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A few more mechanical-flight formulas without the aid of polar diagrams

Description: The reliability of the assumption of a parabolic shape of the polar curve is investigated and found satisfactory for all practical purposes. It is further shown that the aerodynamically best possible or "ideal" airplane is produced on this assumption. Lastly, detailed suggestions are given on the possibilities of application of this method of calculation. It especially simplifies the design and evaluation of structural changes and the determination of the limits of technical possibilities. The present report deals only with the relations of the airfoils. The mutual action of the airfoils, engine and propeller will be treated in a subsequent report.
Date: March 1, 1928
Creator: Schrenk, Martin
Partner: UNT Libraries Government Documents Department

Measurement of profile drag on an airplane in flight by the momentum method. Part II

Description: The purpose of this section is to survey the present status of scientific knowledge of the causes which produce drag, in order, if possible, to establish the relation between the individual results and the actual phenomena which demonstrate the fundamental importance of surface conditions. A discussion of the boundary layer is followed by: relations between frictional and form drag, application to profile-drag measurements, and different kinds of roughness. High-pressure wind tunnel tests are discussed along with roughness and maximum lift.
Date: March 1, 1930
Creator: Schrenk, Martin
Partner: UNT Libraries Government Documents Department

Take-off and propeller thrust

Description: 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 1, 1933
Creator: Schrenk, Martin
Partner: UNT Libraries Government Documents Department

Boundary layer removal by suction

Description: 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 1, 1941
Creator: Schrenk, O
Partner: UNT Libraries Government Documents Department

Effects of roughness on airfoils

Description: We will here report on the effects of coarsely roughening not only the pressure side but also the suction or upper side of airfoils, as the first group of a larger series of experiments.
Date: September 1, 1927
Creator: Schrenk, O
Partner: UNT Libraries Government Documents Department

Experiments with suction-type wings

Description: The present report collects the investigations of the past years which, while not as yet intended for use in construction, show different possibilities for the building of a suction-type wing and at the same time present some basic explanations concerning the problem of suction. Experiments and results with a thick wing profile are detailed as well as boundary layer removal by suction and sink action. Experiments with flap profiles are also included.
Date: August 1, 1935
Creator: Schrenk, O
Partner: UNT Libraries Government Documents Department

Model experiments on the forces and moments acting on an end plate fitted to a wing

Description: This paper reports on 4-component balance measurements with and without angle of sideslip made on an airfoil with end plate at one tip. In addition, pressure distribution measurements on the end plate served as a basis for the determination of the forces on the end plate and for the bending moments.
Date: April 1, 1938
Creator: Schrenk, O
Partner: UNT Libraries Government Documents Department

Systematic investigation of Joukowsky wing sections

Description: Ackeret began systematic polar measurements on Joukowsky wing sections, which were occasionally conducted in the wind tunnel. Under these conditions a considerable number of wing sections were tested during the last four years and the tests are now more or less concluded.
Date: July 1, 1927
Creator: Schrenk, O
Partner: UNT Libraries Government Documents Department

A simple approximation method for obtaining the spanwise lift distribution

Description: The approximation method described makes possible lift-distribution computations in a few minutes. Comparison with an exact method shows satisfactory agreement. The method is of greater applicability than the exact method and includes also the important case of the wing with end plates.
Date: August 1, 1940
Creator: Schrenk, O.
Partner: UNT Libraries Government Documents Department

The boundary layer as a means of controlling the flow of liquids and gases

Description: According to one of the main propositions of the boundary layer theory the scarcely noticeable boundary layer may, under certain conditions, have a decisive influence on the form of the external flow by causing it to separate from the wing surface. These phenomena are known to be caused by a kind of stagnation of the boundary layer at the point of separation. The present report deals with similar phenomena. It is important to note that usually the cause (external interference) directly affects only the layer close to the wall, while its indirect effect extends to a large portion of the external flow.
Date: March 1, 1930
Creator: Schrenk, Oskar
Partner: UNT Libraries Government Documents Department

Experiments with a sphere from which the boundary layer is removed by suction

Description: The task of removing the boundary layer by suction consists in producing, in place of the ordinary flow with the formation of vortices, another kind of flow in which the vortices are eliminated by drawing small quantities of fluid from certain points on the surface into the interior of the body. The experiments with a sphere, which constitute the subject of this report, were made early in the present year .
Date: November 1, 1926
Creator: Schrenk, Oskar
Partner: UNT Libraries Government Documents Department

Experiments with a wing model from which the boundary is removed by suction

Description: The present report deals with a series of tests made for the purpose of improving flow conditions about wings by applying the suction principle (increase of the lift coefficient and reduction of the drag about very thick wing sections). Though not conclusive, the report contains interesting results.
Date: October 1, 1929
Creator: Schrenk, Oskar
Partner: UNT Libraries Government Documents Department

A possible method for preventing the autorotation of airplane wings

Description: At the suggestion of Professor Betz, the following device was tested with the object of reducing the autorotational speed of airplane wings. The model of a normal wing with the Gottigen profile 420, 1 meter span and 0.2 meter chord was provided with a pair of symmetrical slots on the suction side, connected with each other inside the wing. The arrangement of the testing equipment and models are given and the effect of the slots can be seen in the experimental curves that are included.
Date: June 1, 1930
Creator: Schrenk, Oskar
Partner: UNT Libraries Government Documents Department

Accurate Numerical Solutions for Elastic-Plastic Models

Description: The accuracy of two integration algorithms is studied for the common engineering condition of a von Mises, isotropic hardening model under plane stress. Errors in stress predictions for given total strain increments are expressed with contour plots of two parameters: an angle in the pi plane and the difference between the exact and computed yield-surface radii.
Date: March 1980
Creator: Schreyer, H. L.; Kulak, R. F. & Kramer, J. M.
Partner: UNT Libraries Government Documents Department

Reduction of the shimmy tendency of tail and nose-wheel landing gears by installation of specially designed tires

Description: Shimmy of tail and nose wheels may be eliminated by installation of dampers and use of large trail; however, this produces construction and operational disadvantages. It is more favorable to employ, instead of the customary tail-wheel tires, tires with lesser shimmy tendency. A description of the best possible form for these tires follows: furthermore, a few general concepts regarding the effects of the condition of the tire, of the type of rolling motion, and of the landing, are discussed.
Date: July 1, 1955
Creator: Schrode, H
Partner: UNT Libraries Government Documents Department

A simple numerical method for the calculation of the laminar boundary layer

Description: An iteration difference method for the calculation of the incompressible laminar boundary layer is described. The method uses Prandtl's boundary layer equation and the boundary conditions directly and permits the attainment of an arbitrary accuracy. The method has been tested successfully in the continuation of the Blasius profile on the flat plate, on the circular cylinder investigated by Heimenz and on an elliptical cylinder of fineness ratio 1:4. The method makes possible the testing of previously developed methods, all of which contain important assumptions.
Date: April 1, 1952
Creator: Schroder, K
Partner: UNT Libraries Government Documents Department

Determination of resistance and trimming moment of planing water craft

Description: This report presents a new theory which makes it possible to interpret the resistance and the trimming moment for any loading of a planing aircraft when these values are given for one load. This application of the new theory forms the basis of the present paper. Derivations of various conversion formulas are given as well as numerous examples.
Date: May 1931
Creator: Schroder, P
Partner: UNT Libraries Government Documents Department

Towing tests of models as an aid in the design of seaplanes

Description: This report concerns the making and evaluation of a towing test of a seaplane float system. Some of the topics considered are: 1) the influence of the wing cell and power plant on the take-off performance; 2) the determination of the resistance curve for the take-off free to trim; 3) the resistance curves with elevator control (at fixed trims); 4) take-off time and take-off run.
Date: July 1, 1932
Creator: Schroder, P
Partner: UNT Libraries Government Documents Department