Showing papers on "Total pressure published in 1987"
TL;DR: Suarez et al. as discussed by the authors used a model to predict the extent of CO2 degassing and the resulting pH error in a multichambered extractor under controlled conditions.
Abstract: Moisture samples taken from the unsaturated zone with soil water extractors undergo degassing and an upward shift in pH. The measured pH values from commercially available extractors are usually sufficiently in error that they cannot be used in a quantitative manner. A model has been developed that predicts the extent of CO2 degassing and the resulting pH error. Using this model measured pH values can be corrected back to in situ soil water pH provided that precipitation has not occurred in the extractor. Extractors are classified into two groups—single chamber and multichambered. The extractors are evaluated for both operation under constant vacuum (open to the source) and decreasing vacuum (evacuated and then sealed). Analysis of the data and model predictions indicates that the major factor controlling the pH error is the ratio of liquid volume to total extractor volume. Additional factors exerting major influence are the initial extractor gas composition and the total pressure in the extractor when sampled. Variations in soil solution composition and differences in soil CO2 concentrations in carbonate buffered systems had a major effect on pH values but a negligible effect on the extractor induced pH error. Under typical field conditions the multichambered extractor is predicted to give the most satisfactory results; the pH errors were sufficiently small that no corrections for degassing were necessary. Additional Index Words: suction lysimeter, tension lysimeter, ceramic cup, soil moisture, unsaturated zone, carbon dioxide, sampler. Suarez, D.L. 1987. Prediction of pH errors in soil-water extractors due to degassing. Soil Sci. Soc. Am. J. 51:64-67. V EXTRACTORS are commonly used to obtain soil solution samples from the unsaturated zone. They are easy to use and mostly sample water 1 Contribution from the U.S. Salinity Laboratory, USDA-ARS, Riverside, CA 92501. Received 18 Feb. 1986. 2 Geochemist, U.S. Salinity Laboratory, USDA-ARS 4500 Glenwood Dr., Riverside, CA 92501. in the larger pores. Thus the solution samples obtained relate better to solute fluxes than solution extracts taken from soil cores. However, vacuum extractors can extract water only under relatively wet conditions and do not represent average soil water compositions. From the study by Hansen and Harris (1975) it can be concluded that a constant vacuum is preferable in order to minimize the variation in pore sizes sampled. Errors caused by the ion exchange capacity of the extractor are well documented for ceramic (Grover and Lamborn, 1970) and can be minimized by the use of teflon. Available extractors with teflon tips, however, have low bubbling pressures and thus cannot be evacuated to low pressures. An additional problem is that soil solutions buffered by carbonate chemistry undergo an upward shift in pH when collected by extractors. This pH shift is due to CO2 loss from solution during sample collection. When vacuum is applied to an extractor, the partial pressure of CO2 in the extractor is reduced proportionately to the reduction in total pressure. As soil water enters the extractor, the solution degasses and CO2 is released. The loss of dissolved H2CO3 causes an increase in pH as well as potential precipitation of carbonates, phosphates, and oxides in the extractor. Accurate pH measurements are especially necessary when the data are used to determine potential mineralogical controls on solution compositions or when trace species such as heavy metals or phosphate are being measured. Suarez (1986) described the design of a multichambered extractor that reduces the pH error by flushing the sampling chamber with solution and minimizing the relative air volume in the extractor. This study contains an evaluation of the factors contributing to the discrepancy between the pH inside extractors and the pH of the soil water. Additionally, the predicted pH effects are compared with measureSUAREZ: PREDICTION OF pH ERRORS IN SOIL-WATER EXTRACTORS 65 ments taken with a multichambered extractor under controlled conditions. DESCRIPTION OF THE MODEL AND EXPERIMENTAL PROCEDURES A computer program was written to predict the pH shift due to degassing of CO2 from solution. The program uses the gas law (PV = nRT), kH values for O2, N2 (Handbook of Chemistry and Physics, 1957), and CO2 (Harned and Davis, 1943) and a solution chemistry subroutine containing the carbonic acid dissociation constants and ion pairs given in Suarez (1977). The model inputs are soil PC02, soil solution composition, initial PC02 in the extractor, extractor configuration, and initial vacuum applied. The model simulates an extractor by allowing discrete increments of liquid to enter the extractor. For extractors that are closed to the vacuum source, the partial pressure of each gas is initially increased proportionately to the decrease in gas volume for each added increment of liquid. The concentrations of dissolved O2, N2, and CO2 are recalculated to account for mixing of each new liquid increment with the existing solution in the sampler. After each mixing the gas and liquid are equilibrated using the following relationships Py = Py, + (Aqyi Py.KHy).(R.T.VL/VA)/ [1 + (R.T.KHy.VL/VA)} Aqy = Aqyi (Aqy, Pyi-KHy)/ [1 + (R.T.KHy-VL/VA)} where Py is the equilibrium partial pressure of gas y, Pyi is the partial pressure of gas y after mixing, Aqyi is the concentration of dissolved gas y in moles L~' after mixing, KHy is the Henry's Law constant for gas y, R is the universal gas constant (0.812 L-Pa-mole^'-deg"), T is the temperature in degrees Kelvin, VL/VA is the ratio of the liquid to gas volume, andAqv is the equilibrium concentration of the dissolved gas. For CO2 the Ky and Aq values correspond to the sum of dissolved CO2 and H2CO3. The solution pH is then calculated using the solution composition, calculated PC02 and an ion speciation subroutine. After accounting for C mass and the recomputed Aq values, the program cycles until P,, Py, and pH convergence is achieved. For extractors open to the vacuum, the total pressure is fixed by the vacuum source. Upon addition of solution, the mixed solution is allowed to degas until gas-liquid equilibrium is attained and the calculated total pressure equals the total pressure specified. The excess gas leaves the sample chamber and flows to the reservoir connected to the vacuum. After the sample chamber fills, any subsequent solution increment is assumed to displace an equal volume of liquid out of the sampler. The simulation does not consider chemical precipitation. The relationship between pH errors (due to degassing) and extractor design, soil solution composition, soil CO2 partial pressure (PC02), and the ratio liquid/total volume in the extractor, were investigated with the model, with all calculations at 25 °C. Extractors can be either single or multichambered and either connected to the vacuum source (constant vacuum) or closed off from the vacuum source (decreasing vacuum). Multichambered extractors were evaluated by placing them in a container filled with Ca, Na, Cl~, HCOj solutions at 25°C and bubbling them with a CO2-air mixture. The single chamber extractor is similar to a commercially available extractor but smaller. After evacuation, the sampler is isolated from the vacuum source and allowed to partially fill. Samples are taken by pressurizing the unit and collecting solution from the tube extending to the sampler tip. The new multichambered extractor consists of ceramic which is glued to a 50-mm long PVC tube and connected to a 10-mL closed pyrex container with 1 mm i.d. tubing. Tubing extends from the container cap to a solution reservoir which is in turn connected to a constant vacuum source. Samples are obtained by removing, replacing, and immediately capping the 10-mL sampling container (see Suarez, 1986 for construction details). RESULTS AND DISCUSSION Single Chamber Extractors For a single chamber extractor that has been evacuated and then sealed, the extent of the pH shift depends primarily on the relative quantities of liquid and gas in the extractor. The solid line in Fig. 1 shows the pH error predicted for an extractor initially filled with air, then pumped down to a total pressure of 5.05 kPa (0.05 atm), and sealed. If the soil matric potential, or pressure head, is between 0 and —101 kPa, the extractor fills until the total pressure inside the extractor equals 101 kPa + the pressure head. For this simulation the soil CO2 pressure is 1.01 kPa (0.01 atm), and the soil water contains 2 mmolc L~' alkalinity. The calculated pH error (ApH) is the pH of the solution in the extractor minus the pH of the soil solution. As the extractor fills the pH error follows the solid line in Fig. 1. The extractor should fill with water if the water content of the soil is at saturation and sufficient time is allowed after the vacuum is applied. Under these conditions and assuming that any precipitated material redissolves, the final pH error approaches zero, as shown by the solid line in Fig. 1. If the soil water pressure head is <0 (unsaturated conditions) the extractor cannot fill completely and at equilibrium a partial vacuum (with pressure equal to 101 kPa + soil water pressure head) remains in the extractor. Within a few days of an irrigation or major rainfall event the soil pressure head will commonly decrease to field capacity or —10 to —30 kPa (—0.1 to —0.3 atm). Under field conditions, extractors commonly fill until they are 10 to 80% water filled. This
52 citations
01 Jan 1987
TL;DR: In this article, the mass fraction burnt as a function of time in a spark ignition engine has been calculated by two methods: a simple method and a complex model, which allows for dissociation, variable gas properties and heat transfer from the burnt and unburnt gases.
Abstract: Calculations of the mass fraction burnt as a function of time in a spark ignition engine have been made by two methods. The simple method assumes that the mass fraction burnt is in proportion to the fraction of total pressure rise due to combustion.The complex method assumes a two-zone combustion model, and computes the mass fraction burnt that is required to give the observed pressure rise for each 1° crank angle increment. The complex model allows for dissociation, variable gas properties and heat transfer from the burnt and unburnt gases.Notwithstanding the substantial differences between the two models, the results are in surprisingly close agreement. This can be attributed to the fact that the temperature of the burnt gas remains nearly constant during combustion.
46 citations
TL;DR: In this article, the effect of electrostatics on entrainment from a gas-solid fluidized bed was studied in a 0.61m LD column with silica sand and the flux of particles entrained above the transport disengaging height almost doubled when the relative humidity of gas was increased from 10% to 30% and then stabilized when humidity was further increased.
44 citations
TL;DR: In this article, a dynamic model for the activity of Poas Volcano, Costa Rica, is proposed, which leads to the assumption that the kinetic and thermal energies are proportional to the depth at which the mechanical equilibrium is disturbed.
Abstract: A dynamic model for the activity of Poas Volcano, Costa Rica, is proposed. Data collected during a three-year period show that the volcanic processes occur within a small hydrothermal system. Heat is supplied by a magma body in the conduit and is transferred to the surface by fluid convection. Within a given volume of rock, pore pressure builds up due to the upward motion of fluids and the increase in vapor pressure when the temperature rises above the boiling point. Ultimately, the system becomes unstable when the pore pressure overcomes the total pressure. This leads to the assumption that the kinetic and thermal energies are proportional to the depth at which the mechanical equilibrium is disturbed. Laboratory experiments were performed by heating samples of the crater lake deposits. The preliminary results of these experiments show significant analogies with the low-energy activity of the volcano. Following this model we estimated that a phreatic explosion which reaches 200 m in height (comparable to the one observed by Francis et al. in 1978) originates at a depth of 70 m and a temperature of 180° C; these values agree with those reported in the literature. In addition, “magmatic” sulfur, which partitions into the rising hydrothermal fluids, reacts at lower temperature and higher
$$\underset{\raise0.3em\hbox{$\smash{\scriptscriptstyle-}$}}{f} O_2$$
to produce pockets of liquid sulfur in the conduit deposits and the lava dome. These pockets are subsequently erupted forming the pyroclastic sulfur.
40 citations
TL;DR: In this article, the authors investigate electrically neutral surfaces composed of mobile charged particles and show that the long-range tail of the charge correlations is independent of the details of the system, and that the pressure between two such surfaces at large separations, h, is universal, always attractive, and decays like h−3.
33 citations
TL;DR: In this article, a description of the subtidal fluctuations in measured bottom pressure, internal pressures inferred from moored conductivity and temperature observations, and the water column total pressure anomalies computed from a combination of the two components was made.
Abstract: During the Coastal Ocean Dynamics Experiment (CODE) along the northern California continental shelf in the spring and summer of 1981 and 1982, the first comprehensive effort to obtain all of the observations necessary to infer pressure fluctuations throughout the water column was made. This is a description of the subtidal fluctuations in measured bottom pressure, internal pressures inferred from moored conductivity and temperature observations, and the water column total pressure anomalies computed from a combination of the two components. The pressure field during CODE 2 (April-July 1982) is found to be more energetic than that in CODE 1 (April-July 1981), with more than 70% total pressure variance concentrated at frequencies of less than (15 days)−1. The spatial structure of the pressure fluctuation field is characterized by coastal intensification and a tendency for poleward phase propagation. Like the pressures, most of the CODE across-shelf pressure difference variance is found at the lower frequencies, with more than 60% of the total across-shelf pressure difference variance at frequencies of less than (15 days)−1 The CODE across-shelf pressure differences are found to be in geostrophic balance with both alongshelf currents and the total alongshelf transport. The alongshelf pressure difference variance is generally found to be concentrated at the lower frequencies much like that of the across-shelf pressure differences. Most of the pressure and pressure difference variance is found to be highly coherent with wind stress. The 20-day band pressure variability is apparently related to the response of the pressure field during so-called “relaxation events.” The barotropic component of the alongshelf geostrophic transport (i.e., across-shelf pressure difference) has been found to be almost perfectly coherent with regional wind stress τy and to propagate poleward within the CODE region at the same rate as τy and the alongshelf pressure gradient is very important in accelerating the alongshelf flow. The 5-day band pressure variability in the CODE region appears to result from local wind stress fluctuations. The alongshelf pressure gradient was found to be of secondary importance relative to the wind in accelerating the alongshelf flow.
33 citations
TL;DR: In this article, gas samples were extracted from laminar atmospheric pressure CH2 CI2-CH4 -air flat flames using uncooled quartz probes with 0.05 to 0.10 mm orifices.
Abstract: Gas samples have been extracted from laminar atmospheric pressure CH2 CI2-CH4 -air flat flames using uncooled quartz probes with 0.05 to 0.10 mm orifices. The samples ( 50torr total pressure) were analyzed by gas chromatography for a number of major C1 and C2 hydrocarbons, chlorinated hydrocarbons and CO, CO2, O2 CH4 N2and H2 Temperatures were obtained throughout the reaction zone and into the postflame region using Pt-Pt (13 percent Rh) uncoated thermocouples with typical bead diameters of 0.15 mm. Measurements of species concentrations (major and minor stable products) along with temperatures are provided as a function of vertical distance above the burner for three separate flames with Cl/ H ratios of 0.060, 0.33 and 0.72 for φ 0.80. All intermediate species (with the exception of CHC13) are observed to fall below detectable limits when the CH2 CI2 concentration is less than 1 percent of its initial value. Peak values of major intermediates are presented as a function of Cl/ H ratio. In additi...
32 citations
TL;DR: In this article, the authors proposed an osmotic model of frost heave for a normally consolidated, saturated soil which has no ions in the pore water, assuming that the diffused layer of ions near the surface of a soil particle obeys the law of diffused aqueous solutions.
30 citations
TL;DR: In this article, the authors measured the intensity of desorbed OH radicals emitted from Pt, Pd, Rh, Ir, and Ni during the reaction between H2 and O2 and determined the emission yields from different catalysts as a function of total pressure, temperature, and H 2 O 2 partial pressure ratio.
29 citations
TL;DR: In this article, a graphite substrate mounted on a grounded graphite susceptor was inductively heated up to a temperature in the range 200-800 °C, and the mass of the deposit per square centimetre was determined as a function of reaction time, total gas pressure, substrate temperature, r.f. power, gas flow velocity and AlBr3 concentration.
25 citations
Patent•
17 Jul 1987
TL;DR: In this paper, a method for measuring vapor pressure of liquids in which liquid to be measured is placed in a previously-evacuated measuring cell, and influence of the gas dissolved in the liquid on the measuring results is eliminated.
Abstract: Method for measuring vapor pressure of liquids in which liquid to be measured is placed in a previously-evacuated measuring cell, and influence of the gas dissolved in the liquid on the measuring results is eliminated. The liquid to be measured is added in at least two separate portions, with total pressure present in the measuring cell being measured after the addition of each portion and after saturation vapor pressure equilibrium has become established, to obtain a thus-measured value. Gas pressure present in the measuring cell which is due to the gas dissolved in the liquid is derived from at least two thus-measured values which had been obtained at the same measuring temperature in which pressure components due to vapor pressure of the liquid are equal, taking into account the liquid quantity contained in the particular liquid portions and the measuring cell volume with the relation po=RT. The vapor pressure of the liquid is determined by subtracting the derived gas pressure from the total measured pressure. The present invention is also directed to an arrangement for measuring the vapor pressure of liquids, which has a measuring cell and a pressure measuring device connected to the same, as well as to a filling tube and a vacuum connection. The pressure measuring device is connected with the measuring cell through a connecting tube extending nearly to a bottom of the measuring cell. The opening of the connecting tube thereby lies below a liquid level present during the measurement in the measuring cell.
TL;DR: In this article, the output characteristics of a gas-polarographic oxygen sensor using a zirconia electrolyte have been investigated at 450°C and low pressures (~1 mmHg) in O2-N2 gas mixtures with the aim of clarifying those in the Knudsen diffusion region.
Abstract: Output characteristics of a gas-polarographic oxygen sensor using a zirconia electrolyte have been investigated at 450°C and low pressures (~1 mmHg) in O2-N2 gas mixtures with the aim of clarifying those in the Knudsen diffusion region The limiting current obtained at 1 mmHg of the total pressure increased linearly with the oxygen concentration up to 100% in the ambient atmosphere as expected from the theoretical consideration on the output characteristics of the sensor in the Knudsen diffusion region
TL;DR: In this paper, the authors examined the processes limiting the accuracy or range of total pressure measurements in the UHV range by ionization gauges and various methods and designs of uHV ionisation gauges that have been developed to reduce or eliminate these limiting processes.
Abstract: The processes limiting the accuracy or range of total pressure measurements in the UHV range by ionization gauges are examined. These processes include x‐ray induced photoemission, ion currents resulting from electron stimulated desorption, Kingdon orbits of the ions in Bayard–Alpert gauges, variations in electron yield by ion impact at electrode surfaces, and the effects of variations in electrode geometry. The various methods and designs of UHV ionization gauges that have been developed to reduce or eliminate these limiting processes are critically reviewed.
01 Oct 1987
TL;DR: In this article, a comprehensive set of total pressure and three-component laser velocimetry (LV) data has been obtained within two-circular-to-rectangular transition ducts at low subsonic speeds.
Abstract: A comprehensive set of total pressure and three-component laser velocimetry (LV) data has been obtained within two-circular-to-rectangular transition ducts at low subsonic speeds. This set of reference data was acquired for use in identifying secondary flow mechanisms and for assessing the accuracy of computational procedures for calculating such flows. Data were obtained at the inlet and exit planes of an aspect ratio three (AR3) duct having a length-to-diameter ratio (L/D) of one (1) and an aspect ratio six (AR6) duct having an L/D of three (3). Each duct was unseparated throughout its transition section. Cross-flow-vector plots and contour plots of axial velocity, total pressure, static pressure, axial turbulence, and axial vorticity in the exit plane of each duct are presented.
TL;DR: For the mixtures 4-methyl-2-pentanone(1)/water(2), 2-butanol( 1)/water (2) and 1-methyl 2-pyrrolidone (1)/heptane(2) total pressure data have been measured using Barker's method using four parameter Redlich-Kister equation as discussed by the authors.
TL;DR: In this paper, it is observed that as the nitrogen flow is progressively introduced into the plasma, there is an abrupt increase in the total system pressure, which corresponds to the rapid formation of nitride on the entire target surface, has to be minimized in order to obtain easier control of the coating process.
Abstract: The pumping speed of the vacuum system and the location of the gas inlet are two parameters which play a prominent part in the production of titanium nitride by reactive magnetron sputtering. In general it is observed that as the nitrogen flow is progressively introduced into the plasma there is an abrupt increase in the total system pressure. This disturbing, albeit slowly reversible, phenomenon, which corresponds to the rapid formation of nitride on the entire target surface, has to be minimized in order to obtain easier control of the coating process. In this transition zone it is possible to obtain a more progressive variation of the total pressure by locating the nitrogen inlet next to the pumping device and/ or by increasing the pumping speed. In this way, the nitriding process appears to be rapidly reversible, and the resulting nitride composition undergoes very slow variation with an increasing nitrogen flow rate. Deposits with various compositions and hues can therefore be more easily obtained owing to the above-mentioned improvements in the pumping device.
TL;DR: In this article, a bulk flow mechanism was used to remove liquid from the web by a faster diffusion mechanism rather than a slower diffusion mechanism, which can result in lower energy usage if only a part of the moisture is evaporated.
Abstract: High intensity drying occurs when one web surface is heated to the thermodynamic saturation temperature corresponding to the local hydraulic pressure. Rapid vapor generation causes the process to be driven by a total pressure gradient, so vapor leaves the web by a bulk flow mechanism rather than a slower diffusion mechanism. Vapor pressure build-up promotes rapid web heating and offers the opportunity for liquid removal by displacement. Lower energy usage can result if only a part of the moisture is evaporated.
TL;DR: In this article, the authors used a twin gas-operated pressure balance to generate gauge pressure in the range from below 0.5 Pa to 2000 Pa using differential pressure transducers.
Abstract: The accurate generation of gauge pressures in the range from below 0.5 Pa to 2000 Pa using twin gas-operated pressure balances is described. Each gauge pressure is generated by changing the mass on one of the pressure balances while they are both operating. The performance of the twin-pressure-balance instrument was assessed by calibrating differential pressure transducers. The short-term stability of the average difference in pressure between the two pressure balances was about 0.5 mPa (standard deviation), or 5 parts in 109 of the line pressure, and the overall uncertainty (99% confidence limits) in the generated gauge pressure pe was ± (0.9 mPa + 2 × 10-5 pe).
TL;DR: In this paper, the conservation equations for the flow field developed behind a spherical blast wave propagating into a dusty medium (gas seeded with small uniformly distributed solid particles) are formulated and solved numerically by using the random choice method.
Abstract: The conservation equations for the flow field developed behind a spherical blast wave propagating into a dusty medium (gas seeded with small uniformly distributed solid particles) are formulated and solved numerically by using the random choice method. The solution was carried out for the following three cases: (1) the dust is uniformly distributed outside the exploding spherical diaphragm; (2) the dust is uniformly distributed inside the exploding spherical diaphragm; (3) the dust is uniformly distributed inside a spherical layer located outside the exploding spherical diaphragm. The solutions obtained were compared with a similar pure-gas case. It was found that the dust presence weakens the blast wave, i. e. the gas velocity, temperature and pressure immediately behind the blast-wave front were lower than those obtained in a similar pure-gas case. The presence of dust changed the flow field behind the blast wave. The typical blast-wave pressure signature (i. e. a monotonic reduction in the pressure after the jump across the blast-wave front) changed to a different shape. Now the pressure increases after the blast-wave front until it reaches a maximum value followed by a monotonic pressure reduction. The maximum pressure is attained between the blast-wave front and the contact surface. Higher values of total pressure are obtained in the dusty gas case. The initial uniform spatial distribution of the dust particles changed into a bell-shaped pattern with a pronounced peak. The development of the sharp maximum in the dust spatial-density distribution might be of interest in assessing the effects of atmospheric nuclear explosions.
TL;DR: In this paper, a molecular dynamics study of the thermodynamics properties, including equation of state, of hard spheres in a narrow channel is presented, where four densities are studied and it is found that the pressure profile is directly correlated to the density profile.
Abstract: A molecular dynamics study of the thermodynamics properties, including equation of state, of hard spheres in a narrow channel is presented. Four densities are studied and it is found that the pressure profile is directly correlated to the density profile. Further, the fraction of the total pressure due to collisions in a direction normal to the wall is also correlated to the density profile. The equation of state is that of a hard sphere fluid at a density higher then the fluid and it varies across the channel. The motion of particles near the wall is constrained as found earlier in Monte Carlo studies.
Patent•
17 Aug 1987
TL;DR: In this paper, an apparatus for measuring and regulating variable pressure furnace gas chemistry is described, which uses a mass spectrometer for measurements, in the preferred form of the invention, in which gas species percent composition is obtained quantitatively independent of total furnace pressure variation.
Abstract: An apparatus for measuring and regulating the variable pressure furnace gas chemistry is described. The apparatus uses a mass spectrometer for measurements, in the preferred form of the invention, in which gas species percent composition is obtained quantitatively independent of total furnace pressure variation. Using such a real time measurement capability, active control of batch process furnace operations is possible by intrinsic measurement of the part outgassing rather than by assumption of batch part status as a function of extrinsic parameters such as temperature and total pressure. Thus, by a combination of batch process temperature ramp control and variable admittance of suitable gas into the furnace, uniform batch processing is possible by closed loop control, due to renormalization of furnace residual gas chemistry from day to day drift and from batch part chemistry variation. Quantitative measurements of the variable residual pressure is made possible by adjusting in real time the throughput into the mass spectrometer independent of the total pressure variation in the furnace. These measurement means also make possible the real time determination of sinter part densification in vacuum furnaces by measurement of the part outgassing attenuation during pore closure.
01 Jan 1987
TL;DR: In this article, a Lambda = 75 deg delta wing in a supersonic freestream under two conditions which lead to leading-edge vortices is analyzed, and it appears that this is due to truncation error of the convective derivatives.
Abstract: Computations are presented for a Lambda = 75 deg delta wing in a supersonic freestream under two conditions which lead to leading-edge vortices. For one condition, analysis of the computed vortical flow reveals a closed streamline in the core. From varying computational parameters, it appears that this is due to truncation error of the convective derivatives. For the other condition, comparisons are made with wind-tunnel data, and good agreement is noted for pitot pressure distributions, flow angles on the symmetry plane, and the position of an embedded shock. Many of the aerodynamic parameters are shown to be insensitive to grid spacing.
TL;DR: In this paper, Gas-phase water is treated as an equilibrium mixture of the clusters (H2O)i(g), their stability being described by equilibrium constants of the cluster formation, derived from available theoretical information (RRHO MCY-B/EPEN model).
01 Jan 1987
TL;DR: In this article, the authors defined the tension of a gas in solution in a liquid as being equal to the tension in a gas mixture that is in equilibrium with the liquid, and the conditions are not static for oxygen and carbon dioxide in the living body as oxygen is constantly being consumed while carbon dioxide is being produced.
Abstract: The diffusion of a gas is a process by which a net transfer of molecules takes place from a zone in which the gas exerts a high partial pressure to a zone in which it exerts a lower partial pressure. The mechanism of transfer is the random movement of molecules and the term excludes transfer by mass movement of gas in response to a total pressure difference. The partial pressure of a gas in a gas mixture is the pressure that it exerts if it occupied the space alone. The tension of a gas in solution in a liquid is defined as being equal to the tension of the same gas in a gas mixture that is in equilibrium with the liquid. The conditions are not static for oxygen and carbon dioxide in the living body as oxygen is constantly being consumed while carbon dioxide is being produced. Therefore, static equilibrium cannot be attained as in the case of the open bottle of oxygen.
TL;DR: In this paper, the effect of hydrogen added to the rf argon discharge on the physical properties of thin Cu x S films produced by rf sputtering from a Cu 2 S target is studied.
Patent•
ARCO1
TL;DR: In this article, the bubble point pressure, vapor pressure and liquid composition of hydrocarbon liquid flow streams are determined by causing the liquid flow stream to flow through a system having a plurality of eductors at selected various total pressure differentials across the system and measuring the pressure at the minimum pressure point or suction port of the eductor to obtain a reading of the vapor pressure.
Abstract: The bubble point pressure, vapor pressure and liquid composition of hydrocarbon liquid flow streams is determined by causing the liquid flow stream to flow through a system having a plurality of eductors at selected various total pressure differentials across the eductors and measuring the pressure at the minimum pressure point or suction port of the eductors to obtain a reading of the vapor pressure The system may comprise an array of three or more eductors arranged in parallel having flow regulating valves for controlling the flow rate and pressure drop across the eductors, respectively The system may also comprise one eductor connected to a plurality of flow lines, each having flow control and/or shutoff valves arranged to provide for selective control of the flow rate and the resultant total pressure drop Comparative data may be obtained for determining the liquid composition at a particular temperature based on the vapor pressure characteristics of known ranges of liquid compositions expected from the fluid stream being measured
TL;DR: In this paper, a TE CW CO 2 laser with a special gas flow scheme and an auxiliary discharge configuration was described, and an output power exceeding 3000 W/m was obtained at a gas mixture of CO:CO 2 :N 2 :He = 4:10:25:40 and a total pressure of 7.9 kPa.
Abstract: This paper describes a TE CW CO 2 laser with a special gas flow scheme and an auxiliary discharge configuration. In this laser system, mixed gas was forced to flow through a structure of square tubes with meshes on both sides. An array of auxiliary electrodes was added to produce a dc auxiliary discharge between these electrodes and a tubular cathode. By introducing these structures, uniformity and stability of the main discharge could be significantly improved, and more electrical input power could be deposited into the laser gases at higher pressures and higher discharge currents. An output power exceeding 3000 W/m was obtained at a gas mixture of CO:CO 2 :N 2 :He = 4:10:25:40 and a total pressure of 7.9 kPa. Without the auxiliary discharge, the maximum output power was less than 1600 W/m, and a stable discharge could not be obtained at a pressure above 4 kPa. The spatial distributions of unsaturated gain along the direction of gas flow and contours with constant gain were also drawn. By introducing molecular sieve 3A, the system could be operated continously over 15 h under sealed-off conditions.
TL;DR: In this paper, an analysis is made of a thermophysical model of a chemical singlet-oxygen generator, and it is shown that at the exit from a thermally insulated reaction vessel, the water vapor content is approximately three times the oxygen content.
Abstract: An analysis is made of a thermophysical model of a chemical singlet-oxygen generator. It is shown that at the exit from a thermally insulated reaction vessel, the water vapor content is approximately three times the oxygen content. Calculations are made of the water vapor content when the solution is cooled and circulated through the reaction vessel. As the total pressure is increased, the efficiency of purification of the oxygen in a water vapor condensation trap deteriorates strongly. This is one of the reasons for the degradation of the active medium of a cw oxygen–iodine laser with increasing oxygen pressure. For a trap comprising a smooth tube and a thermally insulated reaction vessel, the trap radius R and the oxygen pressure at the exit p'O2 should satisfy the condition p'O2 R<12 Torr, so that the laser active zone contains less than 10% of water vapor and no less than 50% of O2(1Δ). The oxygen pressure range can be increased by cooling the solution in the reaction vessel.
24 Mar 1987