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An Investigation of Hydrofoils in the NACA Tank I : Effect of Dihedral and Depth of Submersion

Description: Tests were conducted on hydrofoil assemblies approximating an arrangement for use under seaplanes or surface boats. A series of hydrofoils, each supported by two struts, was towed at various depths ranging from partial submersions to a depth of 5-chord lengths. At depths greater than 4 or 5 chords, the influence of the surface of the water is small; hydrofoils operating at low speed will have characteristics similar to those of airfoils of the same section.
Date: September 1, 1942
Creator: Land, Norman S. & Benson, James M.
Partner: UNT Libraries Government Documents Department

General formulas and charts for the calculation of airplane performance

Description: This report presents general formulas for the determination of all major airplane performance characteristics. A rigorous analysis is used, making no assumption regarding the attitude of the airplane at which maximum rate of climb occurs, but finding the attitude at which the excess thrust horsepower is maximum. Equations and charts are developed which show the variation of performance due to a change in any of the customary design parameters. Performance determination by use of the formulas and charts is rapid and explicit. The results obtained by this performance method have been found to give agreement with flight tests that is, in general, equal or superior to results obtained by present commonly used methods.
Date: January 1, 1933
Creator: Oswald, W Bailey
Partner: UNT Libraries Government Documents Department

A general integral form of the boundary-layer equation for incompressible flow with an application to the calculation of the separation point of turbulent boundary layers

Description: A general integral form of the boundary-layer equation, valid for either laminar or turbulent incompressible boundary-layer flow, is derived. By using the experimental finding that all velocity profiles of the turbulent boundary layer form essentially a single-parameter family, the general equation is changed to an equation for the space rate of change of the velocity-profile shape parameter. The lack of precise knowledge concerning the surface shear and the distribution of the shearing stress across turbulent boundary layers prevented the attainment of a reliable method for calculating the behavior of turbulent boundary layers.
Date: January 1, 1951
Creator: Tetervin, Neal & Lin, Chia Chiao
Partner: UNT Libraries Government Documents Department

General Potential Theory of Arbitrary Wing Section

Description: This report gives the exact treatment of the problem of determining the 2-dimensional potential flow around wing sections of any type. The treatment is based directly on the solution of this problem as advanced by Theodorsen in NACA-TR-411. The problem condenses into the compact form of an integral equation capable of yielding numerical solutions by a direct process.
Date: January 1, 1934
Creator: Theodorsen, T & Garrick, I E
Partner: UNT Libraries Government Documents Department

General Potential Theory of Arbitrary Wing Sections

Description: The problem of determining the two dimensional potential flow around wing sections of any shape is examined. The problem is condensed into the compact form of an integral equation capable of yielding numerical solutions by a direct process. An attempt is made to analyze and coordinate the results of earlier studies relating to properties of wing sections. The existing approximate theory of thin wing sections and the Joukowski theory with its numerous generalizations are reduced to special cases of the general theory of arbitrary sections, permitting a clearer perspective of the entire field. The method which permits the determination of the velocity at any point of an arbitrary section and the associated lift and moments is described. The method is also discussed in terms for developing new shapes of preassigned aerodynamical properties.
Date: December 1, 1979
Creator: Theodorsen, T. & Garrick, I. E.
Partner: UNT Libraries Government Documents Department

A general small-deflection theory for flat sandwich plates

Description: A small-deflection theory is developed for the elastic behavior of orthotropic flat plates in which deflections due to shear are taken into account. In this theory, which covers all types of flat sandwich construction, a plate is characterized by seven physical constants (five stiffnesses and two Poisson ratios) of which six are independent. Both the energy expression and the differential equations are developed. Boundary conditions corresponding to simply supported, clamped, and elastically restrained edges are considered.
Date: January 1, 1948
Creator: Libove, Charles & Batdorf, S B
Partner: UNT Libraries Government Documents Department

General Theory of Aerodynamic Instability and the Mechanism of Flutter

Description: The aerodynamic forces on an oscillating airfoil or airfoil-aileron combination of three independent degrees of freedom were determined. The problem resolves itself into the solution of certain definite integrals, which were identified as Bessel functions of the first and second kind, and of zero and first order. The theory, based on potential flow and the Kutta condition, is fundamentally equivalent to the conventional wing section theory relating to the steady case. The air forces being known, the mechanism of aerodynamic instability was analyzed. An exact solution, involving potential flow and the adoption of the Kutta condition, was derived. The solution is of a simple form and is expressed by means of an auxiliary parameter k. The flutter velocity, treated as the unknown quantity, was determined as a function of a certain ratio of the frequencies in the separate degrees of freedom for any magnitudes and combinations of the airfoil-aileron parameters.
Date: December 1, 1979
Creator: Theodorsen, Theodore
Partner: UNT Libraries Government Documents Department

Hydrodynamic impact of a system with a single elastic mode II : comparison of experimental force and response with theory

Description: Hydrodynamic impact tests were made on an elastic model approximating a two-mass spring system to determine experimentally the effects of structural flexibility on the hydrodynamic loads encountered during seaplane landing impacts and to correlate the results with theory. A flexible seaplane was represented by a two-mass spring system consisting of a rigid prismatic float connected to a rigid upper mass by an elastic structure. The model had a ratio of sprung mass to hull mass of 0.6 and a natural frequency of 3.0 cycles per second. The tests were conducted in smooth water at fixed trims and included both high and low flight-path angles and a range of velocity. Theoretical and experimental comparisons indicated that the theoretical results agreed well with the experimental results.
Date: January 1, 1952
Creator: Miller, Robert W & Merten, Kenneth F
Partner: UNT Libraries Government Documents Department

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

Description: 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 1, 1950
Creator: Goodman, Alex & Fisher, Lewis R
Partner: UNT Libraries Government Documents Department

An introduction to the physical aspects of helicopter stability

Description: 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: January 1, 1950
Creator: Gessow, Alfred & Amer, Kenneth B
Partner: UNT Libraries Government Documents Department

Interrelation of exhaust-gas constituents

Description: This report presents the results of an investigation conducted to determine the interrelation of the constituents of the exhaust gases of internal-combustion engines and the effect of engine performance on these relations. Six single-cylinder, liquid-cooled tests engines and one 9-cylinder radial air-cooled engine were tested. Various types of combustion chambers were used and the engines were operated at compression ratios from 5.1 to 7.0 using spark ignition and from 13.5 to 15.6 using compression ignition. The investigation covered a range of engine speeds from 1,500 to 2,100 r.p.m. The fuels used were two grades of aviation gasoline, auto diesel fuel, and laboratory diesel fuel. Power, friction, and fuel-consumption data were obtained from the single-cylinder engines at the same time that the exhaust-gas samples were collected.
Date: January 1, 1938
Creator: Gerrish, Harold C & Voss, Fred
Partner: UNT Libraries Government Documents Department

Fabric fastenings

Description: The study of aeronautical fabrics has led to a consideration of the best methods of attaching and fastening together such materials. This report presents the results of an investigation upon the proper methods of attaching fabrics to airplane wings. The methods recommended in this report have been adopted by the military services.
Date: January 1, 1920
Creator: Walen, E D & Fisher, R T
Partner: UNT Libraries Government Documents Department