Comparison of modelled and measured surface wind waves

Prikazana je usporedba rezultata mjerenja i numeričkog modeliranja površinskih vjetrenih valova na Jadranu. Model za valno generiranje uzima podatke o vjetru iz prognoze Aladin. Rabljene su dvije modelske prostorne domene: regionalna (Jadran) i lokalna (kanalski sustav jugoistočnog Jadrana). U lokalnoj domeni upotrijebljena je detaljnija prostorna diskretizacija. Stupanj korelacije izmjerenih i modeliranih vrijednosti primarno ovisi o pouzdanosti ulaznih podataka o vjetru.The comparison between measurement data and numerical modelling results for surface wind waves on the Adriatic is presented. The wave generation model receives wind data from the Aladin forecast. Two spatial model domains are used: regional (Adriatic) and local (south-eastern Adriatic channel system). A detailed spatial discrétisation is used in the local domain. The degree of correlation between the measured and modelled values is primarily dependent on the reliability of input wind data

Hibridni paralelni algoritmi za rešavanje nelinearne Šredingerove jednačine

Numerical methods and algorithms for solving of partial differential equations, especially parallel algorithms, are an important research topic, given the very broad applicability range in all areas of science. Rapid advances of computer technology open up new possibilities for development of faster algorithms and numerical simulations of higher resolution. This is achieved through paralleliza-tion at different levels that  practically all current computers support. In this thesis we develop parallel algorithms for solving one kind of partial differential equations known as nonlinear Schrödinger equation (NLSE) with a convolution integral kernel. Equations of this type arise in many fields of physics such as nonlinear optics, plasma physics and physics of ultracold atoms, as well as economics and quantitative  finance. We focus on a special type of NLSE, the dipolar Gross-Pitaevskii equation (GPE), which characterizes the behavior of ultracold atoms in the state of Bose-Einstein condensation. We present novel parallel algorithms for numerically solving GPE for a wide range of modern parallel computing platforms, from shared memory systems and dedicated hardware accelerators in the form of graphics processing units (GPUs), to   heterogeneous computer clusters. For shared memory systems, we provide an algorithm and implementation targeting multi-core processors us-ing OpenMP. We also extend the algorithm to GPUs using CUDA toolkit and combine the OpenMP and CUDA approaches into a hybrid, heterogeneous al-gorithm that is capable of utilizing all  available resources on a single computer. Given the inherent memory limitation a single  computer has, we develop a distributed memory algorithm based on Message Passing Interface (MPI) and previous shared memory approaches. To maximize the performance of hybrid implementations, we optimize the parameters governing the distribution of data  and workload using a genetic algorithm. Visualization of the increased volume of output data, enabled by the efficiency of newly developed algorithms, represents a challenge in itself. To address this, we integrate the implementations with the state-of-the-art visualization tool (VisIt), and use it to study two use-cases which demonstrate how the developed programs can be applied to simulate real-world systems.Numerički metodi i algoritmi za rešavanje parcijalnih diferencijalnih jednačina, naročito paralelni algoritmi, predstavljaju izuzetno značajnu oblast istraživanja, uzimajući u obzir veoma široku primenljivost u svim oblastima nauke. Veliki napredak informacione tehnologije otvara nove mogućnosti za razvoj bržih al-goritama i  numeričkih simulacija visoke rezolucije. Ovo se ostvaruje kroz para-lelizaciju na različitim nivoima koju poseduju praktično svi moderni računari. U ovoj tezi razvijeni su paralelni algoritmi za rešavanje jedne vrste parcijalnih diferencijalnih jednačina poznate kao nelinearna Šredingerova jednačina sa inte-gralnim konvolucionim kernelom. Jednačine ovog tipa se javljaju u raznim oblas-tima fizike poput nelinearne optike, fizike plazme i fizike ultrahladnih atoma, kao i u ekonomiji i kvantitativnim finansijama. Teza se bavi posebnim oblikom nelinearne Šredingerove jednačine, Gros-Pitaevski jednačinom sa dipol-dipol in-terakcionim članom, koja karakteriše ponašanje ultrahladnih atoma u stanju Boze-Ajnštajn kondenzacije. U tezi su predstavljeni novi paralelni algoritmi za numeričko rešavanje Gros-Pitaevski jednačine za širok spektar modernih računarskih platformi, od sis-tema sa deljenom memorijom i specijalizovanih hardverskih akceleratora u ob-liku grafičkih procesora, do heterogenih računarskih klastera. Za sisteme sa deljenom memorijom, razvijen je  algoritam i implementacija namenjena više-jezgarnim centralnim procesorima  korišćenjem OpenMP tehnologije. Ovaj al-goritam je proširen tako da radi i u  okruženju grafičkih procesora korišćenjem CUDA alata, a takođe je razvijen i  predstavljen hibridni, heterogeni algoritam koji kombinuje OpenMP i CUDA pristupe i koji je u stanju da iskoristi sve raspoložive resurse jednog računara. Imajući u vidu inherentna ograničenja raspoložive memorije koju pojedinačan računar poseduje, razvijen je i algoritam za sisteme sa distribuiranom memorijom zasnovan na Message Passing Interface tehnologiji i prethodnim algoritmima za sisteme sa deljenom memorijom. Da bi se maksimalizovale performanse razvijenih hibridnih implementacija, parametri koji određuju raspodelu podataka i računskog opterećenja su optimizovani korišćenjem genetskog algoritma. Poseban izazov je vizualizacija povećane količine izlaznih podataka, koji nastaju kao rezultat efikasnosti novorazvijenih algoritama. Ovo je u tezi rešeno kroz inte-graciju implementacija sa najsavremenijim alatom za vizualizaciju (VisIt), što je omogućilo proučavanje dva primera koji pokazuju kako razvijeni programi mogu da se iskoriste za simulacije realnih sistema

Removal methods for invasive species Amorpha fruticosa – example of Odransko polje

Amorpha fruticosa is an invasive plant species that occurs in wide range of habitat types, including lowland floodplains. It grows very dense and changes the composition of communities by suppressing indigenous species, resulting in significantly reduced variety of flora in the area. In Odransko polje Amorpha fruticosa is widely spread. One of the tasks of Appropriate assessment of project "Flood protection system of Sisak area" was to determine the locations where material for embankment construction should be taken. The locations should be acceptable both from the aspect of nature protection and from the economic point of view (proximity to embankment due to lowering material transport costs, locations which are not private property, etc.). The locations where A. fruticosa is dominant plant were suggested for excavation. This paper will give overview of removal and disposal methods for this invasive species, which reduce the possibility of its spreading and re-appearing. Also, positive impacts of using proposed locations for material excavation will be shown – decrease in A. fruticosa abundance, increase of habitat diversity, increase in the presence of target habitats and target species habitats etc. Additionally, good practices for selection of excavation sites will be given, including guidelines for their sanation and landscape design

Hydraulic properties of U-shaped stormwater overflows

Opisuju se hidrauličke karakteristike kišnog preljeva U oblika, alternativnog rješenja kojim se omogućuje smanjenje ukupne duljine preljevne građevine. Prikazani su rezultati hidrauličkih ispitivanja koja su provedena zbog toga što su nedostajali podaci o svojstvima preljeva toga oblika. Ispitivanje na fizikalnom modelu poslužilo je i za optimizaciju preljeva koja je provedena u dva koraka. Opisane su i odgovarajuće numeričke analize radi usporedbe s rezultatima na modelu.Authors describe hydraulic properties of the U-shaped stormwater overflows, which constitute an alternative solution for reducing an overall length of traditional stormwater overflow facilities. Results of hydraulic tests conducted to obtain additional data about properties of such overflows are presented. Physical model tests were also conducted to optimise overflow facilities using a two-step process. Appropriate numerical analyses are also given to enable comparison with scale model results

Wave deformation analysis in the Split Port area

Prikazuju se rezultati provedenih istraživanja valnih karakteristika sadašnjeg stanja gradske luke Split i njezinog razvoja pomoću matematičkog i fizikalnog modeliranja valnih deformacija u lučkom akvatoriju. U ovom je radu dan je presjek rezultata provedenih istraživanja valnih deformacija za varijantna rješenja dodatnih gradnji uz kvantifikaciju potencijalnog poboljšanja, zadržavanja ili pogoršanja postojećeg stanja. Uspoređeni su rezultati fizikalnog i numeričkog modeliranja.Results obtained by the study of wave properties in the present day Port of Split, and the study development process, are presented by means of mathematical and physical modelling of wave deformations in the port basin. An overview of results obtained by the study of wave deformations is presented for alternative solutions involving additional construction work. Effects that could be gained by additional improvements, by maintaining the present situation, and by deterioration of the present situation, are quantified. Physical and numerical modelling results are compared

Near-bottom pollution transport modelling

Opisano je modeliranje pronosa pridneno ispuštenog onečišćenja pri stacionarnom tečenju u kanalu jednolikog pravokutnog presjeka s primjenom dvodimenzionalnih i trodimenzionalnih modela. Osim usporedbe rezultata ravninskog i prostornog numeričkog modeliranja raspodjele koncentracije pridneno ispuštenog onečišćenja u kanalu idealiziranih geometrijskih obilježja, dana je i usporedba reprezentativne veličine tzv. brzine miješanja s rezultatima dobivenim fizikalnim modeliranjem.The near-bottom transport of pollution, discharged during stationary flow into a channel of uniform rectangular cross section, is modelled by means of two-dimensional and three-dimensional models. Comparison between in-plane and three-dimensional numerical modelling results, defining distribution of near-bottom pollution in a channel of idealized geometrical properties, is provided. A comparison between the representative value of the so called mixing velocity, and the results obtained by physical modelling, is also presented