Radiant heat transfer between nongray surfaces
Nongray surface property effects on radiant heat transfer between interacting opaque surfaces, analyzing spectral emittance wavelength and temperature dependence
Fischer, W. D.↗
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Effect of thermally expanding surfaces on aerodynamic roll torques for cones.
An experimental and analytical study has been made of the aerodynamic roll torque on smoothly ablating, spinning cones. The tests, conducted in the Ames 3.5-Foot Hypersonic Wind Tunnel, indicated that the smoothly ablating model rolling at 0 deg angle of attack experiences roll damping, but when rolling at angle of attack an aerodynamic torque in the direction of spin arises if thermal expansion of the body surface occurs. An analysis of the spinning body at angle of attack is included to show how the relative importance of the ablator thermal expansion and the surface recession rate determines whether the motion is damped or undamped.
Mcdevitt, J. B.↗
Theoretical analysis of rough-surface shadowing from point-source radiation.
The shadowing function, defined as the probability that a point on a rough surface will be illuminated by radiation from a source at fixed height above the surface, is considered. An exact expression for this probability is derived and evaluated approximately when the surface elevation is a normal random process. The effect of surface correlation is considered and shown to be appreciable. Several numerical computations of the shadowing function are presented.
Hardin, J. C.↗
Solar wind and terrestrial atmosphere effects on lunar sample surface composition
Samples returned from the Apollo missions have been shown to have undergone a partial surface oxidation with the degree of oxidation being dependent on the intensity and duration of exposure to a terrestrial or other oxidizing atmosphere. Exposure to atomic hydrogen at room temperature, or molecular hydrogen above 100 C results in a surface reduction. The adsorption of water vapor on a test sample was found to be only slightly dependent on the state of surface oxidation, a situation consistent with the formation of hydroxyl groups on the surface when a sample is exposed to hydrogen. That hydroxyl groups are indeed formed is substantiated by the release of water vapor (and by release of heavy water following exposure to deuterium), indicating that water vapor can be synthesized from solar wind hydrogen and sample oxygen. Observations of trace amounts of methane indicate that the reduction process is by no means restricted to the formation of water vapor.
Cadenhead, D. A.↗
The Effect of a Planetary Surface Penetrator on the Soil Column Surrounding the Impacting Body
A prototype penetrator instrument was impacted into a dry lake bed. Laboratory studies of the soil surrounding the penetrator revealed that the soil was contaminated by paint and metal from the penetrator's casing. Paint pigment rich in titanium and sulfur was found in the adjacent soil. The highly mobile paint pigment migrated onto viewing ports in the penetrator's exterior. Bulk analysis of the soil adjacent to the impactor showed a significant increase in both elements, as well as the presence of metal chips from the casing and nose cone. It is recommended that great care be taken in the use of coating materials and the metal alloys selected for the penetrator's exterior, or the accuracy of any experiment requiring an uncontaminated in situ sample may be adversely affected.
Blanchard, Maxwell B.↗
Effects of upper-surface blowing and thrust vectoring on low-speed aerodynamic characteristics of a large-scale supersonic transport model
Tests were conducted in the Langley full-scale tunnel to determine the low-speed aerodynamic characteristics of a large-scale arrow-wing supersonic transport configured with engines mounted above the wing for upper surface blowing, and conventional lower surface engines with provisions for thrust vectoring. A limited number of tests were conducted for the upper surface engine configuration in the high lift condition for beta = 10 in order to evaluate lateral directional characteristics, and with the right engine inoperative to evaluate the engine out condition.
Coe, P. L., Jr.↗
Effects of perforated flap surfaces and screens on acoustics of a large externally blown flap model
Various model geometries and combinations of perforated flap surfaces and screens mounted close to the flap surfaces were studied for application to jet-flap noise attenuation for externally blown flap, under-the-wing aircraft. The efforts to reduce jet-flap interaction noise were marginally successful. Maximum attenuations of less than 4 db in overall sound pressure level were obtained in the flyover plane. Noise reductions obtained in the low-to-middle-frequency ranges (up to 7 db) were generally offset by large increases in high-frequency noise (up to 20 db).
Burns, R. J.↗
Effects of upper-surface blowing and thrust vectoring on low speed aerodynamic characteristics of a large-scale supersonic transport model
Tests were conducted in a full scale tunnel to determine the low speed aerodynamic characteristics of a large scale arrow wing supersonic transport configured with engines mounted above the wing for upper surface blowing and conventional lower surface engines having provisions for thrust vectoring. Tests were conducted over an angle of attack range of -10 deg to 34 deg and for Reynolds numbers (based on the mean aerodynamic chord) of 5.17 x 1 million and 3.89 x 1 million. A limited number of tests were also conducted for the upper surface engine configuration in the high lift condition at an angle of sideslip of 10 deg in order to evaluate lateral directional characteristics and with the right engine inoperative in order to evaluate the engine out condition.
Coe, P. L., Jr.↗
Effects of bulk and surface conductivity on the potential developed by dielectrics exposed to electron beams
The charging and discharging of a dielectric material which has bulk and surface conductivities is discussed. Two model problems are solved. In the first problem, a semi-infinite dielectric plane, attached to an infinite grounded conducting substrate and exposed to a monoenergetic electron beam, is analyzed. Bulk and surface conductivities and secondary emission characteristics are taken into account as parameters. In the second problem the dielectric is charged but the electron beam is shut off so only the bulk and surface conductivities enter the calculation. The principal result of the latter calculation is to show that steep tangential gradients develop in the presence of a surface conductivity during decay, and that for asymptotic times the temporal behavior, for a fixed position, is proportional to the square root of t rather than exponential, as expected in the presence of a bulk conductivity.
Rotenberg, M.↗
Some effects of motion and plane reflecting surfaces on the radiation from acoustic sources
The effects of translatory and rotational motion and of the proximity of ground surface on the radiation from acoustic monopole and dipole sources are discussed together with the key equations. It is shown that interference patterns are produced by reflection and absorption at a plane surface and that consequently, the far-field directivity of an acoustic source near the ground can be substantially altered from its free-field value. The kinematic effects discussed include the beaming of sound in the direction of source motion and the shifting of the observer source frequency in a directionally dependent manner. The effects are illustrated by experimental data.
Lansing, D. L.↗
Surface-tension induced instabilities: Effects of lateral boundaries
Convection in circular and rectangular cylinders is analyzed. The governing equations and boundary conditions are formulated, linear and nonlinear stability theory are considered, and the physical implications of the theory are discussed.
Rosenblat, S.↗
RF verification tasks underway at the Harris Corporation for multiple aperture reflector system
Mesh effects on gain and patterns and adjacent aperture coupling effects for "pie" and circular apertures are discussed. Wire effects for Harris model with Langley scale model results included for assessing D/lamda effects, and wire effects with adjacent aperture coupling were determined. Reflector surface distortion effects (pillows and manufacturing roughness) were studied.
Gutwein, T. A.↗
The Effect of Sea-Surface Sun Glitter on Microwave Radiometer Measurements
A relatively simple model for the microwave brightness temperature of sea surface Sun glitter is presented. The model is an accurate closeform approximation for the fourfold Sun glitter integral. The model computations indicate that Sun glitter contamination of on orbit radiometer measurements is appreciable over a large swath area. For winds near 20 m/s, Sun glitter affects the retrieval of environmental parameters for Sun angles as large as 20 to 25 deg. The model predicted biases in retrieved wind speed and sea surface temperature due to neglecting Sun glitter are consistent with those experimentally observed in SEASAT SMMR retrievals. A least squares retrieval algorithm that uses a combined sea and Sun model function shows the potential of retrieving accurate environmental parameters in the presence of Sun glitter so long as the Sun angles and wind speed are above 5 deg and 2 m/s, respectively.
Wentz, F. J.↗
Drag measurements in tubular structure elements. Part 3: Effect of diameter and surface structure on the drag of cylindrical tubes
Measurements on five cylinders with different surfaces show that the supercritical drag coefficient tends to 0.5 for smooth cylinders with maximum critical Re number 4.16 times 10 to the -5 power and to 0.6 for point pattern surfaces with Re number reduced to 2.16 times 10 to the -5 power. For the other surfaces, with increasing roughness the critical Re number decrease while both minimum supercritical drag coefficients increase.
Schulz, G.↗
The effects of mesh reflecting surfaces upon radiometric measurements
Reflector antennas with mesh surfaces have been used in ground and space applications primarily for communication systems. How the requirements for mesh surface reflectors are different for microwave radiometric applications is indicated, a method of measuring the anticipated small dissipation losses of gold-plated mesh using a radiometer system is proposed.
Crosswell, W. F.↗
Effects of nonequilibrium and surface catalysis on Shuttle heat transfer - A review
It is pointed out that the Space Shuttle Orbiter is a hypersonic glide reentry vehicle which spends much of its entry time at relatively tenuous altitudes in which chemical nonequilibrium predominates in the shock layer. On the windward side, dissociation nonequilibrium exists in the inviscid layer and recombination nonequilibrium exists in the boundary layer. The present investigation is concerned with an evaluation of various flowfield predictions, taking into account a comparison of equilibrium and nonequilibrium flowfields coupled with reacting axisymmetric analog boundary-layer solutions and the results of viscous-shock-layer solutions with flight temperature/heat-flux measurements near the windward centerline for the Shuttle flights STS-2, STS-3, and STS-5.
Scott, C. D.↗
Evaluation of two transport aircraft and several ground test vehicle friction measurements obtained for various runway surface types and conditions. A summary of test results from joint FAA/NASA Runway Friction Program
Tests with specially instrumented NASA Boeing 737 and 727 aircraft together with several different ground friction measuring devices were conducted for a variety of runway surface types and conditions. These tests are part of joint FAA/NASA Aircraft/Ground Vehicle Runway Friction Program aimed at obtaining a better understanding of aircraft ground handling performance under adverse weather conditions and defining relationships between aircraft and ground vehicle tire friction measurements. Aircraft braking performance on dry, wet, snow and ice-covered runway conditions is discussed as well as ground vehicle friction data obtained under similar runway conditions. For a given contaminated runway surface condition, the correlation between ground vehicles and aircraft friction data is identified. The influence of major test parameters on friction measurements such as speed, test tire characteristics, type and amount of surface contaminant, and ambient temperature are discussed. The effect of surface type on wet friction levels is also evaluated from comparative data collected on grooved and ungrooved concrete and asphalt surfaces.
Yager, Thomas J.↗
Surface pressure and streamline effects on laminar heating calculations
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Riley, C. J.↗