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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.

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 1, 1940
Creator: Van Der Maas, H J & Wynia, S

Application of the methods of gas dynamics to water flows with free surface II : 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

Application of the methods of gas dynamics to water flows with free surface I : 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

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.
Date: September 1, 1940
Creator: Weinhold, Josef

Experimental results with airfoils tested in the high-speed tunnel at Guidonia

Description: The results are presented of a triple series of tests using force measurements, pressure-distribution measurements, and air flow photographs on airfoil sections suitably selected so that comparison could be made between the experimental and theoretical results. The comparison with existing theory is followed by a discussion of the divergences found, and an attempt is made to find their explanation.
Date: July 1, 1940
Creator: Ferri, Antonio

General relationships between the various systems of reference axes employed in flight mechanics

Description: The different possibilities of orientation of the systems of axes currently employed in flight mechanics are compiled and described. Of the three possible couplings between the wind and aircraft axes, the most suitable coupling is that in which the y axis is made the principal axis of rotation for one of the two coupling angles (angles of attack). In connection with this coupling, an experimental system of axes is introduced, whose axes x(sub e) and z(sub e) are situated in the plane of symmetry of the airplane and rotate about the airplane lateral axis y = y(sub e). This system of axes enables the utilization of the coefficients obtained in the wind tunnel in the flight-mechanic equations by a simple transformation, with the aid of the angle of attack, measured in the plane of symmetry of the airplane.
Date: November 1, 1940
Creator: Rautenberg, H J

The strength of shell and tubular spar wings

Description: The report is a survey of the strength problems arising on shell and tubular spar wings. The treatment of the shell wing strength is primarily confined to those questions which concern the shell wing only; those pertaining to both shell wing and shell body together have already been treated in TM 838. The discussion of stress condition and compressive strength of shell wings and tubular spar wings is prefaced by several considerations concerning the spar and shell design of metal wings from the point of view of strength.
Date: February 1, 1940
Creator: Ebner, H

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.
Date: April 1, 1940
Creator: Cambilargiu, E

Italian high-speed airplane engines

Description: This paper presents an account of Italian high-speed engine designs. The tests were performed on the Fiat AS6 engine, and all components of that engine are discussed from cylinders to superchargers as well as the test set-up. The results of the bench tests are given along with the performance of the engines in various races.
Date: June 1, 1940
Creator: Bona, C F

Some data on the static longitudinal stability and control of airplanes : design of control surfaces

Description: In the solution of a number of problems on the stability and controllability of airplanes, there arises the necessity for knowing the characteristics of the tail surfaces of the types in common use today. Of those characteristics, the most important are the effectiveness and hinge moments of the tail surfaces. As has been shown in the present paper, there exists the possibility of determining these characteristics by the formulas obtained with a degree of accuracy sufficient for the purposes of preliminary computation. These formulas take into account a number of fundamental tail characteristics such as tail cut-outs on the control surface and the form of the control surface leading edge.
Date: May 1, 1940
Creator: Martinov, A & Kolosov, E

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.

Knocking in an internal-combustion engine

Description: The question remains open of the relation between the phenomena of knocking in the engine and the explosion wave. The solution of this problem is the object of this paper. The tests were conducted on an aircraft engine with a pyrex glass window in the cylinder head. Photographs were then taken of various combinations of fuels and conditions.
Date: January 1, 1940
Creator: Sokolik, A & Voinov, A

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.

Variation in Velocity Profile with Change in Surface Roughness of Boundary

Description: The present report deals with the variation of a turbulent velocity profile in flow from rough to smooth wall and vice versa. Expressions obtained for the shear-stress distribution with respect to the distance from the point of junction of the different roughnesses and from the wall distance, are utilized to ascertain the developing velocity distributions. Under simplified assumptions, the use of these formulas renders possible the integration of the motion equations for the shear stress. This calculation is carried out and compared with the experiments.
Date: September 1, 1940
Creator: Jacobs, W.

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.

Rectangular shell plating under uniformly distributed hydrostatic pressure

Description: A check of the calculation methods used by Foppl and Henky for investigating the reliability of shell plating under hydrostatic pressure has proved that the formulas yield practical results within the elastic range of the material. Foppl's approximate calculation leaves one on the safe side. It further was found on the basis of the marked ductility of the shell plating under tensile stress that the strength is from 50 to 100 percent higher in the elastic range than expected by either method.
Date: December 1, 1940
Creator: Neubert, M & Sommer, A

Materials for slack diaphragms

Description: This report deals with systematic experiments carried out on five diaphragm materials with different pretreatment, for the purpose of ascertaining the suitability of such materials for slack diaphragms. The relationship of deflection and load, temperature and moisture, was recorded. Of the explored materials, synthetic leather, balloon cloth, goldbeaters skin, Igelit and Buna, synthetic leather treated with castor oil is the most suitable material for the small pressure range required. Balloon cloth is nearly as good, while goldbeaters skin, Igelit and Buna were found to be below the required standards.
Date: December 1, 1940
Creator: Puschmann, Traute

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.