96 research outputs found
Numerical and laboratory investigation of the hydrodynamic complexity of a river confluence
The paper deals with the hydrodynamic investigation of the junction of two rivers in north-west Hungary in an urban area. The goal of the investigation was to study the flow conditions by means of a 3D k-ε turbulence CFD model and hydraulic scale model. The project gave the opportunity to compare the outcome of the distorted scale model with the ones of the CFD model in field scale, in the distorted hydraulic model scale as well as in undistorted scale, converting all the results to real field scale by assuming Froude similarity. Overall flow patterns, the effect of distortion and the robustness of the k-ε turbulence model in such complex confluence conditions were analysed. Satisfactory agreement was found except for the region straight downstream of the confluence where significant differences between laboratory and numerical results were seen due most probably to the complex swirling and shearing character of the flow. Large scale vortex formation interacting with anisotropic
local turbulence would certainly need differential Reynolds stress turbulence closure
Petrographic studies on the NASA Lunar Sample thin section set: I. : the textural sequence of the basaltic samples and thier description by cellular automata mosaic model and tentative TTT-diagram
Flow Analysis in River Danube by Field Measurement and 3D CFD turbulence modelling
Spatial complexity of turbulent flow conditions has been investigated by means of ADCP
measurements and CFD modelling in river Danube. The study area was a meandering river reach,
characterized by shallows and strongly influenced by various river training works.
High resolution bed survey and freezing plate sampling provided input river bed data for model implementation.
The applied k-ε
turbulence model could well reproduce velocity distributions measured in nature.
Strong spatial variability of the velocity and turbulent kinetic energy fields demonstrated
the necessity of 3D model approach under such fluvial conditions
NUMERICAL MODELLING OF FLOW PATTERNS TO ASSIST THE REVITALISATION OF SECONDARY RIVER BRANCHES IN GEIVIENC AREA
Depth-averaged numerical modelling of steady-state horizontal flow patterns carried out in
the framework of the revitalisation project of the secondary branches in Gemenc Protected
Landscape Area is presented. The feasibility of different variants is investigated in order
to increase the water exchange in the secondary branches without creating unfavorable
hydraulic and related sediment transport as well as navigation conditions. The applied
mathematical model is based on the usual shallow water assumptions. The numerical
solution is performed using finite differences and multigrid iteration technique. The model
is able to reproduce recirculation zones and the horizontal velocity distribution in an
acceptable manner
Determining clast and magnetic fabric of a subaqueous lahar deposit as a tool for reconstructing paleoflow directions and emplacement processes.
Flow-related fabric of a subaqueously emplaced laharic deposit (Rám Hill Pumiceous Sandstone) were investigated around the middle Miocene Keserűs Hill lava dome group (northern Hungary). A twofold methodology, consisting of image analyis on rock surfaces and low-field anisotropy of magnetic susceptibility (AMS), was used to determine large-scale flow paths and emplacement processes. In addition, comparative measurements of magnetic anisotropy were performed by using an MFK1-FA multifunction kappabridge with 3D rotator (Studynka et al. 2014) at Agico, Inc. (Brno, Czech Republic). The results indicate a very good agreement between the azimuths of a-axis of the most elongated clasts from image analysis and the orientation of K1 susceptibilities from the measurements of the two laboratories. This agreement of fabric direction obtained by the two different methods allows to draw the following implications: 1) Fabric direction-derived large-scale flow paths show a near-radial pattern around the proposed eruption centre (Karátson et al. 2007) of the Keserűs Hill lava dome group (Fig. 1). Thus, our new data on paleoflow directions quantitatively confirm the former, one central vent-dominated volcano-structural reconstruction which was proposed on the basis of facies analysis. 2) Aggradation from multiple lahar pulses is presumable due to the vertical variation of shear direction within the exposures
A kora-miocén Pétervásárai Homokkő diagenezis-története
Az eggenburgi korĂş, sekĂ©lytengeri környezetben kĂ©pzĹ‘dött PĂ©tervásárai HomokkĹ‘ FormáciĂłt, mint ismert rezervoár kĹ‘zet felszĂni analĂłgját vizsgáltuk. A szemcseösszetĂ©tel, a diagenezistörtĂ©net Ă©s a porozitásfejlĹ‘dĂ©s rekonstrukciĂłjához
terepi vizsgálatokat Ă©s petrográfiai megfigyelĂ©seket vĂ©geztĂĽnk, melyeket geokĂ©miai mĂ©rĂ©sek egĂ©szĂtettek ki. A vizsgált, aprĂł-durvaszemcsĂ©s, kĹ‘zettörmelĂ©kes homokkĹ‘ben a komponensek mennyisĂ©gi aránya alapján nĂ©gy litofácies kĂĽlön - böztethetĹ‘ meg; ezek a porĂłzus (LF1), mátrixgazdag (LF2), cementgazdag (LF3), Ă©s mátrix- Ă©s cementgazdag (LF4)
homokkĹ‘tĂpusok. A diagenezis során, az eogenezis tartományában kĂ©pzĹ‘dött autigĂ©n ásványok a glaukonit, a fram - boidális pirit, sziderit, káliföldpát továbbnövekedĂ©si cement, kaolinit Ă©s a feltĂ©telezhetĹ‘en nagyon kis mennyisĂ©gű kalcit - cement. A legalább 80 °C-os hĹ‘mĂ©rsĂ©kletet elĂ©rve, a mezogenezis tartományában megjelent a kvarc tovább növekedĂ©si cement, kevert szerkezetű illit/szmektit Ă©s albit keletkezett. ĂŤgy a fokozatosan betemetĹ‘dött homokkĹ‘ben a porozitás folyamatosan csökkent a kompakciĂł Ă©s a megjelenĹ‘ Ăşj ásványfázisok miatt. A legnagyobb mennyisĂ©gben megjelenĹ‘,egyik legkĂ©sĹ‘bbi autigĂ©n ásványfázis a kalcit. Ez fĹ‘leg ásványhelyettesĂtĂ©skĂ©nt, kisebb rĂ©szben pedig cementkĂ©nt,elszigetelt lencsĂ©kben van jelen. A rendelkezĂ©sre állĂł geokĂ©miai adatok alapján, figyelembe vĂ©ve a terĂĽlet földtani felĂ©pĂtĂ©sĂ©t, a kalcit eredete több genetikai modellel is magyarázhatĂł. Ezek szerint kĂ©pzĹ‘dhetett egyrĂ©szt a mezogenezis tartományában, az ĂĽledĂ©kkel betemetĹ‘dött mĂłdosult tengeri eredetű pĂłrusfluidumbĂłl, másrĂ©szt keletkezhetett törĂ©sek mentĂ©n a kĹ‘zettestbe áramlott egzotikus fluidumbĂłl. Ez utĂłbbi esetben is kĂ©t változat lehetsĂ©ges, vagy egy magas hĹ‘mĂ©rsĂ©kletű formáciĂłs fluidumbĂłl vált ki, vagy egy mĂ©lyre cirkulált Ă©s felmelegedett meteorikus eredetű fluidumbĂłl. A homokkĹ‘ jelentĹ‘s porozitással rendelkezik, fĹ‘leg a kalcitot nem tartalmazĂł rĂ©szeken. Ez a porozitás a kiemelkedĂ©s során, a felszĂn közelĂ©ben alakulhatott ki a beszivárgĂł meteorikus vizek oldĂł hatása rĂ©vĂ©n. A feltárásban megjelenĹ‘
különleges mállási formák kialakulásában a homokkő diagenezistörténetének jelentős szerepe volt.
For this paper, the Eggenburgian Pétervására Sandstone — a shallow marine siliciclastic formation — was studied as a surface analogue for known reservoir rocks. Field observation in the area of Kishartyán, detailed petrography (including SEM, CL) and geochemical analysis (XRD, SEM-EDS, stable isotope analysis) were applied to find out more about the diagenetic processes, the burial history, the porosity evolution, and their relationship with the weathering forms. The composition of the fine to very coarse-grained sandstones varies between subarenite and litharenite. The most common detrital grains are mono- and polycrystalline quartz and sedimentary rock fragments (cherts, dolomites and metamorphic rock fragments). Ductile grains are represented by micas and altered volcanoclastic rock fragments. Based on the proportion of components, four lithofacies were distinguished: porous sandstone (LF1), matrix-rich sandstone (LF2),cement-rich sandstone (LF3), and matrix and cement rich sandstone (LF4). The eogenetic minerals are: glauconite,framboidal pyrite, flattened rhombohedral siderite crystals, K-feldspar overgrowth cement, kaolinite, and (supposedly)small amounts of calcite. The maximum burial temperature was likely reached at around 80 °C; this is indicated by the presence of quartz overgrowth cement, mixed layer illite/smectite, and replacive and cementing albite. These minerals were formed in the mesogenetic realm. During eogenesis and mesogenesis, the porosity of the sandstone progressively decreased due to compaction and the precipitation of authigenic minerals. Calcite is one of the latest diagenetic minerals and occurs both as a replacive phase and as cement. The distribution of calcite within the studied sandstone is heterogeneous. Calcite is present in elongated lenses where the sandstone has a very low porosity. Considering the geochemical data and the geological setting, the origin of the calcite can be explained by several genetic models. According to these models, the formation of the calcite may have taken place either in the mesogenetic realm from modified marine pore waters (buried together with the sediment), or from an exotic fluid channelled along fault zones. In the second scenario, there are two possibilities regarding the origin of the parent fluid: namely, (a) a formational fluid or
(b) a deeply circulated, warmed-up meteoric fluid. The high porosity of the sandstone is the result of dissolution by
meteoric water during uplift. Diagenetic evolution of the sandstone had a crucial role in the formation of the weathering
morphology
A Dunántúli-középhegység felső kréta telérkalcitjainak genetikai vizsgálata = Genesis of late Cretaceous calcite dykes from the Transdanubium Central Range
A DunántĂşli-közĂ©phegysĂ©gben számos helyen felfedezett vörös kalcit elĹ‘fordulások genetikájának további tisztázásához járult hozzá a VĂ©rtesben találhatĂł Ă©desvizi mĂ©szkĹ‘kĂşp Ă©s hat további kalcit kibukkanás kĹ‘zettani Ă©s geokĂ©miai vizsgálata. A karbonát tipusos travertinĂł szövettel rendelkezik, jellemzĹ‘ akcesszĂłriái: cirkon, monacit Ă©s xenotim, amelyek mĂ©lysĂ©gi fluidumokhoz köthetĹ‘k. A minták szĂ©n- Ă©s oxigĂ©nizotĂłp Ă©rtĂ©kei, valamint az izotĂłp-tartománya arra utal, hogy magmás eredetű CO2-nak fontos szerepe volt a karbonát keletkezĂ©sĂ©ben. A további vörös kalcit telĂ©rek Ă©s karbonát elĹ‘fordulások (Pilisjászfalu, KeselĹ‘-hegy, Mindszentpuszta, Csáki-vár Ă©s Nagykovácsi) szöveti jellege hasonlĂł. JárulĂ©kos ásványaik: Fe-oxid, Fe-szulfid, szfalerit, rutil, ilmenit, cirkon, apatit, monacit, xenotim Ă©s csillám. A stabilizotĂłp-geokĂ©miai adatok összhangban vannak a korábban vizsgált minták adataival. A folyadĂ©kzárványok kis szalinitásĂşak (max. 3.4 wt% NaCl ekv.) Ă©s a homogenizáciĂłs hĹ‘mĂ©rsĂ©kletĂĽk kicsi (100-180 ÂşC). ElĹ‘zetes irodalmi adatok, valamint kĹ‘zettani Ă©s geokĂ©miai vizsgálataink (SEM+EDX, stabilizotĂłp-geokĂ©mia, mikrotermometria) alapján a vizsgált karbonát elĹ‘fordulások hidrotermás rendszerekhez köthetĹ‘k, amelyek az esetek többsĂ©gĂ©ben kapcsolatba hozhatĂłk a terĂĽlet lamprofĂros magmatizmusával. | Petrographic and geochemical studies of a travertine cone and six calcite vein occurrences (in VĂ©rtes Mts.) were carried out to understand formation of the widely spread red calcite occurrences. The carbonate investigated has a typical travertine texture, the characteristic accessory minerals: zircon, monacite, and xenotime can be related to deep-derived fluids. Their stable carbon and oxygen isotope compositions and the isotopic ranges indicate that magmatic CO2 played an important role during the carbonate formation. The other red calcite veins and carbonate occurrences studied (Pilisjászfalu, KeselĹ‘-hegy, Mindszentpuszta, Vitányvár, Csáki-vár, Nagykovácsi) show similar textural features. Accessory minerals are: Fe-oxide, Fe- sulfide, sphalerite, rutile, ilmenite, zircon, apatite, monazite, xenotime and mica. Their stable isotopic compositions are in agreement with the previously studied calcite dykes. The fluid inclusions have low salinity (max. 3.4 wt% NaCl eq.) and low homogenization temperature (between 100-180 ÂşC). Based on previous and our petrography and geochemical measurements (SEM+EDX, stable isotope studies and microthermometry), the studied carbonate occurrences were originated from a hydrothermal system and in most of cases magmatic fluids, may be associated with lamprophyre dykes, were also recognized in the area
More than 300 km raft on the ice floe. Dumortierite and clinohumite from the Bohemian Massif in Dunavarsány, Middle Hungary
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