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Effect of Periodic Changes of Angle of Attack on Behavior of Airfoils

Description: This report presents the results of a series of experiments, which gave some quantitative results on the effect of periodic changes in the direction of the relative air flow against airfoils. The first series of experiments concerned how the angle of attack of the wing model was changed by causing the latter to oscillate about an axis parallel to the span and at right angles to the air flow. The second series embraced all the experiments in which the direction of the air flow itself was periodically changed.
Date: October 1922
Creator: Katzmayr, R.
Partner: UNT Libraries Government Documents Department

A method for increasing the effectiveness of stabilizing surfaces at high supersonic Mach numbers

Description: Report presenting the use of wedge-shaped airfoil sections to obtain large increases in lift-curve slope at low angles of attack at high supersonic Mach numbers. The use of such sections on the tail surfaces operating at low angles of attack on airplanes or missiles traveling at these speeds can greatly decrease the stabilizing-surface area required.
Date: August 3, 1954
Creator: McLellan, Charles H.
Partner: UNT Libraries Government Documents Department

Aerodynamic characteristics of airfoils at high speeds

Description: From Summary: "This report deals with an experimental investigation of the aerodynamical characteristics of airfoils at high speeds. Lift, drag, and center of pressure measurements were made on six airfoils of the type used by the air service in propeller design, at speeds ranging from 550 to 1,000 feet per second. The results show a definite limit to the speed at which airfoils may efficiently be used to produce lift, the lift coefficient decreasing and the drag coefficient increasing as the speed approaches the speed of sound. The change in lift coefficient is large for thick airfoil sections (camber ratio 0.14 to 0.20) and for high angles of attack. The change is not marked for thin sections (camber ratio 0.10) at low angles of attack, for the speed range employed. At high speeds the center of pressure moves back toward the trailing edge of the airfoil as the speed increases. The results indicate that the use of tip speeds approaching the speed of sound for propellers of customary design involves a serious loss in efficiency."
Date: 1925~
Creator: Briggs, L. J.; Hull, G. F. & Dryden, H. L.
Partner: UNT Libraries Government Documents Department

The aerodynamic characteristics of airfoils as affected by surface roughness

Description: From Summary: "The effect on airfoil characteristics of surface roughness of varying degrees and types at different locations on an airfoil was investigated at high values of the Reynolds number in a variable density wind tunnel. Tests were made on a number of National Advisory Committee for Aeronautics (NACA) 0012 airfoil models on which the nature of the surface was varied from a rough to a very smooth finish. The effect on the airfoil characteristics of varying the location of a rough area in the region of the leading edge was also investigated. Airfoils with surfaces simulating lap joints were also tested. Measurable adverse effects were found to be caused by small irregularities in airfoil surfaces which might ordinarily be overlooked. The flow is sensitive to small irregularities of approximately 0.0002c in depth near the leading edge. The tests made on the surfaces simulating lap joints indicated that such surfaces cause small adverse effects. Additional data from earlier tests of another symmetrical airfoil are also included to indicate the variation of the maximum lift coefficient with the Reynolds number for an airfoil with a polished surface and with a very rough one."
Date: April 1933
Partner: UNT Libraries Government Documents Department

Aerodynamic forces and loadings on symmetrical circular-arc airfoils with plain leading-edge and plain trailing-edge flaps

Description: From Summary: "An investigation has been made in the Langley two-dimensional low-turbulence tunnel and in the Langley two-dimensional low-pressure tunnel of 6- and 10-percent-thick symmetrical circular-arc airfoil sections at low Mach numbers and several Reynolds numbers. The airfoils were equipped with 0.15-chord plain leading-edge flaps and 0.20-chord plan trailing-edge flaps. The section lift and pitching-moment characteristics were determined for both airfoils with the flaps deflected individually and in combination."
Date: 1953
Creator: Cahill, Jones F.; Underwood, William J.; Nuber, Robert J. & Cheesman, Gail A.
Partner: UNT Libraries Government Documents Department

Aerodynamic characteristics of the NACA 64-010 and 0010-1.10 40/1.051 airfoil sections at Mach numbers from 0.30 to 0.85 and Reynolds numbers from 4.0 x 10(exp. 6) to 8.0 x 10(exp. 6)

Description: Report presenting an investigation in the low-turbulence pressure tunnel to determine the aerodynamic characteristics of NACA 64-010 and 0010-1.10 airfoil sections. The investigation covered a range of Mach and Reynolds numbers.
Date: August 1954
Creator: Loftin, Laurence K., Jr.
Partner: UNT Libraries Government Documents Department

Aerodynamic coefficients for an oscillating airfoil with hinged flap, with tables for a Mach number of 0.7

Description: From Introduction: "The fundamental integral equation for the pressure distribution on an oscillating thin airfoil moving at subsonic speed has been derived by Possio in reference 1. Collocation procedures have been used by Possio, Frazer, and Skan, and others to obtain lift and moment on an oscillating first plate. An important contribution has been made by Dietze (see reference 2 and 3), who has developed an iterative procedure for numerical solution of Possio's integral equation."
Date: October 1950
Creator: Turner, M J & Rabinowitz, S
Partner: UNT Libraries Government Documents Department

Airfoil section data obtained in the NACA variable-density tunnel as affected by support interference and other corrections

Description: From Introduction: "The purpose of this report is to present the corrections for application to published results from the variable-density tunnel to give more reliable values of section profile-drag coefficient for airfoils of various thickness."
Date: 1939
Creator: Jacobs, Eastman N. & Abbott, Ira H.
Partner: UNT Libraries Government Documents Department

An evaluation of the characteristics of a 10-percent-thick NACA 66-series airfoil section with a special mean-camber line designed to produce a high critical Mach number

Description: Report presenting testing of the low-speed aerodynamic characteristics of the NACA 66-series airfoil section in the two-dimensional low-turbulence pressure tunnel. Results regarding the critical-speed characteristics and low-speed characteristics are provided.
Date: July 1948
Creator: Loftin, Laurence K., Jr. & Cohen, Kenneth S.
Partner: UNT Libraries Government Documents Department

The effects of variations in Reynolds number between 3.0 x 10sub6 and 25.0 x 10sub6 upon the aerodynamic characteristics of a number of NACA 6-series airfoil sections

Description: Results are presented of an investigation made to determine the two-dimensional lift and drag characteristics of nine NACA 6-series airfoil section at Reynolds numbers of 15.0 x 10sub6, 20.0 x 10sub6, and 25.0 x 10sub6. Also presented are data from NACA Technical Report 824 for the same airfoils at Reynolds numbers of 3.0 x 10sub6, 6.0 x 10sub6, and 9.0 x 10sub6. The airfoils selected represent sections having variations in the airfoil thickness, thickness form, and camber. The characteristics of an airfoil with a split flap were determined in one instance, as was the effect of surface roughness. Qualitative explanations in terms of flow behavior are advanced for the observed types of scale effect.
Date: 1950
Creator: Loftin, Laurence K., Jr. & Bursnall, William J.
Partner: UNT Libraries Government Documents Department

Aerodynamic characteristics of 15 NACA airfoil sections at seven Reynolds numbers from 0.7 x 10(exp 6) to 9.0 x 10(exp 6)

Description: Report presenting an investigation of the two-dimensional aerodynamic characteristics of 15 NACA airfoils at four Reynolds numbers. The results indicate that the drag coefficient at the design lift coefficient and the maximum lift coefficient are the most important aerodynamic characteristics and are most affected by Reynolds number changes.
Date: October 1949
Creator: Loftin, Laurence K., Jr. & Smith, Hamilton A.
Partner: UNT Libraries Government Documents Department

Tests of an NACA 66,2-420 Airfoil of 5-Foot Chord at High Speed, Special Report

Description: This report covers tests of a 5-foot model of the NACA 66,2-420 low-drag airfoil at high speeds including the critical compressibility speed. Section coefficients of lift, drag, and pitching moment, and extensive pressure-distribution data are presented. The section drag coefficient at the design lift coefficient of 0.4 increased from 0.0042 at low speeds to 0.0052 at a Mach number of 0.56 (390 mph at 25,000 ft altitude). The critical Mach number was about 0.60. The results cover a Reynold number range from 4 millions to 17 millions.
Date: September 1942
Creator: Hood, Manley J. & Anderson, Joseph L.
Partner: UNT Libraries Government Documents Department

Tests of Airfoils Designed to Delay the Compressibility Burble

Description: Development of airfoil sections suitable for high-speed applications has generally been difficult because little was known of the flow phenomenon that occurs at high speeds. A definite critical speed has been found at which serious detrimental flow changes occur that lead to serious losses in lift and large increases in drag. This flow phenomenon, called the compressibility burble, was originally a propeller problem, but with the development of higher speed aircraft serious consideration must be given to other parts of the airplane. Fundamental investigations of high-speed airflow phenomenon have provided new information. An important conclusion of this work has been the determination of the critical speed, that is, the speed at which the compressibility burble occurs. The critical speed was shown to be the translational velocity at which the sum of the translational velocity and the maximum local induced velocity at the surface of the airfoil or other body equals the local speed of sound. Obviously then higher critical speeds can be attained through the development of airfoils that have minimum induced velocity for any given value of the lift coefficient. Presumably, the highest critical speed will be attained by an airfoil that has uniform chordwise distribution of induced velocity or, in other words, a flat pressure distribution curve. The ideal airfoil for any given high-speed application is, then, that form which at its operating lift coefficient has uniform chordwise distribution of induced velocity. Accordingly, an analytical search for such airfoil forms has been conducted and these forms are now being investigated experimentally in the 23-inch high-speed wind tunnel. The first airfoils investigated showed marked improvement over those forms already available, not only as to critical speed buy also the drag at low speeds is decreased considerably. Because of the immediate marked improvement, it was considered desirable to extend the ...
Date: June 1939
Creator: Stack, John
Partner: UNT Libraries Government Documents Department

Wind-Tunnel Investigation of an N.A.C.A. 23012 Airfoil with a Slotted Flap and Three Types of Auxiliary Flap

Description: An investigation was made in the N.A.C.A. 7- by 10- foot wind tunnel to determine the aerodynamic section characteristics of an N. A. C. A. 23012 airfoil with a single main slotted flap equipped successively with auxiliary flaps of the plain, split, and slotted types. A test installation mas used in which an airfoil of 7-foot span was mounted vertically between the upper and the lower sides of the closed test section so that two-dimensional flow was approximated. On the basis of maximum lift coefficient, low drag at moderate and high lift coefficients, and high drag at high lift coefficients, the optimum combination of the arrangements was found to be the double slotted flap . All the auxiliary flaps tested, however, increased the magnitudes of the pitching moments over those of the main slotted flap alone.
Date: December 1938
Creator: Wenzinger, Carl J. & Gauvain, William E.
Partner: UNT Libraries Government Documents Department

A Theory of Unstaggered Airfoil Cascades in Compressible Flow

Description: By use of the methods of thin airfoil theory, which include effects of compressibility, relations are developed which permit the rapid determination of the pressure distribution over an unstaggered cascade of airfoils of a given profile, and the determination of the profile shape necessary to yield a given pressure distribution for small chord gap ratios, For incompressible flow the results of the theory are compared with available examples obtained by the more exact method of conformal transformation. Although the theory is developed for small chord/gap ratios, these comparisons show that it may be extended to chord/gap ratios of order unity, at least for low speed flows. Choking of cascades, a phenomenon of particular importance in compressor design, is considered.
Date: September 2, 1947
Creator: Spurr, Robert A. & Allen, H. Julian
Partner: UNT Libraries Government Documents Department

Tests of a Highly Cambered Low-Drag-Airfoil Section with a Lift-Control Flap, Special Report

Description: Tests were made in the NACA two-dimensional low turbulence pressure tunnel of a highly cambered low-drag airfoil (NACA 65,3-618) with a plain flap designed for lift control. The results indicate that such a combination offers attractive possibilities for obtaining low profile-drag coefficients over a wide range of lift coefficients without large reductions of critical speed.
Date: December 1942
Creator: Abbott, Ira H. & Miller, Ralph B.
Partner: UNT Libraries Government Documents Department

Wind-Tunnel Investigation of an NACA 66,2-216 Low-Drag Wing with Split Flaps of Various Sizes, Special Report

Description: An investigation was conducted in the NACA 19-foot pressure wind tunnel of a rectangular wing having NACA 66, 2-216 low-drag airfoil sections and various sizes of simple split flaps. The purpose of the investigation was, primarily, to determine the influence of these flap installations on the aerodynamic characteristics of the wing. Complete lift, drag, and pitching-moment characteristics were determined for a range of test Reynolds numbers from about 2,600,000 to 4,600,000 for each of the installations and for the plain wing. The results of this investigation indicate that values of maximum lift coefficient similar to those of wings with conventional airfoil sections and split flaps can be expected of wings having the NACA 66,2-216 low-drag sections. The increment of maximum lift due to the split flap was found to be practically independent of the Reynolds number over the range investigated. The optimum split flap on the basis of maximum lift appears to have a chord about 20% of the wing chord and a deflection of 60 degrees. The C(sub L) max of the wing with the 0.20c partial-span flap deflected 60 degrees is 2.07 at a Reynolds number of 4,600,000 while with the full-span flap it is approximately 2.53; the increment of the maximum lift coefficient due to the flap is approximately proportional to the flap span. Although the addition of a split flap tends to hasten the stall and to cause it to occur more abruptly, little change in pattern is evidenced by observations of the behavior of wool tufts on the wing.
Date: September 1941
Creator: Muse, Thomas C. & Neely, Robert H.
Partner: UNT Libraries Government Documents Department

Theoretical and Experimental Data for a Number of NACA 6A-Series Airfoil Sections

Description: The NACA 6A-series airfoil sections were designed to eliminate the trailing-edge cusp which is characteristic of the NACA 6-series sections. Theoretical data are presented for NACA 6A-series basic thickness forms having the position of minimum pressure at 30-, 40-, and 50-percent chord and with thickness ratios varying from 6 percent to 15 percent. Also presented are data for a mean line designed to maintain straight sides on the cambered sections. The experimental results of a two dimensional wind tunnel investigation of the aerodynamic characteristics of five NACA 64A-series airfoil sections and two NACA 63A-series airfoil sections are presented. An analysis of these results, which were obtained at Reynolds numbers of 3 x 10(exp 6), 6 x 10(exp 6), and 9 x 10(exp 6), indicates that the section minimum drag and maximum lift characteristics of comparable NACA 6-series and 6A-series airfoil sections are essentially the same. The quarter-chord pitching-moment coefficients and angles of zero lift of NACA 6A-series airfoil sections are slightly more negative than those of corresponding NACA 6-series airfoil sections. The position of the aerodynamic center and the lift-curve slope of smooth NACA 6-series sections. The addition of standard leading-edge roughness causes the lift-curve slope of the newer sections to decrease with increasing airfoil thickness ratio.
Date: December 6, 1946
Creator: Loftin, Laurence K., Jr.
Partner: UNT Libraries Government Documents Department

The Effectiveness at High Speeds of a 20-Percent-Chord Plain Trailing-Edge Flap on the NACA 65-210 Airfoil

Description: "An analysis has been made of the lift control effectiveness of a 20-percent-chord plain trailing-edge flap on the NACA 65-210 airfoil section from section lift-coefficient data obtained at Mach numbers from 0.3 to 0.875. In addition, the effectiveness of the plain flap as a lift-control device has been compared with the corresponding effectiveness of both a spoiler and a dive-recovery flap on the NACA 65-210 airfoil section. The analysis indicates that the plain trailing-edge flap employed on the 10-percent-thick airfoil at Mach numbers as high as 0.875 retains at least 50-percent of its low-speed lift-control effectiveness, and is sufficiently effective in lateral control application, assuming a rigid wing, to provide adequate airplane rolling characteristics" (p. 1).
Date: May 6, 1947
Creator: Stivers, Louis S., Jr.
Partner: UNT Libraries Government Documents Department

The effects of shielding the tips of airfoils

Description: "Tests have recently been made at Langley Memorial Aeronautical Laboratory to ascertain whether the aerodynamic characteristics of an airfoil might be substantially improved by imposing certain limitations upon the air flow about its tips. All of the modified forms were slightly inferior to the plain airfoil at small lift coefficients: however, by mounting thin plates, in planes perpendicular to the span, at the wing tips, the characteristics were improved throughout the range above three-tenths of the maximum lift coefficient. With this form of limitation the detrimental effect was slight; at the higher lift coefficients there resulted a considerable reduction of induced drag and consequently, of power required for sustentation. The slope of the curve of lift versus angle of attack was increased" (p. 347).
Date: 1925
Creator: Reid, Elliott G.
Partner: UNT Libraries Government Documents Department

Airfoil lift with changing angle of attack

Description: From Summary: "Tests have been made in the atmospheric wind tunnel of the National Advisory Committee for Aeronautics to determine the effects of pitching oscillations upon the lift of an airfoil. It has been found that the lift of an airfoil, while pitching, is usually less than that which would exist at the same angle of attack in the stationary condition, although exceptions may occur when the lift is small or if the angle of attack is being rapidly reduced. It is also shown that the behavior of a pitching airfoil may be qualitatively explained on the basis of accepted aerodynamic theory."
Date: September 1927
Creator: Reid, Elliott G.
Partner: UNT Libraries Government Documents Department