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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

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

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

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

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

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

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

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

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

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

Pressure Fluctuations as a Disgnostic Tool for Fluidized Beds.

Description: The validity of using bubbling fluidized bed (BFB) similitude parameters to match a hot BFB to a cold BFB is being studied. Sand in a BFB combustor and copper powder in cold BFB model have been analyzed and found to be out of similitude. In the analysis process, it was determined that the condition of the screen covering the pressure tap affects the quality of pressure data recorded. In addition, distributor plate design and condition will affect the hydrodynamics of the bed. Additional tests are planned to evaluate the validity of similitude concepts in BFB.
Date: October 28, 1997
Creator: Brown, R. C. & Schroeder, J. R.
Partner: UNT Libraries Government Documents Department

Ballooning mode stability for self-consistent pressure and current profiles at the H-mode edge

Description: The edge pressure gradient (H-mode pedestal) for computed equilibria in which the current density profile is consistent with the bootstrap current may not be limited by the first regime ballooning limit. The transition to second stability is easier for: higher elongation, intermediate triangularity, larger ratio, pedestal at larger radius, narrower pedestal width, higher q{sub 95}, and lower collisionality.
Date: November 1, 1997
Creator: Miller, R.L.; Lin-Liu, Y.R.; Osborne, T.H. & Taylor, T.S.
Partner: UNT Libraries Government Documents Department

Poloidal pressure gradients, divertor detachment and marfes

Description: Because the radiation power density from a marfe scales approximately as the square of its plasma pressure, and since increased radiation would aid divertor detachment for high power tokamaks, this paper identifies regions that might permit locally increased plasma pressure in steady state. The magnetic and dynamic (flow) constraints of magneto-hydrodynamics (MHD) are examined for self-consistent locally increased pressure equilibria, in both the magnetically open tokamak scrape-off layer (SOL) and the closed surfaces just inside the last closed flux surface. In most tokamak geometries it is difficult to recycle particles at a sufficient rate to sustain high pressure marfes, but they might be possible near a divertor X-point.
Date: November 1, 1997
Creator: Schaffer, M.J.
Partner: UNT Libraries Government Documents Department

ATR confinement leakage determination

Description: The air leakage rate from the Advanced Test Reactor (ATR) confinement is an important parameter in estimating hypothesized accidental releases of radiation to the environment. The leakage rate must be determined periodically to assure that the confinement has not degraded with time and such determination is one of the technical safety requirements of ATR operation. This paper reviews the methods of confinement leakage determination and presents an analysis of leakage determination under windy conditions, which can complicate the interpretation of the determined leakage rates. The paper also presents results of analyses of building air exchange under windy conditions. High wind can enhance air exchange and this could increase the release rates of radioisotopes following an accident.
Date: June 1, 1998
Creator: Kuan, P. & Buescher, B. J.
Partner: UNT Libraries Government Documents Department

Gradient elution in capillary electrochromatography

Description: In analogy to pressure-driven gradient techniques in high-performance liquid chromatography, a system has been developed for delivering electroosmotically-driven solvent gradients for capillary electrochromatography (CEC). Dynamic gradients with sub-mL/min flow rates are generated by merging two electroosmotic flows that are regulated by computer-controlled voltages. These flows are delivered by two fused-silica capillary arms attached to a T-connector, where they mix and then flow into a capillary column that has been electrokinetically packed with 3-mm reversed-phase particles. The inlet of one capillary arm is placed in a solution reservoir containing one mobile phase and the inlet of the other is placed in a second reservoir containing a second mobile phase. Two independent computer-controlled programmable high-voltage power supplies (0-50 kV)--one providing an increasing ramp and the other providing a decreasing ramp--are used to apply variable high-voltage potentials to the mobile phase reservoirs to regulate the electroosmotic flow in each arm. The ratio of the electroosmotic flow rates between the two arms is changed with time according to the computer-controlled voltages to deliver the required gradient profile to the separation column. Experiments were performed to confirm the composition of the mobile phase during a gradient run and to determine the change of the composition in response to the programmed voltage profile. To demonstrate the performance of electroosmotically-driven gradient elution in CEC, a mixture of 16 polycyclic aromatic hydrocarbons (PAHs) was separated in less than 90 minutes. This gradient technique is expected to be well-suited for generating not only solvent gradients in CEC, but also other types of gradients such as pH- and ionic-strength gradients in capillary electrokinetic separations and analyses.
Date: August 1, 1997
Creator: Anex, D.; Rakestraw, D.J.; Yan, Chao; Dadoo, R. & Zare, R.N.
Partner: UNT Libraries Government Documents Department

Magnetohydodynamics stability of compact stellarators

Description: Recent stability results of external kink modes and vertical modes in compact stellarators are presented. The vertical mode is found to be stabilized by externally generated poloidal flux. A simple stability criterion is derived in the limit of large aspect ratio and constant current density. For a wall at infinite distance from the plasma, the amount of external flux needed for stabilization is given by Fi = (k2 {minus} k)=(k2 + 1), where k is the axisymmetric elongation and Fi is the fraction of the external rotational transform. A systematic parameter study shows that the external kink mode in QAS can be stabilized at high beta ({approximately} 5%) without a conducting wall by magnetic shear via 3D shaping. It is found that external kinks are driven by both parallel current and pressure gradient. The pressure contributes significantly to the overall drive through the curvature term and the Pfirsch-Schluter current.
Date: January 3, 2000
Creator: Fu, G.Y.; Ku, L.P.; Cooper, W.A. & Hirshman, S.H.
Partner: UNT Libraries Government Documents Department

Laboratory Simulation of Response to a Distributed Pressure Load

Description: Responses to a distributed pressure load are typically predicted through the use of a finite-element model. This procedure depends on the model to represent the actual structure accurately. Another technique that is developed in this work is to predict the response based upon an experi- mentally derived model. This model consists of frequency response functions. The pressure distribution is assumed to be known. In this work, the pressure load will be a blast load. The focus of this work will be to simulate a harsh, shock-like environment. Data from a reverse Hopkinson bar (RHB) test is used to generate the response to a symmetric, distributed load. The reverse Hopkinson bar generates a high ampli- tude, high frequency content pulse that excites components at near-blast levels. The frequency response functions gen- erated from the RHB are used to generate an experimental model of the structure, which is then used in conjunction with the known pressure distribution, to estimate the component response to a blast. This result can then be used with a model correlation technique to adjust a finite element model such that data from a true blast test can be used to only fine tune the model. This work details the estimation response due to the blast.
Date: October 21, 1998
Creator: Mayes, R. & Simmermacher, T.
Partner: UNT Libraries Government Documents Department

Mechanistic Studies of Improved Foam EOR Processes

Description: The objective of this research is to widen the application of foam to enhanced oil recovery (EOR) by investigating fundamental mechanisms of foams in porous media. This research will lay the groundwork for more applied research on foams for improved sweep efficiency in miscible gas, steam and surfactant-based EOR. Task 1 investigates the pore-scale interactions between foam bubbles and polymer molecules. Task 2 examines the mechanisms of gas trapping, and interaction between gas trapping and foam effectiveness. Task 3 investigates mechanisms of foam generation in porous media. The most significant progress during this period was made on Tasks 1 and 3. Research on Task 1 focused on selecting and characterizing a surfactant/polymer formulation for initial experiments. The two (high-quality and low-quality) strong-foam regimes were identified from steady-state coreflood data for the formulation without polymer, for comparison with behavior with polymer. This formulation showed unconventional behavior in the low-quality regime in that pressure gradient decreases at increasing liquid injection rate. Such behavior was not seen in most previous studies of foam, but it is consistent with dense-CO{sub 2} foam data recently obtained in our laboratory. We are considering the significance of the unconventional trend in the data and proceeding with initial experiments with polymer. Research on Task 3 focused on foam generation at limited pressure gradient in sandpacks. In these experiments liquid injection rate and pressure drop across the core are held fixed, and gas injection rate responds to creation and properties of foam. Initial experiments included three permeabilities (1.2, 3.6 and 5 darcy), three surfactant concentrations (0.12, 1.2 and 2.4 wt%) and two liquid injection rates (1.29 and 2.76 ft/day). Separating experimental artifacts from physical phenomena in these experiments is difficult and an ongoing process.
Date: March 31, 2003
Creator: Rossen, William R.
Partner: UNT Libraries Government Documents Department

Process System Hydraulics

Description: An analysis of hydraulic characteristics of the reactor plenum and the geometry of the permanent tube slots indicates the effect of the plenum pressure gradient on flow is substantially less than has been used previously to determine process water flows from cumulative fuel assembly resistances. This report details results of that study.
Date: August 9, 2002
Creator: Bland, C.A.
Partner: UNT Libraries Government Documents Department