Rijeka Bay 3D VOF Costal Flow Model

3D multiphase flow was analyzed in the area of Rijeka bay in the Adriatic Sea. The necessary morphology data in the range of interest of the coastal bottom area were collected and the spatial surface was created. The functionality of the 3D model was studied in the large area of the realistic stochastic structure of the bottom and the shore. The probability of meteorological conditions and wind impact in the model has been shown. The obtained results give a detailed view of the velocity fields in the horizontal plane of different depths. Numerical simulation was performed in open source program OpenFOAM with Volume of Fluid (VOF) method using the Eulerian approach. For solving this problem interFOAM solver for two incompressible, isothermal, immiscible fluids was used. The resulting simulations showed dominant flow from the western coast of the Krk island to the eastern coast of the Istrian peninsula. Seawater enters the bay through the Srednja Vrata and Tihi Kanal and exits the bay through the Vela Vrata. This research has shown that using a VOF method can be successfully implemented for describing fluid motion in large areas such as bays and oceans

Introducing languid particle dynamics to a selection of PSO variants

Previous research showed that conditioning a PSO agent's movement based on its personal fitness improvement enhances the standard PSO method. In this article, languid particle dynamics (LPD) technique is used on five adequate and widely used PSO variants. Five unmodified PSO variants were tested against their LPD-implemented counterparts on three search space dimensionalities (10, 20, and 50 dimensions) and 30 test functions of the CEC 2014 benchmark test. In the preliminary phase of the testing four of the five tested PSO variants showed improvement in accuracy. The worst and best-achieving variants from preliminary test went through detailed investigation on 220 and 770 combinations of method parameters, where both variants showed overall gains in accuracy when enhanced with LPD. Finally, the results obtained with best achieving PSO parameters were subject to statistical analysis which showed that the two variants give statistically significant improvements in accuracy for 13-50% of the test functions.Comment: 13 pages, 10 tables, 1 figure. Egyptian Informatics Journal, 201

Numerical Simulation of River Inflows in Rijeka Bay Coastal Area

In this paper, a model of water flow in the Porto Baroš has been developed, which is the part of the Rijeka coastal area, for the purpose of its renovation and conversion. For numerical simulation purposes, the depth of the seabed of Port was previously performed, based on which the geometry and numerical domain of Port were made. By conducting the flow simulation, the analysis was carried out, after which the analyses of the conceptual solutions with the introduction of the pipe discharge were performed with the aim of reducing the water pollution of the Porto Baroš area. Port geometry will be made in commercial SMS software and numerical domains and simulations in OpenFOAM open-source software

Rijeka Bay 3D VOF Costal Flow Model

3D multiphase flow was analyzed in the area of Rijeka bay in the Adriatic Sea. The necessary morphology data in the range of interest of the coastal bottom area were collected and the spatial surface was created. The functionality of the 3D model was studied in the large area of the realistic stochastic structure of the bottom and the shore. The probability of meteorological conditions and wind impact in the model has been shown. The obtained results give a detailed view of the velocity fields in the horizontal plane of different depths. Numerical simulation was performed in open source program OpenFOAM with Volume of Fluid (VOF) method using the Eulerian approach. For solving this problem interFOAM solver for two incompressible, isothermal, immiscible fluids was used. The resulting simulations showed dominant flow from the western coast of the Krk island to the eastern coast of the Istrian peninsula. Seawater enters the bay through the Srednja Vrata and Tihi Kanal and exits the bay through the Vela Vrata. This research has shown that using a VOF method can be successfully implemented for describing fluid motion in large areas such as bays and oceans

Multi-UAV trajectory planning for 3D visual inspection of complex structures

This paper presents a new trajectory planning algorithm for 3D autonomous UAV volume coverage and visual inspection. The algorithm is an extension of a state-of-the-art Heat Equation Driven Area Coverage (HEDAC) multi-agent area coverage algorithm for 3D domains. With a given target exploration density field, the algorithm designs a potential field and directs UAVs to the regions of higher potential, i.e., higher values of remaining density. Collisions between the agents and agents with domain boundaries are prevented by implementing the distance field and correcting the agent's directional vector when the distance threshold is reached. A unit cube test case is considered to evaluate this trajectory planning strategy for volume coverage. For visual inspection applications, the algorithm is supplemented with camera direction control. A field containing the nearest distance from any point in the domain to the structure surface is designed. The gradient of this field is calculated to obtain the camera orientation throughout the trajectory. Three different test cases of varying complexities are considered to validate the proposed method for visual inspection. The simplest scenario is a synthetic portal-like structure inspected using three UAVs. The other two inspection scenarios are based on realistic structures where UAVs are commonly utilized: a wind turbine and a bridge. When deployed to a wind turbine inspection, two simulated UAVs traversing smooth spiral trajectories have successfully explored the entire turbine structure while cameras are directed to the curved surfaces of the turbine's blades. In the bridge test case an efficacious visual inspection of a complex structure is demonstrated by employing a single UAV and five UAVs. The proposed methodology is successful, flexible and applicable in real-world UAV inspection tasks.Comment: 14 page

MPI Associated Scalability of Open-Source CFD Codes for Oil Spill Assessment

General-purpose CFD codes have recently become an increasingly discussed alternative to standardized, simplified and usually empirically calibrated specialized tools for pollution analyses. Commonly, CFD codes tend to provide physically more sensible results and can indicate the underlying cause for a given problem. Use for ecological problems, however, has usually been avoided due to the sizes of computational domains and inherent complexity of the calculations that need to be conducted. Adoption in recent years is mostly driven by significant improvements in computational capabilities and advancements related to code and communication optimizations. Unfortunately, due to substantial branching of codes and accompanying indispensable communication routines, especially in opensource community, performance and consequently applicability of codes, can vary significantly. This article aims to outline key limitations and quantify performance gains which can be obtained in a high-performance computing environment through the use of different communication protocols, when evaluating typical pollution problems such as oil spills. Obtained results indicate that savings of up to 40% in computational time can be achieved, depending on the code and message passing interface implementation for a problem in question, thus demonstrating the importance of communication protocols

Numerical Modeling of Inclined Buoyant Jets for Different Flow Conditions

The processes of discharge of higher density effluent into the recipient of lower density occur during the release of wastewater into the sea from desalination process, which is increasingly common today due to the shortage of drinking water. During such discharges, the goal is to achieve the best possible mixing, so that the impact of water with a high salt concentration on the environment is as small as possible. Since the jet returns to the bottom because of the influence of gravity, the use of nozzles at an angle increases the zone in which mixing occurs. In this paper, a numerical model of effluent discharge was made and buoyancy jets inclined at 45o were observed for different flow regimes. The influence of density and velocity on jet characteristics is shown. The numerical model was developed in OpenFOAM, and a comparison with experimental data from previous research is presented

Numerical Simulation of River Inflows in Rijeka Bay Coastal Area

In this paper, a model of water flow in the Porto Baroš has been developed, which is the part of the Rijeka coastal area, for the purpose of its renovation and conversion. For numerical simulation purposes, the depth of the seabed of Port was previously performed, based on which the geometry and numerical domain of Port were made. By conducting the flow simulation, the analysis was carried out, after which the analyses of the conceptual solutions with the introduction of the pipe discharge were performed with the aim of reducing the water pollution of the Porto Baroš area. Port geometry will be made in commercial SMS software and numerical domains and simulations in OpenFOAM open-source software

NUMERICAL SIMULATION OF CARGO TANKS INERTING

U radu je prikazana problematika inertiranja tankova na brodovima za prijevoz tekućeg tereta. Opisan je sustav za proizvodnju inertnoga plina te su navedeni zahtjevi koje takav sustav mora ispunjavati. Istaknuti su čimbenici koji utječu na kvalitetu inertiranja tankova tereta te karakteristike različitih pristupa pri upuhivanju inertnoga plina. Nadalje, je prikazan matematički model korišten u numeričkoj simulaciji inertiranja te njegova primjena na primjeru tankera za prijevoz tekućeg tereta. Numerička simulacija inertiranja provedena je za slučaj prvog inertiranja tanka nakon primopredaje broda ili inertiranja nakon dokovanja broda. Obrađeno je više slučajeva s različitim smjerovima upuhivanja inertnoga plina u tank tereta sa svrhom određivanja optimalnog smjera. Provedeno je i istraživanje utjecaja brzine upuhivanja inertnoga plina na brzinu promjene koncentracije pojedinih plinova. U zaključku je dan osvrt na dobivene rezultate uz smjernice za poboljšanje predstavljenoga simulacijskog modela.The topic of cargo tanks inerting on board liquid cargo carriers is presented in this paper. The inert gas production system and requirements which such a system has to fulfil are described. Factors that influence the quality of cargo tank inerting as well as different approaches to cargo tanks inerting are pointed out. The mathematical model used in the numerical simulation of cargo tanks inerting and its application on the example of a liquid cargo carrier is described in the paper. The numerical simulation of inerting is performed for a case of the first cargo tank inerting after the ship delivery or after docking. Several examples of different inert gas injection directions were analyzed with an intention to find out an optimal inert gas injection direction. Furthermore, the influence of the inert gas injection velocity on the gas concentration change rate inside the cargo tank is investigated. An overview of the obtained results and guidelines for the improvement of the presented simulation model are given in the conclusion chapter

Modell für die Strömung von Mikroplastikpartikeln im inhomogenen und laminaren Geschwindigkeitsfeld

Iz perspektive održivog razvoja, nerazgradivost te konstantni porast broja čestica mikroplastike u akvatičnim recipijentima zahtijeva urgentan razvoj mjera zaštite od nepovoljnih ekoloških posljedica što između ostalog iziskuje razumijevanje geneze mikroplastike te mehanike gibanja ovakve vrste onečišćenja u biosferi. Iz navedenoga slijedi i motivacija za istraživačkim aktivnostima koje su u ovom radu dokumentirane, a odnose se na prikaz odabrane teorijske osnove za modeliranje gibanja čestica mikroplastike te na relativno jednostavni numerički algoritam razvijen u svrhe modeliranja pronosa čestica mikroplastike u nehomogenom polju brzine tekućine u ravninskom i laminarnom toku. Lagrangeov opis gibanja čestica mikroplastike je neophodan radi nemogućnosti definiranja predmetnog REV-a te kontinuiranog polja koncentracije. Kako analize od praktičnog značaja uvjetuju relativno veliki broj čestica mikroplastike, neophodno je numerički algoritam formirati kroz kompromisno rješenje u okviru kojeg se nastoji minimizirati proračunsko vrijeme te maksimizirati utjecaj svih dominantnih fizikalnih procesa. Predloženi model se tako temelji na sustavu od dvije obične i nelinearne diferencijalne jednadžbe. Kako bi se pritom uvela mogućnost modeliranja čestica različitih oblika, faktor otpora oblika cd je modeliran poopćenim četvero-parametarskim Clift-Gauvinovim modelom u kojem su parametri definirani faktorom sferičnosti čestice mikroplastike odnosno mjerom odstupanja oblika čestice od kugle. Predloženi pristup modeliranja se može inkorporirati u neki od raspoloživih programskih rješenja (npr.OpenFOAM), a na kraju rada je prikazan numerički primjer dobiven implementacijom algoritma u programskom jeziku Python te je iznijet i osvrt na naredne eksperimentalne aktivnosti.From the sustainable development perspective,non-degradability and a constant microplastic particle increase in aquatic recipients require urgent development of protection measures against unfavourable environmental consequences. In order to do that, we firstly need an understanding of the microplastics genesis and the mechanics of its movement in the biosphere. This requiresresearch activities documented in this paper. They are related to the presentation of a selected theoretical basis for modelling the movement of microplastic particles, and a relatively simple numerical algorithm developed for modelling the transport of microplastic particles in inhomogeneous field of fluid velocity in planar and laminar flow.The Lagrange’s description ofthe movement of microplastic articles is necessary because it is impossible to define the subject REV and the continuous concentration field. Analyses of practical importance require a relatively large number of microplastic particles, so it is necessary to develop a numeric algorithm through a compromise solution that attempts to minimise the computational time and maximise the impact of all dominant physical processes. Therefore, the proposed model is based on a system of two ordinary, nonlinear differential equations. In order to introduce the possibility of modelling particles of different shapes, the resistance factor of cdshape is modelled by a generalised four-parameter Clift and Gauvin model, where the parameters are defined by the spherical factor of a microplastic particle or the measure of a particle shape deviation from the sphere. The proposed modelling approach can be incorporated into some available software solutions (e.g. OPENFOAM). The end of the paper contains the presentation of a numerical example obtained by implementing the algorithm in the Python programming language anda review of the next experimental activities.Im Rahmender nachhaltigen Entwicklungist es wegen der Nichtabbaubarkeit und ständiger Erhöhung der Anzahl von Mikroplastikpartikeln in Gewässern erforderlich, Schutzmaßnahmen gegen ungünstige Umweltauswirkungen dirngend zu entwickeln. Das impliziert, dass die Entstehung der Mikroplastik und die Bewegungsmechanik dieser Schadstoffe in der Biosphäre schon gut verstanden sind. Das war auch die Motivation für die hier beschriebenen Untersuchungen, die auch eine Darstellung der theoretischen Grundlage für das Modellieren der Mikroplastikpartikelbewegung einbeziehen sowie einen relativ einfachen numerischen Algorithmus, der zum Zwecke der Modellierung des Transportes von Mikroplastikpartikeln im inhomogenen Flüssigkeitsgeschwindigkeitsfeld in ebener und laminarer Strömung entwickelt worden ist. Die lagrangesche Darstellung der Bewegung von Mikroplastikpartikeln ist unentbehrlich, weil das gegenständliche repräsentative Elementarvolumen (REV) und das kontinuierliche Konzentrationsfeld nicht definiert werden können. Da praxisrelevante Analysen eine relative große Anzahl von Mikroplastikpartikeln benötigen, ist es notwendig, den numerischen Algorithmus als eine Kompromisslösung zu gestalten, im Rahmen derer die Berechnungszeit minimiert und der Einfluss aller dominanten physikalischen Prozesse maximiert wird. Das vorgeschlagene Modell basiert auf einem System von zwei gewöhnlichen und nichtlinearen Differenzengleichungen. Um dabei auch die Modellierung von Partikeln unterschiedlicher Form zu ermöglichen, wurde der Formwiderstandsfaktor cdanhand des verallgemeinerten Vier-Parameter-Modells von Clift und Gauvin modelliert, in dem die Parameter durch die Sphärizität des Mikroplastikpartikels bzw. Maß für die Abweichung der Partikelform von der Kugel definiert werden. Der vorgeschlagene Ansatz zur Modellierung kann in frei erhältliche Simulationspakete (z.B. OpenFOAM) übernommen werden. Am Ende der Arbeit wird ein numerisches Beispiel der Umsetzung des Algorithmus in die Programmiersprache Python dargestellt, und zukünftige Untersuchungsaktivitäten werden erwähnt