59 Matching Results

Search Results

Advanced search parameters have been applied.

Preliminary Investigation in the NACA Low-Turbulence Tunnel of Low-Drag Airfoil Sections Suitable for Admitting Air at the Leading Edge

Description: From Summary: "An investigation was carried out in the NACA low-turbulence tunnel to develop low-drag airfoil sections suitable for admitting air at the leading edge. A thickness distribution having the desired type of pressure distribution was found from tests of a flexible model. Other airfoil shapes were derived from this original shape by varying the thickness, the camper, the leading-edge radius, and the size of the leading-edge opening. Data are presented giving the characteristics of the airfoil shapes in the range of lift coefficients for high-speed and cruising flight."
Date: July 1942
Creator: von Doenhoff, Albert E. & Horton, Elmer A.
Partner: UNT Libraries Government Documents Department

Intensity, scale, and spectra of turbulence in mixing region of free subsonic jet

Description: Report presents the results of the measurements of intensity of turbulence, the longitudinal and lateral correlation coefficients, and the spectra of turbulence in a 3.5-inch-diameter free jet measured with hot-wire anemometers at exit Mach numbers from 0.2 to 0.7 and Reynolds numbers from 192,000 to 725,000.
Date: April 24, 1956
Creator: Laurence, James C.
Partner: UNT Libraries Government Documents Department

The effect of turbulence on the drag of flat plates

Description: "In determining the effect of turbulence on the forces exerted on bodies in the air stream of a wind tunnel, it is commonly assumed that the indications of the standard Pitot-static tube used to determine the air speed are not dependent on the turbulence. To investigate the truth of this assumption, the drag of a normally exposed flat plate, the difference in pressure between the front and rear of a thin circular disk, the rate of rotation of a vane anemometer, and the pressure developed by a standard Pitot-static tube were measured in an air stream for several conditions of turbulence. The results may be interpreted as indicating that there is no appreciable effect of turbulence on the vane anemometer and the standard pitot-static tube, but that there is small effect on the drag of a flat plate and the pressure difference between front and rear of a disk" (p. 129).
Date: June 22, 1935
Creator: Schubauer, G. B. & Dryden, H. L.
Partner: UNT Libraries Government Documents Department

Effect of turbulence in wind-tunnel measurements

Description: This paper gives some quantitative measurements of wind tunnel turbulence and its effect on the air resistance of spheres and airship models, measurements made possible by the hot wire anemometer and associated apparatus in its original form was described in Technical Report no. 320 and some modifications are presented in an appendix to the present paper. One important result of the investigation is a curve by means of which measurements of the air resistance of spheres can be interpreted to give the turbulence quantitatively. Another is the definite proof that the discrepancies in the results on the N. P. L. Standard airship models are due mainly to differences in the turbulences of the wind tunnels in which the tests were made.
Date: August 20, 1929
Creator: Dryden, H. L. & Kuethe, A. M.
Partner: UNT Libraries Government Documents Department

Preliminary experimental investigation of low-speed turbulent boundary layers in adverse pressure gradients

Description: Report presenting measurements of velocity profiles and skin friction in subsonic turbulent boundary layers with adverse pressure gradients. The skin friction in an adverse pressure gradient was found to decrease steadily with distance to a value approaching zero for the region of separation. Results regarding the mean velocity distribution and separation, comparison of experimental values with semiempirical relations, and wall shearing stress are provided.
Date: October 1953
Creator: Sandborn, Virgil A.
Partner: UNT Libraries Government Documents Department

Summary of locations, extents, and intensities of turbulent areas encountered during flight investigations of the jet stream from January 7, 1957 to April 28, 1957

Description: "A summary of the locations, extents, and intensities of turbulent areas encountered during a flight investigation of the jet stream is presented. The data were obtained from NACA VGH time-history records" (p. 1).
Date: March 3, 1958
Creator: Copp, Martin R.
Partner: UNT Libraries Government Documents Department

Preliminary investigation of combustion in flowing gas with various turbulence promoters

Description: Report presenting an investigation of combustion occurring downstream of various turbulence promoters in a 20-inch length of a 1 7/8-inch inside-diameter, water-jacketed tubing using premixed vaporized fuel and air. Among the turbulence promoters investigated were flat plates perforated with 1/8-inch diameter holes, 1/4-inch diameter holes, and a single large hole to give 12.4, 17.2, and 21.5 percent open area respectively.
Date: June 7, 1948
Creator: Haddock, Gordon W. & Childs, J. Howard
Partner: UNT Libraries Government Documents Department

Turbulence in the Wake of a Thin Airfoil at Low Speeds

Description: From Summary: "Experiments have been made to determine the nature of turbulence in the wake of a two-dimensional airfoil at low speeds. The experiments were motivated by the need for data which can be used for analysis of the tail-buffeting problem in aircraft design. Turbulent intensity and power spectra of the velocity fluctuations were measured at a Reynolds number of 1.6 x 10(exp 5) for several angles of attack. Total-head measurements were also obtained in an attempt to relate steady and fluctuating wake properties."
Date: January 1957
Creator: Campbell, George S.
Partner: UNT Libraries Government Documents Department

A theory for the lateral response of airplanes to random atmospheric turbulence

Description: Report presenting a derivation of the lateral motions of an airplane flying through continuous random isotropic turbulence in terms of three different functions and sets of forces. Three airplanes of different size are used to demonstrate the method, illustrate characteristic trends, and exhibit some simplifications possible in the calculations.
Date: May 1957
Creator: Eggleston, John M.
Partner: UNT Libraries Government Documents Department

Turbulent shear spectra and local isotropy in the low-speed boundary layer

Description: "From measurements of turbulent shear spectra together with previously reported longitudinal turbulent energy spectra, the concept of local isotropy in a low-speed boundary layer was examined. Results of these measurements and measurements of the time derivatives of turbulent velocities in the x- and y- directions for various frequency bands showed no evidence of local isotropy in the boundary layer. Several methods (based on isotropy) of evaluating the turbulent dissipation term failed to give consistent answers, further emphasizing a lack of local isotropy" (p. 1).
Date: September 1956
Creator: Sandborn, Virgil A. & Braun, Willis H.
Partner: UNT Libraries Government Documents Department

Some calculations of the lateral response of two airplanes to atmospheric turbulence with relation to the lateral snaking problem

Description: Report presenting calculations of the lateral response to representative time histories of atmospheric turbulence for two airplanes with widely different dynamic properties and explanations for their differences in behavior. The results indicate that atmospheric turbulence can cause and maintain a lateral hunting oscillation of a plane, which can be fairly regular and more pronounced for lightly damped airplanes. This may explain some of the cases of airplane snaking that have not been explained by other causes.
Date: May 1955
Creator: Bird, John D.
Partner: UNT Libraries Government Documents Department

Spectrum of turbulence in a contracting stream

Description: The spectrum concept is employed to study the selective effect of a stream contraction on the longitudinal and lateral turbulent velocity fluctuations of the stream. By a consideration of the effect of the stream contraction on a single plane sinusoidal disturbance wave, mathematically not dissimilar to a triply periodic disturbance treated by G. I. Taylor, the effect on the spectrum tensor of the turbulence and hence on the correlation tensor is determined.
Date: August 30, 1951
Creator: Ribner, H. S. & Tucker, M.
Partner: UNT Libraries Government Documents Department

Scale-effect tests in a turbulent tunnel of the NACA 65(sub 3)-418, a = 1.0 airfoil section with 0.20-airfoil-chord split flap

Description: Report presenting the effect of Reynolds number on the aerodynamic characteristics of a low-drag airfoil section tested under conditions of relatively high stream turbulence. The data are presented as curves of section angle of attack, section profile-drag coefficient, and section pitching-moment coefficient against section lift coefficient for various flap deflections.
Date: September 1944
Creator: Tucker, Warren A. & Wallace, Arthur R.
Partner: UNT Libraries Government Documents Department

The use of wind tunnels to predict flight buffet loads

Description: From Summary: "Methods and techniques developed for the study of buffeting by use of wind-tunnel models are described. Requirements on model damping and frequency characteristics, the model support system, and the effects of wind-tunnel turbulence on buffet tests are outlined. The results are shown of a recent comparison of buffet loads measured on a research airplane with thin unswept wings and on two different models of the airplane in two different wind tunnels."
Date: June 10, 1957
Creator: Davis, Don D., Jr. & Huston, Wilber B.
Partner: UNT Libraries Government Documents Department

Measurements of Lift Fluctuations Due to Turbulence

Description: Note presenting a study of the fluctuating lift of a rigid wing in turbulent flow and the power spectra of the lift and turbulent fluctuations. Using these measurements, the aerodynamic admittance of the wing was obtained. Results regarding the infinite wing and aspect-ratio effect are provided.
Date: March 1957
Creator: Lamson, P.
Partner: UNT Libraries Government Documents Department

The Theories of Turbulence

Description: "The theory of turbulence reached its full growth at the end of the 19th century as a result of the work by Boussinesq and Reynolds. It then underwent a long period of stagnation which ended under the impulse given to it by the development of wind tunnels caused by the needs of aviation. Numerous researchers, attempted to put Reynolds' elementary statistical theory into a more precise form. During the war, some isolated scientists - von Weizsacker and Heisenberg in Germany, Kolmogoroff in Russia, Onsager in the U.S.A. - started a program of research. By a system of assumptions which make it possible to approach the structure of turbulence in well-defined limiting conditions quantitatively, they obtained a certain number of laws on the correlations and the spectrum. Since the late reports have improved the mathematical language of turbulence, it was deemed advisable to start with a detailed account of the mathematical methods applicable to turbulence, inspired at first by the work of the French school, above all for the basic principles, then the work of the foreigners, above all for the theory of the spectrum" (p. 1).
Date: October 1955
Creator: Agostini, L. & Bass, J.
Partner: UNT Libraries Government Documents Department

On the Statistical Theory of Turbulence

Description: A study is made of the spectrum of isotropic turbulence with the aid of the customary method of Fourier analysis. The spectrum of the turbulent motion is derived to the smallest wave lengths, that is, into the laminar region, and correlation functions and pressure fluctuations are calculated. A comparison with experimental results is included. Finally, an attempt is made to derive the numerical value of a constant characteristic of the energy dissipation in isotropic turbulence.
Date: January 1958
Creator: Heisenberg, W.
Partner: UNT Libraries Government Documents Department

A Relation of Wind Shear and Insolation to the Turbulence Encountered by an Airplane in Clear-Air Flight at Low Altitudes

Description: Memorandum presenting the observed gust experience of an airplane and information on the associated meteorological conditions to obtain a simple empirical relation for estimating the intensity of turbulence in the earth's friction layer. The relation does not discriminate between differences in turbulence intensity resulting from variations of flight altitude or diurnal variations of turbulence.
Date: September 13, 1951
Creator: Thompson, James K.
Partner: UNT Libraries Government Documents Department

Flight Investigation of the Effect of Atmospheric Turbulence on the Climb Performance of an Airplane

Description: Note presenting the results of an investigation consisting of a series of one-engine climb tests with a twin-engine transport airplane, which indicate that light turbulence of the type generally present in clear air over flat terrain has no significant effect on the average rate of climb for a series of runs. Turbulence does, however, increase the variation in the rate of climb from run to run. Results regarding mean rate of climb, standard deviation of the rate of climb, effects of climb duration, and implications of these results are provided.
Date: October 1951
Creator: Press, Harry & McClanahan, Herbert C., Jr.
Partner: UNT Libraries Government Documents Department

Development of Turbulence-Measuring Equipment

Description: "Hot wire turbulence-measuring equipment has been developed to meet the more stringent requirements involved in the measurement of fluctuations in flow parameters at supersonic velocities. The higher mean speed necessitates the resolution of higher frequency components than at low speed, and the relatively low turbulence level present at supersonic speed makes necessary an improved noise level for the equipment. The equipment covers the frequency range from 2 to about 70,000 cycles per second" (p. 1).
Date: 1954
Creator: Kovasznay, Leslie S. G.
Partner: UNT Libraries Government Documents Department

Turbulence and Heat Stratification

Description: With applications to meteorology in view, the method of small oscillations is used to investigate the stability of a plane laminar boundary layer in which the density depends in a special way on the distance from the plate. It is found that for a constant Froude number the flow becomes more stable as the Richardson number increases until, at a critical value of the Richardson number that depends on the Froude number, the flow is stable for all disturbance wave lengths and Reynolds numbers. The calculated results are verified by experiment.
Date: October 1950
Creator: Schlichting, Hermann
Partner: UNT Libraries Government Documents Department

Preliminary Measurements of Turbulence and Temperature Fluctuations Behind a Heated Grid

Description: "Preliminary measurements have been made of velocity and temperature fluctuations in the flow behind a heated grid in a uniform airstream. Temperature correlation shows a reasonable degree of isotropy, and the temperature fluctuations die out at large distances more slowly than the turbulence, as has been predicted theoretically under some strongly simplifying postulates" (p. 1).
Date: June 10, 1954
Creator: Kistler, A. L.; O'Brien, V. & Corrsin, S.
Partner: UNT Libraries Government Documents Department