Numerical Solution of Lock-Release Gravity Current with Viscous Self-Similar Regime     

张立柱李行伟  陈国谦 《中国海洋工程》2004,18(1):157-162

Lock-release gravity currents with a viscous self-similar regime are simulated by use of the renormalization group(RNG) k - ε model for Reynolds-stress closure. Besides the turbulent regime with initially a slumping phase of a conslant current front speed and later an inviseid self-similar phase of front speed decreasing as t^-1/3(where t is the time measured from release), the viseous self-similar regime is satisfactorily reproduced with front speed decreasing as t^-4/5,consistent with well known experimental observations.  相似文献   

Oil-generation kinetics for organic facies with Type-II and -IIS kerogen in the Menilite Shales of the Polish Carpathians     

M.D. Lewan  M.J. Kotarba  D. Wi?c?aw 《Geochimica et cosmochimica acta》2006,70(13):3351-3368

The Menilite Shales (Oligocene) of the Polish Carpathians are the source of low-sulfur oils in the thrust belt and some high-sulfur oils in the Carpathian Foredeep. These oil occurrences indicate that the high-sulfur oils in the Foredeep were generated and expelled before major thrusting and the low-sulfur oils in the thrust belt were generated and expelled during or after major thrusting. Two distinct organic facies have been observed in the Menilite Shales. One organic facies has a high clastic sediment input and contains Type-II kerogen. The other organic facies has a lower clastic sediment input and contains Type-IIS kerogen. Representative samples of both organic facies were used to determine kinetic parameters for immiscible oil generation by isothermal hydrous pyrolysis and S₂ generation by non-isothermal open-system pyrolysis. The derived kinetic parameters showed that timing of S₂ generation was not as different between the Type-IIS and -II kerogen based on open-system pyrolysis as compared with immiscible oil generation based on hydrous pyrolysis. Applying these kinetic parameters to a burial history in the Skole unit showed that some expelled oil would have been generated from the organic facies with Type-IIS kerogen before major thrusting with the hydrous-pyrolysis kinetic parameters but not with the open-system pyrolysis kinetic parameters. The inability of open-system pyrolysis to determine earlier petroleum generation from Type-IIS kerogen is attributed to the large polar-rich bitumen component in S₂ generation, rapid loss of sulfur free-radical initiators in the open system, and diminished radical selectivity and rate constant differences at higher temperatures. Hydrous-pyrolysis kinetic parameters are determined in the presence of water at lower temperatures in a closed system, which allows differentiation of bitumen and oil generation, interaction of free-radical initiators, greater radical selectivity, and more distinguishable rate constants as would occur during natural maturation. Kinetic parameters derived from hydrous pyrolysis show good correlations with one another (compensation effect) and kerogen organic-sulfur contents. These correlations allow for indirect determination of hydrous-pyrolysis kinetic parameters on the basis of the organic-sulfur mole fraction of an immature Type-II or -IIS kerogen.  相似文献   

The measurement of soil gases and shallow temperature for determination of active faults in a geothermal area: a case study from Ömer–Gecek,Afyonkarahisar (West Anatolia)     

Ahmet Yıldız  Can Başaran  Metin Bağcı  Ayla Gümüş  Feyzullah Ekrem Çonkar  Yusuf Ulutürk  Hüseyin Ali Yalım 《Arabian Journal of Geosciences》2018,11(8):175

Afyonkarahisar is a very important geothermal province of western Anatolia and has low and medium enthalpy geothermal areas. This study has been carried out for the preparation of distribution maps of soil gases (radon and carbon dioxide) and shallow soil temperature and the exploration of permeable tectonic regions associated with geothermal systems and reveal the origins of radon and carbon dioxide gases. The western district of the study area is characterized by the high radon concentration (168.30 kBq/m³), carbon dioxide ratio (0.30%), and soil temperature (21.0 °C) values. Fethibey and Demirçevre faults, which allow the circulation of geothermal fluids, have been detected in the distribution maps of radon, carbon dioxide, and shallow depth temperature and the directions of the curves in these maps correspond to the strikes of Demirçevre faults. The effect of the fault plays an important role in the change of carbon dioxide concentration along the W-E directional geological section prepared to determine the change of soil gas and shallow depth temperature values depending on lithological differences, fault existence, and geothermal reservoir depth. On the other hand, it was determined that Rn²²² concentration and soil temperature changed as a function of geothermal reservoir depth or lithological difference. Tuffs in Köprülü volcano-sedimentary units are the main source of radon due to their higher uranium contents. Besides, the carbon dioxide in Ömer–Gecek soils has geothermal origin because of the highest carbon dioxide content (99.3%) in non-condense gas. The similarities in patterns of soil temperature, radon, and carbon dioxide indicate that the variation in soil temperatures is related to radon and carbon dioxide emissions. It is concluded that soil gas and temperature measurements can be used to determine the active faults in the initial stage of geothermal exploration successfully.  相似文献   

Examination of the structural characteristics arising in gypsums by the GPR and MASW methods (Sivas,Turkey)     

Naşit Darıcı  Sevda Özel 《Natural Hazards》2018,93(2):661-676

This study was performed at an area of 50?×?48 m² being defined as a new settlement in the northeast of Sivas. In the study, the discontinuities that are not deep and their geophysical characteristics were examined by the GPR and MASW methods. For interpretation, GPR cross sections were prepared as 2D–3D, and MASW cross sections were prepared as 2D. As for geophysical cross sections, about 10 m depth was examined. It was understood that the reflections observed in the form of hyperbolas in GPR cross sections correspond to areas having low S wave velocity (V_s) in MASW cross sections. It was understood that the S wave velocities are lower than 653 m/s, that the seismic velocities in between 653 and 275 m/s indicate partially deteriorated areas and that the S wave velocities of unweathered gypsums are higher than 1275 m/s at these low-velocity zones. Thus, it was thought that the fill material that may arise in the fracture, crack and deterioration areas arises from intercalation and clastic gypsum units, and that it plays a role in having low value S wave velocities. In all the geophysical cross sections, it was understood that the structures with gypsum are intense at the initial 5 m. And a fracture at the south of the study area, that it was estimated might be longer than 40 m, was determined as the largest gypsum structure. It was understood that this fracture starts from a depth of about 5 m in the west and that it slopes down to 7 m depth in the east. According to these results, it was understood that the damage amount arising in time in the gypsum structures from the effect of water may increase, the study area was defined as risky, and the required importance should be attached to these structures especially in foundation engineering.  相似文献   

Study on Flow Field Around Vertical Breakwater Under Different Overtopping Conditions Based on Numerical Simulation     

蒋学炼  吴米玲  李炎保 《中国海洋工程》2010,(4)

A numerical wave flume is constructed based on the Reynolds Averaged Navier-Stokes (RANS) equations with turbulence closure by a modified k-ε model to study the viscous interactions of waves with vertical breakwaters for different overtopping cases. The governing equations,the turbulence model,boundary conditions,and solution method for the numerical wave flume are introduced briefly. The reliability of the numerical wave flume is examined by comparing the numerical results with the experimental measurement...  相似文献   

Umweltproblematik der Aquakultur     

Prof. Dr. Dr. h. c. H. Rosenthal 《Ocean Dynamics》1991,44(5-6):281-282

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Geoid, topography, and the Bouguer plate or shell   总被引：1，自引：1，他引：1  

P. Vaníc˘ek  P. Novák  Z. Martinec 《Journal of Geodesy》2001,75(4):210-215

 Topography plays an important role in solving many geodetic and geophysical problems. In the evaluation of a topographical effect, a planar model, a spherical model or an even more sophisticated model can be used. In most applications, the planar model is considered appropriate: recall the evaluation of gravity reductions of the free-air, Poincaré–Prey or Bouguer kind. For some applications, such as the evaluation of topographical effects in gravimetric geoid computations, it is preferable or even necessary to use at least the spherical model of topography. In modelling the topographical effect, the bulk of the effect comes from the Bouguer plate, in the case of the planar model, or from the Bouguer shell, in the case of the spherical model. The difference between the effects of the Bouguer plate and the Bouguer shell is studied, while the effect of the rest of topography, the terrain, is discussed elsewhere. It is argued that the classical Bouguer plate gravity reduction should be considered as a mathematical construction with unclear physical meaning. It is shown that if the reduction is understood to be reducing observed gravity onto the geoid through the Bouguer plate/shell then both models give practically identical answers, as associated with Poincaré's and Prey's work. It is shown why only the spherical model should be used in the evaluation of topographical effects in the Stokes–Helmert solution of Stokes' boundary-value problem. The reason for this is that the Bouguer plate model does not allow for a physically acceptable condensation scheme for the topography. Received: 24 December 1999 / Accepted: 11 December 2000  相似文献   

Les diatomées de la station néolithique d'Auvernier (Lac de Neuchâtel)     

Marguerite Wuthrich Dr ès sciences h.c. 《Aquatic Sciences - Research Across Boundaries》1971,33(2):533-552

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Die Entstehung einiger tektonischer Grundbegriffe. Ein Beitrag zur Geschichte der Geologie     

Prof. Dr. Dr. h. c. M. Pfannenstiel 《International Journal of Earth Sciences》1969,59(1):1-36

Zusammenfassung Die ersten tektonischen Vorstellungen legte 1669Nic. Steno in seinem Prodromus nieder. Seine Beobachtungen an horizontalen und geneigten Schichten führten später zu dem Begriffe der orogenetischen Diskordanzen. L.Élie de Beaumont ist sein direkter Nachfolger geworden, während J.Hutton ganz unabhängig von beiden den Diskordanzbegriff entwickelte. Die neptunistische Lehre von A. G.Werner ging von einem primären, von Wasserfluten geschaffenen Relief der Erdoberfläche aus, das überschichtet wurde. Doch auchWerner dachte daneben ebenfalls an große Höhlen, deren Decken einbrechen würden. Die neptunistischen Schwierigkeiten ergaben sich aus der Unmöglichkeit einer vertikalen Sedimentation von primär senkrecht gestellten Schichten. Die Anfänge der Erforschung der Tektonik des Rheingrabens werden dargelegt, und es wird besonders gezeigt, daßÉlie de Beaumont, der 1836 von einem eingebrochenen Gewölbe sprach, schon vorher Kenntnis eines eingebrochenen Gewölbes von Island und eines Schichtgewölbes von Württemberg über Schwarz wald — Vogesen nach Lothringen hatte. Die Zeit des Einbruches legteÉ. de Beaumont irrtümlich in die Zeit des Buntsandsteins.Theorien der Gebirgsbildung wurden mit L. v.Buch's Erhebungstheorie und geognostischen Gebirgssystemen um zwei weitere Ideen 1824–1835 erweitert.Élie de Beaumont baute diese Theorie sehr aus und sprach von Revolutionen der Erdkruste (1829). Die Faltengebirge fanden in J.Thurmann (1832) ihren ersten gründlichen Bearbeiter, der am Beispiel des Faltenjuras nachwies, daß doch nur Horizontalkräfte am Werke gewesen sein können und die Erhebungstheorie L. v.Buch's für diese Gebirgsarten keine Erklärung bringe. Zum Schlusse wird die Geschichte des Geologenkompasses gebracht.

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Nic. Steno was the first who developed tectonic ideas in his Prodromus in 1669. His observations in the surroundings of Firenze (Italy) led him to the notion what nowadays is called a discordance by orogeny. He was followed by the French L.Élie de Beaumont, while the Scotchman J.Hutton developed this term of tectonic discordance quite independently of both.The neptunic theory of A. G.Werner in Freiberg (Saxony) started from the idea that the primary relief of the surface of the earth was formed by floods and covered with sediments. Furtheron he assumed large caves, the tops of them having broken down, explaining in this manner very inclined strata. The difficulties in this neptunic theory resulted from the fact that it was impossible to account for a sedimentation in a vertical line as seen in vertical layers.The author gives a survey of the first researches in the tectonics of the Rhinegraben and shows thatÉlie de Beaumont, who in 1836 mentioned the breakdown of the central ridge of a vault, so forming the rift-valley, had already some information of such a pressure arch in Iceland and of a second one stretching from Würtemberg via Black Forest—Vosges to Lorraine.Élie de Beaumont misdated the collapse of this large vault, stating erroneously the time of Buntsandstein (=New Red Sandstone).Between 1824 and 1835 L. v.Buch developed two further theories on orogenesis, that of the elevation-crater hypothesis and that of the geognostic systems of mountains. É.de Beaumont completedBuch's theory and in 1829 he spoke of revolutions of the earth's crust.The first who thoroughly researched the Swiss Jura was J.Thurmann. Quoting the folded strata of this region as an example he proved that only horizontal stresses could have been responsible for the formation of these mountains and that the elevation-crater hypothesis of L. v.Buch acting only with vertical forces could not give any explanation for it.Finally the author recapitulates the history of the geologist's compass.

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Résumé Les premières conceptions tectoniques ont été exposées en 1669 par N.Steno dans son « Prodrome ». Ses observations sur des strates horizontales ou inclinées ont conduit ultérieurement à la notion de discordances orogéniques. L.Élie de Beaumont fut son successeur direct, cependant que J.Hutton, tout à fait indépendamment des deux premiers développa la notion de discordance. La théorie neptuniste de A. G.Werner se basait sur l'existence préalable d'un relief terrestre créé par les flots et qui aurait été noyé sous les strates des dépôts ultérieurs. Pourtant, dans un autre ordre d'idées,Werner pensait aussi à l'existence d'immenses grottes dont les toits s'effondreraient. Les neptunistes éprouvèrent des difficultés résultant de l'impossibilité d'expliquer des couches redressées par une sédimentation verticale. L'auteur expose les débuts des recherches sur la tectonique du fossé rhénan et montre en particulier qu'Élie de Beaumont, qui parla en 1836 d'une voûte effondrée avait déjà auparavant eu connaissance d'une voûte effondrée en Islande et d'une voûter structurale allant du Wurttemberg en Lorraine par-dessus la Forêt-Noire et les Vosges. Par erreur,É de Beaumont plaça le moment de cet effondrement à l'époque du grès bigarré.Avec la théorie des soulèvements et des orogènes géognostiques L. v.Buch enrichit de 1824–1835 les théories orogéniques de deux concepts supplémentaires.Élie de Beaumont les développa et parla de révolution de la croûte terrestre (1829). Les premières recherches approfondies sur les chaînes plissées sont dues à J.Thurmann (1832) qui, d'après l'exemple du Jura plissé, démontra que seules des forces horizontales ont pu avoir été à l'oeuvre et que la théorie des soulèvements de L.von Buch n'apportait pas d'explication pour les chaînes de ce type.Pour terminer, l'auteur expose l'histoire de la boussole du géologue.

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A Sr isotope study on fluorite and siderite from post-orogenic mineral veins in the eastern Harz Mountains,Germany   总被引：2，自引：0，他引：2  

Jens?SchneiderEmail author  Udo?Haack  Klaus?Stedingk 《Mineralium Deposita》2003,38(8):984-991

Rb–Sr isotope data for siderite and fluorite from sediment-hosted epithermal mineral veins in the eastern Harz Mountains (Germany) are presented. Several fluorite and siderite-bearing paragenetic stages have been proposed for these veins, with the most important mineralization being related to a quartz–sulfide and a subsequent calcite–fluorite–quartz stage, which occurred at 226±1 and 209±2 Ma, respectively. Our Rb–Sr data do not permit the identification of distinct generations of siderite and fluorite, but rather reveal straight internal mixing relations, reflecting mixing of fluids or differential fluid–rock interaction processes. This indicates merely two significant phases of mineral deposition related to the quartz–sulfide and calcite–fluorite–quartz stages. It is shown that the Paleozoic sedimentary host rocks of the veins are the most likely source for the siderite Sr, whereas fluorite displays a two-component mixture between sedimentary Sr and radiogenic Sr derived from locally occurring Permian metavolcanic rocks. Editorial handling: B. Lehmann  相似文献