Water-in-oil emulsification and development of model EMU

Oil-spill at sea represents one of the greatest threats for the environment. Immediately after occurence\ud of an oil-spill several physical, chemical and biological processes occur, among which the process of\ud emulsification is one of the most important. Emulsified oil is very difficult to clean; therefore,\ud understnding of the emulsification processes is of great importance for successful clean-up.\ud Preconditions for formation of water-in-oil emulsion are adequate chemical conditions and sufficient\ud wave energy. The behaviour of formed emulsion depends mostly on its stability. After more than half\ud a century of research, scientists have concluded that emulsions are stabilized by viscoelastic\ud asphaltene films, which form around water droplets in oil and that emulsions can be divided into four\ud stability classes: stable emulsion, mesostable emulsions, unstable emulsion and entrained water.\ud Numerical models have been developed parallelly with the development of theory of the water-in-oil\ud emulsification. In this work we describe the development of the water-in-oil emulsification theory, the\ud development of the numerical models in the last few decades and the development of the model EMU.\ud The EMU model was developed using most recent equations for prediction of the emulsion stability\ud and emulsion kinetics. It is the first model developed at the Faculty of Civil and Geodetic Engineering\ud of University of Ljubljana dedicated exclusively to the oil emulsification process. We also present the\ud use of the model on the Macondo oil-spill case study

Flood inundation modelling of flash floods in steep river basins and catchments

The potential flood inundation extent can be estimated with flood inundation models, which can differ in the level of physical and numerical modelling complexity included in the solution procedure. In recent years, several studies have highlighted the benefits of shock-capturing flood inundation models, particularly when modelling a high Froude number or supercritical flows, or in areas prone to the occurrence of rapidly varying flood events, such as flash floods. Nonetheless, decision makers are often reluctant to implement more complex modelling tools into practical flood inundation modelling studies, unless evidence is provided to establish when such refined modelling tools should be used. The main objective of this study was to determine a general threshold value of the bottom slope that could be used by decision makers as an orientation guide to ascertain when to use a specific type of flood inundation model. The results obtained suggest that in torrential river basins or catchments (i.e., river basins and catchments with a bed slope generally greater than 1%), the flood inundation modelling should be conducted by using a flood inundation model that include shock-capturing algorithms in the model solution procedur

Predicting flood hazard indices in torrential or flashy river basins and catchments

Flood hazard maps are one of the main components of any flood risk management strategy. It is predicted that the degree of flood risk is going to significantly increase in the future due to climatic and environmental changes, and hence it is increasingly important that state-of-the-art methods are implemented for assessing human stability in floodwaters. Therefore, this paper focuses on proposing more accurate and detailed guidelines for predicting flood hazard indices in small and steep river basins or catchments, prone to the occurrence of flash flooding. The results obtained in this study indicate that for river basins with an average bed gradient greater than 1% (i.e. torrential or flashy river basins or catchments), then the flood hazard indices should be predicted using criteria which are based on the physical interpretation of the processes that affect the human stability in floodwaters, i.e. mechanics based and experimentally calibrated flood hazard assessment methods

Appropriate model use for predicting elevations and inundation extent for extreme flood events

Flood risk assessment is generally studied using flood simulation models; however, flood risk managers often simplify the computational process; this is called a “simplification strategy”. This study investigates the appropriateness of the “simplification strategy” when used as a flood risk assessment tool for areas prone to flash flooding. The 2004 Boscastle, UK, flash flood was selected as a case study. Three different model structures were considered in this study, including: (1) a shock-capturing model, (2) a regular ADI-type flood model and (3) a diffusion wave model, i.e. a zero-inertia approach. The key findings from this paper strongly suggest that applying the “simplification strategy” is only appropriate for flood simulations with a mild slope and over relatively smooth terrains, whereas in areas susceptible to flash flooding (i.e. steep catchments), following this strategy can lead to significantly erroneous predictions of the main parameters—particularly the peak water levels and the inundation extent. For flood risk assessment of urban areas, where the emergence of flash flooding is possible, it is shown to be necessary to incorporate shock-capturing algorithms in the solution procedure, since these algorithms prevent the formation of spurious oscillations and provide a more realistic simulation of the flood levels

One-dimensional sediment transport modelling with Engelund-Hansen and Ackers-White transport equations for the Lower Danube River

Premeščanje plavin ima lahko negativne posledice za rečno okolje, saj lahko privede do poslabšanja ekološke raznolikosti in povečanja poplavne ogroženosti. Modeliranje premeščanja plavin je tako eno ključnih orodij pri upravljanju porečij in načrtovanju rečnih urejevalnih objektov. V tej študiji smo preverili primernost 1D modeliranja celotne premostitvene zmogljivosti plavin z uporabo transportnih enačb Engelund Hansen in Ackers White za območje spodnje Donave. V študiji smo ovrednotili vpliv zrnavostnega razvrščanja na natančnost 1D modelnih rezultatov, primernost 1D modeliranja premeščanja plavin v okviru inženirskih projektov in primernost enačb Engelund Hansen in Ackers White za oceno pretoka plavin na območju spodnje Donave. Modelne rezultate smo primerjali s terenskimi meritvami, pri čemer smo natančnost modelnih rezultatov ovrednotili s statističnimi testi. Dobljeni rezultati kažejo: (i) zrnavostno razvrščanje nima bistvenega vpliva na rezultate 1D modeliranja, (ii) 1D modeliranje premeščanja plavin podaja dovolj natančne rezultate za praktično inženirsko uporabo (npr. ocena obsega poglabljanja dna) in (iii) enačba Engelund Hansen je načeloma bolj primerna za modeliranje premeščanja plavin na območju spodnje Donave.Sediment transport can have a negative impact on riparian environments, as it can lead to the deterioration of ecological diversity and increase flood risks. Sediment transport modelling is thus a key tool in river basin management and the development of river training structures. In this study, we examined the appropriateness of 1D modelling for total sediment transport loads using the Engelund Hansen and Ackers White transport equations for the Lower Danube River. The study evaluated the effect of sediment grading on the accuracy of 1D model results, the appropriateness of 1D sediment transport modelling within technical or engineering projects, and the appropriateness of the Engelund Hansen and Ackers White equations for estimating sediment yield in the area of the Lower Danube River. The model results have been compared to field measurements, with the accuracy of the modelling results being evaluated with statistical tests. The obtained results show: (i) the sediment grading does not have a significant impact on the 1D modelling results, (ii) 1D sediment transport modelling gives sufficiently accurate results for practical engineering use (e.g. the estimation of dredging activities), and (iii) the Engelund Hansen equation is generally better for sediment transport modelling in the Lower Danube River

Stability of vertical breakwaters by applying the general rules of Eurocode 7

Valobrani so hidrotehnični objekti, namenjeni varovanju obale in obalne infrastrukture, ki so nenehno izpostavljeni delovanju morja. Posledično so izpostavljeni različnim hidrodinamičnim obremenitvam, zato je pomembno, da pri njihovem projektiranju veliko pozornost namenimo njihovi stabilnosti. V tej študiji smo preverili razliko v koeficientu varnosti prevrnitve in zdrsa valobrana, če splošno uporabljeni pristop za izračun stabilnosti valobrana, podan v standardu BS 6349, posodobimo z delnimi varnostnimi faktorji, podanimi v Evrokodu 7. V sklopu primerjalne analize smo uporabili tri različne metode za izračun hidrodinamičnih obremenitev, tj. metodo Sainflou, razširjeno metodo Goda brez možnosti prelivanja valobrana in razširjeno metodo Goda z upoštevanjem prelivanja valobrana. Stabilnost valobrana smo izračunali in primerjali za različne širine valobrana, pri čemer smo v vseh računskih primerih upoštevali konstantne parametre valovanja. Pri izračunu stabilnosti smo se omejili na preverjanje kontrole toge prevrnitve in zdrsa. Dobljeni rezultati kažejo, da ni bistvene razlike v izračunanem koeficientu stabilnosti valobrana med uporabljenima računskima postopkoma, ne glede na izbrano metodo za izračun hidrodinamičnih obremenitev. Za razvoj celovitega pristopa k izračunu stabilnosti valobrana z upoštevanjem Evrokodov bi bilo treba določiti še ključne procese in numerične modele za izračun stabilnosti temeljnih tal ter bolj natančno upoštevati vplive, povezane z obliko in principom gradnje valobrana, gradbenimi materiali in lokalnimi značilnostmi morskega dna.Breakwaters are hydraulic structures designed to protect coastlines and coastal infrastructure, which are constantly exposed to the forces of the sea. Breakwaters are consequently subjected to a variety of hydrodynamic loads, wherefore breakwater stability must be prioritized during the breakwater design process. In this study, we examined the difference in the safety factor against overturning and sliding when the commonly used approach for calculating breakwater stability specified in BS 6349 was updated with the partial safety factors outlined in Eurocode 7. Our comparative analysis employed three different methods to calculate the hydrodynamic loads: the Sainflou method, the extended Goda method without the breakwater overtopping, and the extended Goda method with consideration of breakwater overtopping. The breakwater stability was calculated and compared for different breakwater widths, with constant wave parameters being used in all stability calculations. Within the stability calculations, we considered only overturning and sliding instability mechanisms. The obtained results show that there is no significant difference in the calculated breakwater stability coefficient between the two considered calculation procedures regardless of the method used for the calculation of the hydrodynamic loads. In order to develop a comprehensive approach for the calculation of breakwater stability based on the rules outlined in the Eurocodes, it would be necessary to determine the key processes and numerical models for calculating the stability of the foundation soil and to consider more precisely the impacts related to the breakwater shape and construction technique, construction materials, and local characteristics of the seabed

Mass concrete with EAF steel slag aggregate

Temperature control is the primary concern during the design and construction process of mass concrete structures. As the concrete production has an enormous negative environmental impact, the development of green mass concretes will eventually become as important as the thermal characteristics. Therefore, this paper investigates the use of Electric Arc Furnace (EAF) steel slag aggregate for the partial replacement of the natural aggregate in the production of mass concrete. The impact of EAF steel aggregate on mass concrete workability, strength, and thermal behaviour was analysed. In addition, a cradle-to-gate LCA study was conducted to evaluate the environmental footprint and sustainability potential of the tested mass concrete mixtures. The study results suggest that the use of EAF steel slag aggregate in combination with a low-heat cement with a high content of blast furnace slag can significantly lower the temperature, reduce the environmental impact, and increase the sustainability potential of mass concrete, while at the same time providing sufficient workability and compressive strength. The study results indicate that EAF steel slag can be upcycled into an aggregate for the production of green mass concrete mixtures

A review of river oil spill modeling

River oil spills are generally more frequent and pose greater environmental and public health risk than coastal and offshore oil spills. However, the river oil spill research has received a negligible amount of academic attention in the past three decades, while at the same time the coastal and offshore oil spill research has expanded and evolved tremendously. This paper provides the state-of-the-art review of river oil spill modeling and summarizes the developments in the field from 1994 to present. The review has revealed that the majority of the gaps in knowledge still remain. Thus, there is a need for (i) experimental studies in order to develop and validate new models and better understand the main physicochemical processes, (ii) studies on inter-linking of the governing processes, such as hydrodynamics, advection dispersion, and weathering processes, (iii) adaptation and validation of coastal and offshore oil spill models for applications in riverine environments, and (iv) development of river oil spill remote sensing systems and detection techniques. Finally, there is a need to more actively promote the importance of river oil spill research and modeling in the context of environmental and public health protection, which would form the basis for obtaining more research funding and thus more academic attention

Drava river sediment in clay brick production

The ever-growing worldwide demand for fired clay brick has resulted in the shortage of clay in many parts of the world. Therefore, there is a need to look for more sustainable alternative materials for the brick manufacturing. This study has investigated the potential use of the untreated Drava River sediment as a substitute material for clay in the production of fired bricks, with the research being conducted at both laboratory and industrial level. At the laboratory level, brick specimens were prepared by mixing clay with different river sediment proportions (ranging from 10 to 50 wt%) and were fired at 950 °C, with microstructural and various physical–mechanical properties being analyzed. Elevated carbonate content in Drava river sediment results in higher weight loss during firing at temperatures up to 950 °C, comparing to firing pure brick-making clay. Consequently, the addition of sediment increases porosity of fired bricks, which results in lowering of their mechanical properties. Results reveal that the compressive strength of the pure clay sample was 79.5 MPa, while the compressive strength of the sample with the addition of river sediment from 10 wt% to 50 wt% decreased from 73.9 MPa to 26.2 MPa, respectively. Despite the lower compressive strength, the 26.2 MPa is still above the limit value of 10 MPa specified in the standard EN 772–1 [1]. At the industrial level, hollow clay bricks were prepared with 20 wt% of the river sediment and fired in a tunnel kiln. Inclusion of the river sediment also decreased compressive strength from 38 MPa for pure mixture to 26 MPa for 20 wt% of the sediment addition, confirming usability of Drava sediment in brick production. In addition, LCA study has been conducted to evaluate the environmental impacts associated with the industrial production of classic bricks and bricks with the addition of the river sediment. The obtained results have shown that the bricks made with the addition of the Drava River sediment are sustainable and environmentally friendly and meet all the requirements specified in the relevant regulatory standard