Gas Pressure Profile Research Articles

Fluid Flow Modeling and Simulation for the Coaxial Cable of the LEASAT Antenna System

A preliminary fluid flow modeling, analysis, and simulation of the gas pressure profile within a 259 cm long coaxial cable is presented. This coaxial cable is part of the antenna system of the LEASAT satellite. To eliminate the possibility of any corona or arcing phenomenon inside the coaxial cable during operation of the satellite, it is necessary to not only prove experimentally but also show analytically that the gas pressure inside the cable drops down and stays below 0.01 Ton within 24 hours after the satellite enters into its orbit. In this paper, only the analytical work is discussed. The continuum fluid mechanics and the kinetic theory of gases are applied for modeling and analysis. Computer simulation is done by using an IBM XT and the results are presented.

Operating Regions of a Gas-Puff Z-Pinch and Its X-Ray Radiation

A z-pinch experiment is carried out with a hollow-shaped Ar gas puff. Three types of discharge are found depending on the delay time of discharge from gas-puff detection, and the pinch time is compared with the measured gas pressure profile. Strong X-ray radiation is emitted from spots, a cloud and the anode surface. The number of spikes in the X-ray signal is correlated with spot images of the X-ray photograph. An X-ray burst is sometimes observed in the short-delay-time operation.

The effects of aeration on the gravity flow of particles and gas in vertical standpipes

The effects of aeration on the gravity flow of cohesionless granular materials in a vertical standpipe, fed by a mass-flow hopper at its top and with a coaxial restriction at its foot, are studied both theoretically and experimentally. The theory is based on the description of the gas and particulate phases as two interacting and interpenetrating continua which exchange momentum through the drag force. The differential equations of continuity and motion for each of the two phases are integrated simultaneously to provide particle and gas flow rates, pressure and stress profiles, and void fraction distributions. Under certain operating conditions, the theory predicts the existence of multiple steady states and complex hysteresis phenomena. The predicted pattern of behavior is in good agreement with experimental observations from a laboratory-scale standpipe.

Gas release in comet nuclei.

The evolution of a comet nucleus is investigated, taking into account the crystallization process by which the gas trapped in the ice is released to flow through the porous ice matrix. The equations of conservation of the energy and of the masses of ice and gas are solved throughout the nucleus, to obtain the evolution of the temperature, gas pressure and density profiles. A spherical nucleus composed of cold, porous amorphous ice, with 10% of CO trapped in it, serves as initial model. Several values of density (porosity) and pore size are considered. For each combination of parameters the model is evolved for 20-30 revolutions in comet P/Halley's orbit. Two aspects of the release of gas upon crystallization are analyzed and discussed: (a) the resulting continuous outward flux with high peaks at the time of crystallization, which is a cyclic process in the low-density models and sporadic in the high-density ones; (b) the internal pressures obtained down to depths of a few tens to approximately 200 m (depending on parameters), that are found to exceed the compressional strength of cometary ice. As a result, both cracking and explosions of the overlying ice layer and ejection of gas and ice/dust grains are expected to follow crystallization. They should appear as outbursts or sudden brightening of the comet. The model of 0.2 g cm-3 density is found to reproduce quite well many of the light-curve and activity characteristics of comet P/Halley.

Salt smoke: The formation of submicron sized RbCl particles by thermal evaporation in 0.5–100 Torr of argon and helium

We have shown that it is possible to form submicron-sized particles of a highly ionic compound RbCl by thermally evaporating the reagent salt in 0.5–100 Torr of inert gas. By collecting the particles on a surface and then carefully removing them, bulk powder can be collected. The ambient gas species, pressure, system geometry, and evaporation temperature profile affect the size and geometry of the particles which form. Evidence indicates that if strong convection currents are present during evaporation, the number of individual primary particles in the powder is increased and the number of sintered strings of primary particles is reduced. The primary particle size depends on the geometry of the evaporation source used and is independent of the ambient pressure. In argon, the size of the particles collected is independent of the distance between the collection plates and the source. In helium, the size of the primary particles collected from a single run can vary from ∼10 to 1000 nm; the particle size collected is strongly dependent on the distance of the collection plates from the evaporation source.

Computation of gas pressure profiles relevant to outbursting in coal mines

Computation of gas pressure profiles relevant to outbursting in coal mines

Computation of gas pressure profiles relevant to outbursting in coal mines

AbstractHigh gas pressure gradients in coal seams play an important role in the occurrence of outbursts during underground coal mining. Excess stress resulting from body forces due to high pressure gradients contributes to the structural failure of coal. We present a one‐dimensional model of a dry, rigid coal seam with a moving mine face and determine gas pressures by solving the nonlinear equation for gas flow in a porous medium. An implicit finite difference scheme is used. Since the structure of coal has a dual porosity nature, we consider flow through both the macropores and the micropores. We investigate the effect of changes in mining velocity, idle mining periods and coal properties on the pressure profile in the coal seam. When the yield zone behind the moving mine face is taken into account, the greatest body force occurs on the least competent section of the coal seam.

Unsteady flow of a compressible gas through consolidated porous media—application to deaeration of hoppers

This is a theoretical and experimental study of time-dependent flows of compressible gases in a porous material under isothermal conditions. The time-dependent pressure variation from an initial profile to steady state conditions is solved using a model of a one-dimensional porous plate of constant porosity but variable permeability. The resulting non-linear partial differential equations are solved by computer using numerical methods to obtain gas pressure profiles as a function of time and spatial position. The results are subsequently applied to predict deaeration rates in hoppers filled with fine, cohesive powders having low permeability. The results are compared with experimental data obtained by the authors as well as by other investigators.

The urethral electromyographic and gas pressure profile. Technique and patterns.

A new technique for recording of the urethral pressure profile is described. The technique consists of a combined electromyographic and gas urethral pressure profile recording. Normal and pathological patterns are described. The method provides information of the correlation between intra-urethral pressure and activity in the periurethral striated musculature, and has proved useful in the assessment of neurological dysfunction of the urethra.

不均一充填構造粒子充填層の流速および圧力分布

不均一充填構造粒子充填層の流速および圧力分布