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Soaring flight and the Rhön contests

Description: Explanation of soaring flight. Static and dynamic soaring flight. Results of the Rhon contest. Description of the most important gliders. Notes on Soaring Flight Contests in France and England.
Date: January 1923
Creator: Hoff, Wilhelm
Partner: UNT Libraries Government Documents Department

Boundary Layer

Description: From Introduction: "The fundamental, practically the most important branch of the modern mechanics of a viscous fluid or a gas, is that branch which concerns itself with the study of the boundary layer. The presence of a boundary layer accounts for the origin of the resistance and lift force, the breakdown of the smooth flow about bodies, and other phenomena that are associated with the motion of a body in a real fluid. The concept of boundary layer was clearly formulated by the founder of aerodynamics, N. E. Joukowsky, in his well-known work "On the Form of Ships" published as early as 1890."
Date: May 1956
Creator: Loitsianskii, L. G.
Partner: UNT Libraries Government Documents Department

The critical velocity of a body towed by a cable from an airplane

Description: It is sufficient to consider only the equations of motion of the towed body whereas those of the cable may be left out of consideration. The result obtained makes it possible to determine which factors affect the critical velocity and what modifications of the instrument are necessary for extending the upper limit of that velocity.
Date: July 1937
Creator: Koning, C. & DeHaas, T. P.
Partner: UNT Libraries Government Documents Department

On the stability of oscillations of an airplane wing

Description: During a flight with a Van Berkel W. B. seaplane it was observed that the wing could perform violent oscillations. A theoretical and experimental investigation led to the conclusion, that in some cases an unstable oscillation of the wing-aileron system under the influence of the elastic and aerodynamic forces is possible without further external causes.
Date: August 1923
Creator: Von Baumhauer, A. G. & Koning, C.
Partner: UNT Libraries Government Documents Department

Laying out of a practical air route

Description: Unfortunately the problem of laying out an air route has been approached by all who give it consideration as one of the hardest tasks in the world. Whereas, as a matter of fact, a very serviceable air route can be laid out with an absolute minimum of ground work.
Date: July 1922
Creator: Miner, V. S. & Carroll, T.
Partner: UNT Libraries Government Documents Department

The vector ruling protractor

Description: The theory, structure and working of a vector slide rule is presented in this report. This instrument is used for determining a vector in magnitude and position when given its components and its moment about a point in their plane.
Date: March 1924
Creator: Zahm, A. F.
Partner: UNT Libraries Government Documents Department

The resistance coefficient of commercial round wire grids

Description: From Summary: "The resistance coefficients of commercial types of round wire grids were examined for the purpose of obtaining the necessary data on supercharger test stands for throttling the inducted air to a pressure corresponding to a desired air density. The measurements of the coefficients ranged up to Reynolds numbers of 1000. In the arrangement of two grids in tandem, which was necessary in order to obtain high resistance coefficients with the solidity, that is, mesh density of grid, was found to be accompanied by a further relationship with the mutual spacing of the individual grids."
Date: January 1942
Creator: Eckert, B. & Pflüger, F.
Partner: UNT Libraries Government Documents Department

Experimental and Theoretical Investigations of Cavitation in Water

Description: "The cavitation in nozzles on airfoils of various shape and on a sphere are experimentally investigated. The limits of cavitation and the extension of the zone of the bubbles in different stages of cavitation are photographically established. The pressure in the bubble area is constant and very low, jumping to high values at the end of the area. The analogy with the gas compression shock is adduced and discussed" (p. 1).
Date: May 1945
Creator: Ackeret, J.
Partner: UNT Libraries Government Documents Department

Investigations of Compression Shocks and Boundary Layers in Gases Moving at High Speed

Description: The mutual influences of compression shocks and friction boundary layers were investigated by means of high speed wind tunnels.Schlieren optics provided a clear picture of the flow phenomena and were used for determining the location of the compression shocks, measurement of shock angles, and also for Mach angles. Pressure measurement and humidity measurements were also taken into consideration.Results along with a mathematical model are described.
Date: January 1947
Creator: Ackeret, J.; Feldmann, F. & Rott, N.
Partner: UNT Libraries Government Documents Department

Aerodynamic Heat-Power Engine Operating on a Closed Cycle

Description: "Hot-air engines with dynamic compressors and turbines offer new prospects of success through utilization of units of high efficiencies and through the employment of modern materials of great strength at high temperature. Particular consideration is given to an aerodynamic prime mover operating on a closed circuit and heated externally. Increase of the pressure level of the circulating air permits a great increase of limit load of the unit. This also affords a possibility of regulation for which the internal efficiency of the unit changes but slightly. The effect of pressure and temperature losses is investigated" (p. 1).
Date: November 1942
Creator: Ackeret, J. & Keller, D. C.
Partner: UNT Libraries Government Documents Department

High-speed wind tunnels

Description: Wind tunnel construction and design is discussed especially in relation to subsonic and supersonic speeds. Reynolds Numbers and the theory of compressible flows are also taken into consideration in designing new tunnels.
Date: November 1936
Creator: Ackeret, J.
Partner: UNT Libraries Government Documents Department

Removing boundary layer by suction

Description: "Through the utilization of the "Magnus effect" on the Flettner rotor ship, the attention of the public has been directed to the underlying physical principle. It has been found that the Prandtl boundary-layer theory furnishes a satisfactory explanation of the observed phenomena. The present article deals with the prevention of this separation or detachment of the flow by drawing the boundary layer into the inside of a body through a slot or slots in its surface" (p. 1).
Date: January 1926
Creator: Ackeret, J.
Partner: UNT Libraries Government Documents Department

The development, design and construction of gliders and sailplanes

Description: This report explains and details the history of glider design and construction through the impetus of the Rhon Sailplane contests. Some of the topics considered include: whether the longitudinal stability (dynamic and static) is sufficient in the tailless typo and a consideration that the structural weight of sweptback wings would be greater than that of a corresponding normal wing.
Date: September 1931
Creator: Lippisch, A.
Partner: UNT Libraries Government Documents Department

Method for the determination of the spanwise lift distribution

Description: The method for determination of the spanwise lift distribution is based on the Fourier series for the representation of the lift distribution. The lift distribution, as well as the angle of attack, is split up in four elementary distributions. The insertion of the angle-of-attack distribution in the Fourier series for the lift distribution gives a compound third series which is of particular advantage for the determination of the lift distribution. The method is illustrated in an example and supplemented by a graphical method. Lastly, the results of several comparative calculations with other methods are reported.
Date: October 1935
Creator: Lippisch, A.
Partner: UNT Libraries Government Documents Department

Effect of aerodynamic design on glider performance

Description: The performance of a glider is determined by means of the velocity polar, which represents the connection between horizontal and sinking speed. The mean sinking speed for a given speed range can be determined on the basis of the velocity polar. These data form the basis for the most propitious design of a performance-type glider with a view to long-distance flight.
Date: January 1935
Creator: Lippisch, A.
Partner: UNT Libraries Government Documents Department

Recent experiments at the Gottingen Aerodynamic Institute

Description: This report presents the results of various experiments carried out at the Gottingen Aerodynamic Institute. These include: experiments with Joukowski wing profiles; experiments on an airplane model with a built-in motor and functioning propeller; and the rotating cylinder (Magnus Effect).
Date: July 1925
Creator: Ackeret, J.
Partner: UNT Libraries Government Documents Department

Aeronautical education and research at the Swiss Institute of Technology in Zurich

Description: Progress in the scientific and practical fields of aviation has caused the Swiss Institute of Technology to organize lectures and practical training courses in all three branches of aeronautics and to found centers of scientific research, laboratories, etc., in order to supply the government and industries with scientifically and technically trained engineers.
Date: April 1931
Creator: Karner, L. & Ackeret, J.
Partner: UNT Libraries Government Documents Department

Experiments on airfoils with trailing edge cut away

Description: "Airfoils with their trailing edge cut away are often found on aircraft, as the fins on the hulls of flying boats and the central section of the wings for affording better visibility. It was therefore of some interest to discover the effect of such cutaways on the lift and drag and on the position of the center of pressure. For this purpose, systematic experiments were performed on two different airfoils, a symmetrical airfoil and an airfoil of medium thickness, with successive shortenings of their chords" (p. 1).
Date: September 1927
Creator: Ackeret, J.
Partner: UNT Libraries Government Documents Department

Drag measurements of two thin wing sections at different index values

Description: It is stated that the index value 6000, as found in normal tests of wing sections with a 20 cm chord, falls in the same region where the transition of laminar to turbulent flow takes place on thin flat plates. It is to be expected that slightly cambered, thin wing sections will behave similarly. The following test of two such wing sections were made for the purpose of verifying this supposition.
Date: June 1927
Creator: Ackeret, J.
Partner: UNT Libraries Government Documents Department

Air forces on airfoils moving faster than sound

Description: We are undertaking the task of computing the air forces on a slightly cambered airfoil in the absence of friction and with an infinite aspect ratio. We also assume in advance that the leading edge is very sharp and that its tangent lies in the direction of motion.
Date: June 1925
Creator: Ackeret, J.
Partner: UNT Libraries Government Documents Department

Approximation method for determining the static stability of a monoplane glider

Description: The calculations in this paper afford an approximate solution of the static stability. A derivation of the formulas for moment coefficient of a wing, moment coefficient of elevator, and the total moment of the combined wing and elevator and the moment coefficient with reference to the center of gravity are provided.
Date: November 1927
Creator: Lippisch, A.
Partner: UNT Libraries Government Documents Department

Pressure Distribution Measurements at High Speed and Oblique Incidence of Flow

Description: "The present report contains the results of a series of observations obtained for a wing of symmetrical profile for different angles of yaw. The shock tunnel with 0.4m x 0.4m cross section, of the Institute for Gas Dynamics at L.F.A. - Braunchweig was available for this work. The profile used was a 9 percent, thick hyperbolic profile with maximum thickness 40 percent aft, which was calculated by the method of F. Ringleb (2). Since the conformal transformation of this profile is known, the theoretical pressure distribution could be determined exactly for the case of incompressible flow. Then by the use of the Prandtl rule one may extend the comparison of theory and experiment to the case of higher velocity of incident flow" (p. 1).
Date: March 1947
Creator: Lippisch, A. & Beuschausen, W.
Partner: UNT Libraries Government Documents Department