Behaviour of a sonic wave in dissociating gases

1988 ◽  
Vol 66 (4) ◽  
pp. 334-337 ◽  
Author(s):  
Arisudan Rai ◽  
M. Gaur
Keyword(s):  
Gas Flow ◽  
Singular Surface ◽  
Hyperbolic Partial Differential Equations ◽  
Growth Equation ◽  
Gas Flows ◽  
Present Communication ◽  
Global Behaviour ◽  
Effective Velocity ◽  
Sonic Wave ◽  
Weak Disturbances

The present communication is devoted to the study of weak solutions of the system of hyperbolic partial differential equations in dissociating gas flows. As an application of the singular surface theory, the law of propagation and the growth equation of a sonic wave are obtained, and the breakdown of a sonic wave is also discussed. It is found that weak disturbances in dissociating gases propagate with the effective velocity of sound relative to the gas flow. The effects of dissociation and the wave geometry on the global behaviour of the wave amplitude are discussed. It is concluded that dissociation has a stabilizing effect on the sonic wave in the sense that either it disallows or delays shock formation. The two cases of diverging and converging waves are discussed separately.

Co-Current and Countercurrent Migration of Gas Kicks in “Horizontal” Wells

1999 ◽  
Vol 121 (2) ◽  
pp. 96-101 ◽  
Author(s):  
H. Baca ◽  
J. Smith ◽  
A. T. Bourgoyne ◽  
D. E. Nikitopoulos
Keyword(s):  
Test Section ◽  
Gas Flow ◽  
Gas Injection ◽  
Horizontal Wells ◽  
Gas Flows ◽  
Countercurrent Flow ◽  
Drilling Operations ◽  
Operating Window ◽  
Annular Pipes ◽  
Injection Rates

Results from experiments conducted in downward liquid-gas flows in inclined, eccentric annular pipes, with water and air as the working fluids, are presented. The gas was injected in the middle of the test section length. The operating window, in terms of liquid and gas superficial velocities, within which countercurrent gas flow occurs at two low-dip angles, has been determined experimentally. The countercurrent flow observed was in the slug regime, while the co-current one was stratified. Countercurrent flow fraction and void fraction measurements were carried out at various liquid superficial velocities and gas injection rates and correlated to visual observations through a full-scale transparent test section. Our results indicate that countercurrent flow can be easily generated at small downward dip angles, within the practical range of liquid superficial velocity for drilling operations. Such flow is also favored by low gas injection rates.

scholarly journals Potential of using inert gas flows for controlling the quality of as-grown silicon single crystal

2020 ◽  
Vol 6 (1) ◽  
pp. 1-7
Author(s):  
Tatyana V. Kritskaya ◽  
Vladimir N. Zhuravlev ◽  
Vladimir S. Berdnikov
Keyword(s):  
Single Crystal ◽  
Carbon Content ◽  
Single Crystals ◽  
Gas Flow ◽  
Thermal Stresses ◽  
Crystal Surface ◽  
Gas Flows ◽  
Reaction Products ◽  
Crystal Silicon ◽  
Argon Gas

We have improved the well-known Czochralski single crystal silicon growth method by using two argon gas flows. One flow is the main one (15–20 nl/min) and is directed from top to bottom along the growing single crystal. This flow entrains reaction products of melt and quartz crucible (mainly SiO), removes them from the growth chamber through a port in the bottom of the chamber and provides for the growth of dislocation-free single crystals from large weight charge. Similar processes are well known and have been generally used since the 1970s world over. The second additional gas flow (1.5–2 nl/min) is directed at a 45 arc deg angle to the melt surface in the form of jets emitted from circularly arranged nozzles. This second gas flow initiates the formation of a turbulent melt flow region which separates the crystallization front from oxygen-rich convective flows and accelerates carbon evaporation from the melt. It has been confirmed that oxygen evaporated from the melt (in the form of SiO) acts as transport agent for nonvolatile carbon. Commercial process implementation has shown that carbon content in as-grown single crystals can be reduced to below the carbon content in the charge. Single crystals grown with two argon gas flows have also proven to have highly macro- and micro-homogeneous oxygen distributions, with much greater lengths of single crystal portions in which the oxygen concentration is constant and below the preset limit. Carbon contents of 5–10 times lower than carbon content in the charge can be achieved with low argon gas consumption per one growth process (15–20 nl/min vs 50–80 nl/min for conventional processes). The use of an additional argon gas flow with a 10 times lower flowrate than that of the main flow does not distort the pattern of main (axial) flow circumvention around single crystal surface, does not hamper the “dislocation-free growth” of crystals and does not increase the density of microdefects. This suggests that the new method does not change temperature gradients and does not produce thermal shocks that may generate thermal stresses in single crystals.

scholarly journals Transformation of a mathematical model of gas flow distribution to solve the problems of gas supply system development

2020 ◽  
Vol 219 ◽  
pp. 02001
Author(s):  
Nikolay Ilkevich ◽  
Tatyana Dzyubina ◽  
Zhanna Kalinina
Keyword(s):  
Mathematical Model ◽  
Gas Flow ◽  
System Development ◽  
Flow Distribution ◽  
Supply System ◽  
Economic Environment ◽  
Gas Flows ◽  
Supply Systems ◽  
New Criteria ◽  
Gas Supply

This paper proposes taking into account new properties of gas supply systems in a mathematical model of flow distribution in comparison with the traditional formulation. The approach suggests introducing an arc coefficient, which allows for changes in the magnitude of gas flow passing along the arc, a vector of an increase in the arc throughput, and lower constraints on the gas flow along the arc. We also propose considering a new economic environment, namely, new criteria for optimizing the flow distribution and setting fictitious gas prices for consumers. These criteria enable us to take account of the priority gas supply to a definite group of consumers. As an example, the calculation of gas flows for the aggregated Unified Gas Supply System (UGSS) for 2030 is considered. This calculation takes into account the arc coefficients and the increase in the throughput of arcs.

scholarly journals Cost-effectiveness of Basal Flow Sevoflurane Anaesthesia Using the Komesaroff Vaporizer inside the Circle System

2005 ◽  
Vol 33 (5) ◽  
pp. 609-615 ◽  
Author(s):  
S. P. Nandalan ◽  
R. J. Eltringham ◽  
Q. W. Fan
Keyword(s):  
Gas Flow ◽  
Low Flow ◽  
Gas Flows ◽  
Physical Status ◽  
Mechanically Ventilated ◽  
Sevoflurane Anaesthesia ◽  
Inspiratory Limb ◽  
Low Flow Anaesthesia ◽  
Induction Of Anaesthesia ◽  
Basal Flow

After ethics committee approval, 51 consenting ASA physical status 1 or 2 adult patients were given basal flow sevoflurane anaesthesia using fresh gas flows of 150 to 300 ml.min-1 oxygen. A Komesaroff vaporizer was placed on the inspiratory limb of the circle system. Basal flows were introduced immediately following intravenous induction of anaesthesia. The vaporizer was set to deliver the maximum concentration until the inspired sevoflurane concentration (FSI) reached 3%. The dial was then adjusted to maintain the FSI at 3%. After every 60 minutes, the circuit was washed out with 100% oxygen at a flow rate of 10 l.min-1 for one minute. The FSI reached 3% after an average of 8.5 (3.8) [mean (SD)] minutes. The trends in FSI and the expired sevoflurane concentrations were significantly different (P<0.05) between the mechanically ventilated patients (n=21) and the spontaneously ventilating patients (n=30) and demonstrated a more gradual build-up in the former group. The consumption of sevoflurane was found to be 9.2 (2.8) ml.h-1. This represented a 52.5% cost saving over the clinical application of the Mapleson's ideal fresh gas flow sequence for low-flow anaesthesia.

DSMC Simulation of Rarefied Gas Flow Over a Wall Mounted Cube

2019 ◽  
Author(s):  
Deepak Nabapure ◽  
Ram Chandra Murthy
Keyword(s):  
Gas Flow ◽  
Rarefied Gas ◽  
Flow Behavior ◽  
Direct Simulation Monte Carlo ◽  
Temperature Fields ◽  
Gas Flows ◽  
Rarefied Gas Flows ◽  
Dsmc Simulation ◽  
Recirculation Length ◽  
Velocity Pressure

Abstract The present study investigates the flow behavior of the rarefied gas over a wall-mounted cube. The problem is studied for different cube heights (h) of 9mm and 18mm in the slip and transition regimes. The Direct Simulation Monte Carlo (DSMC) method is employed to evaluate the properties such as velocity, pressure and temperature fields. The Reynolds number (Re) ranges from 403 to 807, and the Knudsen number (Kn) is in the range from 0.05 to 0.103. A typical shock wave is formed in front of the cube. The recirculation length of the vortices normalized with respect to the respective cube heights for Kn = 0.05 and Kn = 0.103 are about 1.11 and 1.95 respectively. Similarly, the center of the vortices is located at about 3.33 and 6.11 times the respective cube heights upstream, for Kn = 0.05 and Kn = 0.103. The local temperature and pressure variations observed upstream of the cube are two orders higher in magnitude and are primarily attributed to strong compressibility effects. The present study paves the way for benchmarking, and forms a basis for understanding the rarefied gas flows over complex geometries.

scholarly journals A survey of the choice of general anaesthetic agents in Australia and New Zealand

2019 ◽  
Vol 47 (3) ◽  
pp. 235-241 ◽  
Author(s):  
Forbes McGain ◽  
Jason R Bishop ◽  
Laura M Elliot-Jones ◽  
David A Story ◽  
Georgina LL Imberger
Keyword(s):  
Nitrous Oxide ◽  
New Zealand ◽  
Gas Flow ◽  
General Anaesthetic ◽  
Gas Flows ◽  
Environmental Costs ◽  
Flow Rates ◽  
Intravenous Anaesthesia ◽  
Anaesthetic Agents ◽  
End Tidal

Strategies to reduce the adverse environmental costs of anaesthesia include choice of agent and fresh gas flows. The current preferences of Australian and New Zealand anaesthetists are unknown. We conducted a survey of Australian and New Zealand anaesthetists to determine the use of volatiles, nitrous oxide and intravenous anaesthesia, lowest fresh gas flow rates, automated end-tidal volatile control, and the rationales for these choices. The survey was answered by 359/1000 (36%), although not all questions and multiple responses within single questions were answered by all respondents. Sevoflurane was preferred by 246/342 (72%, 95% confidence interval (CI) 67%–77%), followed by propofol, 54/340 (16%, 95% CI 12%–20%), desflurane 39/339 (12%, 95% CI 8%–16%) and isoflurane 3/338(1%, 95% CI 0–3%). When asked about all anaesthetics, low-risk clinical profile was the most common reason given for using sevoflurane (129/301 (43%, 95% CI 37%–49%)), reduced postoperative nausea for propofol (297/318 (93%, 95% CI 90%–96%)) and faster induction/awakening times for desflurane (46/313 (79%, 95% CI 74%–83%)). Two-thirds (226/340 (66%, 95% CI 61%–71%)) of respondents used nitrous oxide in 0–20% of general anaesthetics. Low fresh gas flow rates for sevoflurane were used by 310/333 (93%, 95% CI 90%–95%) and for 262/268 (98%, 95% CI 95%–99%) for desflurane. Automated end-tidal control was used by 196/333 (59%, 95% CI 53%–64%). The majority of respondents (>70%) preferred sevoflurane at low flows. These data allow anaesthetists to consider further whether changes are required to the choices of anaesthetic agents for environmental, financial, or any other reasons.

scholarly journals High Velocity Flow Suggested by Wing Components of the Hα Line Profiles in the Selected Planetary Nebulae

2003 ◽  
Vol 209 ◽  
pp. 539-540
Author(s):  
S. Tamura ◽  
M. Otsuka ◽  
A. Tajitsu
Keyword(s):  
High Velocity ◽  
Gas Flow ◽  
Planetary Nebulae ◽  
Gas Flows ◽  
Stellar Winds ◽  
Short Report ◽  
Line Profiles ◽  
Internal Motions ◽  
Velocity Flow ◽  
Gaussian Method

This is a short report on the study of internal motions of selected Planetary nebulae. We have studied this subject with both high (4 or 8 Å/mm) and intermediate (20 Å/mm) dispersion spectrographs. During the course of this work we noticed the existence of a high velocity gas flow distinct from the well known expanding gas, but with smaller velocities than stellar winds (Yadoumaru & Tamura 1994 on Abell 30; Otsuka & Tamura, 2001 on H 4-1). We present subsequent results obtained with the intermediate dispersion spectrograph about 10 selected planetary nebulae. The analyses were made by multiple Gaussian method on the emission line profiles of Hα. High velocity gas flows were recognized by a weak broad wing component.

scholarly journals Star formation and gas flow history of a dwarf irregular galaxy traced by gas-phase and stellar metallicities

2019 ◽  
Vol 491 (2) ◽  
pp. 1759-1770
Author(s):  
Nao Fukagawa
Keyword(s):  
Star Formation ◽  
Gas Phase ◽  
Gas Flow ◽  
Building Blocks ◽  
Gas Flows ◽  
Chemical Abundance ◽  
Irregular Galaxy ◽  
Oxygen Abundance ◽  
History Of ◽  
Ngc 6822

ABSTRACT Studying the evolution of dwarf galaxies can provide insights into the characteristics of systems that can act as building blocks of massive galaxies. This paper discusses the history of star formation and gas flows (inflow and outflow) of a dwarf irregular galaxy in the Local Group, NGC 6822, from the viewpoint of gas-phase and stellar chemical abundance. Gas-phase oxygen abundance, stellar metallicity distribution, and gas fraction data are compared to chemical evolution models in which continuous star formation and gas flows are assumed. If the galaxy is assumed to be a closed or an accretion-dominated system where steeper stellar initial mass functions are allowed, the observed gas-phase oxygen abundance and gas fraction can be explained simultaneously; however, metallicity distributions predicted by the models seem to be inconsistent with the observed distribution, which suggests that the star formation, gas flows, and/or chemical enrichment are more complex than assumed by the models. When NGC 6822 is assumed to be a system dominated by outflow, the observed values of gas-phase oxygen abundance and gas fraction can be explained, and the metallicity distributions predicted by some of the models are also roughly consistent with the observed distribution in the metallicity range of −2.0 ≲ [Fe/H] ≲ −0.5. It should be noted that this result does not necessarily mean that the accretion of gas is completely ruled out. More observables, such as chemical abundance ratios, and detailed modelling may provide deeper insight into the evolution of the system.

scholarly journals Evaluation of a New Extracorporeal CO2 Removal Device in an Experimental Setting

Membranes ◽  
2020 ◽  
Vol 11 (1) ◽  
pp. 8
Author(s):  
Matteo Di Nardo ◽  
Filippo Annoni ◽  
Fuhong Su ◽  
Mirko Belliato ◽  
Roberto Lorusso ◽  
...  
Keyword(s):  
Blood Flow ◽  
Gas Flow ◽  
High Surface ◽  
Surface Membrane ◽  
Respiratory Acidosis ◽  
Chronic Obstructive ◽  
Gas Flows ◽  
Co2 Removal ◽  
Extracorporeal Co2 Removal ◽  
Membrane Lung

Background: Ultra-protective lung ventilation in acute respiratory distress syndrome or early weaning and/or avoidance of mechanical ventilation in decompensated chronic obstructive pulmonary disease may be facilitated by the use of extracorporeal CO2 removal (ECCO2R). We tested the CO2 removal performance of a new ECCO2R (CO2RESET) device in an experimental animal model. Methods: Three healthy pigs were mechanically ventilated and connected to the CO2RESET device (surface area = 1.8 m2, EUROSETS S.r.l., Medolla, Italy). Respiratory settings were adjusted to induce respiratory acidosis with the adjunct of an external source of pure CO2 (target pre membrane lung venous PCO2 (PpreCO2): 80–120 mmHg). The amount of CO2 removed (VCO2, mL/min) by the membrane lung was assessed directly by the ECCO2R device. Results: Before the initiation of ECCO2R, the median PpreCO2 was 102.50 (95.30–118.20) mmHg. Using fixed incremental steps of the sweep gas flow and maintaining a fixed blood flow of 600 mL/min, VCO2 progressively increased from 0 mL/min (gas flow of 0 mL/min) to 170.00 (160.00–200.00) mL/min at a gas flow of 10 L/min. In particular, a high increase of VCO2 was observed increasing the gas flow from 0 to 2 L/min, then, VCO2 tended to progressively achieve a steady-state for higher gas flows. No animal or pump complications were observed. Conclusions: Medium-flow ECCO2R devices with a blood flow of 600 mL/min and a high surface membrane lung (1.8 m2) provided a high VCO2 using moderate sweep gas flows (i.e., >2 L/min) in an experimental swine models with healthy lungs.

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