Etude expérimentale et numérique de la topologie d'une interface gaz/liquide

La topologie interfaciale d'une poche de gaz de grand allongement soumise à un écoulement liquide permanent et immobilisée en amont d'un obstacle, est étudiée expérimentalement et numériquement. Les ondes figées apparaissent dans une zone limitée de l'interface lorsque le nombre de Reynolds est suffisamment important (Re > 16000). Au-delà de ces valeurs de Re, leur longueur d'onde diminue progressivement. Ce comportement peut être expliqué par un modèle basé sur la théorie irrotationnelle des ondes en eau profonde. Il montre que les ondes figées sont générées par la présence de l'obstacle. Il permet également de prédire que les effets capillaires prédominent sur les effets gravitaires. Ceci est particulièrement valable pour Re > 20000. En revanche, la modélisation numérique ne prédit l'existence que d'une seule zone interfaciale, siège d'ondes progressives dont la longueur d'onde correspond à la longueur caractéristique des recirculations au sein de la poche

RESEARCH OF THE BIOTOPE DIVERSITY FOR THE PURPOSES OF ECONOMIC VALUATION OF ECOSYSTEM SERVICES IN CHEPELARE MUNICIPALITY (THE RHODOPES REGION OF BULGARIA)

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Étude expérimentale et numérique des phénomènes à l'interface d'une poche de gaz immobilisée au sein d'un écoulement permanent de liquide

Les phénomènes interfaciaux au sein d'une poche de gaz, immobilisée et soumise à un écoulement liquide permanent sont étudiés par voies expérimentale et numérique. L approche expérimentale concerne trois longueurs de la poche et des régimes d écoulement laminaires et turbulents. Deux régions interfaciales sont identifiées : le front et le corps. Ce dernier correspond à la partie plane de l interface et se divise en trois zones. Il est le siège de deux types d ondes : ondes progressives et ondes figées dont la nature est expliquée par la théorie des ondes en eaux profondes. Un modèle théorique décrivant le transfert de masse, observé à travers l'interface, est développé. Les résultats de l approche numérique reproduisent correctement la forme globale de la poche et du front. En revanche, ils ne prédisent l existence que d'une seule zone interfaciale, siège d'ondes progressives dont la longueur d'onde correspond à la longueur caractéristique des recirculations au sein de la pocheThe phenomena at gas-liquid interface are studied experimentally and numerically. In the experimental part, a gas pocket is immobilized and immerged in a steady liquid flow. Both laminar and turbulent flow regimes are investigated. The study is based on three different gas pockets. Two interfacial regions of the gas pocket are recognized: front and body. The analysis of the body reveals zones where traveling and frozen waves appear. The last are explained using the deep-water-waves theory. Besides, a theoretical model describing the mass transfer across the interface is developed. In the numerical part, two-dimensional unsteady calculations are performed using a commercial code. The modeled shape of the pocket and its front are quite well reconstructed. In contrast, no distinct zones are predicted by the model. The interface is homogeneous and characterized only by traveling waves which wavelength corresponds to the characteristic vortex length encountered inside the gas phaseLYON1-BU.Sciences (692662101) / SudocSudocFranceF

Experimental and numerical investigation of an air pocket immersed in a horizontal water duct flow

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Forests of Breznik municipality

The current study aims to uncover the forest habitat diversity of Breznik municipality, following the EUNIS Classification. Initial data was collected from the Ministry of Environment and Water and the Forestry Management Plans. Forest habitat polygons were spatially processed with the use of the ArcGIS 10.8.1 software package. Field studies were performed to add more detailed information to the analysis. The phytocoenoses of the forest habitats are dominated by Quercus dalechampii, Q. frainetto, Fagus sylvatica, Carpinus betulus. Some artificial plantations with Pinus nigra and P. sylvestris were also present, as well as with non-native species, such as Robinia pseudacacia and Quercus rubra. The results of this study could be used for more in-depth research of the Breznik municipality vegetation

Forest habitats of Godech Municipality, Western Bulgaria

The current study aims at revealing the forest habitat diversity of Godech Municipality, according to the EUNIS habitat classification. Initial data was collected from the Ministry of Environment and Water and the Forestry Management Plans. Subsequently, 418 vegetation plots (relevés) and 3422 verification points were collected during the fieldwork seasons of 2019 and 2020. The research territory is situated in Western Bulgaria in close proximity to the country’s border with the Republic of Serbia. Forests cover a total of 144.85 km2. Their phytocoenoses are dominated by Fagus sylvatica L. (59.22 km2), Quercus cerris L. (14.85 km2), Carpinus betulus L. (4.94 km2), Quercus dalechampii Ten. (2.39 km2), Q. frainetto Ten. (2.99 km2). There are plantations with Pinus nigra J. F. Arnold (20.87 km2), P. sylvestris L. (16.06 km2) and Picea abies H. Karst (11.65 km2) also. Forests are experiencing some major threats, such as logging, pollution and fires

Shrubland habitats in Dragoman municipality: a case study from western Bulgaria

The current research focuses on the investigation of shrubland vegetation in Dragoman municipality. The study is motivated by the willingness of the authors to check the shrubland habitats’ territorial extent and their importance to ecosystem processes, following the increased degree of succession over the last three decades. On the other hand, governmental subsidizing has been common for the last decade, leading to a clearance of lands with shrubs. Shrublands were studied through the application of the Braun-Blanquet approach and were defined by the European Nature Information System (EUNIS) classification. One main habitat type with three subtypes have been defined. Those are the Subcontinental and continental deciduous thickets (F3.24) that covers the largest area, Peri-Pannonic dwarf almond scrub (F3.24122), Moesian oriental hornbeam thickets (F3.2431), Moesian lilac thickets (F3.2432), covering a total area of 52.32 km2. Secondary succession has to be considered among the main reasons for shrubland distribution. The lower number of grazing animals and forest clearings act as boosters for this ecological process. Large areas in Dragoman municipality are characterized also by shallow soils that are unable to sustain forest vegetation, thus giving way to shrubs

Balkan Vegetation Database: historical background, current status and future perspectives

The Balkan Vegetation Database (BVD; GIVD ID: EU-00-019; http://www.givd.info/ID/EU-00- 019) is a regional database that consists of phytosociological relevés from different vegetation types from six countries on the Balkan Peninsula (Albania, Bosnia and Herzegovina, Bulgaria, Kosovo, Montenegro and Serbia). Currently, it contains 9,580 relevés, and most of them (78%) are geo-referenced. The database includes digitized relevés from the literature (79%) and unpublished data (21%). Herein we present descriptive statistics about attributive relevé information. We developed rules that regulate governance of the database, data provision, types of data availability regimes, data requests and terms of use, authorships and relationships with other databases. The database offers an extensive overview about studies on the local, regional and SE European levels including information about flora, vegetation and habitats