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Recent Results on High-Pressure Axial Blowers

Description: "Considerable progress has, in recent times, been attained in the development of the high-pressure axial blower by well-planned research. The efforts are directed toward improving the efficiencies, which are already high for the axial blower, and in particular the delivery pressure heads. For high pressures multistage arrangements are used. Of fundamental importance is the careful design of all structural parts of the blower that are subject to the effects of the flow. In the present report, several recent results and experiences are reported, which are based on results of German engine research" (p. 1).
Date: April 1947
Creator: Eckert, B.
Partner: UNT Libraries Government Documents Department

Experiences with flow-direction instruments

Description: "The method of recording the direction of flows on the basis of the hydrodynamic zero-point measurement has now reached a certain limit, in spite of the good results achieved. While the available flow-direction devices are accurate enough for many purposes, they are all insufficient for perfectly exact prediction of the flow direction. The next problem will be to achieve a point-by point flow-direction record, whereby the test procedure must be simplified, accelerated, and the degree of accuracy of the test data improved" (p. 1).
Date: March 1941
Creator: Eckert, B.
Partner: UNT Libraries Government Documents Department

Possibilities of Reducing the Length of Axial Superchargers for Aircraft Motors

Description: Axial blowers are gaining importance as aircraft engine superchargers. However, the pressure head obtainable per stage is small. Due to the necessary great number of stages, the physical length of the blower becomes too great for an airworthy device. This report discusses several types of construction that permit a reduction in the length of the blower.
Date: January 1947
Creator: Eckert, B.
Partner: UNT Libraries Government Documents Department

Tank tests of twin seaplane floats

Description: The following report contains the most essential data for the hydrodynamic portion of the twin-float problem. The following points were successfully investigated: 1) difference between stationary and nonstationary flow; 2) effect of the shape of the step; 3) effect of distance between floats; 4) effect of nose-heavy and tail-heavy moments; 5) effect of the shape of floats; 6) maneuverability.
Date: October 1928
Creator: Herrmann, H.; Kempf, G. & Kloess, H.
Partner: UNT Libraries Government Documents Department

Protection of wooden airplane parts against moisture by means of varnish

Description: The objects of the experiments herein described were to test the protection afforded by Valspar oil varnish against the absorption of moisture by wooden airplane parts and the consequent changes in their elastic properties and to compare some of the best Dutch varnishes with Valspar.
Date: February 1926
Creator: Wolff, E. B. & Van Ewijk, L. J. G.
Partner: UNT Libraries Government Documents Department

Mechanical properties of some materials used in airplane construction

Description: Since lightness is desirable in airplane construction, greater stresses must be tolerated than in other kinds of construction. It is therefore necessary to have a more accurate knowledge of the greatest stresses that may occur and of the actual properties of the materials used. The Aeronautic Research Laboratories took the limit of elasticity as the basis of the strength calculations. Many tests were made of different steels, woods, aluminum alloys, and fabrics.
Date: January 1928
Creator: Wolff, E. B. & Van Ewijk, L. J. G.
Partner: UNT Libraries Government Documents Department

Preliminary investigation of the effect of a rotating cylinder in a wing

Description: Into the leading edge of a wing with arbitrary cross-section, there is introduced a cylinder, which can be rotated by an electric motor by means of a cord. Observations were made in the wind tunnel on how the lift at different wind velocities was affected by rotating this cylinder.
Date: March 1925
Creator: Wolff, E. B.
Partner: UNT Libraries Government Documents Department

Discussion of the results of the boundary-layer tests of an airfoil fitted with a rotary cylinder

Description: The results of the velocity measurements in the boundary layer described in NACA-TM 411 are here discussed in greater detail. The measurements made were of the velocity distribution in the vicinity of an airfoil model fitted with a rotary cylinder and were undertaken for the purpose of obtaining a closer insight into the phenomena observed in experimenting with this model.
Date: August 1927
Creator: Wolff, E. B. & Koning, C.
Partner: UNT Libraries Government Documents Department

Aerial photography : obtaining a true perspective

Description: Report discussing a demonstration was given within the last few days at the British Museum by Mr. J. W. Gordon, author of "Generalized Linear Perspective" (Constable and Co.), a work describing a newly-worked-out system by which photographs can be made available for the purpose of exactly recording the dimensions of the objects photographed even when the objects themselves are presented foreshortened in the photograph.
Date: April 1923
Partner: UNT Libraries Government Documents Department

Generalization of Joukowski formula to an airfoil of a cascade in compressible gas stream with subsonic velocities

Description: It is shown that the ordinary Joukowski formula for lift force of cascade blades in incompressible flow can be applied to the case of subsonic compressible flow with sufficient accuracy, provided that the density in the formula is taken as the arithmetic mean of the densities far ahead of and behind the cascade.
Date: September 1951
Creator: Loitsianskii, L. G.
Partner: UNT Libraries Government Documents Department

General instability criterion of laminar velocity distributions

Description: The present paper describes the results of a stability investigation on symmetrical velocity profiles in a channel and of boundary-layer profiles. The effect of friction was assumed to be vanishing and did not occur in the stability consideration so far as it had been resorted to for preparatory asymptotic considerations. Proceeding on very general premises as regards the form of the velocity distribution, a proof was deduced of the elementary theorem that velocity profiles with inflection points are unstable.
Date: April 1936
Creator: Tollmien, W.
Partner: UNT Libraries Government Documents Department

Hydrodynamic tests for determining the take-off characteristics of seaplanes

Description: The resistance of water, even at low speeds, may be such as to render it impossible to take off. For this type of aircraft, it is therefore especially important to determine the take-off characteristics. A new and simple graphical method is given and appears to be the only one for the complete solution of the problem.
Date: May 1923
Creator: Verduzio, R.
Partner: UNT Libraries Government Documents Department

Applying the results of experiments on small models in the wind tunnel to the calculation of full-sized aircraft

Description: This report presents the attempt to develop a law which will permit the use of results obtained on small models in a tunnel for the calculation of full-sized airplanes, or if it exists, a law of similitude relating air forces on a full-sized plane to those on a reduced scale model.
Date: April 1922
Creator: Robert
Partner: UNT Libraries Government Documents Department

The temperature of unheated bodies in a high-speed gas stream

Description: From Summary: "The present report deals with temperature measurements on cylinders of 0.2 to 3 millimeters diameter in longitudinal and transverse air flow at speeds of 100 to 300 meters per second. Within the explored test range, that is, the probable laminar boundary layer region, the temperature of the cylinders in axial flow is practically independent of the speed and in good agreement with Pohlhausen's theoretical values; Whereas, in transverse flow, cylinders of certain diameter manifest a close relationship with speed, the ratio of the temperature above the air of the body to the adiabatic stagnation temperature decreases with rising speed and then rises again from a Mach number of 0.6. The importance of this "specific temperature" of the body for heat-transfer studies at high speed is discussed."
Date: December 1941
Creator: Eckert, E. & Weise, W.
Partner: UNT Libraries Government Documents Department

The stress criterion of a tension member with graded flexural stiffness: contribution to the problem of "clamping effect" outside of the elastic range

Description: The approximate size of the stress criterion of a bar on two supports stressed beyond the elastic range is assessed by an approximation. The calculation proceeds from the premise of "substitute flexural stiffness" so defined that the part stressed beyond the elastic range may be considered as following Hooke's law when determining the flexural deformation quantities. For the determination of the substitute flexural stiffness, it is presumed that the material is already stressed so much beyond the yield point as to be strain-hardened. The data are directly applicable to materials having no definite yield point. For the rest, von Karman's method for compressed and subsequently deflected bars serves as basis for the calculation.
Date: September 1936
Creator: Kaul, Hans W.
Partner: UNT Libraries Government Documents Department

Temperature recording in high-speed gases

Description: The development of suitable thermometer shapes giving the amount of temperature rise if possible without calibration and affording ready repetition is predicated upon a fundamental elucidation of this heating on a number of elementary body forms. This report provides results of tests at subsonic and supersonic velocities.
Date: August 1941
Creator: Eckert, E.
Partner: UNT Libraries Government Documents Department

Boundary Layer Theory, Part 2, Turbulent Flows

Description: From Summary: "The flow laws of the actual flows at high Reynolds numbers differ considerably from those of the laminar flows treated in the preceding part. These actual flows show a special characteristic, denoted as turbulence. The character of a turbulent flow is most easily understood the case of the pipe flow. Consider the flow through a straight pipe of circular cross section and with a smooth wall. For laminar flow each fluid particle moves with uniform velocity along a rectilinear path."
Date: April 1949
Creator: Schlichting, H.
Partner: UNT Libraries Government Documents Department

Experimental investigation of the problem of surface roughness

Description: Based on the universal laws of turbulent velocity distribution at rough and smooth walls, there is in the present work presented a method that allows surface roughness tests and in particular, measurements on the roughness of ship surfaces to be carried out in a much simpler manner. The types of roughness investigated were in the form of flat, rough plates installed in a square-section rectangular channel, the other three walls always being smooth. Twenty-one plates of various roughness were investigated, the roughness elements being the following: spheres of diameter 0.41 and 0.21, respectively, spherical segments, cones, and "short" and "long" angles.
Date: April 1937
Creator: Schlichting, H.
Partner: UNT Libraries Government Documents Department

Airfoil Theory at Supersonic Speed

Description: From Summary: "A theory is developed for the airfoil of finite span at supersonic speed analogous to the Prandtl airfoil theory of 1918-1919 for incompressible flow. In addition to the profile and induced drags, account must be taken at supersonic flow of still another drag, namely, the wave drag, which is independent of the wing aspect ratio. Both wave and induced drags are proportional to the square of the lift and depend on the Mach number, that is, the ratio of flight to sound speed. In general, in the case of supersonic flow, the drag-lift ratio is considerably less favorable than is the case for incompressible flow."
Date: June 1939
Creator: Schlichting, H.
Partner: UNT Libraries Government Documents Department

Amplitude distribution and energy balance of small disturbances in plate flow

Description: From Introduction: "The present report, therefore, deals first, with the distribution of the amplitude of the disturbance over the flow section, that is, the calculation of the characteristic functions and second, with the study of the energy distribution and energy balance of the disturbance motion. The investigations are based upon the disturbances of the laminar flow past a flat plate which are situated exactly at the boundary between amplification and damping (neutral oscillations)."
Date: April 1950
Creator: Schlichting, H.
Partner: UNT Libraries Government Documents Department