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Component and over-all performance evaluation of an axial-flow turbojet engine over a range of engine-inlet Reynolds numbers

Description: Report presenting an investigation in an altitude test chamber to evaluate the performance of an axial-flow turbojet engine over a range of engine-inlet Reynolds numbers. Reducing the engine inlet Reynolds number resulted in a reduction of corrected air flow and compressor efficiency but did not affect the compressor pressure ratio at a given corrected engine speed.
Date: July 10, 1952
Creator: Walker, Curtis L.; Huntley, S. C. & Braithwaite, W. M.
Partner: UNT Libraries Government Documents Department

The effects of Reynolds number at Mach numbers up to 0.94 on the loading on a 35 degree swept-back wing having NACA 65(1)A012 streamwise sections

Description: Report presenting an investigation of the effects of a variation of Reynolds number on the forces, moments, and surface pressures on a semispan model of a wing with 35 degrees of sweepback, an aspect ratio of 5, a taper ratio of 0.7, and the NACA 65(sub 1)A012 section in planes parallel to the plane of symmetry.
Date: June 16, 1952
Creator: Tinling, Bruce E. & Lopez, Armando E.
Partner: UNT Libraries Government Documents Department

Investigation of Reynolds number effects for a series of cone-cylinder bodies at Mach numbers of 1.62, 1.93, and 2.41

Description: From Summary: "An investigation of the Reynolds number for transition and the skin-friction drag at zero lift of eight cone-cylinder bodies having various fineness ratios has been made at Mach numbers of 1.62, 1.93, and 2.41 over a Reynolds number range from 0.3 x 10(exp 6) to 10 x 10(exp 6). The accuracy of the skin-friction data was not sufficient to permit any general conclusions to be drawn. The Reynolds number for transition was found to be dependent upon both the tunnel stagnation pressure and Mach number."
Date: October 7, 1953
Creator: Grigsby, Carl E. & Ogburn, Edmund L.
Partner: UNT Libraries Government Documents Department

Tests of a model horizontal tail of aspect ratio 4.5 in the Ames 12-foot pressure wind tunnel I : quarter-chord line swept back 35 degrees

Description: Report presenting wind-tunnel tests that have been conducted to evaluate the independent effects of Reynolds and Mach numbers on the aerodynamic characteristics of a horizontal tail of aspect ratio 4.5 with a plain sealed elevator with a tab. Lift, drag, pitching moment, elevator hinge moment, tab hinge moment, streamwise distribution of static pressure at the midsemispan, and pressure difference across the elevator-nose seal were measured.
Date: September 9, 1949
Creator: Tinling, Bruce E. & Dickson, Jerald K.
Partner: UNT Libraries Government Documents Department

Experimental Pressure Distributions and Force Coefficients on Block Forms for Varying Mach Number, Reynolds Number, and Yaw Angle

Description: Abstact: "Wind tunnel tests were performed to determine pressure distributions and normal force coefficients on three block forms on mounting planes. The dimension ratios of the blocks were 1:1:1, 1:1:2, and 1:1:4. Results are given for variation in Mach number from 0.066 to 0.8, in Reynolds number from 0.28 x 10(exp 6) to 4 x 10(exp 6), and in yaw angle from 0 to 90 degrees. Results show a Reynolds number independence over the range examined. Windward face force coefficients for a given block form are approximately proportional to the ratio of impact to dynamic pressure. Pressure distribution and resultant coefficients are affected by mounting planes."
Date: January 1959
Creator: Hankins, Dorris M.
Partner: UNT Libraries Government Documents Department

Friction Factor Measurements in an Equally Spaced Triangular Tube Array

Description: Friction factor data for adiabatic cross-flow of water in a staggered tube array was obtained over a Reynolds number range (based on hydraulic diameter and gap velocity) of about 10,000 to 250,000. The tubes were 12.7mm (0.5 inch) outer diameter, in a uniformly spaced triangular arrangement with a pitch-to-diameter ratio of 1.5. The friction factor was compared to several literature correlations, and was found to be best matched by the Idelchik correlation. Other correlations were found to vary significantly from the test data. Based on the test data, a new correlation is proposed for this tube bundle geometry which covers the entire Reynolds number range tested.
Date: March 19, 2007
Creator: Vassallo P, Symolon P
Partner: UNT Libraries Government Documents Department

Synthetic jets at large Reynolds number and comparison to continuous jets

Description: Experimental measurements and flow visualization of synthetic jets and similar continuous jets are described. The dimensionless stroke length necessary to form a 2-D synthetic jet is between 5 and 10, with wider-nozzle jets consistently requiring a smaller value. Synthetic jets are wider, slower and have more momentum than similar continuous jets. Synthetic jets are generated using four nozzle widths that vary by a factor of four, and the driving frequency is varied over an order of magnitude. The resultant jets are in the range 13.5 < L{sub o}/h < 80.8 and 695 < Re{sub Uo} < 14700. In spite of the large range of stroke lengths, the near-field behavior of the synthetic jets scales with L{sub o}/h.
Date: January 1, 2001
Creator: Smith, B. L. (Barton L.) & Swift, G. W. (Gregory W.)
Partner: UNT Libraries Government Documents Department

Aerodynamic study of a wing-fuselage combination employing a wing swept back 63 degrees : characteristics throughout the subsonic speed range with the wing cambered and twisted for a uniform load at a lift coefficient of 0.25

Description: Report presenting wind-tunnel testing to determine the independent effects of Mach and Reynolds numbers on the aerodynamic characteristics of a wing-fuselage combination with a wing with the leading edge swept back 63 degrees and with camber and twist. Results regarding the fuselage alone and the effects of camber and twist are also provided.
Date: August 15, 1949
Creator: Jones, J. Lloyd & Demele, Fred A.
Partner: UNT Libraries Government Documents Department

Large-eddy simulation of very large kinetic and magnetic Reynolds number isotropic magnetohydrodynamic turbulence using a spectral subgrid model

Description: A spectral subggrid-scale eddy viscosity and magnetic resisitivity model based on the eddy-damped quasi-normal Markovian (EDQNM) spectral kinetic and magnetic energy transfer presented in [12] is used in large-eddy simulation (LES) of large kinetic and magnetic Reynold number magneto-hydrodynamic (MHD) turbulence. The proposed model is assessed via a posteri tests on three-dimensional, incompressible, isotropic, non-helical, freely-decaying MHD turbulence at asymptotically large Reynolds numbers. Using LES with an initial condition characterized by an Alfv{acute e}n ratio of kinetic to magnetic energy {tau}{sub A} equal to unity, it is shown that at the kinetic energy spectrum E{sub K}(k) and magnetic energy spectrum E{sub M}(k) exhibit Kolmogorov -5/3 inertial subrange scalings in the LES, consistent with the EDQNM model.
Date: July 5, 2006
Creator: Gomez, T; Sagaut, P; Schilling, O & Zhou, Y
Partner: UNT Libraries Government Documents Department

Implications of turbulence interactions: A path toward addressing very high Reynolds number flows

Description: The classical 'turbulence problem' is narrowed down and redefined for scientific and engineering applications. From an application perspective, accurate computation of large-scale transport of the turbulent flows is needed. In this paper, a scaling analysis that allows for the large-scales of very high Reynolds number turbulent flows - to be handled by the available supercomputers is proposed. Current understanding of turbulence interactions of incompressible turbulence, which forms the foundation of our argument, is reviewed. Furthermore, the data redundancy in the inertial range is demonstrated. Two distinctive interactions, namely, the distance and near-grid interactions, are inspected for large-scale simulations. The distant interactions in the subgrid scales in an inertial range can be effectively modelled by an eddy damping. The near-grid interactions must be carefully incorporated.
Date: May 15, 2006
Creator: Zhou, Y
Partner: UNT Libraries Government Documents Department

Implicit turbulence modeling for high reynolds number flows.

Description: We continue our investigation of the implicit turbulence modeling property of the nonoscillatory finite volume scheme MPDATA. We start by comparing MPDATA simulations of decaying turbulence in a triply periodic cube with analogous pseudospectral studies. In the regime of direct numerical simulation, MPDATA is shown to agree closely with the pseudospectral model. As viscosity is reduced, the two model results diverge. We study the MPDATA results in the inviscid limit, using a combination of mathematical analysis and computational experiment. We validate the inviscid MPDATA results as representing the turbulent flow in the limit of very high Reynolds number.
Date: January 1, 2001
Creator: Margolin, L. G.; Smolarkiewicz, P. K. (Piotr K.) & Wyszogrodzki, A. A. (Andrzej A.)
Partner: UNT Libraries Government Documents Department

A preliminary investigation of Large Eddy Simulation (LES) of the flow around a cylinder at ReD = 3900 using a commercial CFD code

Description: Engineering fluid mechanics simulations at high Reynolds numbers have traditionally been performed using the Reynolds-Averaged Navier Stokes (RANS) equations and a turbulence model. The RANS methodology has well-documented shortcomings in the modeling of separated or bluff body wake flows that are characterized by unsteady vortex shedding. The resulting turbulence statistics are strongly influenced by the detailed structure and dynamics of the large eddies, which are poorly captured using RANS models (Rodi 1997; Krishnan et al. 2004). The Large Eddy Simulation (LES) methodology offers the potential to more accurately simulate these flows as it resolves the large-scale unsteady motions and entails modeling of only the smallest-scale turbulence structures. Commercial computational fluid dynamics products are beginning to offer LES capability, allowing practicing engineers an opportunity to apply this turbulence modeling technique to much wider array of problems than in dedicated research codes. Here, we present a preliminary evaluation of the LES capability in the commercial CFD solver StarCD by simulating the flow around a cylinder at a Reynolds number based on the cylinder diameter, D, of 3900 using the constant coefficient Smagorinsky LES model. The results are compared to both the experimental and computational results provided in Kravchenko & Moin (2000). We find that StarCD provides predictions of lift and drag coefficients that are within 15% of the experimental values. Reasonable agreement is obtained between the time-averaged velocity statistics and the published data. The differences in these metrics may be due to the use of a truncated domain in the spanwise direction and the short time-averaging period used for the statistics presented here. The instantaneous flow field visualizations show a coarser, larger-scale structure than the study of Kravchenko & Moin (2000), which may be a product of the LES implementation or of the domain and resolution used. Based on this preliminary study, ...
Date: February 14, 2006
Creator: Paschkewitz, J S
Partner: UNT Libraries Government Documents Department

PIV Experiments to Measure Flow Phenomena in a Scaled Model of a VHTR Lower Plenum

Description: A report of experimental data collected at the Matched-Index-of-Refraction (MIR) Laboratory in support of contract DE-AC07-05ID14517 and the INL Standard Problem on measurements of flow phenomena occurring in a lower plenum of a typical prismatic VHTR concept reactor to assess CFD code is presented. Background on the experimental setup and procedures is provided along with several samples of data obtained from the 3-D PIV system and an assessment of experimental uncertainty is provided. Data collected in this study include 3-dimensional velocity-field descriptions of the flow in all four inlet jets and the entire lower plenum with inlet jet Reynolds numbers (ReJet) of approximately 4300 and 12,400. These investigations have generated over 2 terabytes of data that has been processed to describe the various velocity components in formats suitable for external release and archived on removable hard disks. The processed data from both experimental studies are available in multi-column text format.
Date: September 1, 2006
Creator: Hugh M. McIlroy, Jr.; McEligot, Donald M.; Schultz, Richard R.; Christensen, Daniel; Pink, Robert J. & Johnson, Ryan C.
Partner: UNT Libraries Government Documents Department

Research proposal for development of an electron stripper using a thin liquid lithium film for rare isotope accelerator.

Description: Hydrodynamic instability phenomena in a thin liquid lithium film, which has been proposed for the first stripper in the driver linac of Rare Isotope Accelerator (RIA), were discussed. Since it was considered that film instability could significantly impair the feasibility of the liquid lithium film stripper concept, potential issues and research tasks in the RIA project due to these instability phenomena were raised. In order to investigate these instability phenomena, a research proposal plan was developed. In the theoretical part of this research proposal, a use of the linear stability theory was suggested. In the experimental part, it was pointed out that the concept of Reynolds number and Weber number scaling may allow conducting a preliminary experiment using inert simulants, hence reducing technical difficulty, complexity, and cost of the experiments. After confirming the thin film formation in the preliminary experiment using simulants, demonstration experiments using liquid lithium were proposed.
Date: March 6, 2006
Creator: Momozaki, Y.
Partner: UNT Libraries Government Documents Department

A comparison of dispersion calculations in bluff body wakes using LES and unsteady RANS

Description: Accurate modeling of the dispersion behavior of sprays or particles is critical for a variety of problems including combustion, urban pollution or release events, and splash and spray transport around heavy vehicles. Bluff body wakes are particularly challenging since these flows are both highly separated and strongly unsteady. Attempting to model the dispersion of droplets or particles interacting with bluff body wakes is even more difficult since small differences in the flow field encountered by particles can lead to large differences in the dispersion behavior. Particles with finite inertia can exhibit additional complicating effects such as preferential concentration. In this preliminary study, we consider the dispersion of solid particles in the wake of a rectangular plane at a Reynolds number (Re) of 10000 and that of droplets in the wake of a simplified tractor-trailer geometry at Re = 2 x 10{sup 6} using both the Large Eddy Simulation (LES) and Unsteady Reynolds-Averaged Navier-Stokes (URANS) turbulence modeling approaches. The calculations were performed using identical meshes for both the LES and URANS models. Particle stresses are not backcoupled to the carrier fluid velocity solution. In the case of the rectangular plane wake, the LES calculation predicts a finer-scale and more persistent wake structure than the URANS one; the resulting particle dispersion is considerably ({approx} 40%) underpredicted for low inertia particles. For the case of the simplified tractor-trailer geometry, although the LES is underresolved, similar trends are observed with strong differences in the vertical and horizontal dispersion of the smallest particles. These results suggest that it may be necessary to use LES to accurately capture the dispersion behavior of small, low inertia particles or droplets, but that URANS may be sufficient for problems in which only large particles with substantial inertia are of primary concern.
Date: January 19, 2006
Creator: Paschkewitz, J S
Partner: UNT Libraries Government Documents Department

Verification Test Suite (VERTS) For Rail Gun Applications using ALE3D: 2-D Hydrodynamics & Thermal Cases

Description: A verification test suite has been assessed with primary focus on low reynolds number flow of liquid metals. This is representative of the interface between the armature and rail in gun applications. The computational multiphysics framework, ALE3D, is used. The main objective of the current study is to provide guidance and gain confidence in the results obtained with ALE3D. A verification test suite based on 2-D cases is proposed and includes the lid-driven cavity and the Couette flow are investigated. The hydro and thermal fields are assumed to be steady and laminar in nature. Results are compared with analytical solutions and previously published data. Mesh resolution studies are performed along with various models for the equation of state.
Date: April 17, 2008
Creator: Najjar, F M; Solberg, J & White, D
Partner: UNT Libraries Government Documents Department

Statistics of particle concentration in free-surface turbulence

Description: Particles on the surface of an incompressible fluid maintained in a turbulent steady-state cluster into spatio-temporally complex flow structures. We experimentally study the statistics of particle concentration n(r, t) over various coarse-grained scales r' in the inertial range. Another control parameter is the Taylor Microscale Reynolds number Re{sub {lambda}}. The focus is on the steady state probability density function {Pi}(n{sub r}). Attention is also given to the variance {sigma}{sup 2}(r, t) of this PDF, since it yields information about the topology of the coagulated structures. Where possible, the results are compared and contrasted with those obtained in a recent analytical and numerical study of two-dimensional synthetic turbulence by Ducasse and Pumir. There, but not here, the dimensionless compressibility C is an important control parameter.
Date: January 1, 2009
Creator: Bandi, Mahesh M; Larkin, J & Goldburg, W
Partner: UNT Libraries Government Documents Department

Soft inertial microfluidics for high throughput separation of bacteria from human blood cells

Description: We developed a new approach to separate bacteria from human blood cells based on soft inertial force induced migration with flow defined curved and focused sample flow inside a microfluidic device. This approach relies on a combination of an asymmetrical sheath flow and proper channel geometry to generate a soft inertial force on the sample fluid in the curved and focused sample flow segment to deflect larger particles away while the smaller ones are kept on or near the original flow streamline. The curved and focused sample flow and inertial effect were visualized and verified using a fluorescent dye primed in the device. First the particle behavior was studied in detail using 9.9 and 1.0 {micro}m particles with a polymer-based prototype. The prototype device is compact with an active size of 3 mm{sup 2}. The soft inertial effect and deflection distance were proportional to the fluid Reynolds number (Re) and particle Reynolds number (Re{sub p}), respectively. We successfully demonstrated separation of bacteria (Escherichia coli) from human red blood cells at high cell concentrations (above 10{sup 8}/mL), using a sample flow rate of up to 18 {micro}L/min. This resulted in at least a 300-fold enrichment of bacteria at a wide range of flow rates with a controlled flow spreading. The separated cells were proven to be viable. Proteins from fractions before and after cell separation were analyzed by gel electrophoresis and staining to verify the removal of red blood cell proteins from the bacterial cell fraction. This novel microfluidic process is robust, reproducible, simple to perform, and has a high throughput compared to other cell sorting systems. Microfluidic systems based on these principles could easily be manufactured for clinical laboratory and biomedical applications.
Date: January 5, 2009
Creator: Wu, Zhigang; Willing, Ben; Bjerketorp, Joakim; Jansson, Janet K. & Hjort, Klas
Partner: UNT Libraries Government Documents Department

On the geometry of two-dimensional slices of irregular level sets in turbulent flows

Description: Isoscalar surfaces in turbulent flows are found to be more complex than (self-similar) fractals, in both the far field of liquid-phase turbulent jets and in a realization of Rayleigh-Taylor-instability flow. In particular, they exhibit a scale-dependent coverage dimension, D{sub 2}((lambda)), for 2-D slices of scalar level sets, that increases with scale, from unity, at small scales, to 2, at large scales. For the jet flow and Reynolds numbers investigated, the isoscalar-surface geometry is both scalar-threshold- and Re-dependent; the level-set (coverage) length decreases with increasing Re, indicating enhanced mixing with increasing Reynolds number; and the size distribution of closed regions is well described by lognormal statistics at small scales. A similar D{sub 2}((lambda)) behavior is found for level-set data of 3-D density-interface behavior in recent direct numerical-simulation studies of Rayleigh-Taylor-instability flow. A comparison of (spatial) spectral and isoscalar coverage statistics will be disc
Date: March 20, 1998
Creator: Catrakis, H.J.; Cook, A.W.; Dimotakis, P.E. & Patton, J.M.
Partner: UNT Libraries Government Documents Department