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General algebraic method applied to control analysis of complex engine types (open access)

General algebraic method applied to control analysis of complex engine types

"A general algebraic method of attack on the problem of controlling gas-turbine engines having any number of independent variables was utilized employing operational functions to describe the assumed linear characteristics for the engine, the control, and the other units in the system. Matrices were used to describe the various units of the system, to form a combined system showing all effects, and to form a single condensed matrix showing the principal effects. This method directly led to the conditions on the control system for noninteraction so that any setting disturbance would affect only its corresponding controlled variable" (p. 581).
Date: April 25, 1949
Creator: Boksenbom, Aaron S. & Hood, Richard
System: The UNT Digital Library
Effect of Reynolds Number in Turbulent-Flow Range on Flame Speeds of Bunsen Burner Flames (open access)

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

"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.
System: The UNT Digital Library
The reversibility theorem for thin airfoils in subsonic and supersonic flow (open access)

The reversibility theorem for thin airfoils in subsonic and supersonic flow

A method introduced by Munk is extended to prove that the light-curve slope of thin wings in either subsonic flow or supersonic flow is the same when the direction of flight of the wing is reversed. It is also shown that the wing reversal does not change the thickness drag, damping-in-roll parameter or the damping-in-pitch parameter.
Date: June 26, 1949
Creator: Brown, Clinton E.
System: The UNT Digital Library
Summary of section data on trailing-edge high-lift devices (open access)

Summary of section data on trailing-edge high-lift devices

"A summary has been made of available data on the characteristics of airfoil sections with trailing-edge high-lift devices. Data for plain, split, and slotted flaps are collected and analyzed. The effects of each of the variables involved in the design of the various types of flap are examined and, in cases where sufficient data are given, optimum configurations are deduced. Wherever possible, the effects of airfoil section, Reynolds number, and leading-edge roughness are shown. For single and double slotted flaps, where a large amount of unrelated data are available, maximum lift coefficients of many configurations are presented in tables" (p. 1).
Date: 1949
Creator: Cahill, Jones F.
System: The UNT Digital Library
Laminar mixing of a compressible fluid (open access)

Laminar mixing of a compressible fluid

From Summary: "A theoretical investigation of the velocity profiles for laminar mixing of a high-velocity stream with a region of fluid at rest has been made assuming that the Prandtl number is unity. A method which involves only quadratures is presented for calculating the velocity profile in the mixing layer for an arbitrary value of the free-stream Mach number. Detailed velocity profiles have been calculated for free-stream Mach numbers of 0, 1, 2, 3, and 5."
Date: January 5, 1949
Creator: Chapman, Dean R.
System: The UNT Digital Library
Icing-protection requirements for reciprocating-engine induction system (open access)

Icing-protection requirements for reciprocating-engine induction system

From Summary: "Despite the development of relatively ice-free fuel-metering systems, the widespread use of alternate and heated-air intakes, and the use of alcohol for emergency de-icing, icing of aircraft-engine induction systems is a serious problem. Investigations have been made to study and to combat all phases of this icing problem. From these investigations, criterions for safe operation and for design of new induction systems have been established. The results were obtained from laboratory investigations of carburetor-supercharger combinations, wind-tunnel investigations of air scoops, multicylinder-engine studies, and flight investigations. Characteristics of three forms of ice, impact, throttling, and fuel evaporation were studied."
Date: June 20, 1949
Creator: Coles, Willard D.; Rollin, Vern G. & Mulholland, Donald R.
System: The UNT Digital Library
Spectra and diffusion in a round turbulent jet (open access)

Spectra and diffusion in a round turbulent jet

"In a round turbulent jet at room temperature, measurement of the shear correlation coefficient as a function of frequency (through band-pass filters) has given a rather direct verification of Kolmogoroff's local-isotropy hypothesis. One-dimensional power spectra of velocity and temperature fluctuations, measured in unheated and heated jets, respectively, have been contrasted. Under the same conditions, the two corresponding transverse correlation functions have been measured and compared" (p. 1).
Date: August 17, 1949
Creator: Corrsin, Stanley & Uberoi, Mahinder S.
System: The UNT Digital Library
Method of designing cascade blades with prescribed velocity distributions in compressible potential flows (open access)

Method of designing cascade blades with prescribed velocity distributions in compressible potential flows

By use of the assumption that the pressure-volume relation is linear, a solution to the problem of designing a cascade for a given turning and with a prescribed velocity distribution along the blade in a potential flow of a compressible perfect fluid was obtained by a method of correspondence between potential flows of compressible and incompressible fluids. The designing of an isolated airfoil with a prescribed velocity distribution along the airfoil is considered as a special case of cascade. If the prescribed velocity distribution is not theoretically attainable, the method provides a means of modifying the distribution so as to obtain a physically significant blade shape. Numerical examples are included.
Date: October 1, 1949
Creator: Costello, George R.
System: The UNT Digital Library
Theoretical antisymmetric span loading for wings of arbitrary plan form at subsonic speeds (open access)

Theoretical antisymmetric span loading for wings of arbitrary plan form at subsonic speeds

A simplified lifting-surface theory that includes effects of compressibility and spanwise variation of section lift-curve slope is used to provide charts with which antisymmetric loading due to arbitrary antisymmetric angle of attack can be found for wings having symmetric plan forms with a constant spanwise sweep angle of the quarter-chord line. Consideration is given to the flexible wing in roll. Aerodynamic characteristics due to rolling, deflected ailerons, and sideslip of wings with dihedral are considered. Solutions are presented for straight-tapered wings for a range of swept plan forms.
Date: December 22, 1949
Creator: DeYoung, John
System: The UNT Digital Library
Summary of Information Relating to Gust Loads on Airplanes (open access)

Summary of Information Relating to Gust Loads on Airplanes

"Available information on gust structure, airplane reactions, and pertinent operating statistics has been examined. This report attempts to coordinate this information with reference to the prediction of gust loads on airplanes. The material covered represents research up to October 1947" (p. 807).
Date: August 5, 1949
Creator: Donely, Philip
System: The UNT Digital Library
The design of low-turbulence wind tunnels (open access)

The design of low-turbulence wind tunnels

From Summary: "Within the past 10 years there have been placed in operation in the United States four low-turbulence wind tunnels of moderate cross-sectional area and speed, one at the National Bureau of Standards, two at the NACA Langley Laboratory, and one at the NACA Ames Laboratory. This paper reviews briefly the state of knowledge and those features which make possible the attainment of low turbulence in wind tunnels. Specific applications to two wind tunnels are described."
Date: 1949
Creator: Dryden, Hugh L. & Abbott, Ira H.
System: The UNT Digital Library
Effect of tunnel configuration and testing technique on cascade performance (open access)

Effect of tunnel configuration and testing technique on cascade performance

"An investigation has been conducted to determine the influence of aspect ratio, boundary-layer control by means of slots and porous surfaces, Reynolds number, and tunnel end-wall condition upon the performance of airfoils in cascades. A representative compressor-blade section (the NACA 65-(12)(10) of aspect ratios of 1, 2, and 4 has been tested at low speeds in cascades with solid and with porous side walls. Two-dimensional flow was established in porous-wall cascades of each of the three aspect ratios tested; the flow was not two-dimensional in any of the solid-wall cascades" (p. 263).
Date: November 30, 1949
Creator: Erwin, John R. & Emery, James C.
System: The UNT Digital Library
Use of source distributions for evaluating theoretical aerodynamics of thin finite wings at supersonic speeds (open access)

Use of source distributions for evaluating theoretical aerodynamics of thin finite wings at supersonic speeds

From Summary: "A series of publications on the source-distribution methods for evaluating the aerodynamics of thin wings at supersonic speeds is summarized, extended, and unified. Included in the first part are the deviations of: (a) the linearized partial-differential equation for unsteady flow at a substantially constant Mach number. b) The source-distribution solution for the perturbation-velocity potential that satisfies the boundary conditions of tangential flow at the surface and in the plane of the wing; and (c) the integral equation for determining the strength and the location of sources to describe the interaction effects (as represented by upwash) of the bottom and top wing surfaces through the region between the finite wing boundary and the foremost Mach wave. The second part deals with steady-state thin-wing problems. The third part of the report approximates the integral equation for unsteady upwash and includes a solution of approximate equation. Expressions are then derived to evaluate the load distributions for time-dependent finite-wing motions."
Date: June 17, 1949
Creator: Evvard, John C.
System: The UNT Digital Library
Fundamental effects of aging on creep properties of solution-treated low-carbon N-155 alloy (open access)

Fundamental effects of aging on creep properties of solution-treated low-carbon N-155 alloy

A method is developed whereby the fundamental mechanisms are investigated by which processing, heat treatment, and chemical composition control the properties of alloys at high temperatures. The method used metallographic examination -- both optical and electronic --studies of x-ray diffraction-line widths, intensities, and lattice parameters, and hardness surveys to evaluate fundamental structural conditions. Mechanical properties at high temperatures are then measured and correlated with these measured structural conditions. In accordance with this method, a study was made of the fundamental mechanism by which aging controlled the short-time creep and rupture properties of solution-treated low-carbon n-155 alloy at 1200 degrees F.
Date: January 18, 1949
Creator: Frey, D. N.; Freeman, J. W. & White, A. E.
System: The UNT Digital Library
An introduction to the physical aspects of helicopter stability (open access)

An introduction to the physical aspects of helicopter stability

In order to provide engineers interested in rotating-wing aircraft, but with no specialized training in stability theory, some understanding of the factors that influence the flying qualities of the helicopter, an explanation is made of both the static stability and the stick-fixed oscillation in hovering and forward flight in terms of fundamental physical quantities. Three significant stability factors -- static stability with angle of attack, static stability with speed, and damping due to a pitching or rolling velocity -- are explained in detail.
Date: September 19, 1949
Creator: Gessow, Alfred & Amer, Kenneth B.
System: The UNT Digital Library
Investigation of Fretting by Microscopic Observation (open access)

Investigation of Fretting by Microscopic Observation

"An experimental investigation, using microscopic observation and color motion photomicrographs of the action, was conducted to determine the cause of fretting. Glass and other noncorrosive materials, as well as metals, were used as specimens. A very simple apparatus vibrated convex surfaces in contact with stationary flat surfaces at frequencies of 120 cycles or less than l cycle per second, an amplitude of 0.0001 inch, and load of 0.2 pound" (p. 135).
Date: August 31, 1949
Creator: Godfrey, Douglas
System: The UNT Digital Library
Attainable Circulation About Airfoils in Cascade (open access)

Attainable Circulation About Airfoils in Cascade

"From consideration of available information on boundary-layer behavior, a relation among profile thickness, maximum surface velocity, Reynolds number, velocity diagram, and solidity is established for a cascade of airfoils immersed in a two-dimensional incompressible fluid flow. Several cascades are computed to show the effect of various cascade design parameters on minimum required cascade solidity. Comparisons with experimentally determined blade performance show that the derived blade loadings are equal or higher for moderate flow deceleration and somewhat lower for large deceleration. Blades with completely laminar flow appear practical for impulse or reaction blading" (p. 117).
Date: September 1949
Creator: Goldstein, Arthur W. & Mager, Artur
System: The UNT Digital Library
Investigation with an interferometer of the turbulent mixing of a free supersonic jet (open access)

Investigation with an interferometer of the turbulent mixing of a free supersonic jet

The free turbulent mixing of a supersonic jet of Mach number 1.6 has been experimentally investigated. An interferometer, of which a description is given, was used for the investigation. Density and velocity distributions through the mixing zone have been obtained. It was found that there was similarity in distribution at the cross sections investigated and that, in the subsonic portion of the mixing zone, the velocity distribution fitted the theoretical distribution for incompressible flow. It was found that the rates of spread of the mixing zone both into the jet and into the ambient air were less than those of subsonic jets.
Date: January 21, 1949
Creator: Gooderum, Paul B.; Wood, George P. & Brevoort, Maurice J.
System: The UNT Digital Library
Investigation at low speeds of the effect of aspect ratio and sweep on rolling stability derivatives of untapered wings (open access)

Investigation at low speeds of the effect of aspect ratio and sweep on rolling stability derivatives of untapered wings

A low-scale wind-tunnel investigation was conducted in rolling flow to determine the effects of aspect ratio and sweep (when varied independently) on the rolling stability derivatives for a series of untapered wings. The rolling-flow equipment of the Langley stability tunnel was used for the tests. The data of the investigation have been used to develop a method of accounting for the effects of the drag on the yawing moment due to rolling throughout the lift range.
Date: January 19, 1949
Creator: Goodman, Alex & Fisher, Lewis R.
System: The UNT Digital Library
The development of cambered airfoil sections having favorable lift characteristics at supercritical Mach numbers (open access)

The development of cambered airfoil sections having favorable lift characteristics at supercritical Mach numbers

Several groups of new airfoil sections, designated as the NACA 8-series, are derived analytically to have lift characteristics at supercritical Mach numbers which are favorable in the sense that the abrupt loss of lift, characteristic of the usual airfoil section at Mach numbers above the critical, is avoided. Aerodynamic characteristics determined from two-dimensional wind-tunnel tests at Mach numbers up to approximately 0.9 are presented for each of the derived airfoils. Comparisons are made between the characteristics of these airfoils and the corresponding characteristics of representative NACA 6-series airfoils.
Date: 1949
Creator: Graham, Donald J.
System: The UNT Digital Library
Plastic Buckling of a Rectangular Plate Under Edge Thrusts (open access)

Plastic Buckling of a Rectangular Plate Under Edge Thrusts

"The fundamental equations for the plastic buckling of a rectangular plate under edge thrusts are developed on the basis of a new set of stress-strain relations for the behavior of a metal in the plastic range. These relations are derived for buckling from a state of uniform compression. The fundamental equation for the buckling of a simply compressed plate together with typical boundary conditions is then developed and the results are applied to calculating the buckling loads of a thin strip, a simply supported plate, and a cruciform section" (p. 1).
Date: 1949
Creator: Handelman, G. H. & Prager, W.
System: The UNT Digital Library
Recommendations for Numerical Solution of Reinforced-Panel and Fuselage-Ring Problems (open access)

Recommendations for Numerical Solution of Reinforced-Panel and Fuselage-Ring Problems

"Procedures are recommended for solving the equations of equilibrium of reinforced panels and isolated fuselage rings as represented by the external loads and the operations table established according to Southwell's method. From the solution of these equations the stress distribution can be easily determined. The method of systematic relaxations, the matrix-calculus method, and several other methods applicable in special cases are discussed" (p. 1).
Date: 1949
Creator: Hoff, N. J. & Libby, Paul A.
System: The UNT Digital Library
An apparatus for varying effective dihedral in flight with application to a study of tolerable dihedral on a conventional fighter airplane (open access)

An apparatus for varying effective dihedral in flight with application to a study of tolerable dihedral on a conventional fighter airplane

From Summary: "An apparatus for varying effective dihedral in flight by means of servo actuation of the ailerons in response to sideslip angle is described. The results of brief flight tests of the apparatus on a conventional fighter airplane are presented and discussed. The results of an investigation employing the apparatus to determine the tolerable (safe for normal fighter operation) range of effective dihedral on the test airplane are presented."
Date: August 24, 1949
Creator: Kauffman, William M.; Liddell, Charles J., Jr.; Smith, Allan & Van Dyke, Rudolph D., Jr.
System: The UNT Digital Library
An Analysis of Supersonic Aerodynamic Heating With Continuous Fluid Injection (open access)

An Analysis of Supersonic Aerodynamic Heating With Continuous Fluid Injection

From Introduction: "The aerodynamic heating problem assumes considerable importance at high-supersonic speeds. Sanger and Bredt (reference 1) have calculated the high-speed aerodynamic forces and equilibrium surface temperature at extremely high altitudes where the molecular mean free path is large (free-molecule-flow region) compared with a characteristic body dimension. The theoretical investigation of Lees (reference 2) on the stability of the laminar boundary layer in compressible flow indicates that the laminar boundary layer is completely stable at all Reynolds numbers at supersonic speeds for a sufficiently low ratio of surface temperature to stream temperature."
Date: September 29, 1949
Creator: Klunker, E. B. & Ivey, H. Reese
System: The UNT Digital Library