, KUMAR ARUN, KUMAR SUNIL, SREEJYOTHI S, RAJ VIMAL, SANKARARAMAN SANKARANARAYANA IYER, 2021, izvirni znanstveni članek Opis: The paper reports the design, construction, and calibration of the prototype of a spirometer based on electronic
speckle interferometry (ESPI). The conventional ESPI setup is modified by incorporating a DNM (Diaphragm-Nozzle-Mouthpiece) module comprising a metallic diaphragm, regulated airflow channel, and a mouthpiece. The
exhaled air after a deep breathe is channelled to the DNM module where the diaphragm gets deformed. From the
circular fringe pattern obtained by subtracting the speckled images before and after deformation of the metallic
diaphragm, the radius of curvature (R) due to deformation is calculated using the principle of Newton’s rings.
The value of R and peak expiratory flow rate (PEFR) from the standard spirometer reading are correlated. From
the 640 observations spread over the range 100 - 500 L/min in the standard spirometer, an empirical relation
is set in terms of R from the scatter plot. The ESPI spirometer (ESPIS) is validated by determining the value of
R corresponding to a particular PEFR from the empirical relation and also from the standard spirometer. The
PEFR calculated from ESPIS matches well with the standard spirometer reading, which suggests that the system
designed and constructed can be used for biomedical applications for assessing lungs’ efficiency. Ključne besede: Speckle, Spirometer, DNM module, ESPIS, Peak expiratory flow rate Objavljeno v RUNG: 28.06.2022; Ogledov: 1112; Prenosov: 0 Gradivo ima več datotek! Več... |
4. Determination of Iron in Environmental Water Samples by FIA-TLSMiha Tomšič, Leja Goljat, Hanna Budasheva, Dorota Korte, Arne Bratkič, Mladen Franko, 2019, izvirni znanstveni članek Opis: The determination of low concentration of iron in natural waters can be difficult due to the complexity of natural water, but primarily because it requires preconcentration of the sample with solvent extraction. In this work we report on results of thermal lens spectrometry (TLS) coupled to flow injection analysis (FIA) as a highly sensitive FIA-TLS method of iron detection. The concentration of iron redox species was determined using 1,10-phenanthroline (PHN), that forms stable complexes with Fe(II) ions which are characterized by an absorption maximum at 508 nm. The TLS system using a 633 nm probe laser and 530 nm pump laser beam was exploited for on-line detection in flow injection analysis, where a PHN solution was used as the carrier solution for FIA. The concentration of the complexing agent affects the quality of the TLS signal, and the optimal concentration was found at 1 mM PHN. The achieved limits of detection (LODs) for Fe(II) and total iron were 33 nM for Fe(II) and 21 nM for total iron concentration. The method was further validated by determining the linear concentration range, specificity in terms of analytical yield and by determining concentration of iron in a water sample from a local water stream. Ključne besede: Flow injection analysis, iron concentration, thermal lens spectroscopy Objavljeno v RUNG: 18.12.2019; Ogledov: 3189; Prenosov: 105 Celotno besedilo (690,39 KB) |
5. CONTRIBUTION TO DEVELOPMENT OF MESHLESS METHODS FOR FREE AND MOVING BOUNDARY PROBLEMSNAZIA TALAT, 2018, doktorska disertacija Ključne besede: Two-phase flow, free and moving boundaries, computational fluid dynamics, phasefield formulation, 2D problems, axisymmetric problems, diffuse approximate
meshless method, Rayleigh-Taylor instability, Boussinesq approximation, variable
density and viscosity, flow focusing, dripping, jetting Objavljeno v RUNG: 11.09.2018; Ogledov: 5043; Prenosov: 178 (1 glas) Celotno besedilo (4,24 MB) |
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7. Rapid and Sensitive Determination of ChE Activity in Blood PlasmaAndrej Jerkič, Tjaša Birsa, Mojca Žorž, Dorota Korte, Martina Bergant Marušič, Mladen Franko, 2018, objavljeni povzetek znanstvenega prispevka na konferenci Ključne besede: flow injection analysis, thermal lens spectrometric detection, acetylcholinesterase, butyrylcholinesterase, enzyme activity Objavljeno v RUNG: 16.07.2018; Ogledov: 4277; Prenosov: 0 Gradivo ima več datotek! Več... |
8. Simulation Of Gas Focused Liquid JetsRizwan Zahoor, 2018, doktorska disertacija Opis: The main aim of dissertation is to develop an experimentally verified computational fluid dynamic (CFD) model of micron-sized liquid jet, produced by an injection molded Gas Dynamic Virtual Nozzle (GDVN). In these nozzles, liquid jets are efficiently orientedly transporting mass and momentum. They are produced by intelligently projecting hydrodynamic focusing effect from a high-speed stream of a co-flowing lower density and lower viscosity gas on a stream of liquid from a feeding capillary. Liquid micro-jets are used for delivery of protein crystal samples in a hard X-ray beam in serial femtosecond crystallography experiments. The diffraction patterns of crystals are collected just before their destruction. The samples are hard to crystallize and very precious, so a thorough knowledge of the jet used in delivering them is required. The jet characteristics are analyzed as a function of operating parameters, geometry and material properties.
The physical model is described by mixture formulation and Navier-Stokes equations for transient, Newtonian, two-phase, compressible flow. Multiphase flow problem is solved with finite volume method (FVM), where fluid-fluid interface tracking is obtained with volume of fluid (VOF). The implementation of FVM-VOF CFD model is available in open source codes OpenFOAM and Gerris. They are validated by performing a series of standard interface advection and multiphase flow test cases. Both open source codes are compared for their abilities in solving GDVN flow problem. Due to the compressible nature of the focusing gas flow, OpenFOAM was chosen for GDVN simulations, since Gerris has no compressible flow option.
Constant effective material properties are used in the phases together with ideal gas density constitutive relation. A mixture model of the two-phase system is solved in axisymmetry. The discretization of the nozzle and chamber system uses approximately 300 000 finite volumes. Mesh independent results are obtained with the finite volumes of the size 0.25 µm in the vicinity of the jet and drops. The simulations are compared with experimental results according to the jet thickness and length for distilled water jet and helium focusing gas, discharging into low-pressure environment of 150 Pa. Reynolds numbers of the liquid and gas are in the range 413-3828 and 17-1222, respectively and Weber number in the range 3-353. A reasonably good agreement with experimental and scaling results is found for the range of nozzle operating parameters never tackled before.
Subsequently, a numerical study of effects of nozzle geometry on stability, shape and flow characteristics of micron-sized liquid jets is performed. The jet characteristics are described as a function of (i) capillary-to-orifice distance, (ii) nozzle outlet orifice diameter and (iii) liquid feeding capillary angle. The study is performed for two sets of liquid flow rates while keeping the gas flow rate unchanged. It is observed that for each value of capillary-to-orifice distance and nozzle outlet diameter, there exists a minimum liquid flow rate below which the jet stability cannot be achieved. It is found that the changes in the nozzle outlet diameter have the biggest influence on the jet diameter, length and velocity, while the liquid capillary angle has no observable effect on the jet characteristic. Change in capillary-to-orifice distance does not affect the flow field around micro jet, so the jet stability and shape is found to be affected by the way liquid-gas interacts near meniscus.
The same numerical model is used to additionally analyze the jet performance under the influence of Argon, Carbon dioxide and Nitrogen focusing gases. The study shows that the helium gas at the same mass flow rate provides twice the length of the jet compared to other gases. The jet focused with helium is also much thinner, faster and interestingly shows no considerable temperature drop at the nozzle outlet.
This work for the first time discuss the computational model of an injection molded micron-sized nozzle and produces valuable information for their design. Ključne besede: Microfluidics, gas dynamic virtual nozzle, flow focusing, micro-jet, convective instability, absolute instability, compressible multiphase flows, dripping, spurting, jetting, jet thickness, jet length, computational fluid dynamics, finite volume method, volume of fluid method Objavljeno v RUNG: 27.03.2018; Ogledov: 6368; Prenosov: 170 Celotno besedilo (11,47 MB) |
9. Influence of Gas Dynamic Virtual Nozzle Geometry on Micro-Jet CharacteristicsRizwan Zahoor, Saša Bajt, Božidar Šarler, 2018, izvirni znanstveni članek Opis: In this paper we present a numerical study investigating the effects of nozzle geometry on stability, shape and flow characteristics of micron-sized liquid jets, produced by injection molded gas dynamic virtual nozzles (GDVNs) operating in vacuum. The jet characteristics are described as a function of (i) capillary-to-orifice distance, (ii) nozzle outlet orifice diameter, and (iii) liquid feeding capillary angle. An experimentally verified numerical model of GDVN with laminar two-phase Newtonian compressible flow, based on finite volume method and volume of fluid interface tracking, is used to assess the changes. The study is performed for two sets of liquid flow rates while keeping the gas flow rate constant. It is observed that for each value of capillary-to-orifice distance and nozzle outlet diameter there is a minimum liquid flow rate below which the jet is unstable. We find that the nozzle outlet diameter has the biggest influence on the jet diameter, length and velocity, while liquid capillary angle has no observable effect on jet characteristic. Varying capillary-to-orifice distance does not affect the flow field around micro-jet. It is found that the liquid and the gas interaction near the meniscus primarily affect the jet stability and shape Ključne besede: Gas dynamic virtual nozzle, Micro-jet, Compressible multiphase flow, Finite volume method, Volume of fluid, Jetting, Dripping Objavljeno v RUNG: 09.03.2018; Ogledov: 5028; Prenosov: 0 Gradivo ima več datotek! Več... |
10. Speciation and Determination of Ionic and Trace-Level Colloidal Silver in Selected Personal Care Products by Thermal Lens SpectrometryDorota Korte, Ales Grahovac, Andrej Jerkic, Olga Vajdle, Jasmina Anojčić, Valeria Guzsvány, Bojan Budič, Mladen Franko, 2018, izvirni znanstveni članek Ključne besede: Silver nanoparticles, Colloidal silver, Personal care
products, Thermal lens spectrometric determination, Flow injection
analysis Objavljeno v RUNG: 26.02.2018; Ogledov: 4180; Prenosov: 0 Gradivo ima več datotek! Več... |