Mathematical simulation of hydrocarbon evaporation from water surfaces : master's thesis

Nakon izljeva na morsku površinu nafta može izgubiti do 40% svoje mase unutar prvih nekoliko sati. Nafta je smjesa tvari te se njeno isparavanje bitno razlikuje od isparavanja vode. Isparavanje vode je regulirano graničnim slojem zraka iznad vodene površine. Isparavanje nafte nije regulirano na isti način kao voda te je uglavnom neovisno o brzini vjetra i površini isparavanja. Unatoč tome što im mehanizmi isparavanja nisu regulirani na jednak način, početna jednadžba za razmatranje isparavanja nafte je jednadžba isparavanja vode: E ≥ KCTuS. Promatrana su dva modela koji predviđaju isparavanje nafte: semianalitički model i fugitivni model. U semianalitičkom modelu naftna mrlja se dijeli na N manjih mrlja koje imaju različita svojstva. Za određeni vremenski period računa se isparavanje za svaku unaprijed određenu komponentu iz sastava nafte, komponente koje su potpuno isparile ili potonule se uklanjaju iz računu u sljedećem koraku. Komponente se svedu na novu, jednaku debljinu i račun se ponavlja. Fugitivni model djeli područje izljeva na dva dijela: voda i sediment. Voda se dijeli na suspendirane čvrste tvari i živu tvar, a sediment na čvrste tvari i pornu vodu. Model predviđa povećanje vodenog dijela zbog širenja izljeva te u obzir uzima morske struje i kemijsku degradaciju nafte. Porastom transporta nafte morem te zbog povećanog rizika od akcidentnih situacija razvijaju se novi računalni programi za predviđanje starenja i kretanja naftnih mrlja.Abstract: After an oil spill on the ocean surface the spilled petroleum can lose up to 40% of its initial weight due to evaporation.Petroleum is a complex mixture of different components and the evaporation of petroleum is very different from that of water. Evaporation of water if regulated by a air boundary layer above the surface. Petroleum evaporation is not regulated in the same way and it is mostly uneffected by wind or slik area. Despite of the difference in the regulaton mechanism of petroleum and water the initial equation for the early work on petroleum evaporation is the euation for water evaporation: E≥KCTuS. Two different models are observed: semi-analythical and fugacity model. In the semi-analythical model the spill is divided into N number of smaller parts wich have different propeties. For a give time period the evaporation of these part is calculated, evaporated or sunk components are removed from further calcualtions. the remaining components are the unified to a sema layer thicknes and the calculation is then repeated for a new time period. The fugacity model divides the spill area into two components: water and sediment. Water is further divided int suspended solids and biota. Sediment is divided into pore water and solid matter. This model predicts the grow of the water part due to the spreading of the oil spill. It also takes into consideration the sea curents and chemical degradation of petroleum. With the increase of petroleum transportation and growing risk of accidents new computer programs for predicting the fate of oil spills and their weathering are developed