567 Matching Results

Search Results

Advanced search parameters have been applied.

Alternating-current equipment for the measurement of fluctuations of air speed in turbulent flow

Description: From Summary: "Recent electrical and mechanical improvements have been made in the equipment developed at the National Bureau of Standards for measurement of fluctuations of air speed in turbulent flow. Data useful in the design of similar equipment are presented. The design of rectified alternating-current power supplies for such apparatus is treated briefly, and the effect of the power supplies on the performance of the equipment is discussed."
Date: March 1937
Creator: Mock, W. C., Jr.
Partner: UNT Libraries Government Documents Department

Turbulence-intensity measurements in a jet of air issuing from a long tube

Description: Report presenting data for turbulent-velocity-fluctuation components and mean-velocity distributions measured in the subsonic jet issuing from a pipe in which a fully developed turbulent flow was established. Axial and radial components of the fluctuation velocities were examined as functions of Reynolds number and position in the jet.
Date: May 1951
Creator: Little, Barney H., Jr. & Wilbur, Stafford W.
Partner: UNT Libraries Government Documents Department

Analysis of Turbulent Flow and Heat Transfer on a Flat Plate at High Mach Numbers With Variable Fluid Properties

Description: From Introduction: "In the turbulent case, however, the results of the various analyses disagree markedly because of the different assumptions made by various authors. These analyses are reviewed in references 1 to 3. The analysis is extended to flow and heat transfer in a boundary layer at high Mach numbers in this paper. (Some preliminary results were presented in ref. 11.)"
Date: April 1958
Creator: Deissler, R. G. & Loeffler, A. L., Jr.
Partner: UNT Libraries Government Documents Department

Turbulent Flow Between Rotating Cylinders

Description: "The turbulent air flow between rotating cylinders was investigated. The distributions of mean speed and of turbulence were measured in the gap between a rotating inner and a stationary outer cylinder. The measurements led to the conclusion that the turbulent flow in the gap cannot be considered two dimensional, but that a particular type of secondary motion takes place. It is shown that the experimentally found velocity distribution can be fully understood under the assumption that this secondary motion consists of three-dimensional ring-shape vortices" (p. 1).
Date: March 1943
Creator: Shih-I, Pai
Partner: UNT Libraries Government Documents Department

Effect of Transition in Cross-Sectional Shape on the Development of the Velocity and Pressure Distribution of Turbulent Flow in Pipes

Description: With regard to the change in shape of the cross section while the area remains constant, no investigation results are as yet available. Such an investigation will be the subject of the present paper. For this purpose it is necessary to consider the velocity and pressure relations over each entire cross section so that we are confronted with a three-dimensional problem.
Date: August 1939
Creator: Mayer, Edwin
Partner: UNT Libraries Government Documents Department

Turbulent Flow Through Porous Resistances Slightly Inclined to the Flow Direction

Description: "Analytical and experimental studies have been made of the channel flow of air through porous resistances inclined at an angle of 3.5 degrees to the axis of the channel with the air discharging to the atmosphere. These studies determine the channel wall shape that would yield a uniform discharge through the porous resistance" (p. 1).
Date: February 1958
Creator: Loeffler, Albert L., Jr. & Perlmutter, Morris
Partner: UNT Libraries Government Documents Department

The Microstructure of Turbulent Flow

Description: "In 1941 a general theory of locally isotropic turbulence was proposed by Kolmogoroff which permitted the prediction of a number of laws of turbulent flow for large Reynolds numbers. The most important of these laws, the dependence of the mean square of the difference in velocities at two points on their distance and the dependence of the coefficient of turbulence diffusion on the scale of the phenomenon, were obtained by both Kolmogoroff and Obukhoff in the same year. At the present time these laws have been experimentally confirmed by direct measurements carried out in aerodynamic wind tunnels in the laboratory, in the atmosphere, and also on the ocean" (p. 1).
Date: June 1953
Creator: Obukhoff, A. M. & Yaglom, A. M.
Partner: UNT Libraries Government Documents Department

On Combustion in a Turbulent Flow

Description: "The characteristics introduced by the turbulence in the process of the flame propagation are considered. On the basis of geometrical and dimensional considerations an expression is obtained for the velocity of the flame propagation in a flow of large scale of turbulence" (p. 1).
Date: February 1947
Creator: Shelkin, K. I.
Partner: UNT Libraries Government Documents Department

Analysis of Turbulent Flow and Heat Transfer in Noncircular Passages

Description: From Introduction: "In reference 1, wall temperature distributions for turbulent flow in rectangular and triangular ducts were calculated by using experimental velocity distributions and average heat-transfer coefficients, together with assumed similarity of the wall heat-transfer and wall shear-stress variations; no attempt was made to calculate either the heat-transfer coefficients or the velocity and temperature distributions in the fluid field. Some calculations of velocity and shear-stress distributions in corners are reported in reference 2."
Date: September 1958
Creator: Deissler, Robert G. & Taylor, Maynard F.
Partner: UNT Libraries Government Documents Department

The Turbulent Flow in Diffusers of Small Divergence Angle

Description: "The turbulent flow in a conical diffuser represents the type of turbulent boundary layer with positive longitudinal pressure gradient. In contrast to the boundary layer problem, however, it is not necessary that the pressure distribution along the limits of the boundary layer(along the axis of the diffuser) be given, since this distribution can be obtained from the computation. This circumstance, together with the greater simplicity of the problem as a whole, provides a useful basis for the study of the extension of the results of semiempirical theories to the case of motion with a positive pressure gradient" (p. 1).
Date: October 1947
Creator: Gourzhienko, G. A.
Partner: UNT Libraries Government Documents Department

Analysis of Turbulent Heat Transfer and Flow in the Entrance Regions of Smooth Passages

Description: From Introduction: "Flow and heat transfer in the entrance regions of channels have been subjects of considerable interest. The laminar flow case has been analyzed in references 1 (pp. 299-310), 2, and 3 (pp.451-464), for instance, and the turbulent case, in references 4 and 5."
Date: October 1953
Creator: Deissler, Robert G.
Partner: UNT Libraries Government Documents Department

Analytical and Experimental Investigation of Adiabatic Turbulent Flow in Smooth Tubes

Description: Note presenting equations derived for the prediction of velocity distributions for fully developed adiabtic turbulent flow in smooth tubes; both the incompressible and compressible flow cases were treated. The analysis produced a single equation that represents flow in both the conventional buffer layer and the laminar layer. The results for fully developed flow were correlated by using conventional dimensionless velocity and distance parameters, and agreed closely with those of Nikuradse and other investigators.
Date: July 1950
Creator: Deissler, Robert G.
Partner: UNT Libraries Government Documents Department

Turbulent boundary-layer and skin-friction measurements in axial flow along cylinders at Mach numbers between 0.5 and 3.6

Description: Report presenting experiments that have been conducted to determine average skin-friction coefficients in the absence of heat transfer for completely turbulent flow along the cylindrical portion of cone-cylinder bodies of revolution with several overall fineness ratios. Numerous boundary-layer surveys were made to enable all data to be based on an effective starting position of the turbulent flow. Results regarding tripping devices to insure turbulent flow, effect of nose shape, attainment of equilibrium in the blowdown tunnel, a comparison of data from wind tunnels, effect of pressure gradient, and skin friction values using several different configurations are provided.
Date: March 1954
Creator: Chapman, Dean R. & Kester, Robert H.
Partner: UNT Libraries Government Documents Department

Turbulence and Temperature Fluctuations Behind a Heated Grid

Description: "In the approximately isotropic velocity and temperature fluctuation fields behind a hot grid, measurements were made of fluctuation levels and of various double and triple correlation functions. The double and triple correlation coefficient functions are of roughly the same spatial extent for the vector and scalar fields. As anticipated from theoretical considerations, the temperature fluctuations die out more slowly than does the turbulence" (p. 1).
Date: August 1958
Creator: Mills, R. R., Jr.; Kistler, A. L.; O'Brien, V. & Corrsin, S.
Partner: UNT Libraries Government Documents Department

Measurement and Analysis of Turbulent Flow Containing Periodic Flow Fluctuations

Description: Memorandum presenting techniques for the measurement of the energy spectrum of flow fluctuations in both axial and lateral flow directions. A simple spectrum analysis is presented by which quantitative distinction may be made between turbulence and the flow disturbances associated with sound waves in ducts. Results regarding the measurement and analysis of turbulent-flow fields containing random and periodic flow fluctuations, effect of random sound disturbances on turbulence spectrum, and effect of combustion on combustor approach-stream spectrum are provided.
Date: August 19, 1953
Creator: Mickelsen, William R. & Laurence, James C.
Partner: UNT Libraries Government Documents Department

Laws of Flow in Rough Pipes

Description: An experimental investigation is made of the turbulent flow of water in pipes with various degrees of relative roughness. The pipes range in size from 25 to 100 millimeters in diameter and from 1800 to 7050 millimeters in length. Flow velocities permitted Reynolds numbers from about 10 (sup. 4) to 10 (sup. 6). The laws of resistance and velocity distributions were obtained as a function of relative roughness and Reynolds number. Mixing length, as described by Prandtl's mixing-length formula, is discussed in relation to the experimental results.
Date: November 1950
Creator: Nikuradse, J.
Partner: UNT Libraries Government Documents Department

Effect of Reynolds Number in Turbulent-Flow Range on Flame Speeds of Bunsen Burner Flames

Description: "The effect of flow conditions on the geometry of the turbulent Bunsen flame was investigated. Turbulent flame speed is defined in terms of flame geometry and data are presented showing the effect of Reynolds number of flow in the range of 3000 to 35,000 on flame speed for burner diameters from 1/4 to 1 1/8 inches and three fuels -- acetylene, ethylene, and propane. The normal flame speed of an explosive mixture was shown to be an important factor in determining its turbulent flame speed, and it was deduced from the data that turbulent flame speed is a function of both the Reynolds number of the turbulent flow in the burner tube and of the tube diameter" (p. 1).
Date: 1949
Creator: Bollinger, Lowell M. & Williams, David T.
Partner: UNT Libraries Government Documents Department

Dynamic Multiscale Averaging (DMA) of Turbulent Flow

Description: A new approach called dynamic multiscale averaging (DMA) for computing the effects of turbulent flow is described. The new method encompasses multiple applications of temporal and spatial averaging, that is, multiscale operations. Initially, a direct numerical simulation (DNS) is performed for a relatively short time; it is envisioned that this short time should be long enough to capture several fluctuating time periods of the smallest scales. The flow field variables are subject to running time averaging during the DNS. After the relatively short time, the time-averaged variables are volume averaged onto a coarser grid. Both time and volume averaging of the describing equations generate correlations in the averaged equations. These correlations are computed from the flow field and added as source terms to the computation on the next coarser mesh. They represent coupling between the two adjacent scales. Since they are computed directly from first principles, there is no modeling involved. However, there is approximation involved in the coupling correlations as the flow field has been computed for only a relatively short time. After the time and spatial averaging operations are applied at a given stage, new computations are performed on the next coarser mesh using a larger time step. The process continues until the coarsest scale needed is reached. New correlations are created for each averaging procedure. The number of averaging operations needed is expected to be problem dependent. The new DMA approach is applied to a relatively low Reynolds number flow in a square duct segment. Time-averaged stream-wise velocity and vorticity contours from the DMA approach appear to be very similar to a full DNS for a similar flow reported in the literature. Expected symmetry for the final results is produced for the DMA method. The results obtained indicate that DMA holds significant potential in being able to ...
Date: September 1, 2012
Creator: Johnson, Richard W.
Partner: UNT Libraries Government Documents Department


Description: Experimental data and theoretical calculations are presented for the mass-transfer rate to rotating disks and rotating rings when laminar, transition, and fully developed turbulent flow exist upon different portions of the surface. Good agreement of data and the model is obtained for rotating disks and relatively thick rotating rings. Results of the calculations for thin rings generally exceed the experimental data measured in transition and turbulent flow. A y{sup +{sup 3}} form for the eddy diffusivity is used to fit the data. No improvement is noticed with a form involving both y{sup +{sup 3}} and y{sup +{sup 3}}.
Date: July 1, 1980
Creator: Law Jr., C.G.; Pierini, P. & Newman, J.
Partner: UNT Libraries Government Documents Department

Buoyancy-generated variable-density turbulence

Description: Both a one-point (engineering) and a two-point (spectral) model are tested against numerical data. Deficiencies in these variable-density models are disucssed and modifications are suggested. Attention is restricted to turbulent interactions of two miscible, incompressible Newtonian fluids of different densities. Departures from the limits of validity of the Boussinesq approximation are examined. Results of the buoyancy-generated turbulence are compared with variable-density model predictions. 3 figs, 6 refs.
Date: June 1, 1996
Creator: Sandoval, D.L.; Clark, T.T. & Riley, J.J.
Partner: UNT Libraries Government Documents Department

A PIV Methodology for High-Resolution Measurement of Flow Statistics

Description: Particle-image velocimetry (PIV) is a flow-diagnostic technique that provides velocity fields from a comparison of images of particulate-laden flow. We have developed a PIV processing methodology that extracts measurements of the particle-displacement histogram from a flow video or ensemble of flow-image pairs. Single-pixel measurement of mean velocity can be obtained from an ensemble of {Omicron}10{sup 3} images. Measurements of higher-order moments of the velocity histogram require spatial averaging (i.e., lower spatial resolution), larger ensembles of images, or a combination of the two. We present single-pixel-resolution PIV measurements of a steady microflow and high-resolution measurements of the velocity histogram of a stationary turbulent flow. This methodology has applications in quantifying velocity statistics in other stochastic flows, e.g., bulk and near-wall boiling.
Date: November 5, 2000
Creator: Cummings, Eric B.; Schefer, Robert W. & Chung, Jacob N.
Partner: UNT Libraries Government Documents Department

Self-Consistent Multiscale Theory of Internal Wave, Mean-Flow Interactions

Description: This is the final report of a three-year, Laboratory Directed Research and Development (LDRD) project at Los Alamos National Laboratory (LANL). The research reported here produced new effective ways to solve multiscale problems in nonlinear fluid dynamics, such as turbulent flow and global ocean circulation. This was accomplished by first developing new methods for averaging over random or rapidly varying phases in nonlinear systems at multiple scales. We then used these methods to derive new equations for analyzing the mean behavior of fluctuation processes coupled self consistently to nonlinear fluid dynamics. This project extends a technology base relevant to a variety of multiscale problems in fluid dynamics of interest to the Laboratory and applies this technology to those problems. The project's theoretical and mathematical developments also help advance our understanding of the scientific principles underlying the control of complex behavior in fluid dynamical systems with strong spatial and temporal internal variability.
Date: June 3, 1999
Creator: Holm, D.D.; Aceves, A.; Allen, J.S.; Alber, M.; Camassa, R.; Cendra, H. et al.
Partner: UNT Libraries Government Documents Department

Effect of equivalence ratio on premixed flame response to unsteady strain-rate and curvature

Description: The detailed dynamical response of flames in turbulent reacting flow involves a complex interaction between unsteady flow structures and flame chemistry. Two essential features of this interaction are the unsteady strain-rate and curvature disturbances to the reaction zone. In this work, the authors focus on a single flow length/time scale feature in two dimensions (2D), and its effect on a premixed flame for a range of mixture conditions. In particular, they study the interaction of a premixed freely propagating methane-air flame with a 2D counter-rotating vortex pair in an unbounded domain. In earlier work, they studied this flow using C{sub 1} kinetics, at stoichiometric conditions. Notable observations include the shift of the reaction zone into the products on the vortex-pair centerline, leading to depletion of H, O and OH, and the consequent general drop in reaction rates on the centerline flame segment. Curvature-induced focusing/defocusing effects were observed at the positively curved flame cusp, leading to modifications in internal transport fluxes of various species and radicals in the flame, and associated effects on H production and fuel consumption rates. These results were extended to more detailed kinetics, using other C{sub 1} and C{sub 2} mechanisms, which demonstrated the effect of choice of chemical mechanism on the observed transient flame response. The present study focuses on the dependence of the transient flame response on reactants mixture equivalence ratio. Two reactants mixture conditions are studied: case 1 is a stoichiometric conditions - equivalence ratio {Phi} = 1.0, and case 2 is rich at {Phi} = 1.2. In both cases, the reactants are 20% N{sub 2}-diluted.
Date: November 1, 1997
Creator: Najm, H.N.; Wyckoff, P.S. & Knio, O.M.
Partner: UNT Libraries Government Documents Department

Cap Bubble Drift Velocity in a Confined Test Section

Description: In the two-group interfacial area transport equation, bubbles are categorized into two groups, i.e., spherical/distorted bubbles as group 1 and cap/slug/churn-turbulent bubbles as group 2. The bubble rise velocities for both groups of bubbles may be estimated by the drift flux model by applying different distribution parameters and drift velocities for both groups. However, the drift velocity for group 2 bubbles is not always applicable (when the wall effect becomes important) as in the current test loop of interest where the flow channel is confined by two parallel flat walls, with a dimension of 200-mm in width and 10-mm in gap. The previous experiments indicated that no stable slug flow existed in this test section, which was designed to permit visualization of the flow patterns and bubble characteristics without the distortion associated with curved surfaces. In fact, distorted cap bubbly and churn-turbulent flow was observed. Therefore, it is essential to developed a correlation for cap bubble drift velocity in this confined flow channel. Since the rise velocity of a cap bubble depends on its size, a high-speed movie camera is used to capture images of cap bubbles to obtain the bubble size information. Meanwhile, the rise velocity of cap and elongated bubbles (called cap bubbles hereafter) is investigated by examining the captured images frame by frame. As a result, the conventional correlation of drift velocity for slug bubbles is modified and acceptable agreements between the measurements and correlation estimation are achieved.
Date: October 9, 2002
Creator: Sun, Xiaodong; Kim, Seungjin; Ishii, Mamoru; Lincoln, Frank W. & Beus, Stephen G.
Partner: UNT Libraries Government Documents Department