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 Collection: National Advisory Committee for Aeronautics Collection
Flow and Force Equations for a Body Revolving in a Fluid

Flow and Force Equations for a Body Revolving in a Fluid

Date: December 1, 1979
Creator: Zahm, A. F.
Description: A general method for finding the steady flow velocity relative to a body in plane curvilinear motion, whence the pressure is found by Bernoulli's energy principle is described. Integration of the pressure supplies basic formulas for the zonal forces and moments on the revolving body. The application of the steady flow method for calculating the velocity and pressure at all points of the flow inside and outside an ellipsoid and some of its limiting forms is presented and graphs those quantities for the latter forms. In some useful cases experimental pressures are plotted for comparison with theoretical. The pressure, and thence the zonal force and moment, on hulls in plane curvilinear flight are calculated. General equations for the resultant fluid forces and moments on trisymmetrical bodies moving through a perfect fluid are derived. Formulas for potential coefficients and inertia coefficients for an ellipsoid and its limiting forms are presented.
Contributing Partner: UNT Libraries Government Documents Department
The Inertia Coefficients of an Airship in a Frictionless Fluid

The Inertia Coefficients of an Airship in a Frictionless Fluid

Date: December 1, 1979
Creator: Bateman, H.
Description: The apparent inertia of an airship hull is examined. The exact solution of the aerodynamical problem is studied for hulls of various shapes with special attention given to the case of an ellipsoidal hull. So that the results for the ellipsoidal hull may be readily adapted to other cases, they are expressed in terms of the area and perimeter of the largest cross section perpendicular to the direction of motion by means of a formula involving a coefficient kappa which varies only slowly when the shape of the hull is changed, being 0.637 for a circular or elliptic disk, 0.5 for a sphere, and about 0.25 for a spheroid of fineness ratio. The case of rotation of an airship hull is investigated and a coefficient is defined with the same advantages as the corresponding coefficient for rectilinear motion.
Contributing Partner: UNT Libraries Government Documents Department
The Aerodynamic Forces on Airship Hulls

The Aerodynamic Forces on Airship Hulls

Date: December 1, 1979
Creator: Munk, M. M.
Description: The new method for making computations in connection with the study of rigid airships, which was used in the investigation of Navy's ZR-1 by the special subcommittee of the National Advisory Committee for Aeronautics appointed for this purpose is presented. The general theory of the air forces on airship hulls of the type mentioned is described and an attempt was made to develop the results from the very fundamentals of mechanics.
Contributing Partner: UNT Libraries Government Documents Department
Experience with geared propeller drives for aviation engines

Experience with geared propeller drives for aviation engines

Date: September 1, 1920
Creator: Kutzbach, K
Description: I. The development of the gear wheels: (a) bending stresses; (b) compressive stresses; (c) heating; (d) precision of manufacture. II. General arrangement of the gearing. III. Vibration in the shaft transmission. An overview is given of experience with geared propeller drives for aviation engines. The development of gear wheels is discussed with emphasis upon bending stresses, compressive stresses, heating, and precision in manufacturing. With respect to the general arrangement of gear drives for airplanes, some principal rules of mechanical engineering that apply with special force are noted. The primary vibrations in the shaft transmission are discussed. With respect to vibration, various methods for computing vibration frequency and the influence of elastic couplings are discussed.
Contributing Partner: UNT Libraries Government Documents Department
Tests of the Daimler D-IVa engine at a high altitude test bench

Tests of the Daimler D-IVa engine at a high altitude test bench

Date: October 1, 1920
Creator: Noack, W G
Description: Reports of tests of a Daimler IVa engine at the test-bench at Friedrichshafen, show that the decrease of power of that engine, at high altitudes, was established, and that the manner of its working when air is supplied at a certain pressure was explained. These tests were preparatory to the installation of compressors in giant aircraft for the purpose of maintaining constant power at high altitudes.
Contributing Partner: UNT Libraries Government Documents Department
Italian and French experiments on wind tunnels

Italian and French experiments on wind tunnels

Date: November 1, 1920
Creator: Knight, WM
Description: Given here are the results of experiments conducted by Colonel Costanzi of the Italian Army to determine the influence of the surrounding building in which a wind tunnel was installed on the efficiency of the installation, and how the efficiency of the installation was affected by the design of the tunnel. Also given are the results of a series of experiments by Eiffel on 34 models of tunnels of different dimensions. This series of experiments was started in order to find out if, by changing the shape of the nozzle or of the diffuser of the large tunnel at Auteuil, the efficiency of the installation could be improved.
Contributing Partner: UNT Libraries Government Documents Department
Notes on specifications for French airplane competitions

Notes on specifications for French airplane competitions

Date: October 1, 1920
Creator: Margoulis, W
Description: Given here are the rules officially adopted by the Aeronautical Commission of the Aero Club of France for a flight competition to be held in France in 1920 at the Villacoublay Aerodrome. The prize will be awarded to the pilot who succeeds in obtaining the highest maximum and lowest minimum speeds, and in landing within the shortest distance.
Contributing Partner: UNT Libraries Government Documents Department
The determination of the effective resistance of a spindle supporting a model airfoil

The determination of the effective resistance of a spindle supporting a model airfoil

Date: January 1, 1921
Creator: Davidson, W E
Description: An attempt was made to determine the effect of spindle interference on the lift of the airfoil by measuring moments about the axis parallel to the direction of air flow. The values obtained are of the same degree as the experimental error, and for the present this effect will be neglected. The results obtained using a U.S.A. 15 wing (plotted here) show that the correction is nearly constant from 0 degrees to 10 degrees incidence and that at greater angles its value becomes erratic. At such angles, however, the wing drag is so high that the spindle correction and its attendant errors become relatively small and unimportant.
Contributing Partner: UNT Libraries Government Documents Department
Loads and calculations of army airplanes

Loads and calculations of army airplanes

Date: February 1, 1921
Creator: Stelmachowski, Ing
Description: By comparing airplanes of known strength that have resisted all the usual and even extreme air loads with those that under like conditions were found to be insufficiently strong, the researchers, aided by scientific investigations, developed standards which are satisfactory for the calculation of airplane structures. Given here are standards applicable to loads on wing trusses, load factors for use in stress analysis, load factors required in sand testing, loads on control surfaces, loads on wing ribs, loads on landing gear, and rigidity of materials.
Contributing Partner: UNT Libraries Government Documents Department
Progress made in the construction of giant airplanes in Germany during the war

Progress made in the construction of giant airplanes in Germany during the war

Date: December 1, 1920
Creator: Baumann, A
Description: The construction of giant airplanes was begun in Germany in August, 1914. The tables annexed here show that a large number of airplanes weighing up to 15.5 tons were constructed and tested in Germany during the War, and it is certain that no other country turned out airplanes of this weight nor in such large numbers. An examination of the tables shows that by the end of the War all the manufacturers had arrived at a well-defined type, namely an airplane of about 12 tons with four engines of 260 horsepower each. The aircraft listed here are discussed with regard to useful weight and aerodynamic qualities.
Contributing Partner: UNT Libraries Government Documents Department