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Effect of favorable pressure gradients on transition for several bodies of revolution at Mach 3.12

Description: Report presenting experimental results relating to the effect of pressure gradient on the location of transition for several constant-pressure-gradient models an two power-profile models. Results regarding the local flow conditions, recovery-factor distributions, effect of unit Reynolds number, and effect of pressure gradient are provided.
Date: July 1958
Creator: Jack, John R.
Partner: UNT Libraries Government Documents Department

Effect of bluntness on transition for a cone and a hollow cylinder at Mach 3.1

Description: Bluntness was more effective in displacing transition downstream on a cylinder than on a cone. The downstream displacement of transition is related to the formation of a shock layer within which the Reynolds and Mach numbers are reduced and to pressure gradients that exist over the forward part of the model. Round bluntness in general had a favorable effect, whereas sharp-cornered flat bluntness above a certain size had unfavorable effects on the location of the transition point.
Date: May 1957
Creator: Brinich, Paul F. & Sands, Norman
Partner: UNT Libraries Government Documents Department

Cooling requirements for stability of laminar boundary layer with small pressure gradient at supersonic speeds

Description: Report presenting the amount of cooling required to stabilize the two-dimensional supersonic laminar boundary layer for all Reynolds numbers for flows with pressure gradients of a magnitude usually encountered over slender aerodynamic shapes. It is determined that small pressure gradients have an appreciable effect on stability.
Date: March 1954
Creator: Low, George M.
Partner: UNT Libraries Government Documents Department

A Procedure for Calculating the Development of Turbulent Boundary Layers Under the Influence of Adverse Pressure Gradients

Description: Note presenting a procedure based on the kinetic-energy equation and an extended form of the momentum equation that has been devised for calculating the development of turbulent boundary layers, in adverse pressure gradients, for that class of flows for which the fluid density in all points and total pressure outside the boundary layer are invariant. Results regarding two-dimensional flow, conical-diffuser flow, separation, and the application of the procedure are provided.
Date: September 1951
Creator: Rubert, Kennedy F. & Persh, Jerome
Partner: UNT Libraries Government Documents Department

Some Features of Artificially Thickened Fully Developed Turbulent Boundary Layers with Zero Pressure Gradient

Description: Report gives an account of an investigation conducted to determine the feasibility of artificially thickening a turbulent boundary layer on a flat plate. A description is given of several methods used to thicken artificially the boundary layer. It is shown that it is possible to do substantial thickening and obtain a fully developed turbulent boundary layer, which is free from any distortions introduced by the thickening process, and, as such, is a suitable medium for fundamental research.
Date: September 15, 1950
Creator: Klebanoff, P. S. & Diehl, Z. W.
Partner: UNT Libraries Government Documents Department

Boundary-Layer Displacement Effects in Air at Mach Numbers of 6.8 and 9.6

Description: "Measurements are presented for pressure gradients induced by a laminar boundary layer on a flat plate in air at a Mach number of 9.6 and for the drag of thin wings at a Mach number of about 6.8 and zero angle of attack. The pressure measurements at a Mach number of 9.6 were made in the presence of substantial heat transfer from the boundary layer to the plate surface. The measured pressure distribution o the surface of the plate was predicted with good accuracy by a modification to insulated-plate displacement theory which allows for the effect of the heat transfer and temperature gradient along the surface on the boundary-layer displacement thickness" (p. 1).
Date: 1959
Creator: Bertram, Mitchel H.
Partner: UNT Libraries Government Documents Department

Similar Solutions for the Compressible Laminar Boundary Layer with Heat Transfer and Pressure Gradient

Description: "Stewartson's transformation is applied to the laminar compressible boundary-layer equations and the requirement of similarity is introduced, resulting in a set of ordinary nonlinear differential equations previously quoted by Stewartson, but unsolved. The requirements of the system are Prandtl number of 1.0, linear viscosity-temperature relation across the boundary layer, an isothermal surface, and the particular distributions of free-stream velocity consistent with similar solutions. This system admits axial pressure gradients of arbitrary magnitude, heat flux normal to the surface, and arbitrary Mach numbers" (p. 1).
Date: October 15, 1954
Creator: Cohen, Clarence B. & Reshotko, Eli
Partner: UNT Libraries Government Documents Department

The source of elliptic flow and initial conditions for hydrodynamical calculations

Description: A model for energy, pressure and flow velocity distributions at the beginning of relativistic heavy ion collisions is presented, which can be used as initial condition for hydrodynamical calculations. The results show that QGP forms a tilted disk, such that the direction of the largest pressure gradient stays in the reaction plane, but deviates from both the beam and the usual transverse flow directions. Such initial condition may lead to the creation of antiflow or third flow component.
Date: August 2000
Creator: Strottman, D.; Csernai, L. & Magas, V.
Partner: UNT Libraries Government Documents Department

Pressure Gradient Passivation of Carbonaceous Material Normally Susceptible to Spontaneous Combustion

Description: This invention is a process for the passivation or deactivation with respect to oxygen of a carbonaceous material by the exposure of the carbonaceous material to an oxygenated gas in which the oxygenated gas pressure is increased from a first pressure to a second pressure and then the pressure is changed to a third pressure. Preferably a cyclic process which comprises exposing the carbonaceous material to the gas at low pressure and increasing the pressure to a second higher pressure and then returning the pressure to a lower pressure is used. The cycle is repeated at least twice wherein the higher pressure may be increased after a selected number of cycles.
Date: July 15, 1999
Creator: Ochs, Thomas L.; Sands, William D.; Schroeder, Karl; Summers, Cathy A. & Utz, Bruce R.
Partner: UNT Libraries Government Documents Department

Simplified Method for Estimating Compressible Laminar Heat Transfer With Pressure Gradient

Description: "In the present report an approximation is made in the method of Technical Note 3326, which simplifies the calculation of heat transfer. Good agreement with the method of Technical Note 3326 is expected for isothermal surfaces with adverse and small favorable pressure gradients regardless of surface temperature and also for flow with large favorable pressure gradient over highly cooled surfaces" (p. 1).
Date: December 1956
Creator: Reshotko, Eli
Partner: UNT Libraries Government Documents Department

1982 THERMAL SHALLOW RESERVOIR TESTING

Description: An extensive study of the Thermal Shallow Reservoir at The Geysers was performed in 1982 to improve our understanding of the source and flow patterns of steam in the shallow anomaly and how they relate to the Thermal 4 blowout. This project included gathering and analyzing pressure transient, enthalpy, tracer and chemical data and developing a reservoir model that was consistent with this data. Following the pressure transient testing and analysis, a convection-plume with lateral-flow model was proposed. Subsequent analysis of enthalpy, tracer and chemical data corroborated this model. The high flowrate wells--Thermal 4, Thermal 10, Thermal 11 and Magma 1--produce from the high-pressure, high-permeability upflow zone. The source of this upflow is a limited fracture system connecting the shallow anomaly with the underlying main reservoir. The outlying low-pressure, low-permeability wells are supplied by lateral flow of steam from the central area. The pressure gradient from the core to the periphery is caused by condensation in the flanks.
Date: January 22, 1985
Creator: Mogen, P.; Pittinger, L. & Magers, M.
Partner: UNT Libraries Government Documents Department

ELM Suppression in Low Edge Collisionality H-Mode Discharges Using n=3 Magnetic Perturbations

Description: Using resonant magnetic perturbations with toroidal mode number n = 3, we have produced H-mode discharges without edge localized modes (ELMs) which run with constant density and radiated power for periods up to about 2550 ms (17 energy confinement times). These ELM suppression results are achieved at pedestal collisionalities close to those desired for next step burning plasma experiments such as ITER and provide a means of eliminating the rapid erosion of divertor components in such machines which could be caused by giant ELMs. The ELM suppression is due to an enhancement in the edge particle transport which reduces the edge pressure gradient and pedestal current density below the threshold for peeling-ballooning modes. These n = 3 magnetic perturbations provide a means of active control of edge plasma transport.
Date: July 11, 2005
Creator: Burrell, K H; Evans, T E; Doyle, E J; Fenstermacher, M E; Groebner, R J; Leonard, A W et al.
Partner: UNT Libraries Government Documents Department

Pressure gradient passivation of carbonaceous material normally susceptible to spontaneous combustion

Description: This invention is a process for the passivation or deactivation with respect to oxygen of a carbonaceous material by the exposure of the carbonaceous material to an oxygenated gas in which the oxygenated gas pressure is increased from a first pressure to a second pressure and then the pressure is changed to a third pressure. Preferably a cyclic process which comprises exposing the carbonaceous material to the gas at low pressure and increasing the pressure to a second higher pressure and then returning the pressure to a lower pressure is used. The cycle is repeated at least twice wherein the higher pressure may be increased after a selected number of cycles.
Date: January 29, 2002
Creator: Ochs, Thomas L.; Sands, William D.; Schroeder, Karl; Summers, Cathy A. & Utz, Bruce R.
Partner: UNT Libraries Government Documents Department

Field Study and Numerical Simulation of Sub Slab Ventilation Systems

Description: The effectiveness of the technique of subslab ventilation (SSV) for limiting radon entry into basements was investigated through complementary experimentation and numerical modeling. Subslab pressure fields resulting from SSV were measured in six well-characterized basements, each with a different combination of soil and aggregate permeability. The relationship between air velocity and pressure gradient was measured in the laboratory for the three types of aggregate installed beneath the basement slabs. A new numerical model of SSV was developed and verified with the field data. This model simulates non-Darcy flow in the aggregate. We demonstrate that non-Darcy effects significantly impact SSV performance. Field data and numerical simulations indicate that increasing the aggregate permeability within the investigated range of 2 x 10{sup -8} m{sup 2} to 3 x 10{sup -7} m{sup 2} substantially improves the extension of the subslab pressure field due to SSV operation. Sealing of cracks in the slab and excavation of a small pit where the SSV pipe penetrates the slab also dramatically improve this pressure field extension. Our findings are consistent with the results of prior field studies; however, the studies reported here have improved our understanding of factors affecting SSV performance. The dependence of SSV performance on the relevant parameters are currently under investigation with the model.
Date: May 1, 1992
Creator: Bonnefous, Y.C.; Gadgil, A.J.; Fisk, W.J.; Prill, R.J. & Nematollahi, A.R.
Partner: UNT Libraries Government Documents Department

Influence of Subslab Aggregate Permeability of SSV Performance

Description: The effectiveness of the technique of subslab ventilation (SSV) for limiting radon entry into basements was investigated through complementary experimentation and numerical modeling. Determination of the impact of subslab aggregate permeability on SSV performance was a primary objective. Subslab pressure fields resulting from SSV were measured in six well-characterized basements, each with a different combination of soil and aggregate permeability. The relationship between air velocity and pressure gradient within the three types of aggregate installed beneath the basement slabs was measured in the laboratory. A new numerical model of SSV was developed and verified with the field data. This model simulates non-Darcy flow in the aggregate. We demonstrate that non-Darcy effects significantly impact SSV performance. Field data and numerical simulations indicate that increasing the aggregate permeability within the investigated range of 2 x 10{sup -8} m{sup 2} to 3 x 10{sup -7} m{sup 2} substantially improves the extension of the subslab pressure field due to SSV operation. Subslab pressure field extension also improves as soil permeability decreases between 10{sup -9} m{sup 2} and 10{sup -10} m{sup 2}. With a slab-wall gap thickness of 1 mm and the range of aggregate permeability investigated, further reductions in soil permeability do not significantly improve the subslab pressure field extension. Sealing of cracks in the slab and excavation of a small pit where the SSV pipe penetrates the slab also dramatically improve this pressure field extension. A large ratio of aggregate permeability to soil permeability reduces the need for large depressurizations at the SSV pit. Our findings are consistent with the results of prior field studies; however, our understanding of SSV is improved and the dependence of SSV performance on the relevant parameters can now be quantified with the model.
Date: September 1, 1991
Creator: Gadgil, A.J.; Bonnefous, Y.C.; Fisk, W.J.; Prill, R.J. & Nematollahi, A.
Partner: UNT Libraries Government Documents Department

Implementation of a Hybrid Controller for Ventilation Control Using Soft Computing

Description: Many industrial facilities utilize pressure control gradients to prevent migration of hazardous species from containment areas to occupied zones, often using Proportional-Integral-Derivative (PID) control systems. When operators rebalance the facility, variation from the desired gradients can occur and the operating conditions can change enough that the PID parameters are no longer adequate to maintain a stable system. As the goal of the ventilation control system is to optimize the pressure gradients and associated flows for the facility, Linear Quadratic Tracking (LQT) is a method that provides a time-based approach to guiding facility interactions. However, LQT methods are susceptible to modeling and measurement errors, and therefore the additional use of Soft Computing methods are proposed for implementation to account for these errors and nonlinearities.
Date: June 1, 2005
Creator: Rieger, Craig G. & Naidu, D. Subbaram
Partner: UNT Libraries Government Documents Department

CONFORMANCE IMPROVEMENT USING GELS

Description: This technical progress report describes work performed from June 20 through December 19, 2001, for the project, ''Conformance Improvement Using Gels''. Interest has increased in some new polymeric products that purport to substantially reduce permeability to water while causing minimum permeability reduction to oil. In view of this interest, we are currently studying BJ's Aqua Con. Results from six corefloods revealed that the Aqua Con gelant consistently reduced permeability to water more than that to oil. However, the magnitude of the disproportionate permeability reduction varied significantly for the various experiments. Thus, as with most materials tested to date, the issue of reproducibility and control of the disproportionate permeability remains to be resolved. Concern exists about the ability of gels to resist washout after placement in fractures. We examined whether a width constriction in the middle of a fracture would cause different gel washout behavior upstream versus downstream of the constriction. Tests were performed using a formed Cr(III)-acetate-HPAM gel in a 48-in.-long fracture with three sections of equal length, but with widths of 0.08-, 0.02-, and 0.08-in., respectively. The pressure gradients during gel extrusion (i.e., placement) were similar in the two 0.08-in.-wide fracture sections, even though they were separated by a 0.02-in.-wide fracture section. The constriction associated with the middle fracture section may have inhibited gel washout during the first pulse of brine injection after gel placement. However, during subsequent phases of brine injection, the constriction did not inhibit washout in the upstream fracture section any more than in the downstream section.
Date: February 28, 2002
Creator: Seright, Randall S.
Partner: UNT Libraries Government Documents Department

Numerical simulation studies of the long-term evolution of a CO2 plume in a saline aquifer with a sloping caprock

Description: We have used the TOUGH2-MP/ECO2N code to perform numerical simulation studies of the long-term behavior of CO{sub 2} stored in an aquifer with a sloping caprock. This problem is of great practical interest, and is very challenging due to the importance of multi-scale processes. We find that the mechanism of plume advance is different from what is seen in a forced immiscible displacement, such as gas injection into a water-saturated medium. Instead of pushing the water forward, the plume advances because the vertical pressure gradients within the plume are smaller than hydrostatic, causing the groundwater column to collapse ahead of the plume tip. Increased resistance to vertical flow of aqueous phase in anisotropic media leads to reduced speed of updip plume advancement. Vertical equilibrium models that ignore effects of vertical flow will overpredict the speed of plume advancement. The CO{sub 2} plume becomes thinner as it advances, yet the speed of advancement remains constant over the entire simulation period of up to 400 years, with migration distances of more than 80 km. Our simulations include dissolution of CO{sub 2} into the aqueous phase and associated density increase, and molecular diffusion. However, no convection develops in the aqueous phase because it is suppressed by the relatively coarse (sub-) horizontal gridding required in a regional-scale model. A first crude sub-grid-scale model was developed to represent convective enhancement of CO{sub 2} dissolution. This process is found to greatly reduce the thickness of the CO{sub 2} plume, but, for the parameters used in our simulations, does not affect the speed of plume advancement.
Date: December 28, 2010
Creator: Pruess, K. & Nordbotten, J.
Partner: UNT Libraries Government Documents Department

Short Term Climatological Wind Data as a Tool for Wind Forecasting

Description: Utilizing short-term climatological wind data can enhance wind speed and wind direction forecasts. An analysis of regional or tower-based wind rose summaries can be useful forecast guides especially when synoptic-scale pressure gradients are weak. Predictive data from multiple models can be plotted against short-term climatological wind data to assess deviations from expected norms and differences between forecast models. Site-specific comparisons between predicted data and observed climatological distributions can provide further insights to the forecaster. These methods can be applied to any location where sufficient climatological data (at least two years) is available.
Date: January 28, 2004
Creator: Parker, MJ
Partner: UNT Libraries Government Documents Department

EFFECT OF PARTICLE SOURCES ON THE STRUCTURE OF THE H-MODE PEDESTAL

Description: Techniques of dimensional analysis have been applied to deuterium and hydrogen plasmas in DIII-D to test the postulate that the edge particle source plays a role in forming the edge H-mode density profile. These experiments show that the pedestal density scale length is typically a factor of two to three larger in hydrogen plasmas than in deuterium plasmas with dimensionally similar ion parameters. These results are in agreement with the postulate [1,2] that the density scale length is primarily determined by the local particle source, rather than by the shape of a hypothetical particle transport barrier. The electron temperature scale length displays a similar trend, albeit with a weaker density dependence. Thus the pedestal pressure gradient scale length is larger in hydrogen. It is also observed that the frequency of a coherent mode, localized within the pedestal, increases with the local density (i.e. inversely with the local density scale length) irrespective of the working gas species. This frequency is a factor of two lower in a hydrogen discharge than in a dimensionally similar deuterium plasma, a result which cannot be explained solely in terms of plasma physics variables.
Date: July 1, 2002
Creator: MAHDAVI, M.A.; R.J.GROEBNER; LEONARD, A.W.; LUCE, T.C.; McKEE, G.R.; MOYER, R.A. et al.
Partner: UNT Libraries Government Documents Department

Flow Regimes of Air-Water Counterflow Through Cross Corrugated Parallel Plates

Description: Heretofore unknown flow regimes of air-water counterflow through a pair of transparent vertical parallel cross corrugated plates were observed via high-speed video. Air flows upward driven by pressure gradient and water, downward driven by gravity. The crimp geometry of the corrugations was drawn from typical corrugated sheets used as filling material in modern structured packed towers. Four regimes were featured, namely, rivulet, bicontinuous, flooding fronts, and flooding waves. It is conceivable that the regimes observed might constitute the basis for understanding how gas and liquid phases contend for available space in the interstices of structured packings in packed towers. Flow regime transitions were expressed in terms of liquid load (liquid superficial velocity) and gas flow factor parameters commonly used in pressure drop and capacity curves. We have carefully examined the range of parameters equivalent to the ill-understood high-liquid-flow operation in packed towers. More importantly, our findings should prove valuable in validating improved first-principles modeling of gas-liquid flows in these industrially important devices.
Date: June 7, 2000
Creator: de Almeida, V.F.
Partner: UNT Libraries Government Documents Department