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Designing Seaplane Hulls and Floats

Description: Experimental data, such as the results of tank tests of models, render it possible to predict, at least in principle, as to how a hull or float of a given shape will comport itself. We will see further along, however, how uncertain these methods are and how they leave room for empiricism, which will reign for a long time yet in seaplane research bureaus.
Date: August 1926
Creator: Benoit
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Some Experiences Regarding the Nonlinearity of Hot Wires

Description: "We compare here the results of some experiences with the formulas established in our preceding report 'Nonlinear Theory of a Hot-Wire Anemometer.' We shall show that the nonlinear term plays a role as important as the thermal conduction in the calculation of the thermal inertia of the hot wire" (p. 1).
Date: June 1952
Creator: Betchov, R. & Welling, W.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Axial Superchargers

Description: Improvements, however, have been attained which permit a shortening of the structure without any impairment of the efficiency. The axial supercharger has a better efficiency and a simpler design than the radial supercharger. The relatively narrow range in which it operates satisfactorily should not be a very disturbing factor for practical flight problems. The length of this type of supercharger may be reduced considerably if some impairment in the efficiency is permitted.
Date: August 1944
Creator: Betz, A.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Behavior of Vortex Systems

Description: Progressive application of the Kutta-Joukowsky theorem to the relationship between airfoil lift and circulation affords a number of formulas concerning the conduct of vortex systems. The application of this line of reasoning to several problems of airfoil theory yields an insight into many hitherto little observed relations. This report is confined to plane flow, hence all vortex filaments are straight and mutually parallel (perpendicular to the plane of flow).
Date: June 1933
Creator: Betz, A.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Considerations on Propeller Efficiency

Description: The propeller cannot be considered alone, but the mutual interference between propeller and airplane must be considered. These difficulties are so great when the joint action of propeller and airplane is considered, that the aerodynamic laboratory at Gottingen originally abandoned the idea of applying the efficiency conception of the test results. These difficulties and the methods by which they are overcome are outlined in this report.
Date: September 1928
Creator: Betz, A.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Experiments on Airfoils With Aileron and Slot

Description: The present report contains the results of a few experiments on three airfoils to which the rear portions, having chords respectively 1/4, 1/3, and 2/5 of the total chords, are hinged so as to form ailerons, especial attention being given to the shape of the slot between the aileron and the main portion of the aileron.
Date: November 1927
Creator: Betz, A.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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The Ground Effect on Lifting Propellers

Description: In what follows an estimate will be made of the magnitude of the ground effect. For the two cases where the distance a of the propeller from the ground is very small, and very large, respectively, in comparison with the propeller radius r(sub o) the relations may be simply expressed. We consider first the effect of the ground, assuming that the thrust is held constant, as may be done by a suitable change in the propeller speed.
Date: August 1937
Creator: Betz, A.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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The "Magnus Effect" - the Principle of the Flettner Rotor

Description: The phenomenon of the Magnus effect consists in the fact that a revolving body moving relatively to the surrounding fluid (air) is subjected not only to drag (i.e., a force acting in a direction opposite to that of the direction of motion), but also to a lift.
Date: April 1925
Creator: Betz, A.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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A Method for the Direct Determination of Wing-Section Drag

Description: In order that the method may be more easily understood, we will first consider the simpler case when there is no lift, but only drag, and when the streamlines at the measuring point behind the obstacle are nearly parallel. Moreover, the flow is assumed not to deviate much from the two-dimensional flow.
Date: November 1925
Creator: Betz, A.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Modification of Wing-Section Shape to Assure a Predetermined Change in Pressure Distribution

Description: "In order to find an airfoil for a predetermined pressure distribution, the problem must be posed so that the pressure distribution creates no drag. Another fundamental difficulty is that it is impossible to specify a pressure distribution without first knowing the place where these pressures are to be applied, i.e., the wing-section shape. This difficulty may be avoided by directing the pressure distribution along the contour of the wing section. Then it becomes possible to define the change i… more
Date: March 1935
Creator: Betz, A.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Propeller Problems

Description: This report tries to give a comprehensive survey of the most important propeller problems such as the shape of propellers and the effect of atmospheric conditions on propeller performance.
Date: December 1928
Creator: Betz, A.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Velocity and Pressure Distribution Behind Bodies in an Air Current

Description: The following experiments on the air flow behind bodies were made for the purpose of assisting in the explanation of the phenomena connected with air resistance. The first two series of experiments dealt with the phenomena behind a cylinder. The third series of experiments was carried out behind a streamlined strut.
Date: July 1924
Creator: Betz, A.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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The Vortex Theory and Its Significance in Aviation

Description: This report will present ideas closely related to the vortex conception and illustrate them in the simplest possible terms. In addition to these general considerations, this report will attempt to show the application of the vortex theory in connection with the wing theory.
Date: July 1930
Creator: Betz, A.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Windmills in the Light of Modern Research

Description: The chief contribution of modern research in the field of windmills is a better understanding of the phenomena and of the available means for the accomplishment of certain results, but also of the natural limits to their productive capacity.
Date: August 1928
Creator: Betz, A.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Design of Centrifugal Impeller Blades

Description: This paper restricts itself to radial impellers with cylindrical blades since, as Prasil has shown, the flow about an arbitrarily curved surface of revolution may be reduced to this normal form we have chosen by a relatively simple conformal transformation. This method starts from the simple hypotheses of the older centrifugal impeller theory by first assuming an impeller with an infinite number of blades. How the flow is then modified is then investigated.
Date: July 1939
Creator: Betz, A. & Flügge-Lotz, I.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Reduction of Wing Lift by the Drag

Description: Drag and loss of lift of a wing are attributable to the same cause, wake formation, thus indicating that there is some relation between both. The analysis of measurements on Joukowsky sections revealed a typical course of curves for the interdependence between drag and loss of lift. The shape of the curves apparently depends quite regularly on the mean camber and on the thickness of the profile.
Date: August 1932
Creator: Betz, A. & Lotz, J.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Application of the Theory of Free Jets

Description: Based upon Kirchoff's theory of free jets the flow through different screen arrangements of flat plates, as chiefly encountered with turbines in the cavitation zone is defined. It is shown by experiments that these theoretical results are very well representative in most cases of the conditions of discharge from water in air and consequently by cavitation. In addition, the experiments reveal a picture of the discrepancies between the actual flow and the theory of discharge of air in air (of wat… more
Date: April 1932
Creator: Betz, A. & Petersohn, E.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Contribution to the Aileron Theory

Description: "In an attempt to treat theoretically the effect of ailerons, difficulty arises because an aileron may begin at any point of the wing. Hence the question arises as to how the transition of the lift distribution proceeds at such a point, since the effect of the aileron (i.e., the moment generated about the longitudinal axis) depends largely on this distribution. In order to answer this question regarding the lift distribution during irregular variations in the angle of attack at first independen… more
Date: December 1929
Creator: Betz, A. & Petersohn, E.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Diagrams for Calculation of Airfoil Lattices

Description: "The field for curved blades is represented by a vortex series with a vortex removed at the blade point. Further, an example of calculation of a curved blade from this series is given, whereby the necessary accuracy required of the different methods in practice is shown according to the case considered" (p. 1).
Date: July 1942
Creator: Betz, Albert
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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The Theory of Contra-Vanes Applied to the Propeller

Description: "The optimum circulation distribution and hence the maximum theoretical thrust obtainable for contra-vanes fitted behind propellers is markedly dependent on the number of guide vanes. The outer portion of the vanes, even if projecting considerably beyond the edge of the propeller slipstream, still contribute appreciably to this theoretical gain of thrust. But, owing to the always existing friction of the vanes, the limit of the optimum vane length lies at relatively small diameters" (p. 1).
Date: September 1939
Creator: Betz, Albert
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Problems Concerning the Stability and Maneuverability of Airplanes

Description: "The stability of an airplane can be easily determined by wind-tunnel tests, especially by simple tests with models mounted wind-vane fashion. However, each stability curve plotted by this method is valid only for a certain setting of the corresponding control surface, i.e., it characterizes the stability of the airplane with the control stick in a given position. The problems thus defined are studied from the point of view of longitudinal and transverse stability. Directional stability is not … more
Date: March 1932
Creator: Biche, Jean
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Influence of Cut-Outs in Elevator on the Static Longitudinal Stability and on the Static Elevator Effect

Description: "The rudder effect of a sport airplane at high angles of attack was to be improved. This made it necessary to make a cut-out in the center of the continuous elevator so as to enlarge the rudder downward. This cut-out which reduced the rudder area by 12.5 percent changed the static stability of the airplane as well as the elevator effect" (p. 1).
Date: August 1934
Creator: Biechteler, Curt
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Tests for the Elimination of Tail Flutter

Description: "On various low-wing monoplanes the horizontal tail surfaces flutter in flight at large angles of attack and occasionally in curvilinear flight. This flutter leads to torsional vibrations of the rear end of the fuselage, as manifested by vibrations of the control stick. According to the earlier DVL investigations tail flutter is due to the influence, on horizontal tail surfaces, of eddies or vortices shed at large angles of attack by the upper surface of the wing root. The cause of tail flutter… more
Date: June 1933
Creator: Biechteler, Curt
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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