General Theory of Aerodynamic Instability and the Mechanism of Flutter (open access)

General Theory of Aerodynamic Instability and the Mechanism of Flutter

"The aerodynamic forces on an oscillating airfoil or airfoil-aileron combination of three independent degrees of freedom have been determined. The problem resolves itself into the solution of certain definite integrals, which have been identified as Bessel functions of the first and second kind and of zero and first order. The theory, being based on potential flow and the Kutta condition, is fundamentally equivalent to the conventional wing-section theory relating to the steady case" (p. 23).
Date: 1949
Creator: Theodorsen, Theodore
System: The UNT Digital Library
The application of the statistical theory of extreme values to gust-load problems (open access)

The application of the statistical theory of extreme values to gust-load problems

From Introduction: "Recent developments in the statistical theory of extreme values (references 4 to 10) have indicated a somewhat more rational approach to the problem of predicting the probability of occurrence The present report summarizes some of these findings, indicates the method of application, and evaluates their applicability to certain gust-load problems ."
Date: July 22, 1949
Creator: Press, Harry
System: The UNT Digital Library
Theoretical lift and damping in roll at supersonic speeds of thin sweptback tapered wings with streamwise tips, subsonic leading edges, and supersonic trailing edges (open access)

Theoretical lift and damping in roll at supersonic speeds of thin sweptback tapered wings with streamwise tips, subsonic leading edges, and supersonic trailing edges

"On the basis of linearized supersonic-flow theory, generalized equations were derived and calculations made for the lift and damping in roll of a limited series of thin sweptback tapered wings. Results are applicable to wings with streamwise tips and for a range of supersonic speeds for which the wing is wholly contained between the Mach cones springing from the wing apex and from the trailing edge of the root section. A further limitation is that the tip Mach lines may not intersect on the wing" (p. 395).
Date: February 15, 1949
Creator: Malvestuto, Frank S., Jr.; Margolis, Kenneth & Ribner, Herbert S.
System: The UNT Digital Library
Critical Stress of Ring-Stiffened Cylinders in Torsion (open access)

Critical Stress of Ring-Stiffened Cylinders in Torsion

"A chart in terms of nondimensional parameters is presented for the theoretical critical stress in torsion of simply supported cylinders stiffened by identical equally spaced rings of zero torsional stiffness. The results are obtained by solving the equation of equilibrium by means of the Galerkin method. Comparison of the theoretical results with experimental results indicates that ring-stiffened cylinders buckle, on the average, at a buckling stress about 15 percent below the theoretical buckling stress" (p. 1).
Date: November 1949
Creator: Stein, Manuel; Sanders, J. Lyell, Jr. & Crate, Harold
System: The UNT Digital Library
On Reflection of Shock Waves from Boundary Layers (open access)

On Reflection of Shock Waves from Boundary Layers

Measurements are presented at Mach numbers from about 1.3 to 1.5 of reflection characteristics and the relative upstream influence of shock waves impinging on a flat surface with both laminar and turbulent boundary layers. The difference between impulse and step waves is discussed and their interaction with the boundary layer is compared. General considerations on the experimental production of shock waves from wedges and cones and examples of reflection of shock waves from supersonic shear layers are also presented.
Date: August 16, 1949
Creator: Liepmann, H. W.; Roshko, A. & Dhawan, S.
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