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Blockage Corrections for Three-Dimensional-Flow Closed-Throat Wind Tunnels, with Consideration of the Effect of Compressibility

Description: Theoretical blockage corrections are presented for a body of revolution and for a three-dimensional, unswept wing in a circular or rectangular wind tunnel. The theory takes account of the effects of the wake and of the compressibility of the fluid, and is based on the assumption that the dimensions of the model are small in comparison with those of the tunnel throat. Formulas are given for correcting a number of the quantities, such as dynamic pressure and Mach number, measured in wind tunnel tests. The report presents a summary and unification of the existing literature on the subject.
Date: January 1, 1951
Creator: Herriot, J. G.

A theoretical study of the effect of forward speed on the free-space sound-pressure field around propellers

Description: Report presenting an analysis of the sound-pressure field of a rotating propeller in forward flight in free space by replacing the normal-pressure distribution over the propeller associated with thrust and torque by a distribution of acoustic pressure doublets acting at the propeller disk. The result is presented for a moving and a fixed observer.
Date: 1954
Creator: Garrick, I. E. & Watkins, Charles E.

Investigation of frequency-response characteristics of engine speed for a typical turbine-propeller engine

Description: Experimental frequency-response characteristics of engine speed for a typical turbine-propeller engine are presented. These data were obtained by subjecting the engine to sinusoidal variations of fuel flow and propeller-blade-angle inputs. Correlation is made between these experimental data and analytical frequency-response characteristics obtained from a linear differential equation derived from steady-state torque-speed relations.
Date: March 24, 1950
Creator: Taylor, Burt L., III & Oppenheimer, Frank L.

A flight evaluation of the longitudinal stability characteristics associated with the pitch-up of a swept-wing airplane in maneuvering flight at transonic speeds

Description: This report presents the results of flight measurements of longitudinal stability and control characteristics made on a swept-wing jet aircraft to determine the origin of the pitch-up encountered in maneuvering flight at transonic speeds. For this purpose measurements were made of elevator angle, tail angle of attack, and wing-fuselage pitching moments (obtained from measurements of the balancing tail loads).
Date: January 1, 1955
Creator: Anderson, Seth B & Bray, Richard S

Free-space oscillating pressures near the tips of rotating propellers

Description: The theory is given for calculating the free-space oscillating pressures associated with a rotating propeller, at any point in space. Because of its complexity this analysis is convenient only for use in the critical region near the propeller tips where the assumptions used by Gutin to simplify his final equations are not valid. Good agreement was found between analytical and experimental results in the tip Mach number range 0.45 to two, three, four, five, six, on eight-blade propellers and for a range of tip clearances from 0.04 to 0.30 times the propeller diameter. If the power coefficient, tip Mach number, and the tip clearance are known for a given propeller, the designer may determine from these charts the average maximum free-space oscillating pressure in the critical region near the plane of rotation. A section of the report is devoted to the fuselage response to these oscillating pressures and indicates some of the factors to be considered in solving the problems of fuselage vibration and noise.
Date: 1950
Creator: Hubbard, Harvey H. & Regier, Arthur A.

Free-stream boundaries of turbulent flows

Description: Report presents the results of an experimental and theoretical study made of the instantaneously sharp and irregular front which is always found to separate turbulent fluid from contiguous "nonturbulent" fluid at a free-stream boundary. This distinct demarcation is known to give an intermittent character to hot-wire signals in the boundary zone. The overall behavior of the front is described statistically in terms of its wrinkle-amplitude growth and its lateral propagation relative to the fluid as functions of downstream coordinate.
Date: 1955
Creator: Corrsin, Stanley & Kistler, Alan L.

Further experiments on the flow and heat transfer in a heated turbulent air jet

Description: Measurements have been made of the mean-total-head and mean-temperature fields in a round turbulent jet with various initial temperatures. The results show that the jet spreads more rapidly as its density becomes lower than that of the receiving medium, even when the difference is not sufficiently great to cause dynamic-pressure function. Rough analytical considerations have given the same relative spread. The effective "turbulent Prandtl number" for a section of the fully developed jet was found to be equal to the true (laminar) Prandtl number within the accuracy measurement.
Date: January 1, 1950
Creator: Corrsin, Stanley & Uberoi, Mahinder S

Friction, wear, and surface damage of metals as affected by solid surface films

Description: As predicted by friction theory, experiments showed that friction and surface damage of metals can be reduced by solid surface films. The ability of materials to form surface films that prevent welding was a very important factor in wear of dry and boundary lubricated surfaces. Films of graphitic carbon on cast irons, nio on nickel alloys, and feo and fe sub 3 o sub 4 on ferrous materials were found to be beneficial. Abrasive films such as fe sub 2 o sub 3 or moo sub 3 were definitely detrimental. It appears that the importance of oxide films to friction and wear processes has not been fully appreciated.
Date: January 1, 1956
Creator: Bisson, Edmond E.; Johnson, Robert L.; Swikert, Max A. & Godfrey, Douglas

Frequency response of linear systems from transient data

Description: Methods are presented that use general correlative time-response input and output data for a linear system to determine the frequency-response function of that system. These methods give an exact description of any linear system for which such transient data are available. Examples are shown of application of a method to both an underdamped and a critically damped exact second-order system, and to an exact first-order system with and without dead time. Experimental data for a turbine-propeller engine showing the response of engine speed to change in propeller-blade angle are presented and analyzed.
Date: January 1, 1950
Creator: Laverne, Melvin E. & Boksenbom, Aaron S.

Investigation of fretting by microscopic observation

Description: An experimental investigation, using microscopic observation and color motion photomicrographs of the action, was conducted to determine the cause of fretting. Glass and other noncorrosive materials, as well as metals, were used as specimens. A very simple apparatus vibrated convex surfaces in contact with stationary flat surfaces at frequencies of 120 cycles or less than l cycle per second, an amplitude of 0.0001 inch, and load of 0.2 pound.
Date: January 1, 1951
Creator: Godfrey, Douglas

Interaction of a free flame front with a turbulence field

Description: Small-perturbation spectral-analysis techniques are used to obtain the root-mean-square flame-generated turbulence velocities and the attenuating pressure fluctuations stemming from interaction of a constant-pressure flame front with a field of isotropic turbulence in the absence of turbulence decay processes.
Date: January 1, 1956
Creator: Tucker, Maurice

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: January 1, 1956
Creator: Laurence, James C

Integrals and integral equations in linearized wing theory

Description: The formulas of subsonic and supersonic wing theory for source, doublet, and vortex distributions are reviewed and a systematic presentation is provided which relates these distributions to the pressure and to the vertical induced velocity in the plane of the wing. It is shown that care must be used in treating the singularities involved in the analysis and that the order of integration is not always reversible. Concepts suggested by the irreversibility of order of integration are shown to be useful in the inversion of singular integral equations when operational techniques are used. A number of examples are given to illustrate the methods presented, attention being directed to supersonic flight speed.
Date: January 1, 1951
Creator: Lomax, Harvard; Heaslet, Max A & Fuller, Franklyn B

Initial results of instrument-flying trials conducted in a single-rotor helicopter

Description: Instrument-flying trials have been conducted in a single-rotor helicopter, the maneuver stability of which could be changed from satisfactory to unsatisfactory. The results indicated that existing longitudinal flying-qualities requirements based on contact flight were adequate for instrument flight at speeds above that for minimum power. However, lateral-directional problems were encountered at low speeds and during precision maneuvers. The adequacy, for helicopter use, of standard airplane instruments was also investigated, and the conclusion was reached that special instruments would be desirable under all conditions, and necessary for sustained low-speed instrument flight.
Date: January 1, 1953
Creator: Crim, Almer D; Reeder, John P & Whitten, James B

Investigation of turbulent flow in a two-dimensional channel

Description: A detailed exploration of the field of mean and fluctuating quantities in a two-dimensional turbulent channel flow is presented. The measurements were repeated at three Reynolds numbers, 12,300, 30,800, and 61,600, based on the half width of the channel and the maximum mean velocity. A channel of 5-inch width and 12:1 aspect ratio was used for the investigation. Mean-speed and axial-fluctuation measurements were made well within the laminar sublayer. The semitheoretical predictions concerning the extent of the laminar sublayer were confirmed. The distribution of the velocity fluctuations in the direction of mean flow u' shows that the influence of the viscosity extends farther from the wall than indicated by the mean velocity profile, the region of influence being approximately four times as wide.
Date: January 1, 1951
Creator: Laufer, John

Investigation of the aerodynamic characteristics of a model wing-propeller combination and of the wing and propeller separately at angles of attack up to 90 degrees

Description: This report presents the results of an investigation conducted in the Langley 300 mph 7- by 10-foot wind tunnel for the purpose of determining the aerodynamic characteristics of a model wing-propeller combination, and of the wing and propeller separately at angles of attack up to 90 degrees. The tests covered thrust coefficients corresponding to free-stream velocities from zero forward speed to the normal range of cruising speeds. The results indicate that increasing the thrust coefficient increases the angle of attack for maximum lift and greatly diminishes the usual reduction in lift above the angle of attack for maximum lift.
Date: January 1, 1956
Creator: Kuhn, Richard E & Draper, John W

Investigation of wear and friction properties under sliding conditions of some materials suitable for cages of rolling-contact bearings

Description: An investigation of wear and friction properties of a number of materials sliding against SAE 52100 steel was conducted. These materials included brass, bronze, beryllium copper, monel, nichrome v, 24s-t aluminum, nodular iron, and gray cast iron. The metals investigated may be useful as possible cage (separator or retainer) materials for rolling-contact bearings of high-speed turbine engines. The ability of materials to form surface films that prevent welding is a most important factor in both dry friction and boundary lubrication. On the basis of wear and resistance to welding only, the cast irons were the most promising materials investigated; they showed the least wear and the least tendency to surface failure when run dry, and when boundary lubricated they showed the highest load capacity. On the basis of mechanical properties, nodular iron is superior to gray cast iron. Bronze had the lowest friction coefficient under dry sliding conditions. The results with brass, beryllium copper, and aluminum were poor and these materials do not appear, with regard to friction and wear, to be suitable for cages.
Date: January 1, 1952
Creator: Johnson, Robert L; Swikert, Max A & Bisson, Edmond E

Investigation of separated flows in supersonic and subsonic streams with emphasis on the effect of transition

Description: Report presents the results of experimental and theoretical research conducted on flow separation associated with steps, bases, compression corners, curved surfaces, shock-wave boundary-layer reflections, and configurations producing leading-edge separation. Results were obtained from pressure-distribution measurements, shadowgraph observations, high-speed motion pictures, and oil-film studies. The maximum scope of measurement encompassed Mach numbers between 0.4 and 3.6, and length Reynolds numbers between 4,000 and 5,000,000.
Date: November 29, 1956
Creator: Chapman, Dean R.; Kuehn, Donald M. & Larson, Howard K.

Investigation of separation of the turbulent boundary layer

Description: An investigation was conducted on a turbulent boundary layer near a smooth surface with pressure gradients sufficient to cause flow separation. The reynolds number was high, but the speeds were entirely within the incompressible flow range. The investigation consisted of measurements of mean flow, three components of turbulence intensity, turbulent shearing stress, and correlations between two fluctuation components at a point and between the same component of different points. The results are given in the form of tables and graphs. The discussion deals first with separation and then with the more fundamental question of basic concepts of turbulent flow.
Date: January 1, 1951
Creator: Schubauer, G B & Klebanoff, P S

Investigation of spoiler ailerons for use as speed brakes or glide-path controls on two NACA 65-series wings equipped with full-span slotted flaps

Description: A wind-tunnel investigation was made to determine the characteristics of spoiler ailerons used as speed brakes or glide-path controls on an NACA 65-210 wing and an NACA 65-215 wing equipped with full-span slotted flaps. Several plug aileron and retractable-aileron configurations were investigated on two wing models with the full-span flaps retracted and deflected. Tests were made at various Mach numbers between 0.13 and 0.71. The results of this investigation have indicated that the use of plug or retractable ailerons, either alone or in conjunction with wing flaps, as speed brakes or glide-path controls is feasible and very effective.
Date: January 1, 1951
Creator: Fischel, Jack & Watson, James M

A method for the design of sweptback wings warped to produce specified flight characteristics at supersonic speeds

Description: One of the problems connected with the sweptback wing is the difficulty of controlling the location of the center of pressure and hence the pitching moment. A method is presented for designing a wing to be self-trimming at a given set of flight conditions. Concurrently, the spanwise distribution of load on the wing is made to be approximately elliptical, in an effort to maintain low wing drag.
Date: January 1, 1955
Creator: Tucker, Warren A

Measurements of free-space oscillating pressures near propellers at flight Mach numbers to 0.72

Description: In the course of a short flight program initiated to check the theory of Garrick and Watkins (NACA rep. 1198), a series of measurements at three stations were made of the oscillating pressures near a tapered-blade plan-form propeller and rectangular-blade plan form propeller at flight Mach numbers up to 0.72. In contradiction to the results for the propeller studied in NACA rep. 1198, the oscillating pressures in the plane ahead of the propeller were found to be higher than those immediately behind the propeller. Factors such as variation in torque and thrust distribution, since the blades of the present investigation were operating above their design forward speed, may account for this contradiction. The effect of blade plan form shows that a tapered-blade plan-form propeller will produce lower sound-pressure levels than a rectangular-blade plan-form propeller for the low blade-passage harmonics (the frequencies where structural considerations are important) and produce higher sound-pressure levels for the higher blade-passage harmonics (frequencies where passenger comfort is important).
Date: January 1, 1958
Creator: Kurbjun, Max C & Vogeley, Arthur W

Method of analysis for compressible flow through mixed-flow centrifugal impellers of arbitrary design

Description: A method is presented for analysis of the compressible flow between the hub and the shroud of mixed-flow impellers of arbitrary design. Axial symmetry was assumed, but the forces in the meridional (hub to shroud) plane, which are derived from tangential pressure gradients, were taken into account. The method was applied to an experimental mixed-flow impeller. The analysis of the flow in the meridional plane of the impeller showed that the rotational forces, the blade curvature, and the hub-shroud profile can introduce severe velocity gradients along the hub and the shroud surfaces. Choked flow at the impeller inlet as determined by the analysis was verified by experimental results.
Date: April 13, 1950
Creator: Hamrick, Joseph T.; Ginsburg, Ambrose & Osborn, Walter M.