Latest content added for UNT Digital Library Collection: National Advisory Committee for Aeronautics (NACA)http://digital.library.unt.edu/explore/collections/NACA/browse/?sort=added_a&fq=untl_institution:UNTGD2011-11-11T19:22:00-06:00UNT LibrariesThis is a custom feed for browsing UNT Digital Library Collection: National Advisory Committee for Aeronautics (NACA)Flow and Force Equations for a Body Revolving in a Fluid2011-11-11T19:22:00-06:00http://digital.library.unt.edu/ark:/67531/metadc53409/<p><a href="http://digital.library.unt.edu/ark:/67531/metadc53409/"><img alt="Flow and Force Equations for a Body Revolving in a Fluid" title="Flow and Force Equations for a Body Revolving in a Fluid" src="http://digital.library.unt.edu/ark:/67531/metadc53409/thumbnail/"/></a></p><p>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.</p>The Inertia Coefficients of an Airship in a Frictionless Fluid2011-11-11T19:22:00-06:00http://digital.library.unt.edu/ark:/67531/metadc53406/<p><a href="http://digital.library.unt.edu/ark:/67531/metadc53406/"><img alt="The Inertia Coefficients of an Airship in a Frictionless Fluid" title="The Inertia Coefficients of an Airship in a Frictionless Fluid" src="http://digital.library.unt.edu/ark:/67531/metadc53406/thumbnail/"/></a></p><p>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.</p>Empirical relation between induced velocity, thrust, and rate of descent of a helicopter rotor as determined by wind-tunnel tests on four model rotors2011-11-11T19:22:00-06:00http://digital.library.unt.edu/ark:/67531/metadc53597/<p><a href="http://digital.library.unt.edu/ark:/67531/metadc53597/"><img alt="Empirical relation between induced velocity, thrust, and rate of descent of a helicopter rotor as determined by wind-tunnel tests on four model rotors" title="Empirical relation between induced velocity, thrust, and rate of descent of a helicopter rotor as determined by wind-tunnel tests on four model rotors" src="http://digital.library.unt.edu/ark:/67531/metadc53597/thumbnail/"/></a></p><p>The empirical relation between the induced velocity, thrust, and rate of vertical descent of a helicopter rotor was calculated from wind tunnel force tests on four model rotors by the application of blade-element theory to the measured values of the thrust, torque, blade angle, and equivalent free-stream rate of descent. The model tests covered the useful range of C(sub t)/sigma(sub e) (where C(sub t) is the thrust coefficient and sigma(sub e) is the effective solidity) and the range of vertical descent from hovering to descent velocities slightly greater than those for autorotation. The three bladed models, each of which had an effective solidity of 0.05 and NACA 0015 blade airfoil sections, were as follows: (1) constant-chord, untwisted blades of 3-ft radius; (2) untwisted blades of 3-ft radius having a 3/1 taper; (3) constant-chord blades of 3-ft radius having a linear twist of 12 degrees (washout) from axis of rotation to tip; and (4) constant-chord, untwisted blades of 2-ft radius. Because of the incorporation of a correction for blade dynamic twist and the use of a method of measuring the approximate equivalent free-stream velocity, it is believed that the data obtained from this program are more applicable to free-flight calculations than the data from previous model tests.</p>Development of a supersonic area rule and an application to the design of a wing-body combination having high lift-to-drag ratios2011-11-11T19:22:00-06:00http://digital.library.unt.edu/ark:/67531/metadc53042/<p><a href="http://digital.library.unt.edu/ark:/67531/metadc53042/"><img alt="Development of a supersonic area rule and an application to the design of a wing-body combination having high lift-to-drag ratios" title="Development of a supersonic area rule and an application to the design of a wing-body combination having high lift-to-drag ratios" src="http://digital.library.unt.edu/ark:/67531/metadc53042/thumbnail/"/></a></p><p>None</p>Evolution of the helicopter2011-11-11T19:22:00-06:00http://digital.library.unt.edu/ark:/67531/metadc53094/<p><a href="http://digital.library.unt.edu/ark:/67531/metadc53094/"><img alt="Evolution of the helicopter" title="Evolution of the helicopter" src="http://digital.library.unt.edu/ark:/67531/metadc53094/thumbnail/"/></a></p><p>None</p>Wing pressure distributions over the lift range of the convair xf-92a delta-wing airplane at subsonic and transonic speeds2011-11-11T19:22:00-06:00http://digital.library.unt.edu/ark:/67531/metadc53093/<p><a href="http://digital.library.unt.edu/ark:/67531/metadc53093/"><img alt="Wing pressure distributions over the lift range of the convair xf-92a delta-wing airplane at subsonic and transonic speeds" title="Wing pressure distributions over the lift range of the convair xf-92a delta-wing airplane at subsonic and transonic speeds" src="http://digital.library.unt.edu/ark:/67531/metadc53093/thumbnail/"/></a></p><p>None</p>Determination of rate, area, and distribution of impingement of waterdrops on various airfoils from trajectories obtained on the differential analyzer2011-11-11T19:22:00-06:00http://digital.library.unt.edu/ark:/67531/metadc53095/<p><a href="http://digital.library.unt.edu/ark:/67531/metadc53095/"><img alt="Determination of rate, area, and distribution of impingement of waterdrops on various airfoils from trajectories obtained on the differential analyzer" title="Determination of rate, area, and distribution of impingement of waterdrops on various airfoils from trajectories obtained on the differential analyzer" src="http://digital.library.unt.edu/ark:/67531/metadc53095/thumbnail/"/></a></p><p>None</p>Moments of cambered round bodies2011-11-11T19:22:00-06:00http://digital.library.unt.edu/ark:/67531/metadc53600/<p><a href="http://digital.library.unt.edu/ark:/67531/metadc53600/"><img alt="Moments of cambered round bodies" title="Moments of cambered round bodies" src="http://digital.library.unt.edu/ark:/67531/metadc53600/thumbnail/"/></a></p><p>Results are presented for the moments and position of force centers of a series of cambered round bodies derived from a torpedo-like body of revolution. The effects of placing fins on the rear of the body of revolution are also included.</p>Compilation and Analysis of US Turbojet and Ram-Jet Engine Characteristics2011-11-11T19:22:00-06:00http://digital.library.unt.edu/ark:/67531/metadc53273/<p><a href="http://digital.library.unt.edu/ark:/67531/metadc53273/"><img alt="Compilation and Analysis of US Turbojet and Ram-Jet Engine Characteristics" title="Compilation and Analysis of US Turbojet and Ram-Jet Engine Characteristics" src="http://digital.library.unt.edu/ark:/67531/metadc53273/thumbnail/"/></a></p><p>None</p>The factors that determine the minimum speed of an airplane2011-11-11T19:22:00-06:00http://digital.library.unt.edu/ark:/67531/metadc53737/<p><a href="http://digital.library.unt.edu/ark:/67531/metadc53737/"><img alt="The factors that determine the minimum speed of an airplane" title="The factors that determine the minimum speed of an airplane" src="http://digital.library.unt.edu/ark:/67531/metadc53737/thumbnail/"/></a></p><p>The author argues that because of a general misunderstanding of the principles of flight at low speed, there are a large number of airplanes that could be made to fly several miles per hour slower than at present by making slight modifications. In order to show how greatly the wing section affects the minimum speed, curves are plotted against various loadings. The disposition of wings on the airplane slightly affects the lift coefficient, and a few such cases are discussed. Another factor that has an effect on minimum speed is the extra lift exerted by the slip stream on the wings. Also discussed are procedures to be followed by the pilot, especially with regard to stick movements during low speed flight. Also covered are stalling, yaw, rolling moments, lateral control, and the effectiveness of ailerons and rudders.</p>