329 Matching Results

Search Results

Advanced search parameters have been applied.

Pressure distribution over airfoils at high speeds

Description: This report deals with the pressure distribution over airfoils at high speeds, and describes an extension of an investigation of the aerodynamic characteristics of certain airfoils which was presented in NACA Technical Report no. 207. The results presented in report no. 207 have been confirmed and extended to higher speeds through a more extensive and systematic series of tests. Observations were also made of the air flow near the surface of the airfoils, and the large changes in lift coefficients were shown to be associated with a sudden breaking away of the flow from the upper surface. The tests were made on models of 1-inch chord and comparison with the earlier measurements on models of 3-inch chord shows that the sudden change in the lift coefficient is due to compressibility and not to a change in the Reynolds number. The Reynolds number still has a large effect, however, on the drag coefficient. The pressure distribution observations furnish the propeller designer with data on the load distribution at high speeds, and also give a better picture of the air-flow changes.
Date: 1927
Creator: Briggs, L. J. & Dryden, H. L.
Partner: UNT Libraries Government Documents Department

Effects of rocket-armament exhaust gas on the performance of a supersonic-inlet J34-turbojet-engine installation at Mach 2.0

Description: Report presenting an investigation of the effects of rocket-armament-exhaust-gas ingestion on the performance of a supersonic-inlet J34-turbojet-engine installation at Mach 2. Rockets were fired from two different spike positions and with the engine at high or low speed. Results regarding engine air flow, temperature, and flame-out are provided.
Date: February 20, 1956
Creator: Beheim, Milton A. & Evans, Phillip J.
Partner: UNT Libraries Government Documents Department

Effects of a J34 turbojet engine on supersonic diffuser performance

Description: Report presenting testing of a translating cone inlet with a variable bypass at Mach numbers 1.6, 1.8, and 2.0 with both a choked exit plug and a J34 turbojet engine. The main difference between the two options was increased inlet subcritical stability with the engine. Results regarding basic diffuser performance, inlet stability, buzz amplitude and frequency, and diffuser-exit profiles are provided.
Date: January 4, 1956
Creator: Beheim, Milton A. & Englert, Gerald W.
Partner: UNT Libraries Government Documents Department

Using SPARK as a Solver for Modelica

Description: Modelica is an object-oriented acausal modeling language that is well positioned to become a de-facto standard for expressing models of complex physical systems. To simulate a model expressed in Modelica, it needs to be translated into executable code. For generating run-time efficient code, such a translation needs to employ algebraic formula manipulations. As the SPARK solver has been shown to be competitive for generating such code but currently cannot be used with the Modelica language, we report in this paper how SPARK's symbolic and numerical algorithms can be implemented in OpenModelica, an open-source implementation of a Modelica modeling and simulation environment. We also report benchmark results that show that for our air flow network simulation benchmark, the SPARK solver is competitive with Dymola, which is believed to provide the best solver for Modelica.
Date: June 30, 2008
Creator: Wetter, Michael; Wetter, Michael; Haves, Philip; Moshier, Michael A. & Sowell, Edward F.
Partner: UNT Libraries Government Documents Department

Two-dimensional subsonic compressible flows past arbitrary bodies by the variational method

Description: Instead of solving the nonlinear differential equation which governs the compressible flow, an approximate method of solution by means of the variational method is used. The general problem of steady irrotational flow past an arbitrary body is formulated. Two examples were carried out, namely, the flow past a circular cylinder and the flow past a thin curved surface. The variational method yields results of velocity and pressure distributions which compare excellently with those found by existing methods. These results indicate that the variational method will yield good approximate solution for flow past both thick and thin bodies at both high and low Mach numbers.
Date: March 1951
Creator: Wang, Chi-Teh
Partner: UNT Libraries Government Documents Department

The 7 by 10 foot wind tunnel of the National Advisory Committee for Aeronautics

Description: This report presents a description of the 7 by 10 foot wind tunnel and associated apparatus of the National Advisory Committee for Aeronautics. Included also are calibration test results and characteristic test data of both static force tests and autorotation tests made in the tunnel.
Date: 1933
Creator: Harris, Thomas A
Partner: UNT Libraries Government Documents Department

Design of Injectors for Low-Pressure Air Flow

Description: Report issued by the Bureau of Mines discussing the design of low-pressure injectors. As stated in the scope of paper, "this paper purposes to present and discuss methods of designing injectors for low-pressure air flow according to Professor Week's theory, with special reference to their use in mine and tunnel ventilation" (p. 1). This report includes tables, and illustrations.
Date: 1945
Creator: McElroy, G. E.
Partner: UNT Libraries Government Documents Department

Considerations of air flow in combustion chambers of high-speed compression-ignition engines

Description: The air flow in combustion chambers is divided into three fundamental classes - induced, forced, and residual. A generalized resume is given of the present status of air flow investigations and of the work done at this and other laboratories to determine the direction and velocity of air movement in auxiliary and integral combustion chambers. The effects of air flow on engine performance are mentioned to show that although air flow improves the combustion efficiency, considerable induction, friction, and thermal losses must be guarded against.
Date: April 1932
Creator: Spanogle, J. A. & Moore, C. S.
Partner: UNT Libraries Government Documents Department

Filter Media Recommendation Review

Description: The original filter recommended by PNNL for the RASA is somewhat difficult to dissolve and has been discontinued by the manufacturer (3M) because the manufacturing process (substrate blown microfiber, or SBMF) has been superceded by a simpler process (scrim-free blown microfiber, or BMF). Several new potential filters have been evaluated by PNNL and by an independent commercial lab. A superior product has been identified which provides higher trapping efficiency, higher air flow, is easier to dissolve, and is thinner, accommodating more filters per RASA roll. This filter is recommended for all ground-based sampling, and with additional mechanical support, it could be useful for airborne sampling, as well.
Date: January 7, 2002
Creator: Thompson, Robert C.; Miley, Harry S. & Arthur, Richard J.
Partner: UNT Libraries Government Documents Department

EXPERIMENTAL BUBBLE FORMATION IN A LARGE SCALE SYSTEM FOR NEWTONIAN AND NONNEWTONIAN FLUIDS

Description: The complexities of bubble formation in liquids increase as the system size increases, and a photographic study is presented here to provide some insight into the dynamics of bubble formation for large systems. Air was injected at the bottom of a 28 feet tall by 30 inch diameter column. Different fluids were subjected to different air flow rates at different fluid depths. The fluids were water and non-Newtonian, Bingham plastic fluids, which have yield stresses requiring an applied force to initiate movement, or shearing, of the fluid. Tests showed that bubble formation was significantly different in the two types of fluids. In water, a field of bubbles was formed, which consisted of numerous, distributed, 1/4 to 3/8 inch diameter bubbles. In the Bingham fluid, large bubbles of 6 to 12 inches in diameter were formed, which depended on the air flow rate. This paper provides comprehensive photographic results related to bubble formation in these fluids.
Date: June 26, 2008
Creator: Leishear, R & Michael Restivo, M
Partner: UNT Libraries Government Documents Department

Two-Dimensional Irrotational Transonic Flows of a Compressible Fluid

Description: The methods of NACA TN No. 995 have been slightly modified and extended in include flows with circulation by considering the alteration of the singularities of the incompressible solution due to the presence of the hypergeometric functions in the analytic continuation of the solution. It was found that for finite Mach numbers the only case in which the nature of the singularity can remain unchanged is for a ratio of specific heats equal to -1. From a study of two particular flows it seems that the effect of geometry cannot be neglected, and the conventional "pressure-correction" formulas are not valid, even in the subsonic region if the body is thick, especially if there is a supersonic region in the flow.
Date: June 1948
Creator: Kuo, Yung-Huai
Partner: UNT Libraries Government Documents Department

A model for simulating airflow and pollutant dispersion around buildings

Description: A three-dimensional, numerical mode1 for simulating airflow and pollutant dispersion around buildings is described. The model is based on an innovative finite element approach and fully implicit time integration techniques. Linear and nonlinear eddy viscosity/diffusivity submodels are provided for turbulence parameterization. Mode1 predictions for the flow-field and dispersion patterns around a surface-mounted cube are compared with measured data from laboratory experiments.
Date: February 24, 1999
Creator: Chan, S T & Lee, R L
Partner: UNT Libraries Government Documents Department

Characterizing buildings for airflow models: What should we measure?

Description: Airflow models of buildings require dozens to hundreds of parameter values, depending on the complexity of the building and the level of fidelity desired for the model. Values for many of the parameters are usually subject to very large uncertainties (possibly an order of magnitude). Experiments can be used to calibrate or ''tune'' the model: input parameters can be adjusted until predicted quantities match observations. However, experimental time and equipment are always limited and some parameters are hard to measure, so it is generally impractical to perform an exhaustive set of measurements. Consequently, large uncertainties in some parameters typically remain even after tuning the model. We propose a method to help determine which measurements will maximally reduce the uncertainties in those input parameters that have the greatest influence on behavior of interest to researchers. Implications for experimental design are discussed.
Date: June 2004
Creator: Price, P. N.; Chang, S. C. & Sohn, M. D.
Partner: UNT Libraries Government Documents Department

Effect of inlet-air-flow-distortions on steady-state performance of J65-B-3 turbojet engine

Description: The effects of inlet-air-flow distortions on the performance of the J65-B-3 turbojet engine were determined over a range of altitudes from 15,000 to 50,000 feet at a flight Mach number of 0.8. Radial inlet-air-flow distortions apparently do not affect the radial distribution of pressure after the first few compressor stages, while the circumferential inlet-air-flow distortion carried completely through the engine. For the distortions investigated, at rated exhaust-gas temperature and fixed-area exhaust-nozzle operation, the primary effect of the radial inlet-air-flow distortions was to reduce the engine air flow, and the primary effect of the circumferential distortion was to impose a temperature profile on the turbine, both resulting in reduction of thrust.
Date: January 25, 1956
Creator: Smith, Ivan D.; Braithwaite, W. M. & Calvert, Howard F.
Partner: UNT Libraries Government Documents Department

Effects of inlet-flow-air distortion on steady-state altitude performance of an axial-flow turbojet engine

Description: Report presenting the effects of inlet-air-flow distortion on the steady-state performance of a current axial-flow turbojet engine studied in an NACA altitude test chamber at a range of altitudes and simulated Mach number of 0.8. Radial distortions of various shapes up to 22 percent of the average engine-inlet total pressure and circumferential distortions up to 26 percent were imposed. Results regarding propagation through the engine, compressor-interstage performance and stall, effects on component performance, effects on overall engine performance, and effect on compressor blade vibration are provided.
Date: September 27, 1955
Creator: Conrad, E. William; Hanson, Morgan P. & McAulay, John E.
Partner: UNT Libraries Government Documents Department

HAWT performance with dynamic stall

Description: In this report we calculated the effects of flow nonuniformities (wing shear, tower wake, yaw, and large-scale turbulence) on the performance of a horizontal axis wind turbine, accounting for dynamic stall. We modified the PROP program to incorporate and compare these effects with the uniform flow case. The MIT model, which predicts dynamic lift coefficients substantially higher than the static maximum values and includes a crude model of the vortex roll-off phenomenon, represented dynamic stall. As associated model for drag was also used. The dynamic stall model was tested against experimental data for three typical reduced frequencies. Good instantaneous correlation was obtained. The effects of nonuniformities with and without the dynamic stall were calculated using the Westinghouse Mod O and Enertech 44/25 turbines. Modeling the dynamic stall has little effect on performance. Furthermore, the performance with nonuniform flow differed only slightly from the uniform flow case. Thus the now PROP model provides a powerful general capability to handle nonuniform flows.
Date: February 1, 1986
Creator: Hibbs, B.D.
Partner: UNT Libraries Government Documents Department

FINAL REPORT: EDDY-COVARIANCE FLUX TOWER AND TRACER TECHNOLOGY SUPPORT FOR THE UNIVERSITY OF GEORGIA PROPOSAL: FROM TOWER TO PIXEL: INTEGRATION OF PATCH-SIZE NEE USING EXPERIMENTAL MODELING FOOTPRINT ANALYSIS.

Description: Brookhaven National Laboratory has been funded since October of 2000 to provide assistance to the University of Georgia in conducting footprint analyses of individual towers based on meteorology and trace gas measurements. Brookhaven researchers conducted air flow measurements using perfluorocarbon tracers and meteorological instrumentation for three experimental campaigns at an AmeriFlux research site maintained by Dr. Monique Leclerc near Gainesville, FL. In addition, BNL provided assistance with remote data collection and distribution from remote field sites operated by Dr. John Hom of the US Forest Service in the Pine Barrens of New Jersey and at FACE research sites in North Carolina and Wisconsin.
Date: September 1, 2007
Creator: LEWIN,K.F.; NAGY, J. & WATSON, T.B.
Partner: UNT Libraries Government Documents Department

A review of Plutonium (Pu) combustion releases in air for inhalation hazard evaluation.

Description: Experimental data are compiled and reviewed for aerosol particle releases due to combustion in air of Plutonium (Pu). The aerosol release fraction (ARF), which is the mass of Pu aerosolized, divided by the mass of Pu oxidized, is dependent on whether the oxidizing Pu sample is static (i.e. stationary) or dynamic (i.e. falling in air). ARF data are compiled for sample masses ranging from 30 mg to 1770 g, oxidizing temperatures varying from 113 C to {approx}1000 C, and air flow rates varying from 0.05 m/s to 5.25 m/s. The measured ARFs range over five orders of magnitude. The maximum observed static ARF is 2.4 x 10{sup -3}, and this is the recommended ARF for safety studies of static Pu combustion.
Date: September 1, 2003
Creator: McClellan, Yvonne; Murata, Kenneth K. & Gelbard, Fred
Partner: UNT Libraries Government Documents Department

Review of Literature on Terminal Box Control, Occupancy Sensing Technology and Multi-zone Demand Control Ventilation (DCV)

Description: This report presents an overall review of the standard requirement, the terminal box control, occupancy sensing technology and DCV. There is system-specific guidance for single-zone systems, but DCV application guidance for multi-zone variable air volume (VAV) systems is not available. No real-world implementation case studies have been found using the CO2-based DCV. The review results also show that the constant minimum air flow set point causes excessive fan power consumption and potential simultaneous heating and cooling. Occupancy-based control (OBC) is needed for the terminal box in order to achieve deep energy savings. Key to OBC is a technology for sensing the actual occupancy of the zone served in real time. Several technologies show promise, but none currently fully meets the need with adequate accuracy and sufficiently low cost.
Date: March 1, 2012
Creator: Liu, Guopeng; Dasu, Aravind R. & Zhang, Jian
Partner: UNT Libraries Government Documents Department