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  Partner: UNT Libraries Government Documents Department
 Collection: National Advisory Committee for Aeronautics Collection
Flow and Drag Formulas for Simple Quadrics

Flow and Drag Formulas for Simple Quadrics

Date: January 1, 1927
Creator: Zahm, A F
Description: This report gives the pressure distribution and resistance found by theory and experiment for simple quadrics fixed in an infinite uniform stream of practically incompressible fluid. The experimental values pertain to air and some liquids, especially water; the theoretical refer sometimes to perfect, again to viscid fluids. For the cases treated the concordance of theory and measurement is so close as to make a resume of results desirable. Incidentally formulas for the velocity at all points of the flow field are given, some being new forms for ready use derived in a previous paper. (author).
Contributing Partner: UNT Libraries Government Documents Department
Flow and Force Equations for a Body Revolving in a Fluid

Flow and Force Equations for a Body Revolving in a Fluid

Date: January 1, 1930
Creator: Zahm, A F
Description: Part I gives 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. Integration of the pressure supplies basic formulas for the zonal forces and moments on the revolving body. Part II, applying this steady-flow method, finds the velocity and pressure at all points of the flow inside and outside an ellipsoid and some of its limiting forms, and graphs those quantities for the latter forms. Part III finds the pressure, and thence the zonal force and moment, on hulls in plane curvilinear flight. Part IV derives general equations for the resultant fluid forces and moments on trisymmetrical bodies moving through a perfect fluid, and in some cases compares the moment values with those found for bodies moving in air. Part V furnishes ready formulas for potential coefficients and inertia coefficients for an ellipsoid and its limiting forms. Thence are derived tables giving numerical values of those coefficients for a comprehensive range of shapes.
Contributing Partner: UNT Libraries Government Documents Department
Influence of model surface and air flow texture on resistance of aerodynamic bodies

Influence of model surface and air flow texture on resistance of aerodynamic bodies

Date: January 1, 1923
Creator: Zahm, A F
Description: This report is an analysis of two resistance equations which have particular application in the comparison of tests from different aerodynamical laboratories.
Contributing Partner: UNT Libraries Government Documents Department
Periodic stresses in gyroscopic bodies, with applications to air screws

Periodic stresses in gyroscopic bodies, with applications to air screws

Date: January 1, 1918
Creator: Zahm, A F
Description: Report discusses periodic stresses in gyroscopic bodies with applications to air screws caused by particle mass. Report concludes that all modern air screws obey the laws found for plane groups of particles. In particular the two-bladers exert on the shaft a rhythmic gyroscopic torque; the multibladers a steady one; both easily calculable for any given conditions of motion and mass distribution.
Contributing Partner: UNT Libraries Government Documents Department
Pressure of air on coming to rest from various speeds

Pressure of air on coming to rest from various speeds

Date: January 1, 1927
Creator: Zahm, A F
Description: The text gives theoretical formulas from which is computed a table for the pressure of air on coming to rest from various speeds, such as those of aircraft and propeller blades. Pressure graphs are given for speeds from 1 cm. Sec. up to those of swift projectiles.
Contributing Partner: UNT Libraries Government Documents Department
Relation of rib spacing to stress in wing planes

Relation of rib spacing to stress in wing planes

Date: May 1, 1920
Creator: Zahm, A F
Description: The stress relations to the fabric and the rib consequent upon a change of spacing between ribs in a wing plane are discussed. Considering the wing plane as a static structure, and ignoring the question of aerodynamic efficiency, it appears that the unit stress in the rib and fabric will remain constant for constant p if the linear dimensions of both rib and fabric are increased alike, viz., if wing and fabric remain geometrically similar. Since the bulge and the structural dimensions remain geometrically similar, the whole distended plane remains so, and hence should have the same pressure distribution and efficiency. If therefore the Burgess rule of making the rib spacing always one-fifth of the chord of the plane be valid, it must be valid for all others that are mechanically similar in structure and covering.
Contributing Partner: UNT Libraries Government Documents Department
The six-component wind balance

The six-component wind balance

Date: January 1, 1923
Creator: Zahm, A F
Description: Dr. Zahm's report is a description of the six-component wind-tunnel balance in use at the Aerodynamic Laboratory, Washington Navy Yard. The description of the balance gives the mechanical details and the method of operation, and is accompanied by line drawings showing the construction of the balance. The balance is of particular interest, as it allows the model to be set up quickly and accurately in roll, pitch, and yaw, without stopping the wind. It is possible to measure automatically, directly, and independently the drag, cross-wind force, and lift; also the rolling, pitching, and yawing moments. It is also possible to make the balance self-recording.
Contributing Partner: UNT Libraries Government Documents Department
Stability equations for airship hulls

Stability equations for airship hulls

Date: January 1, 1926
Creator: Zahm, A F
Description: In the text are derived simple formulae for determining, directly from the data of wind tunnel tests of a model of an airship hull, what shall be the approximate character of oscillation, in pitch or yaw, of the full-scale airship when slightly disturbed from steady forward motion. (author).
Contributing Partner: UNT Libraries Government Documents Department
Theories of flow similitude

Theories of flow similitude

Date: January 1, 1929
Creator: Zahm, A F
Description: The laws of comparison of dynamically similar fluid motions are derived by three different methods based on the same principle and yielding the same or equivalent formulas. This report outlines the three current methods of comparing dynamically similar motions, more especially of fluids, initiated respectively by Newton, Stokes (or Helmholtz), and Rayleigh. These three methods, viz., the integral, the differential, and the dimensional, are enough alike to be studied profitably together. They are treated in succession then compared. (author).
Contributing Partner: UNT Libraries Government Documents Department
The vector ruling protractor

The vector ruling protractor

Date: March 1, 1924
Creator: Zahm, A F
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.
Contributing Partner: UNT Libraries Government Documents Department