The (im)possibility of reducing the meteotsunami amplitude by constructing protective breakwaters

Plitkovodni gravitacijski val uzrokovan gibanjem atmosferskog poremećaja povećava svoju amplitudu kroz energetski transfer omogućen Proudmanovom rezonancijom. Nailaskom na lučki bazen oblika lijevka dešava se dodatna amplificija valnog signala. Ukoliko valna grupa koja nailazi sadrži i frekvencije bliske lučkim vlastitim frekvencijama moguća je i pojava rezonancije s daljnjim povećenjem valnih amplituda. Cjelokupna pojava naziva se meteocunami, a primjer te pojave desio se i 21.6.1978. u Veloj Luci, pri čemu su registrirane valne visine od 6 m. U radu je provedena numerička analiza dinamike morskih razi u krajnjoj točki Vele Luke uslijed valne pobude s maksimalnim visinama od 0,19 m ispred ulaza u zaljev Vela Luka. Kao odgovor na valnu pobudu u krajnjoj točki luke dobivene su valne visine od 5,5 m. Analiziran je utjecaj hipotetskih vertikalnih nepropusnih lukobrana, na valne visine u samoj Veloj luci. Korištene su dvije varijante pozicije ispred ulaza u Velu Luku. Modelski rezultati ukazuju na relativno malo smanjenje valnih visina.Shallow water gravity wave caused by motion of atmospheric disturbances increases its amplitude through energy transfer enabled by the Proudman resonance. The waveform signals get further amplified reaching the funnel shaped port basin. If the incoming wave group contains frequencies close to the port\u27s eigen frequencies the resonance with a further increase of wave amplitude is likely to occur. The whole phenomenon is called meteotsunami, and an example of this phenomenon occurred on 21 June 1978 in Vela Luka, where the wave height was registered to be 6 m. The paper deals with carrying out the numerical analysis of the sea level dynamics in the final point brought about due to wave excitation with a maximum height of 0,19 m in front of the entrance to the Vela Luka Bay. In response to the wave excitation in the port\u27s final point, the obtained wave height was 5,5 m. Furthermore, the analysis involving the influence of hypothetical vertical impermeable breakwaters, set on two variant positions outside the entrance to Vela Luka was carried out. The model results indicate that there is a relatively small decrease in wave height

Perforated vertical wall as a waterfront structure

Polazi se od toga da je perforirani vertikalni zid obalna građevina kojom se utječe na veličinu reflektiranih valova, a time i na veličinu valova ispred obale, na prelijevanje preko konstrukcije, opterećenje konstrukcije i eroziju nožice temeljnog nasipa. Prikazane su neke postojeće građevine i laboratorijska istraživanja provedena na perforiranim konstrukcijama radi analize refleksijskih svojstava takvih konstrukcija odnosno njihovih oblikovnih i geometrijskih karakteristika.It is initially stated that a perforated vertical wall is a waterfront structure which influences the size of reflected waves, and hence the size of waves in front of the coast, the incidence of spilling over the structure, structure loading level, and erosion at foundation level. Authors present some existing structures as well as laboratory testing conducted on perforated structures, in order to analyse reflective properties of such structures, i.e. their characteristics relating to shape and geometry

Neural networks and their application in water management

U radu su detaljnije opisane neuralne mreže koje su dnaas sve češće u primjeni pri rješavanju problema iznimno visokog stupnja složenosti. Uz definiranje neuralnih mreža, dana je njihova podjela, prikaz strukture i osobina te je izdvojen pregled povijesnog razvoja. Istaknuta je primjenu neuralnih mreža unutar područja vodnog gospodarstva i to prije svega na području Hrvatske. Pri tome su ukratko opisane najznačajnije neuralne mreže koje su do danas razvijene i rabljene u praksi.Neural networks, nowadays increasingly used for solving problems of exceptionally high level of complexity, are described in great detail. After definition of neural networks, their classification is given, and their structure and properties are presented. An overview of their historic development is also given. An emphasis is placed on the use of neural networks in water management, especially in the territory of Croatia. At that, most significant neural networks developed so far and used in current practice are briefly presented

NUMERICAL MODELLING OF THE MORPHODYNAMICS OF THE PLOČE GRAVEL BEACH IN RIJEKA

The morphodynamics of an artificial gravel beach in the Bay of Rijeka (Ploče Beach) was analyzed. The morphological changes of the beach face were monitored through an intense situation of gravitational surface wind waves from the incident SSW direction. A numerical modeling technique was applied, after initially establishing a numerical model for wave deformation. A model for sediment transport was established based on its results. Both models were based on the finite volume method. In addition, the partial contribution of the longshore component of sediment transport was analyzed based on empirical formulae. The modeling results were verified by comparing the positions and amounts of eroded/accumulated material along the beach with the processing of terrain images in the form of point clouds. The erosion and accumulation positions of the beach sediment material, obtained by numerical model simulations, corresponded to the surveyed positions. The total volume of eroded and accumulated material based on terrain image processing corresponded to the model values

Hindcast of Significant Wave Heights in Sheltered Basins Using Machine Learning and the Copernicus Database

Long-term time series of wave parameters play a critical role in coastal structure design and maritime activities. At sites with limited buoy measurements, methods are used to extend the available time series data. To date, wave hindcasting research using machine learning methods has mainly focused on filling in missing buoy measurements or finding a mapping function between two nearshore buoy locations. This work aims to implement machine learning methods for hindcasting wave parameters using only publicly available Copernicus data. Ensemble regression and artificial neural networks were used as machine learning methods and the optimal hyperparameters were determined by the Bayesian optimization algorithm. As inputs, data from the MEDSEA reanalysis wave model were used for the wave parameters and data from the ERA5 atmospheric reanalysis model were used for the wind parameters. The results of this study show that the normalized RMSE of the test data improved by 29% for Rijeka and 12% for Split compared to the original MEDSEA wave hindcast at buoy locations. The proposed method was extremely efficient in removing bias in the original MEDSEA hindcasts (e.g., NBIAS = -0.35 for Rijeka) to negligible values for both Split and Rijeka (NBIAS < 0.03)

NUMERICAL INVESTIGATIONS OF FLUSHING TIME IN SMALL MARINAS

This paper presents the results of 2D and 3D numerical simulations of sea circulation and water mass exchange for a marina with hypothetical dimensions (L/B=2 and L/B=0.5) to calculate the return flow factor. The return flow factor b was analyzed in relation to the marina entrance width, sea current velocity outside the marina (0, 1, 2, and 5 cm/s) and the sea surface level oscillation dynamics. The basic comparative parameter is the e-flushing time, Tf. The intensity of forced circulation is calculated to achieve time Tf of less than 10 days. The impact of the wind field on the e-flushing time for different marina widths was analyzed using a 3D numerical model. The numerical simulation results indicate that the e-flushing time Tf depends on the amplitude of the tidal signal, secondary to the width of the marina inlet, and the smallest amount on the velocity field in the outer region. Conversely, the return flow factor b depends on the width of the marina entrance, less on the tidal signal amplitude, and least on the current velocity outside the marina if currents are ≥ 1 cm/s. Forced circulation of 1 m3/s is only required for the marina with a smaller tidal amplitude (position Dubrovnik) to achieve Tf<10 days. If at the observed location wind is a dominant sea circulation generator, a wider marina entrance will allow faster sea exchange

Analysis of vertical pressure load exerted on horizontal RC plates by wave impact

U radu se analiziraju tlačna dinamička opterećenja na donju pokrovnu plohu kesonske konstrukcije pri djelovanju valova na primjeru zagrebačke obale u luci Rijeka. Osim mjerenja na fizikalnom modelu, primijenjeni su empirijski obrasci s ulaznim podacima iz linearne teorije valova i iz numeričkog modela. Usporedbom izmjerenih i modeliranih vrijednosti procijenjena je pouzdanost primijenjenih metodologija. Najbolje slaganje modelskih rezultata s izmjerenima postignuto je primjenom linearne valne teorije i empirijskog obrasca prema Kaplanu (1995).The analysis of dynamic pressure load exerted on the caisson structure bottom cover plate subjected to wave action is presented and illustrated by the example of Zagreb Pier in the Port of Rijeka. In addition to physical model measurements, empirical models are applied using input data from the linear wave theory and numerical model. The reliability of the applied methodology is assessed through comparison of measured and modelled values. The best correspondence between the measured and modelled results is obtained using the linear wave theory and the Kaplan\u27s (1995) empirical model

Basic plan dimensions of marinas in Croatia

Radi unaprjeđenja urbanističkog i ekonomskog planiranja nautičkog turizma u Hrvatskoj, u ovom je radu provedena analiza i prezentacija tlocrtnih parametara 39 postojećih hrvatskih marina. Prikupljeni tlocrtni parametri su: broj vezova, broj suhih vezova, duljina lukobrana, duljina fiksnih gatova, duljina pontona, duljina obala, površina akvatorija, površina teritorija, ukupna površina, površina suhog veza i površina parkirališta. U radu su prikazane ovisnosti navedenih parametara u funkciji broja vezova u moru te su definirani prosječni statistički pokazatelji navedenih parametara koji karakteriziraju gradnju marina u Hrvatskoj.The analysis and presentation of plan view parameters for 39 marinas operating in Croatia is made in the paper to enhance improvement of the spatial and economic planning of nautical tourism in Croatia. The following plan view parameters were collected: number of berths, number of dry berths, breakwater length, fixed pier length, pontoon length, waterfront length, water basin area, territory area, total area, dry berth area, and parking area. The dependence of these parameters on the number of sea berths is presented, and average statistical indicators of these parameters, which characterise marine construction in Croatia, are defined

Optimizing rinsing process for the rapid water-conditioning filters

Istraživanjem na hidrauličkom fizikalnom modelu provedena je optimizacija procesa ispiranja brzih filtara u postrojenjima za kondicioniranje vode. Optimalizacija u smislu određivanja minimalnog vremena potrebnog za cjelokupni proces ispiranja pri kome stabilnost podnica neće biti ugrožena, a odnošanje filtarskog materijala će biti minimalno. Rezultati mjerenja na hidrauličkom fizikalnom modelu uspoređeni su s rezultatima mjerenja u filtarskom polju na stvarnom uređaju.The rinsing process optimization for rapid filters of water conditioning plants was conducted by means of an appropriate hydraulic physical model testing. The optimization was aimed at defining the minimum time needed to complete the entire rinsing process without damaging the floor stability, and with a minimum loss of filtering material. The hydraulic physical model test results were compared with measurement results obtained at the filtering field on a real-size device

Examples of trends in water management systems under influence of modern technologies

Dobivanje pouzdanih i pravovremenih informacija o trenutačnom i o budućem stanju voda omogućava učinkovito upravljanje vodnogospodarskim sustavima. U ovom se radu prikazuju prednosti i izazovi primjene naprednih tehnologija pri prikupljanju, obradi i integraciji podataka unutar nekoliko primjera sustava gospodarenja vodama. Pokazuje se kako napredne tehnologije imaju izraženu učinkovitost u preciznom praćenju različitih fenomena okoliša, u povećanju sigurnosti vodnih resursa i objekata te omogućavaju smanjenje potrošnje vode i energije uz povećanje kvalitete vode.Reliable and timely information about the current and future condition of water enables an efficient management of water management systems. Advantages and challenges of the use of modern technologies in the collection, analysis, and integration of data, are presented in this paper by means of several examples of water management systems. It is shown how advanced technologies demonstrate a pronounced efficiency in accurate monitoring of various environmental phenomena and in increasing safety of water resources and facilities, while also enabling low water and energy consumption, with simultaneous increase in water quality