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Abstract: The development of new numerical methods for fluid flow simulations is challenging but such tools may help to understand flow problems better. Here, the Boundary-Domain Integral Method is applied to simulate laminar fluid flow governed by a dimensionless velocity–vorticity formulation of the Navier–Stokes equation. The Reynolds number is chosen in all examples small enough to ensure laminar flow conditions. The false transient approach is utilized to improve stability. As all boundary element methods, the Boundary-Domain Integral Method has a quadratic complexity. Here, the ℋ2 -methodology is applied to obtain an almost linear complexity. This acceleration technique is not only applied to the boundary only part but more important to the domain related part of the formulation. The application of the ℋ2 -methodology does not allow to use the rigid body method to determine the singular integrals and the integral free term as done until now. It is shown how to apply the technique of Guigiani and Gigante to handle the strongly singular integrals in this application. Further, a parametric study shows the influence of the introduced approximation parameters. For this purpose the example of a lid driven cavity is utilized. The second example demonstrates the performance of the proposed method by simulating the Hagen–Poiseuille flow in a pipe. The third example considers the flow around a rigid cylinder to show the behavior of the method for an unstructured grid. All examples show that the proposed method results in an almost linear complexity as the mathematical analysis promisses.
Keywords: boundary-domain integral method, velocity–vorticity, adaptive cross approximation, modified helmholtz equation, Yukawa potential, fast multipole method, ℋ-structure
Published in DKUM: 28.11.2024; Views: 0; Downloads: 10
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Abstract: V učbeniku Vektorska analiza avtorja, dr. Tina Sovič in dr. Simon Špacapan, predstavita vektorske in skalarne funkcije ene in več spremenljivk. Obravnavata glavne teme iz tega področja, kot so krivulje in ploskve v prostoru, odvod vektorskih funkcij, dvojni in trojni integral, ter krivuljni in ploskovni integral skalarne in vektorske funkcije. Namen učbenika je tudi predstaviti praktične aplikacije teorije vektorskih funkcij na področju inženirske prakse, ki se pojavlja pri reševanju različnih problemov v realnem življenju. Učbenik je opremljen s številnimi grafičnimi prikazi, ki nazorno prikazujejo obravnavano temo, številnimi zgledi, ki na konkretnih primerih prikazujejo uporabo teorije v računskih nalogah, ter nekaterimi vajami, ki so namenjene za samostojno reševanje študentov.
Keywords: vektorska funkcija, skalarna funkcija, krivulje, ploskve, mnogoterni integral, krivuljni integral, ploskovni integral
Published in DKUM: 25.07.2023; Views: 436; Downloads: 100
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Abstract: V magistrskem delu je obravnavan problem nedoslednosti v matematičnih učbenikih za gimnazije, ki so potrjeni za uporabo s strani Ministrstva za izobraževanje, znanost in šport. Magistrsko delo je razdeljeno na poglavja, v katerih so obravnavani posamezni tematski sklopi iz veljavnega učnega načrta. Pri vsakem poglavju so predstavljene vpeljave pojmov iz učnega načrta, kot so zapisane v obravnavanih učbenikih. Izkaže se, da so mnoge med njimi pomanjkljive ali celo nekorektne. V vsakem poglavju je predstavljena tudi možna rešitev, kako vpeljavo narediti korektno.
Keywords: nedoslednosti, matematični učbeniki, gimnazijsko izobraževanje, naraščanje in padanje funkcij, geometrijsko zaporedje, sestavljene funkcije, nedoločeni integral, limita in zveznost funkcije
Published in DKUM: 26.05.2022; Views: 877; Downloads: 83
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Abstract: Most civil engineering structures are subjected to cyclic loading during their service life, such as retaining walls, wave loading on offshore structures, seismic loading and the traffic loading of pavements. In the case of an integral abutment bridge (IAB), as an example, the backfill granular material is subject to slow cyclic stress and strain changes under drained conditions. These bridges are constructed so that the top deck is longitudinally continuous. In other words, IABs are joint-less bridges where the superstructure is connected with the abutment. The rigid connection enables the abutment and superstructure to act as a single structural unit, i.e., the expansion joints which are widely used in traditional bridges are removed in IABs. This removal is mainly due to the high costs of maintenance. The behavior of IABs is dominated by the cyclical temperature changes in the bridge deck. This results in the imposition of cyclical horizontal displacements to the backfill soil of the abutments. The present research is an effort to investigate the induced passive pressure on the IABs, using a laboratory model and an analytical approach. The results indicate that the passive pressure distribution is non-linear and its maximum value along the wall is dependent on the magnitude of the wall rotation and number of cycles. It seems that there are two different mechanisms for this behavior. In the above part of the wall, sand behaves as a plastic material. A decline in the passive pressure in the bottom part, however, is the result of arching.
Keywords: integral abutment bridge, cyclic displacement, passive pressure, arching
Published in DKUM: 14.06.2018; Views: 1056; Downloads: 146
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Abstract: The functioning of a port and shipping system must be perfect in order to provide a competitive advantage and stable position in maritime market. The importance of logistics in business success of port and shipping organizations in contemporary conditions has become crucial. Due to that fact, more and more efforts are put in the designing of integral logistics systems. Thanks to a complex, systemic and networking approach, logistics today is improving the speed and efficiency of operations and significantly influences cost reduction and therewith fulfills one of the basic strategic functions, anticipating necessary key competences of the firm. It is a resource framework for the overcoming of strategic limitations and a method for the enhancement of the competitive position and all marketing and management functions. In addition to that, the integration of partners requires, by rule, a consistent restructuring of the total chain dedicated to the creation of added value, i.e. reengineering of logistics and production business processes. Flexible and small structural units are created, cooperating among each other in a decentralized manner, retaining their key competences and strategic significance for the integral network dominated by a single leading firm as a center of the system, i.e. focus of the supply chain. The paper analyzes the formation of new logistics and marketing paradigm of the beginning of the new century and millennium, anticipating the overcoming of the traditional 3PL three-party logistics concept and formation of contemporary 4PL concept.
Keywords: logistics, ports, logistic services, integral logistics systems, third party logistics, 3PL, fourth party logistics, 4PL, outsourcing
Published in DKUM: 09.05.2018; Views: 1350; Downloads: 110
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