Fluid Discharge Rate Research Articles

Wellbore fluid sonic conditions during blowouts

The understanding of high-velocity two-phase flow is critical for predicting worst-case discharge scenarios. During a blowout, the fluid discharge rate can be very high, and its velocity may reach the sonic speed at the surface. Therefore, it is crucial to understand the fluid dynamics and flow characteristics of multiphase flow in the high-velocity range. In this investigation, two-phase (air-water) flow experiments were conducted to study the flow evolution in extreme high-velocities occurring during worst-case discharge. The experiments were performed in a vertical pipe section with a diameter of 83 mm and a length of 5.5 m. A fully transparent viewport was installed on the test section to monitor the flow pattern. The superficial gas velocities were ranging approximately from 8 to 160 m/s. During the test, the pressure gradient was monitored while increasing the gas rate at a constant liquid rate. Under subsonic conditions, the pressure gradient increase with superficial gas velocity indicating the establishment of friction dominated flow regime. However, the pressure-gradient trend changed when shock waves formed in the test section. With increasing the superficial gas velocity at a given liquid rate, the pressure gradient attained its maximum when flow transition occurred and shock waves formed in the test section, which were observed through the viewport. Under sonic conditions, increasing the superficial gas velocity a constant liquid flow rate reduced the pressure-gradient.After examining various two-phase flow sonic velocity models and measurements, a new correlation has been developed to predict sonic conditions during worst-case discharge. Experimental results are compared with predictions of existing wave propagation models and demonstrated reasonable agreement. Subsequently, a computational tool has been developed to estimate fluid flow rates for worst-case discharge scenarios involving sonic flow conditions. The new correlation has been implemented in the computational tool to forecast the establishment of sonic flow conditions in the wellbore. The computational tool shows a reasonable agreement with commercial packages for basic worst-case discharge circumstances. A sensitivity analysis performed using the computational model suggests that the discharge rate varies with the in-situ parameters such as skin factor, pay-zone height, and reservoir permeability.

Exploring the efficacy of using various coolants on lithium-ion 18650 cell employing conjugate heat transfer simulation

Abstract In an era of depleting oil reserves, the turmoil of the energy crisis is getting worse every year. Adding to this the economic and political situations between crude oil-exporting nations are of major concern. Modification in internal combustion engines has reached limiting value, rendering them obsolete for future demands. Thus, Battery electric vehicles are the future of the automobile industry. Possessing advantages like zero-emission and high mechanical efficiency, the limitations of battery technology is hindering advancements in electric vehicles. Thermal management, charging time and energy density are major fields of research. Lithium-ion batteries, which are a core to this technology, exhibit poor performance beyond operating temperature ranges. An optimum working range is hence required. In order to study the cooling of the cell, Lithium-18650 cell is simulated for the different cooling conditions using SimScale™. A single cell is placed in a control volume and the fluid flow is set along the axis of the cell for the analysis. Heat is assumed to be generated at the centre of the cell. Parameters such as velocity (thus fluid discharge rate), current discharge (thus heat generated) are varied for each run of the simulation. Various coolant fluids viz. water, air, ethylene glycol, aluminium oxide in water nanofluid are used. Fluid velocity is varied as 0.01 m / s , 0.05 m / s , 0.5 m / s and 1 m / s . The current discharge is varied as 1C – 0.0896 W in 3600 s, 2C – 0.5248 W in 1800 s, 3C – 1.0284 W in 1200 s. Considering the various permutations of parameters, yields a total of 48 simulations, for four fluids, and are compared for the best combination of fluid and parameter governing cooling of the cell.

Episodic fluid flow in an active fault

Abstract We present a reconstruction of episodic fluid flow over the past ∼250 k.y. along the Malpais normal fault, which hosts the Beowawe hydrothermal system (Nevada, USA), using a novel combination of the apatite (U-Th)/He (AHe) thermochronometer and a model of the thermal effects of fluid flow. Samples show partial resetting of the AHe thermochronometer in a 40-m-wide zone around the fault. Numerical models using current fluid temperatures and discharge rates indicate that fluid flow events lasting 2 k.y. or more lead to fully reset samples. Episodic fluid pulses lasting 1 k.y. result in partially reset samples, with 30–40 individual fluid pulses required to match the data. Episodic fluid flow is also supported by an overturned geothermal gradient in a borehole that crosses the fault, and by breaks in stable isotope trends in hydrothermal sinter deposits that coincide with two independently dated earthquakes in the past 20 k.y. This suggests a system where fluid flow is triggered by repeated seismic activity, and that seals itself over ∼1 k.y. due to the formation of clays and silicates in the fault damage zone. Hydrothermal activity is younger than the 6–10 Ma age of the fault, which means that deep (∼5 km) fluid flow was initiated only after a large part of the 230 m of fault offset had taken place.

Geology and Fluid Discharge at Dorado Outcrop, a Low Temperature Ridge‐Flank Hydrothermal System

AbstractTwo expeditions to Dorado Outcrop on the eastern flank of the East Pacific Rise and west of the Middle America Trench collected images, video, rocks, and sediment samples and measured temperature and fluid discharge rates to document the physical and biogeochemical characteristics of a regional, low‐temperature (~15 °C) hydrothermal system. Analysis of video and images identified lava morphologies: pillow, lobate, and sheet flows. Glasses from collected lavas were consistent with an off‐axis formation. Hydrothermal discharge generally occurs through pillow lavas but is patchy, sporadic, and sometimes ceases at particular sites of discharge. Yearlong temperature measurements at five of these discharge sites show daily ranges that oscillate with tidal frequencies by 6 °C or more. Instantaneous fluid discharge rates (0.16 to 0.19 L/s) were determined resulting in a calculated discharge of ~200 L/s when integrated over the area defined by the most robust fluid discharge. Such discharge has a power output of 10–12 MW. Hydrothermal seepage through thin sediment adjacent to the outcrop accounts for <3% of this discharge, but seepage may support an oxic sediment column. High extractable Mn concentrations and depleted δ13C in the low but variable organic solid phase suggest that hydrothermal fluids provide a source for manganese accumulation and likely enhance the oxidation of organic carbon. Comparisons of the physical and geochemical characteristics at Dorado and Baby Bare Outcrops, the latter being the only other site of ridge‐flank hydrothermal discharge that has been sampled directly, suggest commonalities and differences that have implications for future discoveries.

Field experimental investigation of bit stick-out for different soil strengths during deepwater conductor injection

The jetting method of deepwater conductor installation is the most widely applied method of underwater well construction. The degree of bit stick-out from the running conductor assembly directly affects the efficiency of the injection process and the bearing safety of the conductor after installation, a key factor in deepwater drilling design. In order to improve the efficiency and safety of conductor installation, it is necessary to determine a reasonable range of bit stick-out for soil formations with different shear strengths. In this paper, a modified model for selecting the bit stick-out is developed based on the theory of water jet ground breaking and the conservation of momentum. The key factors influencing the optimal bit stick-out, such as hydraulic parameters, formation strength, and the ratio of bit-to-conductor dimensions, are also considered. Orthogonal experiments of conductor jetting were conducted in in-situ soil strata with different soil strengths. The influence law of parameter change on bit stick-out is studied, including hydraulic parameters change, bit stick-out variation and running assembly structural change. The results indicate that the bit stick-out is a key factor affecting the efficient jetting of the conductor as well as the bearing capacity of the conductor after injection. For different soil shear strengths, the effects of bit stick-out on the jetting efficiency and bearing capacity are different. In soil strata with low shear strength, the bit stick-out from the running assembly has little influence on the jetting efficiency, but a significant influence on the bearing capacity of the conductor, and hydraulic factors dominate the jetting efficiency and conductor stability. In soil strata with relatively high shear strength, the bit stick-out has a significant influence on the installation efficiency and a relatively small influence on conductor bearing capacity. An optimal drill bit stick-out is then determined that provides the highest jetting efficiency under a given drilling fluid discharge rate. From the field experiments, the optimal bit stick-out is determined to be 147.4 mm, and the range of reasonable bit stick-out is 96.6–198.2 mm. In total, these research results provide a design basis and theoretical guidance for optimizing the bit stick-out of deepwater conductor running assemblies.

Measurement of colloidal phenomena during flow through refractive index matched porous media.

Colloidal phenomena in porous media, natural or engineered, are important in a breadth of science and technology applications, but fundamental understanding is hampered by the difficulty in measuring colloid deposit morphology in situ. To partially address this need, this paper describes a static light scattering apparatus using a flow cell filled with refractive index matched (RIM) porous media, allowing real-time measurement of colloidal phenomena as a function of depth within the flow cell. A laser interacts with the colloids in the pore space and their structures, but not with the RIM media. The intensity of scattered light is measured as a function of scattering angle, which allows characterization of colloid deposit morphology as a fractal dimension and a radius of gyration. In parallel, fluid discharge rate and pressure drop are recorded to determine permeability, a key parameter for any application involving flow through porous media. This apparatus should prove useful in any application requiring characterization of colloidal phenomena within porous media. Additionally, this paper describes how to use granular Nafion as RIM porous media.

Carbon isotope and abundance systematics of Icelandic geothermal gases, fluids and subglacial basalts with implications for mantle plume-related CO2 fluxes

We report new carbon dioxide (CO2) abundance and isotope data for 71 geothermal gases and fluids from both high-temperature (HT>150°C at 1km depth) and low-temperature (LT<150°C at 1km depth) geothermal systems located within neovolcanic zones and older segments of the Icelandic crust, respectively. These data are supplemented by CO2 data obtained by stepped heating of 47 subglacial basaltic glasses collected from the neovolcanic zones. The sample suite has been characterized previously for He–Ne (geothermal) and He–Ne–Ar (basalt) systematics (Füri et al., 2010), allowing elemental ratios to be calculated for individual samples. Geothermal fluids are characterized by a wide range in carbon isotope ratios (δ13C), from −18.8‰ to +4.6‰ (vs. VPDB), and CO2/3He values that span eight orders of magnitude, from 1×104 to 2×1012. Extreme geothermal values suggest that original source compositions have been extensively modified by hydrothermal processes such as degassing and/or calcite precipitation. Basaltic glasses are also characterized by a wide range in δ13C values, from −27.2‰ to −3.6‰, whereas CO2/3He values span a narrower range, from 1×108 to 1×1012. The combination of both low δ13C values and low CO2 contents in basalts indicates that magmas are extensively and variably degassed. Using an equilibrium degassing model, we estimate that pre-eruptive basaltic melts beneath Iceland contain ∼531±64ppm CO2 with δ13C values of −2.5±1.1‰, in good agreement with estimates from olivine-hosted melt inclusions (Metrich et al., 1991) and depleted MORB mantle (DMM) CO2 source estimates (Marty, 2012). In addition, pre-eruptive CO2 compositions are estimated for individual segments of the Icelandic axial rift zones, and show a marked decrease from north to south (Northern Rift Zone=550±66ppm; Eastern Rift Zone=371±45ppm; Western Rift Zone=206±24ppm). Notably, these results are model dependent, and selection of a lower δ13C fractionation factor will result in lower source estimates and larger uncertainties associated with the initial δ13C estimate. Degassing can adequately explain low CO2 contents in basalts; however, degassing alone is unlikely to generate the entire spectrum of observed δ13C variations, and we suggest that melt–crust interaction, involving a low δ13C component, may also contribute to observed signatures. Using representative samples, the CO2 flux from Iceland is estimated using three independent methods: (1) combining measured CO2/3He values (in gases and basalts) with 3He flux estimates (Hilton et al., 1990), (2) merging basaltic emplacement rates of Iceland with pre-eruptive magma source estimates of ∼531±64ppm CO2, and (3) combining fluid CO2 contents with estimated regional fluid discharge rates. These methods yield CO2 flux estimates from of 0.2–23×1010 mol a−1, which represent ∼0.1–10% of the estimated global ridge flux (2.2×1012 mol a−1; Marty and Tolstikhin, 1998).

North Cascadia heat flux and fluid flow from gas hydrates: Modeling 3‐D topographic effects

AbstractThe bottom‐simulating reflector (BSR) of gas hydrate is well imaged from two perpendicular seismic grids in the region of a large carbonate mound, informally called Cucumber Ridge off Vancouver Island. We use a new method to calculate 3‐D heat flow map from the BSR depths, in which we incorporate 3‐D topographic corrections after calibrated by the drilling results from nearby (Integrated) Ocean Drilling Program Site 889 and Site U1327. We then estimate the associated fluid flow by relating it to the topographically corrected heat flux anomalies. In the midslope region, a heat flux anomaly of 1 mW/m2 can be associated with an approximate focused fluid flow rate of 0.09 mm/yr. Around Cucumber Ridge, high rates of focused fluid flow were observed at steep slopes with values more than double the average regional diffusive fluid discharge rate of 0.56 mm/yr. As well, in some areas of relatively flat seafloor, the focused fluid flow rates still exceeded 0.5 mm/yr. On the seismic lines the regions of focused fluid flow were commonly associated with seismic blanking zones above the BSR and sometimes with strong reflectors below the BSR, indicating that the faults/fractures provide high‐permeability pathways for fluids to carry methane from BSR depths to the seafloor. These high fluid flow regions cover mostly the western portion of our area with gas hydrate concentration estimations of ~6% based on empirical correlations from Hydrate Ridge in south off Oregon, significantly higher than previously recognized values of ~2.5% in the eastern portion determined from Site U1327.

Hydrology, hydrochemistry and geothermal potential of El Chichón volcano-hydrothermal system, Mexico

Fluid and heat discharge rates of thermal springs of El Chichón volcano were measured using the chloride inventory method. Four of the five known groups of hot springs discharge near-neutral Na–Ca–Cl–SO 4 waters with a similar composition (Cl ∼ 1500–2000 mg kg −1 and Cl/SO 4 ∼ 3) and temperatures in the 50–74 °C range. The other group discharges acidic (pH 2.2–2.7) Na–Cl water of high salinity (>15 g/L). All five groups are located on the volcano slopes, 2–3 km in a straight line from the bottom of the volcano crater. They are in the upper parts of canyons where thermal waters mix with surface meteoric waters and form thermal streams. All these streams flow into the Río Magdalena, which is the only drainage of all thermal waters coming from the volcano. The total Cl and SO 4 discharges measured in the Río Magdalena downstream from its junction with all the thermal streams are very close to the sum of the transported Cl and SO 4 by each of these streams, indicating that the infiltration through the river bed is low. The net discharge rate of hydrothermal Cl measured for all thermal springs is about 468 g s −1, which corresponds to 234 kg s −1 of hot water with Cl = 2000 mg kg −1. Together with earlier calculations of the hydrothermal steam output from the volcano crater, the total natural heat output from El Chichón is estimated to be about 160 MWt. Such a high and concentrated discharge of thermal waters from a hydrothermal system is not common and may indicate the high geothermal potential of the system. For the deep water temperatures in the 200–250 °C range (based on geothermometry), and a mass flow rate of 234 kg s −1, the total heat being discharged by the upflowing hot waters may be 175–210 MWt.

Pb IN THE PACMANUS SEA-FLOOR HYDROTHERMAL SYSTEM, EASTERN MANUS BASIN: NUMERICAL MODELING OF A MAGMATIC VERSUS LEACHED ORIGIN

Mass balance calculations of metal leaching and deposition in the PACMANUS submarine hydrothermal vent field in the eastern Manus basin in the Bismarck Sea off the east coast of Papua New Guinea indicate that simple leaching of the underlying volcanic pile by hydrothermal fluids cannot account for the Pb found in associated sulfide deposits and Pb-enriched altered volcanic rocks. With 100 percent leaching, transport, and precipitation efficiencies, 1.69 km3 of volcanic rock would need to be leached to account for Pb. Applying realistic leaching efficiencies of 50 to 60 percent and transport-precipitation efficiencies of 10 to 20 percent, 14 to 34 km3 of volcanic rock would need to be leached, assuming a static reaction zone. The estimated available volume of leachable rock is 0.144 km3, much less than required. Applying a dynamic reaction zone model, 98 to 235 volumes of fresh, leachable rock (1 volume = 0.144 km3) would need to be exposed to hydrothermal fluids. This translates into a 588 to 1,410 m migration of the reaction zone. A model incorporating such values would not be tenable. Previously published compositions of melt inclusions in volcanic rocks from PACMANUS indicate an aver-age of 199 ppm Cu, 68 ppm Zn and 5.2 ppm Pb in the melt and 1.3 to 1.7 wt percent of degassed H2O. These data suggest that 37.7 million tonnes (Mt) of magmatic fluid containing 7.2 wt percent Cu and 2.3 wt percent Zn could be released from a 1 km3 body of magma. Using the same metal transfer efficiency of 80 percent, the degassed fluid would have a maximum concentration of 0.17 wt percent Pb, which translates to 58,000 t of Pb from the melt. For the highest known fluid discharge rate of 92,000 g/s and over a 100,000-year period, a concentration of only 12 ppm Pb in the original magmatic component could account for all the Pb in the PACMANUS deposits, assuming that 1 percent of the mixed end-member fluid is of magmatic origin. A wide range of durations of hydrothermal activity and discharge rates, assuming a maximum 0.17 wt percent Pb concentration in the degassed magmatic fluid, can account for the total Pb in the deposit.

Crustal dynamics of Mount Vesuvius from 1998 to 2005: Effects on seismicity and fluid circulation

This paper presents the results of hydrogeochemical and seismological studies carried out at Mount Vesuvius during the period June 1998 to December 2005. Hydrogeochemical data show the occurrence of slowly varying long‐term variations in the total dissolved salts and bicarbonate contents of the groundwaters, accompanied by a general decline in water temperatures. The temporal distributions of air temperature and rainfall in the Vesuvius area suggest that these variations do not depend on changes in the hydrological regime. The changes in the geochemical parameters are accompanied by slight variations in both the seismicity rate and energy release. A further relationship between seismic activity and fluid discharge rate is highlighted by a particular episode that occurred in August 2005, when a soil thermal anomaly was observed a few weeks before the occurrence of a very shallow earthquake. Moment tensor analysis of this earthquake suggests that the most plausible source mechanism is a shear faulting combined with the opening of tensile crack. This feature is often observed in volcanic areas and it is usually related to fluid‐ and/or gas‐driven rock fracturing. The observed seismological, hydrological, and geochemical temporal changes are interpreted not as changes of the volcanic system but in terms of an external forcing as identified in the variation of the regional and local stress field acting on the volcano. This study has inferences onto the evaluation of the state of activity of volcanic systems and the eventual detection of unrest phenomena.

Meander geometry of Venusian canali: Constraints on flow regime and formation time

The similar meander geometries of Venusian canali and terrestrial rivers imply that the in‐channel flow regimes may be comparable. This work details meander geometry measurements from ten lowland canali and compares the extensive data set produced to a variety of solar system channels. The meander properties of Venusian canali do not closely match any channel so far observed on the terrestrial planets. However, analysis of the relationship between meander wavelength and radius of channel curvature confirms previous suggestions that the canali were carved by a low (water‐like) viscosity fluid. Whether the canali are due to thermal and/or mechanical erosion of the plains by an exotic lava, or have some other genesis, the dominant meander wavelengths of 11 to 77 km require peak fluid discharge rates of up to 6.6 × 106 m3 s−1, an order of magnitude larger than terrestrial rivers. Slight decrease in width along the channel length was observed in most investigated canali, perhaps reflecting the effect of downstream loss processes. Cyclical variations in the average channel width were observed in some channels; where topographic data are available, these variations apparently correlate with peaks in plains topography. This indicates that the canali remained active, after their initially rapid formation, long enough to interact with the early stages of plains tectonism.

Kinetics of antigorite dehydration: A real-time X-ray diffraction study

Antigorite dehydration has been studied in situ using time-resolved X-ray diffraction (XRD) in the 1.1–5.5 GPa pressure range. The sequence of XRD spectra reveals that the high-temperature stability limit of antigorite is decreased by 50–100 °C under H 2O-unsaturated conditions. The decomposition of antigorite into the high-temperature products, forsterite + enstatite, proceeds via an intermediate assemblage of forsterite and a “talc-like” phase, observed within a temperature interval of 130 ± 20 °C. The analysis of the transformation-time data using the Avrami model suggests that the breakdown of antigorite and the “talc-like” phase is kinetically controlled by surface growth processes at the edges of grains. The overall transformation rates are 10 to 100 times faster than those observed in water-saturated experiments, and show that the H 2O activity is a strong driving force for dehydration. The breakdown of antigorite in subducting oceanic mantle with such kinetics would result in a fluid discharge rate of the order of 10 − 6 to 10 − 8 s − 1 . This is faster than the viscous relaxation of serpentinites, and could lead to brittle failure or weakening of pre-existing faults. This provides an explanation for the seismicity in the lower plane of double seismic zones.

Hydrothermal seepage patterns above a buried basement ridge, eastern flank of the Juan de Fuca Ridge

We use the distributions of sediment physical properties and modeled basement overpressures to estimate the spatial distribution of fluid seepage through sediments over and around the “First Ridge,” a buried basement ridge on the eastern flank of Juan de Fuca Ridge. Fluid discharge rates differ by 1 order of magnitude because of differences in sediment hydraulic properties and by 2 orders of magnitude resulting from differences in sediment thickness and basement overpressure. Sediment type distribution appears to have resulted from differences in local seafloor relief. Compression index (ease of consolidation) increases with proportion of hemipelagic material, from 0.5 at 30% hemipelagic to 1.4 at 95% hemipelagic. Permeability at 50% porosity decreases with proportion of hemipelagic material, from 2 × 10−16 m2 at 30% hemipelagic to 6 × 10−18 m2 at 95% hemipelagic. Modeled seepage rates, derived from basement overpressures and sediment physical properties, range from 0 to 27 mm/yr. The average seepage rate over the entire 11 km of ridge within our study area is 1.3 mm/yr. On the basis of the model results, half of the total volume flux of seepage from the First Ridge is contributed from 25% of the study area, with flow rates ≥1.1 mm/yr. Low seismic reflection amplitude anomalies are generally correlated with areas of high seepage rates.

Flat vein formation in a transitional crustal setting by self-induced fluid pressure equilibrium — an example from the Géant Dormant gold mine, Canada

Gold-bearing veins grossly define a bimodal distribution within the Earth's crust as demonstrated by epithermal- (0 to 2 km) and mesothermal-type (∼5 to 15 km) deposits. Vein formation in the epithermal and mesothermal environments is commonly attributed to the suction pump and the fault-valve mechanisms, respectively. Characteristics of the Géant Dormant gold-bearing vein network are compatible with neither mechanism. In this paper, vein morphology and geometry, alteration styles, and host rock characteristics are used to constrain the following empirical parameters: tectonic regime, fluid flow vectors, crustal depth, host rock permeability, fluid pressure, mineral precipitating conditions and scale of filling processes (zoning). Based on these parameters, a three-stage model for vein formation is envisaged. The self-equilibrating mechanism involves the formation of mostly flat veins stacked along cross-stratal dikes within an impermeable volcanic pile. The dikes served as flow-restricted fluid feeders and as conduits for fluid discharge to the paleosurface. During the stable prefailure stage, the dike conduits acted as dampers in controlling the fluid discharge rate and in keeping fluid pressure at a constant level needed for the opening of preexisting fractures for vein formation ( P f≈ σ 1+0.3 T) at specific vertical intervals. The formation of veins corresponds to an equilibrating process that releases differential fluid pressure (Δ P) built up vertically in the flow-restricted conduits. The Δ P is induced by the decrease of the lithostatic pressure as long as the hydrothermal fluids move upward at a low velocity. At a critical state, when the deepest veins cannot physically absorb more fluid pressure accumulation, the excess fluid pressure (Δ P) is then transferred upwards along the QFP dikes, leading to the failure of the equilibrium process for vein formation at the network-scale (failure stage). The postfailure stage involves draining to the paleosurface of the underlying pressurized hydrothermal reservoir. At an advanced state, hydrothermal self-sealing leads progressively to the restoration of the initial, prefailure, flow-restricted conditions of the dike conduits. The proposed model involves a crustal depth of 2–5 km and a near-neutral tectonic regime. These characteristics are intermediate to those involved for the suction pump and the fault-valve mechanisms and suggest that each tectonic regime has an optimal crustal depth for the formation of gold-bearing veins.

Origin of fumarolic fluids at Vulcano (Italy). Insights from isotope data and numerical modeling of hydrothermal circulation

Hydrothermal activity is often associated with active volcanic systems. During quiescent times, geochemical monitoring of discharged fluids commonly is carried out to gain insights on the state of evolution of the whole volcanic system. The interest in geochemical monitoring derives from the observation that compositional variations of discharged fluids are commonly observed as a new eruptive phase is approaching. In particular, an increase in the gas components of direct magmatic origin may indicate a higher magma degassing rate at depth, potentially related to a renewal of explosive activity. Surveillance programs devoted to hazard mitigation in active volcanic areas generally include periodic analyses of discharged fluids at various locations on the volcanic edifice. Unfortunately, when significant changes are observed in gas composition, their correct interpretation in terms of system evolution is not always clear and straightforward. Several mechanisms may in fact be responsible for differences in the proportion of magmatic gases and shallower fluid components, and it is not always possible to recognize the magmatic gas fraction. Discrimination among fluids of different origin ideally is accomplished based on the isotope composition that each fluid acquires at the time of its generation. However, this isotope signature can be altered before the fluids reach the surface, because of mixing between fluids of different origin, or due to reactions that modify the original isotope composition. Thus, the interpretation of isotope data sometimes is quite complex and it can be highly misleading. In this work, the origin of the steam discharged at the hydrothermal system of Vulcano (Italy) was investigated by the means of a dual approach: first, the available isotope data on the discharged steam were analyzed. On the basis of on these and other data, a conceptual model of the hydrothermal system was developed and numerical simulations of a multiphase, multicomponent flow through a heterogeneous porous medium were carried out to evaluate the effects of various parameters on the system evolution. Results suggest that the hydrothermal system of Vulcano is controlled by the entrance of large quantities of seawater whose original isotope composition has been altered by water-rock interaction. Rock permeability and its distribution at depth were shown to be a primary parameter, controlling the overall system evolution, the fluid composition, and fluid discharge rate at the surface.

The contractile vacuole fluid discharge rate is determined by the vacuole size immediately before the start of discharge in Paramecium multimicronucleatum

The precise relationship between the rate of contractile vacuole fluid discharge and the vacuole diameter at the start of systole was determined in cells of Paramecium multimicronucleatum subjected to various external conditions. The rate of discharge was higher when the diameter was larger. When the rate of discharge was plotted against the diameter, the points fell around a single parabolic line passing through the origin and were independent of the external conditions employed. This implies that the rate of discharge is proportional to the square of the vacuole diameter. We have previously proposed a hypothesis in which membrane tension in the contractile vacuole is altered as its planar membrane becomes tubular or as tubules become planar membrane (termed the membrane area-proportional tension hypothesis). We propose here that it is this change in membrane tension which determines the vacuole pore shape and sets the subsequent rate of fluid discharge.

Steady incompressible laminar flow in porous media

Steady incompressible laminar flow in porous media is studied. The volume averaging technique is revisited resulting in a new averaging approach to the pressure gradient term. The difference between the traditionally obtained volume averaged equation for very small flow rate and Brinkman's equation is resolved. The Kozeny—Carman theory is modified. By including a two-dimensionally modelled tortuosity and curvature ratio as well as pore cross-sectional area variation, a new semi-empirical equation for the pressure drop for flow through porous media is obtained. The pressure drop dependence on the porosity ε for Darcy's flow region is established as ε −11 3 (1 − ε) 2 as opposed to ε −3(1 − ε) 2 in the original Kozeny—Carman's theory. A modified Reynolds number is also defined. The regions of Darcy's flow and Forchheimer's flow are unified. The wall effects are incorporated into the unified pressure drop equation. The final form of the normalized pressure drop equation for a one-dimensional medium is given by ▪ for d s = d′ s/ D < 0.75. Here f v is the normalized pressure drop factor, — Δ p′ is the pressure across a fixed thickness L of the porous bed, ε is the porosity, d′ s is the equivalent spherical particle diameter, D is the bed diameter, U is the superficial velocity or fluid discharge rate, μ is the dynamic viscosity of the fluid and Re m is the modified Reynolds number. The one-dimensional pressure drop equation is also modified to give a shear factor for use with the volume averaged Navier—Stokes equation and it is given as ▪ where F is the shear factor and Re v is the local modified Reynolds number. The semi-theoretical model was tested with a available and new experimental pressure drop data for packed beds. Further comparison was made with experimental pressure drop data for flow in a fibrous mat. The model was found to correlate well for the whole range of Reynolds number, wall effects and porosity studied.

Fluid discharge resulting from puncture of spherical process vessels

Risk analysis associated with incidents of puncture or rupture of process vessels generally requires estimation of actual or average fluid discharge rates resulting from such an incident. Most formulas developed to date for fluid discharge rates from vessels generally assume that the flow opening is located at the bottom of the vessel; this is undoubtedly due to the previously predominant interest in computing time requirements for gravity drainage of process or storage vessels. An accidental puncture however, such as resulting from a moving vehicle, can occur at almost any elevation. Hence, from a risk analysis point of view, it would be useful to have formulas which would estimate fluid discharge amounts and rates from a flow opening at any arbitrary elevation. In this article, the differential and algebraic equations governing liquid discharge from an opening at any point on the surface of a spherical vessel are solved. This solution is then generalized in terms of dimension-less efflux times, liquid volumes and average release rates as functions of dimensionless elevations.

Elliptic integral solutions for fluid discharge rates from punctured horizontal cylindrical vessels

The problem of determining fluid discharge rates from the side (as opposed to the bottom) of punctured cylindrical and spherical vessels was recently addressed by Crowl 1 . Both vertical and horizontal cylindrical configurations were examined. Analytical solutions to the spherical and vertical cylindrical problems were obtained in rather straightforward fashion. However, the geometry is considerably more complex in the case of the horizontal cylindrical configuration. Crowl does not present an analytical solution to this more complicated problem, but employs numerical methods in order to integrate the governing differential material balance equation. The purpose of this communication is to present a direct analytical solution to the problem of side drainage from a punctured horizontal cylindrical vessel with the use of elliptic integrals, values of which are tabulated in numerous mathematical handbooks 2–4 . Because of their inherently greater accuracy, analytical solutions can serve as standards or benchmarks against which to check the reliability of numerical solutions and, in addition, are generally readily programmable on computers and/or spreadsheets.