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Flow around wings accompanied by separation of vortices

Description: The flow around wings computed by the usual method leads in the case of a finite trailing edge to a stagnation point in the trailing edge due to the Kutta-Joukowsky condition of flow governing this region. As a result, the theoretical pressure distribution differs substantially from the experimental values in the vicinity of the trailing edge. The present report describes an alternative method of calculation in which the rear stagnation point no longer appears. The stream leaves the trailing edge tangentially on the pressure side and a similar tangential separation occurs on the suction side of the profile at a point slightly in front of the trailing edge.
Date: December 1940
Creator: Schmieden, C.

Note on the calculation of boundary layers

Description: The properties of the solutions of the hydrodynamic equations of viscous fluid by "boundary-layer omission" are discussed. A method is indicated for the numerical determination of the solution for a known initial profile u(x(sub o),y) and pressure distribution p(x) within the region.
Date: November 1940
Creator: Prandtl, L.

On the theory of unsteady planing and the motion of a wing with vortex separation

Description: The disturbance imparted to water by a planing body give rise to a wave form of motion on the free surface, the length of the waves increasing indefinitely with increase in the Froude number and being directly proportional to the latter in the case of the plane or two-dimensional problem. At large Froude numbers the effect of the weight shows up to any appreciable extent only at some distance from the body, so that the flow near the body can be considered as part of a flow of an infinitely extending weightless fluid. This paper is a consideration of these characteristics as well as a formulation of the planing problem and its relation to the problem of a thin wing.
Date: May 1940
Creator: Sedov, L.

Constant-pressure blowers

Description: The conventional axial blowers operate on the high-pressure principle. One drawback of this type of blower is the relatively low pressure head, which one attempts to overcome with axial blowers producing very high pressure at a given circumferential speed. The Schicht constant-pressure blower affords pressure ratios considerably higher than those of axial blowers of conventional design with approximately the same efficiency.
Date: January 1940
Creator: Sörensen, E.

Aerodynamics of rotating-wing aircraft with blade-pitch control

Description: From Introduction: "In the present report, with the aid of the usual computation methods, a rotor is investigated the pitch of whose blades is capable of being controlled in such a manner that it varies linearly with the flapping angle. To test the effect of this linkage on the aircraft performance, the theory is applied to an illustrative example."
Date: February 1940
Creator: Pfluger, A

Stresses in single-spar wing constructions with incompletely built-up ribs

Description: It is shown that the force distribution resulting from incomplete ribs in single spar wing structures may be determined with the aid of the shear field method by a statistically indeterminate computation. A numerical computation is given of the force distribution of a wing structure whose two neighboring incomplete ribs with web missing in half the section are torsionally loaded.
Date: March 1940
Creator: Reinitzhuber, F.

Recent work on airfoil theory

Description: The basic ideas of a new method for treating the problem of the airfoil are presented, and a review is given of the problems thus far computed for incompressible and supersonic flows. Test results are reported for the airfoil of circular plan form and the results are shown to agree well with the theory. As a supplement, a theory based on the older methods is presented for the rectangular of small aspect ratio.
Date: December 1940
Creator: Prandtl, L.

The maximum delivery pressure of single-stage radial superchargers for aircraft engines

Description: With the aid of simple considerations and test results, an attempt is made to clear up some obscure points that still exist. The considerations are restricted to those cases where it is in fact of advantage to"force" the large delivery heads required for high altitude and high supercharge with a single-stage supercharger.
Date: August 1940
Creator: von der Nüll, W.

Effect of Wing Loading, Aspect Ratio, and Span Loading of Flight Performances

Description: "An investigation is made of the possible improvements in maximum, cruising, and climbing speeds attainable through increase in the wing loading. The decrease in wing area was considered for the two cases of constant aspect ratio and constant span loading. For a definite flight condition, an investigation is made to determine what loss in flight performance must be sustained if, for given reasons, certain wing loadings are not to be exceeded. With the aid of these general investigations, the trend with respect to wing loading is indicated and the requirements to be imposed on the landing aids are discussed" (p. 1).
Date: January 1940
Creator: Göthert, B.

The Torsion of Box Beams With One Side Lacking

Description: "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.

Measurement of Knock Characteristics in Spark-Ignition Engines

Description: This paper presents a discussion of three potential sources of error in recording engine knocking which are: the natural oscillation of the membrane, the shock process between test contacts, and the danger of burned contacts. Following this discussion, the paper calls attention to various results which make the bouncing-pin indicator appear fundamentally unsuitable for recording knock phenomena.
Date: March 1940
Creator: Schütz, R.

The Lead Susceptibility of Fuels and Its Dependence on the Chemical Composition

Description: 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.

Resonance Vibrations in Intake and Exhaust Pipes of in-Line Engines 3: The Inlet Process of a Four-Stroke-Cycle Engine

Description: Using a previously developed method, the boundary process of four-stroke-cycle engines are set up. The results deviate considerably from those obtained under the assumption that the velocity fluctuation is proportional to the cylinder piston motion. The deviation is less at the position of resonance frequencies. By the method developed, the effect of the resonance vibrations on the volumetric efficiency can be demonstrated.
Date: October 1940
Creator: Lutz, O.

Pressure and Temperature Measurement in Supercharger Investigations

Description: "With the further development of the supercharger, requirements with regard to measuring accuracy increase while at the same time the conditions under which the measurements must be carried out become more difficult. The present paper is a contribution toward the improvement and refinement of the measuring methods. For pressure measurements some suggestions are made with regard to design and location of the measuring stations" (p. 1).
Date: September 1940
Creator: Franz, A.

New Equipment for Testing the Fatigue Strength of Riveted and Welded Joints

Description: "The mechanical and electrical construction of a new experimental instrument for fatigue testing riveted and welded joints is described. This experimental device has the advantage of being able to stress, even with comparatively low magnetic exciter force, structural components in alternate bending by resonance vibrations up to incipient fatigue failure (p .1)".
Date: July 1940
Creator: Müller, W

Experiments on Ball and Roller Bearings Under Conditions of High Speed and Small Oil Supply

Description: This report describes a testing machine on which 35 millimeter bearings (bore) can be run at speeds of the order of 21,000 rpm, while the following factors are recorded: 1) oil circulation through bearing and oil temperature. 2) maximum temperature of outer bearing ring, 3) radial and axial load on bearing, 4) radial, axial, and angular clearance of bearing, 5) power consumption of bearing. The experiments show that the lubrication was most reliable and oil consumption lowest when the oil was introduced through a hole in the outer or inner ring of the bearing.
Date: July 1940
Creator: Getzlaff, Günter

Buckling Tests With a Spar-Rib Grill

Description: "The present report deals with a comparison of mathematically and experimentally defined buckling loads of a spar-rib grill, on the assumption of constant spar section, and infinitely closely spaced ribs with rigidity symmetrical to the grill center. The loads are applied as equal bending moments at both spar ends, as compression in the line connecting the joints, and in the spar center line as the assumedly uniformly distributed spar weight" (p. 1).
Date: September 1940
Creator: Weinhold, Josef

Application of the Methods of Gas Dynamics to Water Flows With Free Surface 1: Flows With No Energy Dissipation

Description: The application is treated in sufficient detail to facilitate as much as possible its application by the engineer who is less familiar with the subject. The present work was undertaken with two objects in view. In the first place, it is considered as a contribution to the water analogy of gas flows, and secondly, a large portion is devoted to the general theory of the two-dimensional supersonic flows.
Date: March 1940
Creator: Preiswerk, Ernst

Application of the Methods of Gas Dynamics to Water Flows With Free Surface 2: Flows With Momentum Discontinuities (Hydraulic Jumps)

Description: In this paper an introduction to shock polar diagrams is given which then leads into an examination of water depths in hydraulic jumps. Energy loss during these jumps is considered along with an extended look at elementary solutions of flow. An experimental test set-up is described and the results presented.
Date: March 1940
Creator: Preiswerk, Ernst

Corrections on the Thermometer Reading in an Air Stream

Description: A method is described for checking a correction formula, based partly on theoretical considerations, for adiabatic compression and friction in flight tests and determining the value of the constant. It is necessary to apply a threefold correction to each thermometer reading. They are a correction for adiabatic compression, friction and for time lag.
Date: October 1940
Creator: Van der Maas, H. J. & Wynia, S.

The Shock-Absorbed System of the Airplane Landing Gear

Description: "A discussion is given of the behavior of the shock-absorbing system, consisting of elastic struts and tires, under landing, take-off, and taxying conditions, and a general formula derived for obtaining the minimum stroke required to satisfy the conditions imposed on the landing gear. Finally, the operation of some typical shock-absorbing systems are examined and the necessity brought out for taking into account, in dynamic landing-gear tests, the effect of the wing lift at the instant of contact with the ground" (p. 1).
Date: March 1940
Creator: Callerio, Pietro

Standards for Discharge Measurement With Standardized Nozzles and Orifices

Description: The following standards give the standardized forms for two throttling devices, standard nozzles and standard orifices, and enable them to be used in circular pipes without calibration. The definition of the standards are applicable in principle to the calibration and use of nonstandardized throttling devices, such as the venturi tube. The standards are valid, likewise, as a basis for discharge measurements in the German acceptance standards.
Date: September 1940