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Measurements and numerical modelling of surface waves in front of the port of split

Leder N., Duplančić Leder T., Lončar G.

TransNav : International Journal on Marine Navigation and Safety of Sea Transportation

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2020

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Vol. 14, no. 1

191--197

EN

Wind generated surface waves were measured at V2 station (φ=43°29.3’ N; λ=16° 27.9’ E) in the Brački Kanal Channel area of the Middle Adriatic, in front of the port of Split. This was undertaken in the time interval from November 2007 to June 2008, by using Datawell MKIII waverider with all its compo-nents. For the analysis and description of extreme sea states maximum recorded wave height Hmax and sig-nificant wave height H1/3 were presented as well as associated wave spectra. The measurement results show that much larger waves appear in the open Adriatic compared to the Middle Adriatic channel area. Numerical modelling of wave generation in the Brački Kanal Channel area and wider island area of the Middle Adriatic Sea was performed by using Mike 21/SW numerical model. Wind field used for the forcing in numerical simulations relies on the results of the prognostic atmospheric model Aladin-CRO. For verification of model results, results of measurement at a waverider station V2 located in front of the port of Split were used. It was concluded that measured and modelled significant wave heights were very well matched.

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Application of neural networks and support vector machine for significant wave height prediction

Berbić J., Ocvirk E., Carević D., Lončar G.

Oceanologia

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2017

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No. 59 (3)

331--349

EN

For the purposes of planning and operation of maritime activities, information about wave height dynamics is of great importance. In the paper, real-time prediction of significant wave heights for the following 0.5–5.5 h is provided, using information from 3 or more time points. In the first stage, predictions are made by varying the quantity of significant wave heights from previous time points and various ways of using data are discussed. Afterwards, in the best model, according to the criteria of practicality and accuracy, the influence of wind is taken into account. Predictions are made using two machine learning methods – artificial neural networks (ANN) and support vector machine (SVM). The models were built using the built-in functions of software Weka, developed by Waikato University, New Zealand.

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Numerical modelling of an oil spill in the northern Adriatic

Lončar G., Leder N., Paladin M.

Oceanologia

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2012

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No. 54 (2)

143-173

EN

Hypothetical cases of oil spills, caused by ship failure in the northern Adriatic, are analysed with the aim of producing three-dimensional models of sea circulation and oil contaminant transport. Sea surface elevations, sea temperature and salinity fields are applied as a forcing argument on the model's open boundaries. The Aladin-HR model with a spatial resolution of 8 km and a time interval of 3 hours is used for atmospheric forcing. River discharges along the coastline in question are introduced as point source terms and are assumed to have zero salinity at their respective locations. The results of the numerical modelling of physical oceanography parameters are validated by measurements carried out in the "Adriatic Sea monitoring programme" in a series of current meter and CTD stations in the period from 1 January 2008 to 15 November 2008. The oil spill model uses the current field obtained from a circulation model. Besides the convective dispersive transport of oil pollution (Lagrangian model of discrete particles), the model takes into account a number of reactive processes such as emulsification, dissolution, evaporation and heat balance between the oil, sea and atmosphere. An actual event took place on 6 February 2008, when the ship "Und Adriyatik" caught fire in the vicinity of the town of Rovinj (Croatia) en route from Istanbul (Turkey) to Trieste (Italy). At the time the fire broke out, the ship was carrying around 800 tons of oil. Thanks to the rapid intervention of the fire department, the fire was extinguished during the following 12 hours, preventing possible catastrophic environmental consequences. Based on this occurrence, five hypothetical scenarios of ship failure with a consequent spill of 800 tons of oil over 12 hours were analysed. The main distinction between the simulated scenarios is the time of the start of the oil spill, corresponding to the times when stronger winds were blowing (> 7 m s-1) with a minimum duration of 24 h within the timeframe. Each scenario includes a simulation of oil transport for a period of two months after the beginning of the oil spill. The results show that the coastal belt between the towns of Porec and Rovinj is seriously exposed to an oil pollution load, especially a few days after a strong and persistent bora (NE wind).

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Influence of density stratification on effluent plume dynamics

Lončar G., Beg Paklar G., Janeković I.

Oceanologia

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2011

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No. 53 (2)

565-585

EN

In this study we modelled sea temperature (T), salinity (S) and density field dynamics using a 3D numerical model applied to Rijeka Bay (Croatia) in order to explore their effect on effluent plume dynamics in the vicinity of four submarine sewage outfalls when the bora wind (NE direction) is blowing. The vertical density stratification in the area studied is strongly related to the bora wind, which contributes significantly to the lowering of the pycnocline depth through enhanced mixing in the vertical, giving rise to changes in the neutral buoyancy level. The features of near-field plume dynamics were calculated with the use of a separate near-field numerical model, using information on the vertical density distribution previously calculated using a 3D numerical model. The results of the numerical simulations and statistical analysis of the wind data indicate a very low probability of complete water column homogenization and consequent effluent plume rise to the sea surface under the influence of the bora wind during the peak tourist season (May-September).