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  Partner: UNT Libraries Government Documents Department
 Decade: 1950-1959
 Serial/Series Title: NACA Technical Notes
 Collection: National Advisory Committee for Aeronautics Collection
Empirical relation between induced velocity, thrust, and rate of descent of a helicopter rotor as determined by wind-tunnel tests on four model rotors

Empirical relation between induced velocity, thrust, and rate of descent of a helicopter rotor as determined by wind-tunnel tests on four model rotors

Date: October 1, 1951
Creator: Castles, Walter, Jr. & Gray, Robin B.
Description: The empirical relation between the induced velocity, thrust, and rate of vertical descent of a helicopter rotor was calculated from wind tunnel force tests on four model rotors by the application of blade-element theory to the measured values of the thrust, torque, blade angle, and equivalent free-stream rate of descent. The model tests covered the useful range of C(sub t)/sigma(sub e) (where C(sub t) is the thrust coefficient and sigma(sub e) is the effective solidity) and the range of vertical descent from hovering to descent velocities slightly greater than those for autorotation. The three bladed models, each of which had an effective solidity of 0.05 and NACA 0015 blade airfoil sections, were as follows: (1) constant-chord, untwisted blades of 3-ft radius; (2) untwisted blades of 3-ft radius having a 3/1 taper; (3) constant-chord blades of 3-ft radius having a linear twist of 12 degrees (washout) from axis of rotation to tip; and (4) constant-chord, untwisted blades of 2-ft radius. Because of the incorporation of a correction for blade dynamic twist and the use of a method of measuring the approximate equivalent free-stream velocity, it is believed that the data obtained from this program are more applicable to free-flight calculations than ...
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Droplet Impingement and Ingestion by Supersonic Nose Inlet in Subsonic Tunnel Conditions

Droplet Impingement and Ingestion by Supersonic Nose Inlet in Subsonic Tunnel Conditions

Date: May 1, 1958
Creator: Gelder, Thomas F.
Description: The amount of water in cloud droplet form ingested by a full-scale supersonic nose inlet with conical centerbody was measured in the NACA Lewis icing tunnel. Local and total water impingement rates on the cowl and centerbody surfaces were also obtained. All measurements were made with a dye-tracer technique. The range of operating and meteorological conditions studied was: angles of attack of 0 deg and 4.2 deg, volume-median droplet diameters from about 11 to 20 microns, and ratios of inlet to free-stream velocity from about 0.4 to 1.8. Although the inlet was designed for supersonic (Mach 2.0) operation of the aircraft, the tunnel measurements were confined to a free-stream velocity of 156 knots (Mach 0.237). The data are extendable to other subsonic speeds and droplet sizes by dimensionless impingement parameters. Impingement and ingestion efficiencies are functions of the ratio of inlet to free-stream velocity as well as droplet size. For the model and range of conditions studied, progressively increasing the inlet velocity ratio from less than to greater than 1.0 increased the centerbody impingement efficiency and shifted the cowl impingement region from the inner- to outer-cowl surfaces, respectively. The ratio of water ingested by the inlet plane to that contained ...
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A Dye-Tracer Technique for Experimentally Obtaining Impingement Characteristics of Arbitrary Bodies and a Method for Determining Droplet Size Distribution

A Dye-Tracer Technique for Experimentally Obtaining Impingement Characteristics of Arbitrary Bodies and a Method for Determining Droplet Size Distribution

Date: March 1, 1955
Creator: VonGlahn, Uwe H.; Gelder, Thomas F. & Smyers, William H., Jr.
Description: A dye-tracer technique has been developed whereby the quantity of dyed water collected on a blotter-wrapped body exposed to an air stream containing a dyed-water spray cloud can be colorimetrically determined in order to obtain local collection efficiencies, total collection efficiency, and rearward extent of impingement on the body. In addition, a method has been developed whereby the impingement characteristics obtained experimentally for a body can be related to theoretical impingement data for the same body in order to determine the droplet size distribution of the impinging cloud. Several cylinders, a ribbon, and an aspirating device to measure cloud liquid-water content were used in the studies presented herein for the purpose of evaluating the dye-tracer technique. Although the experimental techniques used in the dye-tracer technique require careful control, the methods presented herein should be applicable for any wind tunnel provided the humidity of the air stream can be maintained near saturation.
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Effect of Ice and Frost Formations on Drag of NACA 65(sub 1) -212 Airfoil for Various Modes of Thermal Ice Protection

Effect of Ice and Frost Formations on Drag of NACA 65(sub 1) -212 Airfoil for Various Modes of Thermal Ice Protection

Date: June 1, 1953
Creator: Gray, V. H. & Von Glahn, U. H.
Description: The effects of primary and. runback icing and frost formations on the drag of an 8-foot-chord NACA 651-212 airfoil section were investigated over a range of angles of attack from 20 to 80 and airspeeds up to 260 miles per hour for icing conditions with liquid-water contents ranging from 0.25 to 1.4 grams per cubic meter and datum air temperatures of -30 to 30 F. The results showed that glaze-ice formations, either primary or runback, on the upper surface near the leading edge of the airfoil caused large and rapid increases in drag, especially at datum air temperatures approaching 32 F and in the presence of high rates of water catch. Ice formations at lower temperatures (rime ice) did not appreciably increase the drag coefficient over the initial (standard roughness) drag coefficient. Cyclic de-icing of the primary Ice formations on the airfoil leading-edge section permitted the drag coefficient to return almost to the bare airfoil drag value. Runback icing on the lower surface did not present a serious drag problem except when heavy spanwise ridges of runback ice occurred aft of the heatable area. Frost formations caused rapid and large increases in drag with incipient stalling of the airfoil.
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Effects of extreme surface cooling on boundary-layer transition

Effects of extreme surface cooling on boundary-layer transition

Date: October 1, 1957
Creator: Jack, J. R.; Wisniewski, R. J. & Diaconis, N. S.
Description: None
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Correlations Among Ice Measurements, Impingement Rates Icing Conditions, and Drag Coefficients for Unswept NACA 65A004 Airfoil

Correlations Among Ice Measurements, Impingement Rates Icing Conditions, and Drag Coefficients for Unswept NACA 65A004 Airfoil

Date: February 1, 1958
Creator: Gray, Vernon H.
Description: An empirical relation has been obtained by which the change in drag coefficient caused by ice formations on an unswept NACA 65AO04 airfoil section can be determined from the following icing and operating conditions: icing time, airspeed, air total temperature, liquid-water content, cloud droplet impingement efficiencies, airfoil chord length, and angles of attack. The correlation was obtained by use of measured ice heights and ice angles. These measurements were obtained from a variety of ice formations, which were carefully photographed, cross-sectioned, and weighed. Ice weights increased at a constant rate with icing time in a rime icing condition and at progressively increasing rates in glaze icing conditions. Initial rates of ice collection agreed reasonably well with values predicted from droplet impingement data. Experimental droplet impingement rates obtained on this airfoil section agreed with previous theoretical calculations for angles of attack of 40 or less. Disagreement at higher angles of attack was attributed to flow separation from the upper surface of the experimental airfoil model.
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Aerodynamic Effects Caused by Icing of an Unswept NACA 65A004 Airfoil

Aerodynamic Effects Caused by Icing of an Unswept NACA 65A004 Airfoil

Date: February 1, 1958
Creator: Gray, Vernon H. & vonGlahn, Uwe H.
Description: The effects of ice formations on the section lift, drag, and pitching-moment coefficients of an unswept NACA 65A004 airfoil section of 6-foot chord were studied.. The magnitude of the aerodynamic penalties was primarily a function of the shape and size of the ice formation near the leading edge of the airfoil. The exact size and shape of the ice formations were determined photographically and found to be complex functions of the operating and icing conditions. In general, icing of the airfoil at angles of attack less than 40 caused large increases in section drag coefficients (as much as 350 percent in 8 minutes of heavy glaze icing), reductions in section lift coefficients (up to 13 percent), and changes in the pitching-moment coefficient from diving toward climbing moments. At angles of attack greater than 40 the aerodynamic characteristics depended mainly on the ice type. The section drag coefficients generally were reduced by the addition of rime ice (by as much as 45 percent in 8 minutes of icing). In glaze icing, however, the drag increased at these angles of attack. The section lift coefficients were variably affected by rime-ice formations; however, in glaze icing, lift increases at high angles of attack ...
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Comparison of Heat Transfer from Airfoil in Natural and Simulated Icing Conditions

Comparison of Heat Transfer from Airfoil in Natural and Simulated Icing Conditions

Date: September 1, 1951
Creator: Gelder, Thomas F. & Lewis, James P.
Description: An investigation of the heat transfer from an airfoil in clear air and in simulated icing conditions was conducted in the NACA Lewis 6- by 9-foot icing-research tunnel in order to determine the validity of heat-transfer data as obtained in the tunnel. This investiation was made on the same model NACA 65,2-016 airfoil section used in a previous flight study, under similar heating, icing, and operating conditions. The effect of tunnel turbulence, in clear air and in icingwas indicated by the forward movement of transition from laminar to turbulent heat transfer. An analysis of the flight results showed the convective heat transfer in icing to be considerably different from that measured in clear air and. only slightly different from that obtained in the icing-research tunnel during simulated icing.
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Analogy Between Mass and Heat Transfer with Turbulent Flow

Analogy Between Mass and Heat Transfer with Turbulent Flow

Date: October 1, 1953
Creator: Callaghan, Edmund E.
Description: An analysis of combined heat and mass transfer from a flat plate has been made in terms of Prandtl t s simplified physical concept of the turbulent boundary layer. The results of the analysis show that for conditions of reasonably small heat and mass transfer, the ratio of the mass-and heat-transfer coefficients is dependent on the Reynolds number of the boundary layer, the Prandtl number of the medium of diffusion, and the Schmidt number of the diffusing fluid in the medium of diffusion. For the particular case of water evaporating into air, the ratio of mass-transfer coefficient to heat-transfer coefficient is found to be slightly greater than unity.
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Analytical Investigation of Icing Limit for Diamond-Shaped Airfoil in Transonic and Supersonic Flow

Analytical Investigation of Icing Limit for Diamond-Shaped Airfoil in Transonic and Supersonic Flow

Date: January 1, 1953
Creator: Callaghan, Edmund E. & Serafini, John S.
Description: Calculations have been made for the icing limit of a diamond airfoil at zero angle of attack in terms of the stream Mach number, stream temperature, and pressure altitude. The icing limit is defined as a wetted-surface temperature of 320 F and is related to the stream conditions by the method of Hardy. The results show that the point most likely to ice on the airfoil lies immediately behind the shoulder and is subject to possible icing at Mach numbers as high as 1.4.
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