CFD simulation of complex phenomena containing suspensions and flow throughporous media

There is an increasing reliance on computers to solve complex engineering problems. This is because computers, in addition to supporting the development and implementation of adequate and clear models, can especially minimize the financial support required. The ability of computers to perform complex calculations at high speed has enabled the creation of highly complex systems to model real-world phenomena. The complexity of the fluid dynamics problem makes it difficult or impossible to solve equations of an object in a flow exactly. Approximate solutions can be obtained by construction and measurement of prototypes placed in a flow, or by use of a numerical simulation. Since usage of prototypes can be prohibitively time-consuming and expensive, many have turned to simulations to provide insight during the engineering process. In this case the simulation setup and parameters can be altered much more easily than one could with a real-world experiment. The objective of this research work is to develop numerical models for different suspensions (fiber suspensions, blood flow through microvessels and branching geometries, and magnetic fluids), and also fluid flow through porous media. The models will have merit as a scientific tool and will also have practical application in industries. Most of the numerical simulations were done by the commercial software, Fluent, and user defined functions were added to apply a multiscale method and magnetic field. The results from simulation of fiber suspension can elucidate the physics behind the break up of a fiber floc, opening the possibility for developing a meaningful numerical model of the fiber flow. The simulation of blood movement from an arteriole through a venule via a capillary showed that the model based on VOF can successfully predict the deformation and flow of RBCs in an arteriole. Furthermore, the result corresponds to the experimental observation illustrates that the RBC is deformed during the movement. The concluding remarks presented, provide a correct methodology and a mathematical and numerical framework for the simulation of blood flows in branching. Analysis of ferrofluids simulations indicate that the magnetic Soret effect can be even higher than the conventional one and its strength depends on the strength of magnetic field, confirmed experimentally by Völker and Odenbach. It was also shown that when a magnetic field is perpendicular to the temperature gradient, there will be additional increase in the heat transfer compared to the cases where the magnetic field is parallel to the temperature gradient. In addition, the statistical evaluation (Taguchi technique) on magnetic fluids showed that the temperature and initial concentration of the magnetic phase exert the maximum and minimum contribution to the thermodiffusion, respectively. In the simulation of flow through porous media, dimensionless pressure drop was studied at different Reynolds numbers, based on pore permeability and interstitial fluid velocity. The obtained results agreed well with the correlation of Macdonald et al. (1979) for the range of actual flow Reynolds studied. Furthermore, calculated results for the dispersion coefficients in the cylinder geometry were found to be in agreement with those of Seymour and Callaghan.

Understanding Flood Regime Changes in Europe: a state-of-the-art assessment

There is growing concern that flooding is becoming more frequent and severe in Europe. A better understanding of flood regime changes and their drivers is therefore needed. The paper reviews the current knowledge on flood regime changes in European rivers that has traditionally been obtained through two alternative research approaches. The first approach is the data-based detection of changes in observed flood events. Current methods are reviewed together with their challenges and opportunities. For example, observation biases, the merging of different data sources and accounting for nonlinear drivers and responses. The second approach consists of modelled scenarios of future floods. Challenges and opportunities associated with flood change scenarios are discussed such as fully accounting for uncertainties in the modelling cascade and feedbacks. To make progress in flood change research, we suggest that a synthesis of these two approaches is needed. This can be achieved by focusing on long duration records and flood-rich and flood-poor periods rather than on short duration flood trends only, by formally attributing causes of observed flood changes, by validating scenarios against observed flood regime dynamics, and by developing low-dimensional models of flood changes and feedbacks. The paper finishes with a call for a joint European flood change research network.

Puolustusrutiinit organisaation oppimisessa

Tutkimuksessa selvitettiin Chris Argyriksen käsitettä puolustusrutiinit. Koska niiden tutkimus on jäänyt vähäiseksi, työn tarkoitus oli selvittää, voidaanko kohdeorganisaatiossa osoittaa olevan käyttäytymismalleja, jotka viittaisivat puolustusrutiinien olemassaoloon. Teoriaosassa lukija johdateltiin aiheeseen selvittämällä, kuinka organisaatio on osa ympäröivää maailmaa ja sitten, kuinka tärkeää oppiminen on yrityksen menestymiselle ja olemassaololle. Puolustusrutiinien teoriaa tutkittiin pääasiassa Chris Argyriksen materiaalin avulla. Tutkimus oli laadullinen puolistrukturoitu yksilöhaastattelu valitussa kohdeyrityksessä. Empiriaosuuden alussa kerrottiin haastateltavista sekä kohdeyrityksestä ja tutkimuksen suorittamisesta. Lopuksi haastattelujen tulokset esiteltiin lukijalle. Tutkimuksen tuloksien mukaan kohdeorganisaatiossa voitiin havaita lukuisia tilanteita, joissa puolustusrutiinit vaikuttivat jopa hyvinkin voimakkaasti. Lisäksi eri organisaatiotasojen välillä havaittiin toisistaan poikkeavia näkemyksiä. Siksi organisaation jäsenet eivät pystyneet muodostamaan yhtenäistä käsitystä organisaation toiminnasta ja ongelmista. Tämä vaikeuttaa organisaation oppimista, ympäristön muutokseen reagointia ja lopulta yrityksen menestymistä. (Argyris 1996, 67)

De praedicamentalitate

Painovuosi nimekkeestä.

Kinetic measurements during transient film growth on zinc

The electrochemical behaviour of zinc has been extensively studied in alkaline and acid media, but only a few studies have been reported in neutral solutions, particularly in deaerated media. Zinc passivation in neutral medium and the effect of the ClO4- ion on the nucleation and growth of the passive layer is studied in this paper by a transient technique at different electrolyte concentrations and applied potentials. ZnO growth rate was shown to decrease with increasing electrolyte concentration. Moreover, passive layer growth occurred followed by pitting nucleation and growth. Film growth and pit nucleation are explained by means of the Macdonald and Engell-Stolica models.

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Sosiologia humanismin jälkeen : naturalistisen systeemiteorian manifesti

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Evaluation of the dioxin and furan formation thermodynamics in combustion processes of urban solid wastes

Specific combustion programs (Gaseq, Chemical equilibria in perfect gases, Chris Morley) are used to model dioxin and formation in the incineration processes of urban solid wastes. Thanks to these programs, it is possible to establish correlations with the formation mechanisms postulated in literature on the subject. It was found that minimum oxygen quantities are required to obtain a significant formation of these compounds and that more furans than dioxins are formed. Likewise, dioxin and furan formation is related to the presence of carbon monoxide, and dioxin and furan distribution among its different compounds depends on the chlorine and hydrogen relative composition. This is due to the fact that an increased chlorine availability leads to the formation of compounds bearing a higher chlorine concentration (penta-, hexa-, hepta-, and octachlorides), whereas an increased hydrogen availability leads to the formation of compounds bearing a lower chlorine number (mono, di-, tri-, and tetrachlorides).

24+1 kansainvälisten suhteiden perusoppikirjaa : havaintoja ja arvioita

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