Serial/Series Title
Month
152 Matching Results
Results open in a new window/tab.
The New Interpretation of the Laws of Air Resistance
A closer examination of Newton's formula for air resistance shows that it is well to consider the air as an ordinary fluid, and, indeed for most of the velocities considered, as a non-compressible fluid, so long as the dimensions of the moving body are large in comparison with the mean free path of the particles of air.
Date:
April 1923
Creator:
Prandtl, L.
System:
The UNT Digital Library
New Application of Principle of Variable-Camber Airfoil: Lachassagne System
In studying the application of his system of varying the camber of airfoil sections, Mr. Lachassagne has just obtained a series of airfoil sections whose polar envelope presents truly remarkable aerodynamic properties.
Date:
April 1924
Creator:
Toussaint, A.
System:
The UNT Digital Library
Theory of Reversible and Nonreversible Cracks in Solids
The Griffith crack theory is reviewed and certain shortcomings of this theory are discussed. A new description for the shape of a crack is given which takes into account the atomic structure of material. Through consideration of the total energy of the system and the shape of the crack, expressions for crack behavior are derived which are considered to remedy the defects of the Griffith theory.
Date:
April 1955
Creator:
Frenkel, Y. I.
System:
The UNT Digital Library
The Lead Susceptibility of Fuels and Its Dependence on the Chemical Composition
The fact that by the use of tetraethyl lead a number of otherwise unsuitable fuels could be made to meet engine requirements was not sufficiently appreciated. While use of tetraethyl lead is limited, the addition of special leaded fuels that increase the octane number is a requirement for many fuels. In this connection, the extent to which the action of tetraethyl lead through the addition of knock-resistant hydrocarbons to the base gasoline is influenced, is quite important. To the elucidation of this problem and of the storage stability of leaded fuels, the present report is dedicated.
Date:
April 1940
Creator:
Widmaier, O.
System:
The UNT Digital Library
The Torsion of Box Beams With One Side Lacking
"The torsion of box beams of rectangular section, the edges of which are strengthened by flanges, and of which one side is lacking, is analyzed by the energy method. The torsional stresses are generally taken up by the bending of the two parallel walls, the rigidity of which is augmented by the third wall. The result was checked experimentally on duralumin and plywood boxes. The torsion recorded was 10 to 30 percent less than that given by the calculation, owing to self-stiffening" (p. 1).
Date:
April 1940
Creator:
Cambilargiu, E.
System:
The UNT Digital Library
Experimental Investigation of Aircraft Propellers Exposed to Oblique Air Currents
"Two screw propellers, a normal airplane propeller with a pitch/diameter ratio H/D = 0.5 and a helicopter propeller H/D = 0.2 were tested in the large wind tunnel of the Gottigen Aerodynamic Institute. With both propellers the angle between the propeller axis and the direction of the wind was varied from 0 to 90 degrees. In addition to the three force and the three moment components in a wind-fast coordinate system, the corresponding components in a propeller-fast coordinate system, a total of six force and six moment components, together with the propulsive efficiency, were measured or calculated from measurements" (p. 1).
Date:
April 1930
Creator:
Flachsbart, O. & Kröber, G.
System:
The UNT Digital Library
Improving the Performance of Multi-Engined Airplanes by Means of Idling Propellers: The "Free-Wheel" Propeller
In order to demonstrate the importance of free-wheeling propellers, this report considers the braking effect of a propeller on a stopped engine when the propeller is rigidly connected with the engine shaft and also when mounted on a free-wheel hub. The cases of propellers of asymmetric and symmetric section are discussed. The author describes the mechanism of the free-wheel propeller as constructed for this test. The results obtained with the device mounted on a 1,000 horsepower two-engine airplane are given.
Date:
April 1930
Creator:
Pillard, M.
System:
The UNT Digital Library
Ratier Metal Propeller With Pitch Variable in Flight
One of the serious sources of difficulties in variable pitch propellers is the turning moment or torque due to the centrifugal force which tends to bring the mean plane of the blades into the plane of rotation. This moment, which is found elsewhere only in propellers with removable blades, is so great that the aerodynamic forces, as regards their effect on the torsion, become entirely negligible in comparison with it. This report presents the Ratier Company's solution to changing the pitch of airplane propellers.
Date:
April 1930
Creator:
Léglise, Pierre
System:
The UNT Digital Library
The Load Distribution in Bolted or Riveted Joints in Light-Alloy Structures
"This report contains a theoretical discussion of the load distribution in bolted or riveted joints in light-alloy structures which is applicable not only for loads below the limit of proportionality but also for loads above this limit. The theory is developed for double and single shear joints. The methods given are illustrated by numerical examples and the values assumed for the bolt (or rivet) stiffnesses are based partly on theory and partly on known experimental values" (p. 1).
Date:
April 1947
Creator:
Vogt, F.
System:
The UNT Digital Library
Investigation of the Model Me 210 in the Spin Wind Tunnel of the DVL: Fourth Partial Report - Model With Long Fuselage and With a Vee Tail
"After conclusion of the spin investigation of the model Me 210 with elongated fuselage and central vertical tail surfaces (model condition III; reference 3), tests were performed on the same model with a vee tail (model condition IV). Here the entire tail surfaces consist of only one surface with pronounced dihedral. Since the blanketing of the vertical tail surfaces by the horizontal tail surfaces, which may occur in case of standard tail surfaces, does not occur here, one could expect for this type of tail surface favorable spin characteristics, particularly with respect to rudder effectiveness for spin recovery" (p. 1).
Date:
April 1950
Creator:
Huffschmid, A.
System:
The UNT Digital Library
Fatigue Strength of Airplane and Engine Materials
This report was undertaken to give a brief summary of the laws governing the fatigue stresses and of the most important strength coefficients necessary for the correct dimensioning of the structural members. With consideration of the known fatigue strengths, the most important of which for airplane and engine materials are included in the paper, the fatigue strength of the structural parts can at least be approximately estimated.
Date:
April 1934
Creator:
Matthaes, Kurt
System:
The UNT Digital Library
Supplemental Data and Calculations of the Lateral Stability of Airplanes
In connection with the DVL Report 272 on the theory of the lateral stability of airplanes, the formal results are here amplified in some respects and their technical significance again briefly explained. Three numerical examples show how model tests for checking the lateral stability are to be evaluated and supplemented, if necessary, and how the stability limits depend on the design of the airplane and on the conditions of flight.
Date:
April 1934
Creator:
Mathias, Gotthold
System:
The UNT Digital Library
The Calculation of Lateral Stability With Free Controls
The discussion of the structural methods for obtaining lateral stability discloses the remarkable influence of the constant fuselage and wing proportions to the yawing moments. For the effectiveness of modifications in vertical tail surfaces and tail length, these quotas - little observed heretofore, in this connection - are decisive. This also applies to the amount of dihedral of the wing with regard to the roll stability of the complete wing already existing without angle of the dihedral.
Date:
April 1934
Creator:
Mathias, Gotthold
System:
The UNT Digital Library
The Efficiency of Combustion Turbines With Constant-Pressure Combustion
"Of the two fundamental cycles employed in combustion turbines, namely, the explosion (or constant-volume) cycle and the constant-pressure cycle, the latter is considered more in detail and its efficiency is derived with the aid of the cycle diagrams for the several cases with adiabatic and isothermal compression and expansion strokes and with and without utilization of the exhaust heat. Account is also taken of the separate efficiencies of the turbine and compressor and of the pressure losses and heat transfer in the piping. The results show that without the utilization of the exhaust heat the efficiencies for the two cases of adiabatic and isothermal compression is offset by the increase in the heat supplied" (p. 1).
Date:
April 1941
Creator:
Piening, Werner
System:
The UNT Digital Library
Boundary Layer Removal by Suction
Flight-test data and wind-tunnel data on suction profiles are substantially in agreement. The lift values found in the model test can be actually flown and used as a basis for the design. To visualize the action of the suction, the flow conditions with and without suction on the upper surface were photographed; figures 12 to 15 are sections of the film.
Date:
April 1941
Creator:
Schrenk, O.
System:
The UNT Digital Library
Potential Flow Through Centrifugal Pumps and Turbines
"The methods of conformal transformation up to the present have been applied to the potential flows in the rotation of solid bodies only to a limited extent. This report deals with aspects of centrifugal pumps and turbines such as: the complex potential for rotation, potential for the flow due to the blade rotation, velocities at the blade tip, comparison with "infinite number of blades," and a variable number of blades" (p. 1).
Date:
April 1941
Creator:
Sörensen, E.
System:
The UNT Digital Library
Take-Off and Propeller Thrust
As a result of previous reports, it was endeavored to obtain, along with the truest possible comprehension of the course of thrust, a complete, simple and clear formula for the whole take-off distance up to a certain altitude, which shall give the correct relative weight to all the factors.
Date:
April 1933
Creator:
Schrenk, Martin
System:
The UNT Digital Library
The Critical Shear Load of Rectangular Plates
This report gives formulas for analyzing the critical shear load of a simply supported square, isotropic (simple flat plate), or orthogonal anisotropic plate (a plate in which the rigidity in two directions perpendicular to each other is different, i.e. plywood or corrugated sheet), these formulas, although arrived at by approximation method, seem to agree fairly well with experimental results.
Date:
April 1933
Creator:
Seydel, Edgar
System:
The UNT Digital Library
Scale effect of model in seaplane-float investigations
For the purpose of solving all the problems involved, an investigation was made with flat, rectangular planing surfaces. The investigation of a flat, rectangular planing surface, which can be considered as the portion of a flat float bottom lying in front of the step, has the advantage that the frictional resistance can be determined directly from the test results. Normal and tangential forces act on the lower side of the planing surface towed through still water, while the upper side and the lateral edges are under constant atmospheric pressure.
Date:
April 1933
Creator:
Sottorf, W.
System:
The UNT Digital Library
The Effect of Turbulence on the Flame Velocity in Gas Mixtures
"The present report deals with the effect of turbulence on the propagation of the flame. Being based upon experiments with laminar as well as turbulent Bunsen flames, both the physico-chemical and the hydro-dynamical aspects of the problem are analyzed. A number of new deductions, interesting from the point of view of engine combustion and other very rapidly changing flame reactions, are made" (p. 1).
Date:
April 1947
Creator:
Damköhler, Gerhard
System:
The UNT Digital Library
Exhaust Turbine and Jet Propulsion Systems
DVL experimental and analytical work on the cooling of turbine blades by using ram air as the working fluid over a sector or sectors of the turbine annulus area is summarized. The subsonic performance of ram-jet, turbo-jet, and turbine-propeller engines with both constant pressure and pulsating-flow combustion is investigated. Comparison is made with the performance of a reciprocating engine and the advantages of the gas turbine and jet-propulsion engines are analyzed. Nacelle installation methods and power-level control are discussed.
Date:
April 1951
Creator:
Leist, Karl & Knörnschild, Eugen
System:
The UNT Digital Library
Method of Successive Approximations for the Solution of Certain Problems in Aerodynamics
A method of successive approximations for the solution of problems in the fields of diffusion, boundary-layer flow, and heat-transfer is illustrated by solving problems in each of these fields. In most of the examples, the approximate solutions are compared with known accurate solutions and the agreement is shown to be good.
Date:
April 1951
Creator:
Shvets, M. E.
System:
The UNT Digital Library
Contribution to the Theory of the Heated Duct Radiator
A method is developed with no neglect of certain factors in mass flow of air and in the drag of the heated radiator, i.e., one under actual operating conditions, as compared with the corresponding values in the cold state, may be simply computed. Although a symmetrical duct radiator has been used to bring out the flow relations, the results apply equally as well to the unsymmetrical radiator shapes usual in airplane construction.
Date:
April 1939
Creator:
Winter, H.
System:
The UNT Digital Library
Investigations and Tests in the Towing Basin at Guidonia
The experimental methods at the Guidonia towing basin are discussed including specifications. Some of the components examined are the bridge towing carriage, side towing carriage, catapult installation, and dynamometer systems. Tests were performed on hulls and floats, as well as motor boats and torpedo shaped bodies. Theoretical investigations were also performed to determine pressure distributions on geometrically simple bodies, propagation of small wave motions, and planing and submerged surfaces.
Date:
April 1939
Creator:
Cremona, C.
System:
The UNT Digital Library