Dome Geometry Research Articles

Interrelation between induced seismic instabilities and complex geological structure

From 1982 to 1989, more than 520 local seismic events were recorded by a permanent network of 9 telemetered stations over an active gas field (Lacq, France). The geological data of 46 boreholes coupled to several tens of kilometers of seismic profiles, concentrated in a small volume of 15 × 15 × 10 km3, allow the development of a very precise velocity structure, exhibiting a dome geometry limited by faulted strips. The discretized velocity model includes almost 20000 blocks with 500 m × 500 m × 250 m minimum dimensions. A relocation technique using this a priori detailed 3D velocity model allows precise locations of induced earthquakes. 351 relocated hypocenters show that of the seismic activity concentrated on geometrical discontinuities of the local dome structure. The locations of seismic events are correlated with geomechanical layers of the structure. Spatial and temporal migration of seismic ruptures mimics the different permeability rings of the reservoir which are progressively depleted by gas extraction. Most of these events are at present confined close to major thrust planes which limit the dome structure laterally, and in depth onto preexisting faults in the basement below the gas field. The occurence of these deep clusters demonstrates that fluid manipulation in the sedimentary covers can activate preexisting basement faults. This result changes previous assessments of local seismic risk and provides new insights into fault mechanisms in areas with complex geological structure.

Floral morphogenesis in Anagallis: Scanning-electron-micrograph sequences from individual growing meristems before, during, and after the transition to flowering

Non-destructive scanning electron microscopy allows one to visualize changing patterns of individual cells during epidermal development in single meristems. Cell growth and division can be followed in parallel with morphogenesis. The method is applied here to the shoot apex of Anagallis arvensis L. before, during, and after floral transition. Phyllotaxis is decussate; photoperiodic induction of the plant leads to the production of a flower in the axil of each leaf. As seen from above, the recently formed oval vegetative dome is bounded on its slightly longer sides by creases of adjacent leaf bases. The rounded ends of the dome are bounded by connecting tissue, horizontal bands of node cells between the opposed leaf bases. The major growth axis runs parallel to the leaf bases. While slow-growing at the dome center, this axis extends at its periphery to form a new leaf above each band of connecting tissue. Connecting tissue then forms between the new leaves and a new dome is defined at 90° to the former. The growth axis then changes by 90°. This is the vegetative cycle. The first observed departure from vegetative growth is that the connecting tissue becomes longer relative to the leaf creases. Presumably because of this, the major growth axis does not change in the usual way. Extension on the dome continues between the older leaves until the axis typically buckles a second time, on each side, to form a second crease parallel to the new leaf-base crease. The tissue between these two creases becomes the flower primordium. The second crease also delimits the side of a new apical dome with the major axis and growth direction altered by 90°. During this inflorescence cycle the connecting tissue is relatively longer than before. Much activity is common to both cycles. It is concluded that the complex geometrical features of the inflorescence cycle may result from a change in a biophysical boundary condition involving dome geometry, rather than a comprehensive revision of apical morphogenesis.

Net alignment of cellulose in the periclinal walls of the shoot apex surface cells in Kalanchoe blossfeldiana. I. Transition from vegetative to reproductive morphogenesis

The apical dome geometry and the pattern of net cellulose alignment in the periclinal walls of the surface cells of Kalanchoe blossfeldiana were examined during vegetative morphogenesis, during reproductive morphogenesis, and during the transition between the two development states. Photoperiodically induced and noninduced shoot apices were dissected, stained, and viewed under a dissecting microscope. The surface cell layer(s) was removed from the stem apex and examined under a polarizing microscope. The results indicated that correlations exist between the pattern of cellulose alignment on the apex surface and the pattern of organ initiation. Tangential cellulose alignment is always present at the periphery of the shoot apex, and alignment of cellulose at the incipient sites of organ formation is such as to provide circumferential reinforcement for emerging organs. The results also showed that a change in dome geometry is one of the earliest events during the floral transition. This change in geometry is correlated with a change in the pattern of surface cellulose and leads to a change in the developmental state of the apex. Key words: shoot, phyllotaxis, cellulose, flower, organogenesis.

Net alignment of cellulose in the periclinal walls of the shoot apex surface cells in Kalanchoe blossfeldiana. II. Flower development

Dome geometry and the pattern of net cellulose alignment in the periclinal walls of the surface cells of Kalanchoe blossfeldiana were examined during sequential stages of flower development. Floral apices of photoperiodically induced plants were dissected, stained, and observed under a dissecting microscope. The outermost cell layer(s) of the surface was surgically removed from the floral apex and viewed under a polarizing microscope. Correlations were found between the geometry of the dome, the pattern of cellulose in the surface cells, and the pattern of initiation of floral organs at the apex. Tangentially aligned cellulose was always observed around the periphery of the floral dome, whereas no net alignment of cellulose typically occurred in the centermost region. Circumferential reinforcement of cellulose was consistently observed at sites of incipient organ initiation, and the pattern of cellulose alignment on emerging primordia correlated with the type of organ development. No strict dependence was evident between the number and positioning of one whorl of floral ogans and that of the previous whorl. Key words: shoot, cellulose, flower, floral, organogenesis.

Buckling of near-perfect steel torispherical and hemispherical shells subjected to external pressure

The aims of the present series of tests on externally pressurized machined steel domed ends were twofold. The first was to verify the recently predicted and unusual variation of a dome's buckling resistance with the knuckle radius-to-diameter (r/D} ratio. The second was to verify that optimizing a dome's geometry, while keeping the weight constant, can bring substantial increases in the buckling strength. The agreement between the experimental results and the theoretical predictions is very good. The initial increase in the buckling strength, its reversal, the minimum buckling strength, and the rapid increase thereafter, all as predicted by theory, are confirmed by tests. The tests on near-perfect shells highlight the sensitivity of the buckling strength of torispherical shells to the r/D ratio, in the range 0.4 < r/D < 0.5. In the optimization study, in which the geometric ratios D/t, r/D, and RS/D were varied, the ratio of the buckling strengths of the best and the worst shapes is more than 5:1. The best and worst shapes have the same weight; it is clear that optimizing a dome's shape can produce substantial increases in strength. The good agreement between the test results and theoretical predictions is further confirmation of the adequacy of the BOSOR 5 shell buckling program for problems of this type.

Seismicity induced by gas production: II. Lithology correlated events, induced stresses and deformation

A 3D relocation technique permits precise locations of induced earthquakes. Geostatistical processing using the data of 87 boreholes provides the basis of a precise 3D structure, with a dome geometry. Conventional laboratory mechanical tests performed on deep rock samples (1000 m to 5000 m) define the rock properties at depths similar to those of the seismic events (1<ML<4.2) that range from 1 to 7 km.

Recommended procedures for measuring the performance of positive-displacement mechanical vacuum pumps

It is essential that uniform and realistic test procedures be used for measuring the performance of vacuum apparatus. This paper recommends procedures for measuring the pumping speeds and ultimate pressures of positive-displacement mechanical vacuum pumps. It replaces outdated material originally published in three separate sections between 1963 and 1967. Changes include emphasis on more modern pressure gauges such as the capacitance manometer and spinning rotor gauge, an attempt to harmonize procedures with existing international standards, a shift to Système International units of pressure, and minor rewording to include dry vacuum pumps. Minor changes have been made in test dome geometry to reduce sources of error. Material has been added concerning some of the causes of pumping speed variations during continuous operation of a given pump. Other new material covers the problems of measuring water vapor tolerance and water vapor pumping capacity. Practical details which minimize measuring errors are discussed.

A Detailed Characterization of the Velocity and Thermal Fields in a Model Can Combustor With Wall Jet Injection

This work represents a first step in the establishment of a data base to study the interaction and influence of liquid fuel injection, wall jet interaction, and dome geometry on the fuel air mixing process in a flowfield representative of a practical combustor. In particular, the aerodynamic and thermal fields of a model gas turbine combustor are characterized via detailed spatial maps of velocity and temperature. Measurements are performed at an overall equivalence ratio of 0.3 with a petroleum JP-4 fuel. The results reveal that the flowfield characteristics are significantly altered in the presence of reaction. Strong on-axis backmixing in the dome region, present in the isothermal flow, is dissipated in the case of reaction. The thermal field exhibits the primary, secondary, and dilution zone progression of temperatures characteristic of practical gas turbine combustors. A parametric variation on atomizing air reveals a substantial sensitivity of the mixing in this flow to nozzle performance and spray symmetry.

On the Structure and Metamorphism of the Roc de Frausa Massif (Eastern Pyrenees)

AbstractThe Roc de Frausa Massif, located at the Eastern Pyrenees, is formed by a stratoid Pre-Hercynian deformed granite (orthogneiss) interbedded with metasedimentary series. Hercynian granitoids (St. Llorenc — La Jonquera pluton) surround the southern and eastern part of the massif and Hercynian basic igneous rocks (Ceret stock) occupy the central part of it. The Pre-Hercynian granite and the sedimentary series were involved, during the Hercynian orogeny, in complex polyphasic tectonics and metamorphism. As a result, an ubiquitous penetrative foliation was developed during the earlier stages. This foliation was subsequently folded into a complex antiformal structural formed by a double dome : Roc de Frausa dome and Mas Blanc dome. Main lithological boundaries (gneiss — metasediments and metasediments — granitoids) are broadly parallel to the regional foliation, and they all display the dome geometry. Interference fold pattern between two late phases, an ealier one with NE-SW trending folds and a younge...

A model gas turbine combustor with wall jets and optical access for turbulent mixing, fuel effects, and spray studies

A model laboratory reactor is presented and characterized for the study of spray-fired combustion in a swirl-stabilized, complex, three-dimensional flow representative of a gas turbine combustor. The reactor features optical access for non-intrusive diagnostics, and clean boundary conditions for modeling. The aerodynamic and thermal fields are characterized using laser anemometry and a thermocouple probe respectively. The droplet size and droplet velocity fields are resolved using phase Doppler interferometry. The performance of the reactor is found to be representative of a practical combustor with a well defined dome region primary zone, a secondary zone between the two rows of wall jets in which reaction persists, and a relatively well-mixed and cool dilution zone. A parametric study of the dome geometry indicates that the structure of the dome region recirculation is relatively insensitive to a change from a step to a 45° divergent dome expansion. A parametric study of the dome swirl, primary jet, and dilution jet flows shows that the primary air provides closure to the dome recirculation and enhances the turbulent mixing. The reactor is attractive for studies of turbulent mixing, fuel effects, and spray dynamics in this class of flows.

Thermal anomalies on the flanks of a salt dome

Downhole temperature measurements from six wells in the vicinity of an offshore Louisiana salt dome show increasingly higher temperatures with decreasing distance from the dome. We have analyzed this temperature distribution taking into account the effects of lithologic variations, overpressuring and salt dome geometry. Temperatures calculated using a steady-state thermal conduction numerical model are in agreement with measured values. The implication is that the thermal conductivity contrast between salt and surrounding sands and shales can produce all of the observed temperature anomaly; no other heat transfer mechanism, such as fluid flow, is required. The magnitude of the temperature increase induced by the salt dome, up to ≈30°C, may cause a substantial increase in the hydrocarbon maturation rate.