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Free Oscillations of an Atmosphere in Which Temperature Increases Linearly With Height

Description: Note presenting the concept that when the temperature in the atmosphere increases linearly with height, the speed of propagation of long waves does not approach a limit with increasing wave length, as in the case of an atmosphere in which the temperature at great heights is assumed to be constant or decreasing, but increases linearly with the period.
Date: October 1950
Creator: Pekeris, C. L.
Partner: UNT Libraries Government Documents Department

Stability of Systems Containing a Heat Source - The Rayleigh Criterion

Description: "The stability of systems containing a heat source is examined from the energy point of view. Rayleigh's criterion is derived. In the case of a flame, it is found that Rayleigh's criterion must be modified slightly if the specific-heat ratios of the burned and unburned gases are different" (p. 1).
Date: June 26, 1956
Creator: Chu, Boa-Teh
Partner: UNT Libraries Government Documents Department

Laminar-boundary-layer oscillations and transition on a flat plate

Description: Report presenting an investigation of oscillations in the laminar boundary layer on a flat plate and their relation to transition to turbulent flow. The characteristics of boundary-layer oscillations were studied most successfully when the oscillations were artificially produced by a vibrating ribbon placed in the boundary layer near the surface. A review of theory regarding laminar-boundary-layer oscillations is provided.
Date: April 1943
Creator: Schubauer, G. B. & Skramstad, H. K.
Partner: UNT Libraries Government Documents Department

A Theoretical Investigation of the Lateral Oscillations of an Airplane With Free Rudder With Special Reference to the Effect of Friction

Description: Report presenting charts showing the variation in dynamic stability with the rudder hinge-moment characteristics. A stabilizing rudder floating tendency combined with a high degree of aerodynamic balance is shown to lead to oscillations of increasing amplitude.
Date: March 1943
Creator: Greenberg, Harry & Sternfield, Leonard
Partner: UNT Libraries Government Documents Department

A Theoretical Investigation of the Rolling Oscillations of an Airplane With Ailerons Free

Description: "An analysis is made of the stability of an airplane with ailerons free, with particular attention to the motions when the ailerons have a tendency to float against the wind. The present analysis supersedes the aileron investigation contained in NACA Technical Report no. 709. The equations of motion are first written to include yawing and sideslipping, and it is demonstrated that the principal effects of freeing the ailerons can be determined without regard to these motions" (p. 255).
Date: November 19, 1943
Creator: Cohen, Doris
Partner: UNT Libraries Government Documents Department

Effect of Finite Span on the Airload Distributions for Oscillating Wings 2 - Methods of Calculation and Examples of Application

Description: Note presenting lift and moment distributions calculated for oscillating wings of finite span on the basis of the three-dimensional theory of part I of the report. The results obtained are compared with the corresponding results of the two-dimensional theory.
Date: October 1947
Creator: Reissner, Eric & Stevens, John E.
Partner: UNT Libraries Government Documents Department

Wind-Tunnel Investigations on Flexural-Torsional Wing Flutter

Description: "For the purpose of testing the theory of an oscillating airfoil of two degrees of freedom, a wing was mounted in the wind tunnel between two walls in such a manner that it could execute vertical (flexural) oscillations as well as torsional oscillations about an arbitrary axis parallel to the span. It was possible to vary the inertia and elasticity parameters and also to increase artificially the negligibly small natural damping of the system. The oscillations were recorded to a strongly magnified scale" (p. 1).
Date: September 1938
Creator: Voigt, H.
Partner: UNT Libraries Government Documents Department

Study of Vortex Shedding as Related to Self-Excited Torsional Oscillations of an Airfoil

Description: Note presenting the results of the experimental investigation of the self-excited torsional oscillation of an NACA 0006 airfoil suspended elastically. The relationship between the torsional oscillation and the shedding of vortices was investigated for this airfoil. Two types of oscillation phenomena were found: one was exhibited by cases with angles of attack just above stall and one was exhibited by cases with higher angles of attack.
Date: September 1951
Creator: Chuan, Raymond L. & Magnus, Richard J.
Partner: UNT Libraries Government Documents Department

Theoretical analysis of oscillations of a towed cable

Description: Report presenting a theoretical study of the oscillations of a towed cable, which indicated that oscillations traveling downwind along the cable are amplified by aerodynamic forces when the airspeed is greater than the speed of propagation of waves along the cable. The theory provides a possible explanation for the violent motions of towed airspeed heads which appear above a certain speed.
Date: 1949
Creator: Phillips, William H.
Partner: UNT Libraries Government Documents Department

Effects of blade plan form on free-space oscillating pressures near propellers at flight Mach numbers to 0.72

Description: Report presenting a series of measurements made on the oscillating pressures near a tapered-blade-plan-form propeller at flight Mach numbers up to 0.72. Flight Mach number, power, and engine speed were controlled in an attempt to duplicate the conditions of a previous flight investigation. Results regarding effects of flight Mach number, effect of engine speed, and effects of engine power are provided.
Date: August 1957
Creator: Kurbjun, Max C.
Partner: UNT Libraries Government Documents Department

Measurement of aerodynamic forces for various mean angles of attack on an airfoil oscillating in pitch and on two finite-span wings oscillating in bending with emphasis on damping in the stall

Description: "The oscillating air forces on a two-dimensional wing oscillating in pitch about the midchord have been measured at various mean angles of attack and at Mach numbers of 0.35 and 0.7. The magnitudes of normal-force and pitching-moment coefficients were much higher at high angles of attack than at low angles of attack for some conditions. Large regions of negative damping in pitch were found, and it was shown that the effect of increasing the Mach number 0.35 to 0.7 was to decrease the initial angle of attack at which negative damping occurred" (p. 521).
Date: January 21, 1956
Creator: Rainey, A. Gerald
Partner: UNT Libraries Government Documents Department

Measurement of aerodynamic forces for various mean angles of attack on an airfoil oscillating in pitch and on two finite-span wings oscillating in bending with emphasis on damping in the stall

Description: Report presenting measurements of the oscillating air forces on a two-dimensional wing oscillating in pitch about the midchord that have been measured at various mean angles of attack and at two different Mach numbers. The magnitudes of normal-force and pitching-moment coefficients were found to be much higher at large angles of attack than at low angles of attack for some conditions. Results regarding the effects at low angles of attack, high angles of attack, and a description of finite-span wings oscillating in first bending mode are provided.
Date: May 1956
Creator: Rainey, A. Gerald
Partner: UNT Libraries Government Documents Department

Velocity potential and air forces associated with a triangular wing in supersonic flow, with subsonic leading edges, and deforming harmonically according to a general quadratic equation

Description: Report presenting the velocity potential for a triangular wing with subsonic leading edges experiencing harmonic deformations in supersonic flow. The oscillations considered are such that the amplitude of wing distortion can be represented by a general quadratic expression for a surface.
Date: September 1953
Creator: Watkins, Charles E. & Berman, Julian H.
Partner: UNT Libraries Government Documents Department

Some effects of aspect ratio and tail length on the contribution of a vertical tail to unsteady lateral damping and directional stability of a model oscillating continuously in yaw

Description: Report presenting a fuselage-vertical-tail combination with tails of two aspect ratios, each of which was tested at four tail lengths, and oscillated in yaw through a range of reduced-frequency parameter corresponding to the lateral motions of airplanes. Three phase angles were measured with the tail in the presence of the fuselage.
Date: January 1954
Creator: Fisher, Lewis R.
Partner: UNT Libraries Government Documents Department

A wind-tunnel test technique for measuring the dynamic rotary stability derivatives at subsonic and supersonic speeds

Description: "A method is described for measuring the dynamic stability derivatives of a model airplane in a wind tunnel. The characteristic features of this system are that single-degree-of-freedom oscillations were used to obtain combinations of rolling, yawing and pitching motions; that the oscillations were excited and controlled by velocity feedback which permitted operation under conditions unfavorable for more conventional types of oscillatory testing; and that data processing was greatly simplified by using analog computer elements in the strain-gage circuitry. A small number of experimental data are included to illustrate the general scope of results obtainable with this system" (p. 1).
Date: September 20, 1954
Creator: Beam, Benjamin H.
Partner: UNT Libraries Government Documents Department

Note on flutter of a 60 degree delta wing encountered at low-supersonic speeds during the flight of a rocket-propelled model

Description: From Summary: "An analysis of the flight time history of a rocket-propelled model of a 60 degree delta-wing airplane configuration, fired for the purpose of obtaining zero-lift drag data, indicated wing flutter and subsequent failure at low-supersonic Mach numbers. This flutter occurred during the unpowered decelerating portion of the flight. The behavior of the model during flight is discussed and the mass and stiffness characteristics of a duplicate wing are presented."
Date: May 14, 1951
Creator: Lauten, William T., Jr. & Mitcham, Grady L.
Partner: UNT Libraries Government Documents Department

Some calculations of the lateral response of two airplanes to atmospheric turbulence with relation to the lateral snaking problem

Description: Report presenting calculations of the lateral response to representative time histories of atmospheric turbulence for two airplanes with widely different dynamic properties and explanations for their differences in behavior. The results indicate that atmospheric turbulence can cause and maintain a lateral hunting oscillation of a plane, which can be fairly regular and more pronounced for lightly damped airplanes. This may explain some of the cases of airplane snaking that have not been explained by other causes.
Date: May 1955
Creator: Bird, John D.
Partner: UNT Libraries Government Documents Department

Low-speed tests of a free-to-yaw model in two wind tunnels of different turbulence

Description: Report presenting tests at low speeds in the low turbulence pressure tunnel and the stability tunnel in order to determine the extent of any resulting oscillations of a model mounted with freedom in yaw and to demonstrate the extent to which directional fluctuations in an air stream can be responsible for the oscillations.
Date: February 26, 1952
Creator: Cahill, Jones F. & Bird, John D.
Partner: UNT Libraries Government Documents Department

Dynamic stability of vehicles traversing ascending or descending paths through the atmosphere

Description: From Summary: "An analysis is given of the oscillatory motions of vehicles which traverse ascending and descending paths through the atmosphere at high speed. The specific case of a skip path is examined in detail, and this leads to a form of solution for the oscillatory motion which should recur over any trajectory. The distinguishing feature of this form is the appearance of the Bessel rather than the trigonometric function as the characteristic mode of oscillation."
Date: July 1958
Creator: Tobak, Murray & Allen, H. Julian
Partner: UNT Libraries Government Documents Department

Low-speed study of the effects of frequency on the stability derivatives of wings oscillating in yaw with particular reference to high angle of attack conditions

Description: Report presenting a low-speed investigation in the free-flight tunnel to provide basic information regarding the effect of frequency on wings oscillating in yaw. The investigation consisted of both free-oscillation tests and forced-oscillation tests of a 60 delta wing, a 45 degree sweptback wing of aspect ratio 2.61, and an unswept wing of aspect ratio 3 over a range of angles of attack. Results regarding the static force test results, directional stability, cross derivative, effective dihedral, and flow separation are provided.
Date: November 1, 1955
Creator: Campbell, John P.; Johnson, Joseph L., Jr. & Hewes, Donald E.
Partner: UNT Libraries Government Documents Department

An experimental investigation of the hinge-moment characteristics of a constant-chord control surface oscillating at high frequency

Description: From Summary: "The results of an experimental investigation of the hinge-moment characteristics of a constant-chord control surface oscillating at high frequency is presented. The control surface was mounted on an aspect-ratio-2 triangular wing. The aerodynamic restoring-moment coefficient and damping-moment coefficient were determined at a frequency of 260 cycles per second for a Mach number range of 0.6 to 0.8 and 1.3 to 1.9 at angles of attack of 5 degrees and 10 degrees. The test results showed linear theory to be a reliable guide to the prediction of the trend of the restoring-moment coefficient with Mach number for the supersonic speed range of the investigation but overestimated the magnitude of the coefficient."
Date: December 28, 1955
Creator: Reese, David E., Jr. & Carlson, William C. A.
Partner: UNT Libraries Government Documents Department

Method for calculating the aerodynamic loading on an oscillating finite wing in subsonic and sonic flow

Description: Report presenting a method for determining the air forces on an oscillating finite wing of general plan form in subsonic flow, including the limiting case of sonic flow. The method is applied to rectangular and delta wings and is compared to existing theory.
Date: August 1956
Creator: Runyan, Harry L. & Woolston, Donald S.
Partner: UNT Libraries Government Documents Department