1,437 Matching Results

Search Results

Kinetics of Chemical Reactions in Flames

Description: In part I of the paper the theory of flame propagation is developed along the lines followed by Frank-Kamenetsky and one of the writers. The development of chain processes in flames is considered. A basis is given for the application of the method of stationary concentrations to reactions in flames; reactions with branching chains are analyzed. The case of a diffusion coefficient different from the coefficient of temperature conductivity is considered.
Date: June 1946
Creator: Zeldovich, Y. & Semenov, N.
Partner: UNT Libraries Government Documents Department

Equations for Adiabatic but Rotational Steady Gas Flows without Friction

Description: This paper makes the following assumptions: 1) The flowing gases are assumed to have uniform energy distribution. ("Isoenergetic gas flows," that is valid with the same constants for the the energy equation entire flow.) This is correct, for example, for gas flows issuing from a region of constant pressure, density, temperature, end velocity. This property is not destroyed by compression shocks because of the universal validity of the energy law. 2) The gas behaves adiabatically, not during the compression shock itself but both before and after the shock. However, the adiabatic equation (p/rho(sup kappa) = C) is not valid for the entire gas flow with the same constant C but rather with an appropriate individual constant for each portion of the gas. For steady flows, this means that the constant C of the adiabatic equation is a function of the stream function. Consequently, a gas that has been flowing "isentropically",that is, with the same constant C of the adiabatic equation throughout (for example, in origination from a region of constant density, temperature, and velocity) no longer remains isentropic after a compression shock if the compression shock is not extremely simple (wedge shaped in a two-dimensional flow or cone shaped in a rotationally symmetrical flow). The solution of nonisentropic flows is therefore an urgent necessity.
Date: August 1, 1947
Creator: Schäefer, Manfred
Partner: UNT Libraries Government Documents Department

Two-Dimensional Potential Flows

Description: Contents include the following: Characteristic differential equations - initial and boundary conditions. Integration of the second characteristic differential equations. Direct application of Meyer's characteristic hodograph table for construction of two-dimensional potential flows. Prandtl-Busemann method. Development of the pressure variation for small deflection angles. Numerical table: relation between deflection, pressure, velocity, mach number and mach angle for isentropic changes of state according to Prandtl-Meyer for air (k = 1.405). References.
Date: November 1949
Creator: Schäefer, Manfred & Tollmien, W.
Partner: UNT Libraries Government Documents Department

Rotationally Symmetric Potential Flows

Description: This paper includes the following topics: 1) Characteristic differential equations; 2) Treatment of practical examples; 3) First example: Diffuser; and 4) Second Example: Nozzle.
Date: November 1949
Creator: Schäefer, Manfred & Tollmien, W.
Partner: UNT Libraries Government Documents Department

Theory of Characteristics

Description: The theory of characteristics will be presented generally for quasilinear differential equations of the second order in two variables. This is necessary because of the manifold requirements to be demanded from the theory of characteristics.
Date: September 1949
Creator: Tollmien, W.
Partner: UNT Libraries Government Documents Department

Application of the Method of Coordinate Perturbation to Unsteady Duct Flow

Description: The method of coordinate perturbation is applied to the unsteady flow of a compressible fluid in ducts of variable cross section. Solutions, in the form of perturbation series, are obtained for unsteady flows in ducts for which the logarithmic derivative of area variation with respect to the space coordinate is a function of the 'smallness' parameter of the perturbation series. This technique is applied to the problem of the interaction of a disturbance and a shock wave in a diffuser flow. It is found that, for a special choice of the function describing the disturbance, the path of the shock wave can be expressed in closed form to first order. The method is then applied to the determination of the flow field behind a shock wave moving on a prescribed path in the x,t-plane. Perturbation series solutions for quite general paths are developed. The perturbation series solutions are compared with the more exact solutions obtained by the application of the method of characteristics. The approximate solutions are shown to be in reasonably accurate agreement with the solutions obtained by the method of characteristics.
Date: September 1958
Creator: Himmel, Seymour C.
Partner: UNT Libraries Government Documents Department

Effect of the Acceleration of Elongated Bodies of Revolution Upon the Resistance in a Compressible Flow

Description: The problem of the motion of an elongated body of revolution in an incompressible fluid may, as is known, be solved approximately with the aid of the distribution of sources along the axis of the body. In determining the velocity field, the question of whether the body moves uniformly or with an acceleration is no factor in the problem. The presence of acceleration must be taken into account in determining the pressures acting on the body. The resistance of the body arising from the accelerated motion may be computed either directly on the basis of these pressures or with the aid of the so-called associated masses (inertia coefficients). A different condition holds in the case of the motion of bodies in a compressible gas. In this case the finite velocity of sound must be taken into account.
Date: May 1949
Creator: Frankl, F. I.
Partner: UNT Libraries Government Documents Department

On the Formation of Shock Waves in Subsonic Flows With Local Supersonic Velocities

Description: In the flow about a body with large subsonic velocity if the velocity of the approaching flow is sufficiently large, regions of local supersonic velocities are formed about the body. It is known from experiment that these regions downstream of the flow are always bounded by shock waves; a continuous transition of the supersonic velocity to the subsonic under the conditions indicated has never been observed. A similar phenomenon occurs in pipes. If at two cross sections of the pipe the velocity is subsonic and between these sections regions of local supersonic velocity are formed without completely occupying a single cross section, these regions are always bounded by shock waves.
Date: April 1950
Creator: Frankl, F. I.
Partner: UNT Libraries Government Documents Department

Fire prevention on aircraft

Description: The following discussion is at first restricted to the light-oil engines now in use. We shall consider how far it is possible to reduce fire hazards by changes in the design of the engines and carburetors and in the arrangement of the fuel pipes.
Date: July 1, 1931
Creator: Kuhn, Fritz
Partner: UNT Libraries Government Documents Department

First experiences with the rotating laboratory

Description: This report describes experiences with a rotating cylinder to explore the effects of motion and flow upon human sensory organs. One observation was that the variation of the resultant line of gravity (from gravity and centrifugal force) was not felt so strongly as might be expected. The impressions produced by the physical effects on the members of the body, especially the ones caused by the deflecting force (Coriolis force), are exactly what the laws of physics would lead us to expect, although somewhat surprising when observed in one's own body.
Date: July 1926
Creator: Prandtl, L.
Partner: UNT Libraries Government Documents Department

Experiments with needle bearings

Description: Experiments and results are presented in testing needle bearings, especially in comparison with roller bearings. Reduction in coefficient of friction is discussed as well as experimental methods and recording devices.
Date: May 1, 1933
Creator: Ferretti, Pericle
Partner: UNT Libraries Government Documents Department

Flap gear for airplanes : a new scheme in which variation is automatic

Description: A variable flap gear, which would function automatically and require no attention during flight appeared to be an attractive idea even in its early stages of development. The advantages of variable camber are described as well as the designs of these automatic flaps.
Date: April 1, 1927
Creator: Tiltman, A Hessell
Partner: UNT Libraries Government Documents Department

Flat sheet metal girders with very thin metal web. Part II : sheet metal girders with spars resistant to bending - oblique uprights - stiffness

Description: Noting that the stiffness of the girder increases very rapidly as Beta increases, the result can be summed up as follows: When the cross stress preponderates in one direction and when the web plate is to be given the dimensions commensurate to its stresses, it is advisable (regardless of any ensuing structural difficulties) to set the uprights at about Beta = 120 degrees, thereby lowering the weight of the plate wall 15 percent (in contrast to Beta = 90 degrees), and raising the stiffness 55 percent. But, when the cross stresses alternate and are approximately of the same intensity in both directions, or, if the web plate thickness is determined by other structural reasons, then Beta = 90 degrees should be chosen.
Date: February 1, 1931
Creator: Wagner, Herbert
Partner: UNT Libraries Government Documents Department

Experiments with intubed propellers

Description: This report describes the results of experiments with a new method of propulsion involving propellers operating in conjunction with a Venturi tube forming the only fuselage of the "turbine wing.".
Date: January 1, 1932
Creator: Stipa, L
Partner: UNT Libraries Government Documents Department

Flight-test data on the static fore-and-aft stability of various German airplanes

Description: The static longitudinal stability of an airplane with locked elevator is usually determined by analysis and model tests. The present report proposes to supply the results of such measurements. The method consisted of recording the dynamic pressure versus elevator displacement at different center-of-gravity positions in unaccelerated flight.
Date: May 1, 1933
Creator: Hubner, Walter
Partner: UNT Libraries Government Documents Department

Flow in smooth straight pipes at velocities above and below sound velocity

Description: To investigate the laws of flow of compressible fluids in pipes, tests were carried out with air flowing at velocities below and above that of sound in straight smooth pipes. Air was chosen as the flow medium. In order that the effect of compressibility may be brought out most effectively, the velocity should lie between 100 and 500 m/s (200 and 1,000 mph); that is, be of the order of magnitude of the velocity of sound in air. The behavior of the compression shock in a smooth cylindrical pipe was also investigated. The compression shock can occur at any position in the pipe, depending on the throttling downstream, and travels upstream with increasing throttling up to the pipe entrance, so that only subsonic velocities occur in the pipe.
Date: January 1, 1938
Creator: Frossel, W.
Partner: UNT Libraries Government Documents Department

The flow of gases in narrow channels

Description: Measurements were made of the flow of gases through various narrow channels a few microns wide at average pressures from 0.00003 to 40 cm. Hg. The flow rate, defined as the product of pressure and volume rate of flow at unit pressure difference, first decreased linearly with decrease in mean pressure in the channel, in agreement with laminar-flow theory, reached a minimum when the mean path length was approximately equal to the channel width, and then increased to a constant value. The product of flow rate and square root of molecular number was approximately the same function of mean path length for all gases for a given channel.
Date: August 1, 1951
Creator: Rasmussen, R E H
Partner: UNT Libraries Government Documents Department

Flow phenomena on plates and airfoils of short span

Description: Investigations on the flow phenomena at plates and cambered models were carried out with the aid of force measurements, some pressure distribution measurements, and photographic observation. The experimental methods are described and the results given. Section III of this work gives a comprehensive account of the results and enables us to see how nearly the lift line and lift surface theories agree with the experimental results.
Date: June 1, 1936
Creator: Winter, H
Partner: UNT Libraries Government Documents Department

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.
Partner: UNT Libraries Government Documents Department

Flow of Gas Through Turbine Lattices

Description: This report is concerned with fluid mechanics of two-dimensional cascades, particularly turbine cascades. Methods of solving the incompressible ideal flow in cascades are presented. The causes and the order of magnitude of the two-dimensional losses at subsonic velocities are discussed. Methods are presented for estimating the flow and losses at high subsonic velocities. Transonic and supersonic flows in lattices are then analyzed. Some three-dimensional features of the flow in turbines are noted.
Date: May 1, 1956
Creator: Deich, M E
Partner: UNT Libraries Government Documents Department

Functioning of reduction gears on airplane engines

Description: In undertaking to analyze the functioning conditions of a reduction gear on an aviation engine, we will consider an ordinary twelve-cylinder V-engine. The reduction gear employed consists either of a pair of spur gears, one of which is integral with the engine shaft and the other with the propeller shaft, or of a planetary system of gears.
Date: March 1926
Creator: Matteucci, Raffaelli
Partner: UNT Libraries Government Documents Department