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Experimental damping in pitch of 45 degree triangular wings

Description: Report presenting the results of an experimental wind-tunnel investigation of the damping in pitch of two triangular wings having leading edges swept back 45 degrees are presented. The wings differed only in airfoil section. Results regarding the damping coefficients, aeroelastic effects at supersonic speeds, Reynolds number effects, and application of the results to the prediction of the dynamic behavior of full-scale aircraft are provided.
Date: December 1, 1950
Creator: Tobak, Murray; Reese, David E., Jr. & Beam, Benjamin H.
Partner: UNT Libraries Government Documents Department

The damping due to roll of triangular, trapezoidal, and related plan forms in supersonic flow

Description: Report presenting solutions obtained for the damping in roll of triangular, trapezoidal, rectangular, and two swept-back plan forms. The results indicate that as the aspect ratio is increased, the limiting value of the damping in roll for trapezoidal and rectangular plan forms is equal to the value for two-dimensional flow which is twice the limiting value for triangular plan forms.
Date: March 1948
Creator: Jones, Arthur L. & Alksne, Alberta
Partner: UNT Libraries Government Documents Department

Flutter calculations in three degrees of freedom

Description: From Summary: "The present paper is a continuation of the general study of flutter published in NACA reports nos. 496 and 685. The paper is mainly devoted to flutter in three degrees of freedom (bending, torsion, and aileron) for which a number of selected cases have been calculated and presented in graphical form. The results are analyzed and discussed with regard to the effects of structural damping, of fractional-span ailerons, and of mass-balancing. The analysis shows that more emphasis should be put on the effect of structural damping and less on mass-balancing."
Date: June 7, 1941
Creator: Theodorsen, Theodore & Garrick, I. E.
Partner: UNT Libraries Government Documents Department

Results of an experimental investigation of small viscous dampers

Description: Report presenting the results of an experimental investigation of several small viscous dampers. The characteristics of the dampers are presented in the form of the magnitudes of the damping forces and spring forces as a function of the maximum velocity of the piston. The results indicated that the temperature has a large effect on the force produced by the dampers and demonstrated the necessity for consideration of the heat generated and dissipated as a result of work done by the dampers.
Date: June 1958
Creator: Silveira, Milton A.; Maglieri, Domenic J. & Brooks, George W.
Partner: UNT Libraries Government Documents Department

An experimental investigation at subsonic and supersonic speeds of the torsional damping characteristics of a constant-chord control surface of an aspect ratio 2 triangular wing

Description: Report presenting the results of a wind-tunnel investigation of the torsional damping characteristics of a constant-chord control surface. The results indicated that the damping coefficient at supersonic speeds was near zero with a tendency toward instability at low supersonic Mach numbers. Results regarding theory, damping moments, and restoring moments are provided.
Date: July 2, 1953
Creator: Reese, David E., Jr.
Partner: UNT Libraries Government Documents Department

A free-flight technique for measuring damping in roll by use of rocket-powered models and some initial results for rectangular wings

Description: Report presenting a simplified method for obtaining free-flight measurements of damping in roll through the use of rocket-powered models. Initial configurations have been tested for a range of Mach numbers. Results regarding the rolling velocity with two different airfoil sections and damping-in-roll coefficient are provided.
Date: December 20, 1949
Creator: Edmondson, James L. & Sanders, E. Claude, Jr.
Partner: UNT Libraries Government Documents Department

Damping characteristics of dashpots

Description: An investigation of the damping characteristics of dashpots was carried out combining theory and experiment. Laminar flow was assumed and three equations for the steady velocity of a piston moving in a cylinder filled with liquid were derived. In the first equation, the piston was assumed coaxial in the cylinder and, in the second equation, the piston was assumed eccentric in the cylinder with an element of the piston in contact with the cylinder wall. The third equation is for a piston of circular cross section in an elliptical cylinder. Experiments showed that the piston is normally eccentric in the cylinder. The pistons tested were 1.25 and 2 inches in diameter 0.062 to 1.00 inch long, and the clearances varied from 1.36 to 5.16 x 10 to the 3rd power inch. The difference in pressure on the two sides of the piston varied from about 2 to 55 pounds per square inch. The piston velocities for each assembly were measured with damping liquids of three different viscosities. At high piston velocities, when turbulent flow exists, the observed velocities were much lower than the velocities calculated on the basis of laminar flow. Results for a wide range of Reynolds numbers are presented in graphical form.
Date: October 1941
Creator: Peterson, John B.
Partner: UNT Libraries Government Documents Department

Damping in pitch and roll of triangular wings at supersonic speeds

Description: A method is derived for calculating the damping coefficients in pitch and roll for a series of triangular wings and a restricted series of sweptback wings at supersonic speeds. The elementary "supersonic source" solution of the linearized equation of motion is used to find the potential function of a line of doublets, and the flows are obtained by surface distributions of these doublet lines. The damping derivatives for triangular wings are found to be a function of the ratio of the tangent of the apex angle to the tangent of the Mach angle. As this ratio becomes equal to and greater than 1.0 for triangular wings, the damping derivatives, in pitch and in roll, become constant. The damping derivative in roll becomes equal to one-half the value calculated for an infinite rectangular wing, and the damping derivative in pitch for pitching about the apex becomes equal to 3.375 times that of an infinite rectangular wing.
Date: December 12, 1947
Creator: Brown, Clinton E. & Adams, Mac C.
Partner: UNT Libraries Government Documents Department

Damping in roll of straight and 45 degree swept wings of various taper ratios determined at high subsonic, transonic, and supersonic speeds with rocket-powered models

Description: Report presenting rocket-powered flight testing to determine the damping in roll of several wings of 0 degree and 45 degree quarter-chord-line sweep with various taper ratios for a range of Mach numbers. Damping in roll decreased with decreasing taper ratio at roughly the same rate for swept and unswept wings and also decreased by sweeping the quarter-chord line. The experimental results were also consistently lower than what was predicted by theory.
Date: October 10, 1951
Creator: Sanders, E. Claude, Jr.
Partner: UNT Libraries Government Documents Department

Damping in pitch and roll of triangular wings at supersonic speeds

Description: The expressions for the damping derivatives in pitch and roll of triangular wings are derived by means of the linearized theory. In the method used, the wing is represented by an unknown distribution of doublets. An integral equation containing the unknown distribution is set up and solved by analogy with known incompressible flow relations. It is pointed out that the results may be used to obtain damping coefficients of a limited series of sweptback wings, the most interesting of which are the so-called "arrow wings.".
Date: April 1948
Creator: Brown, Clinton E. & Adams, Mac C.
Partner: UNT Libraries Government Documents Department

Damping in roll of rocket-powered test vehicles having swept, tapered wings of low aspect ratio

Description: From Summary: "Flight tests of rocket-powered models have been conducted to determine the damping in roll of a group of swept, tapered wings designed for flight in the transonic speed region. The Mach number range of these tests was from approximately 0.7 to 1.4. The experimental damping in roll for all configurations was less than predicted by linearized theory throughout the Mach umber range of these tests. The only wing in this group that experienced an appreciable transonic lateral trim change was the one with a 7-percent-thick circular-arc airfoil section."
Date: October 8, 1951
Creator: Sanders, E. Claude, Jr. & Edmondson, James L.
Partner: UNT Libraries Government Documents Department

The damping in roll of rocket-powered test vehicles having rectangular wings with NACA 65-006 and symmetrical double-wedge airfoil sections of aspect ratio 4.5

Description: Report presenting a free-flight investigation of two rocket-powered model configurations to determine the damping in roll. The model had rectangular wings of 4.5 aspect ratio and were the same except for the airfoil sections.Results regarding rolling velocity and total-drag coefficient are provided.
Date: March 29, 1950
Creator: Dietz, Albert E. & Edmondson, James L.
Partner: UNT Libraries Government Documents Department

Free-flight tests of 45 degree swept wings of aspect ratio 3.15 and taper ratio 0.54 to measure wing damping of the first bending mode and to investigate the possibility of flutter at transonic speeds

Description: Report presenting free-flight tests made on two pairs of wings of aspect ratio 3.15, taper ratio 0.54, and 45 degrees sweepback in the transonic speed range to measure wing damping and to investigate the possibility of flutter. Results regarding the flight test and analysis and discussion are provided.
Date: October 12, 1954
Creator: O'Kelly, Burke R.; Lundstrom, Reginald R. & Lauten, William T., Jr.
Partner: UNT Libraries Government Documents Department

Dynamic lateral behavior of high-performance aircraft

Description: Report presenting a study of several proposed high-performance aircraft to define some problem areas in dynamic lateral behavior of high-speed aircraft which require specific attention. Aileron control problems and Dutch roll characteristics with and without artificial damping were explored in depth.
Date: August 6, 1958
Creator: Moul, Martin T. & Paulson, John W.
Partner: UNT Libraries Government Documents Department

A flight investigation of the effects of varied lateral damping on the effectiveness of a fighter airplane as a gun platform

Description: Flight tests were conducted at three conditions of damping and two atmospheric turbulence levels with fixed-reticle, gyro computing, and telescopic gunsights. Results of simulated strafing runs indicate that the gun-line dispersion could be expected to be decreased about 7 percent by increased lateral damping and to be increased about 85 percent by decreased damping and about 40 percent by rough air of the type encountered. Use of the telescopic sight indicated a 20-percent decrease in gun-line dispersion.
Date: January 1958
Creator: Kuehnel, Helmut A.; Beckhardt, Arnold R. & Champine, Robert A.
Partner: UNT Libraries Government Documents Department

Theoretical damping in roll and rolling moment due to differential wing incidence for slender cruciform wings and wing-body combinations

Description: A method of analysis based on slender-wing theory is developed to investigate the characteristics in roll of slender cruciform wings and wing-body combinations. The method makes use of the conformal mapping processes of classical hydrodynamics which transform the region outside a circle and the region outside an arbitrary arrangement of line segments intersecting at the origin. The method of analysis may be utilized to solve other slender cruciform wing-body problems involving arbitrarily assigned boundary conditions. (author).
Date: 1952
Creator: Adams, Gaynor J. & Dugan, Duane W.
Partner: UNT Libraries Government Documents Department

Estimation of the damping in roll of supersonic-leading-edge wing-body combinations

Description: From Summary: "A description is given of a linear-theory method for the estimation of the damping in roll of supersonic-leading-edge wings mounted on cylindrical bodies. The error resulting from an approximation essential to the method is shown to be small. The damping in roll is calculated for configurations having rectangular and triangular wings; for most of the range of variables the net effect of the body is to decrease the damping in roll."
Date: July 1950
Creator: Tucker, Warren A. & Piland, Robert O.
Partner: UNT Libraries Government Documents Department

Investigation of damping liquids for aircraft instruments

Description: "This report covers the results of an investigation carried on at the Bureau of Standards under a research authorization from, and with the financial assistance of, the National Advisory Committee for Aeronautics. The choice of a damping liquid for aircraft instruments is difficult owing to the range of temperature at which aircraft operate. Temperature changes affect the viscosity tremendously. The investigation was undertaken with the object of finding liquids of various viscosities otherwise suitable which had a minimum change in viscosity with temperature" (p. 405).
Date: May 16, 1928
Creator: Keulegan, G. H.
Partner: UNT Libraries Government Documents Department

Determination of the damping moment in yawing for tapered wings with partial-span flaps

Description: Report presenting a method for determining the damping moment in yawing for tapered wings with partial-span flaps. Charts are given for untwisted wings with various taper ratios, aspect ratios, and center-span flaps. Theoretical and experimental results are provided.
Date: August 1943
Creator: Harmon, Sidney M.
Partner: UNT Libraries Government Documents Department

Damping formulas and experimental values of damping in flutter models

Description: The problem of determining values of structural damping for use in flutter calculations is discussed. The concept of equivalent viscous damping is reviewed and its relation to the structural damping coefficient g introduced in NACA Technical Report No. 685 is shown. The theory of normal modes is reviewed and a number of methods are described for separating the motions associated with different modes. Equations are developed for use in evaluating the damping parameters from experimental data. Experimental results of measurements of damping in several flutter models are presented.
Date: February 1940
Creator: Coleman, Robert P.
Partner: UNT Libraries Government Documents Department

Aerodynamic Characteristics of Damping Screens

Description: From Summary: "The experimental investigation of damping screens described herein was undertaken primarily to test theories of the effects of damping screens and to obtain information on the performance of screens in oblique flow. The characteristics investigated include the damping of longitudinal and lateral components of turbulence, the effect of screens on scale, the conditions for the production of turbulence and eddies by screens, and the damping of spatial variations of mean speed."
Date: January 1950
Creator: Schubauer, G. B.; Spangenberg, W. G. & Klebanoff, P. S.
Partner: UNT Libraries Government Documents Department

Combined Effect of Damping Screens and Streams Convergence on Turbulence

Description: Note presenting an analysis of the combined effect of a series of damping screens followed by an axisymmetric-stream convergence on the mean-square fluctuation-velocity intensities, scales, correlations, and one-dimensional spectra of a turbulence field convected by a main stream. Numerical results for the statistical quantities describing the turbulence field downstream of a screen-contraction configuration are obtained for the case of upstream isotropic turbulence.
Date: January 1953
Creator: Tucker, Maurice
Partner: UNT Libraries Government Documents Department

The Measurement of the Damping in Roll on a JN4h in Flight

Description: "This investigation was carried out by the National Advisory Committee for Aeronautics for the purpose of measuring the value of L sub P in flight. The method consisted in flying with heavy weights on each wing tip, suddenly releasing one of them, and allowing the airplane to roll up to 90 degrees with controls held in neutral while a record was being taken of the airspeed, and angular velocity about the X axis. The results are of interest as they show that the damping found in the wind tunnel by the method of small oscillations is in general 40 per cent higher than the damping in flight" (p. 201).
Date: 1924
Creator: Norton, F. H.
Partner: UNT Libraries Government Documents Department