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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS2010

Why Income Comparison is Rational

A major factor affecting a person s happiness is the gap between their income and their neighbors , independent of their own income. This effect is strongest when the neighbor has moderately higher income. In addition a person s lifetime happiness often follows a "U" shape. Previous models have explained subsets of these phenomena, typically assuming the person has limited ability to assess their own (hedonic) utility. Here I present a model that explains all the phenomena, without such assumptions. In this model greater income of your neighbor is statistical data that, if carefully analyzed, would recommend that you explore for a new income-generating strategy. This explains unhappiness that your neighbor has greater income, as an emotional "prod" that induces you to explore, in accord with careful statistical analysis. It explains the "U" shape of happiness similarly. Another benefit of this model is that it makes many falsifiable predictions.

Wolpert, David H.↗
NASA NTRS2019

The Effect of Incoming Boundary Layer Characteristics on the Performance of a Distributed Propulsion System

An experimental study is conducted in an effort to advance the understanding of flow physics associated with a boundary layer ingesting, distributed propulsion system. The influence of incoming boundary layer thickness and flow distortions are studied on the flow downstream and the overall performance of the system. The propulsion model, fabricated using additive manufacturing and integrated with electrical fans, is mounted on a flat plate and tested at subsonic speeds. Detailed characterization of the incoming boundary layer and subsequent assessment of the downstream flow field is performed using hotwire anemometry. Modification of the incoming boundary layer is achieved by placing tripping devices, such as rods and vortex generating ramps, near the leading edge of the flat plate. The overall performance of the system for different incoming flow conditions is analyzed by comparing magnitudes of exhaust velocities as well as estimated propulsive power to the corresponding baseline values. For a constant input power to the fans, smaller upstream flow distortions and moderately thickened boundary layers result in marginal changes in the flow field downstream. On the other hand, notable reductions in downstream flow velocities and propulsive power are observed in the case of a significantly thicker and/or distorted incoming boundary layer. It is hoped that this study will serve as a database for this technologically relevant flow field that has not been explored adequately before.

Propulsion↗
NASA NTRS1994

Effects of the Venusian atmosphere on incoming meteoroids and the impact crater population

The dense atmosphere on Venus prevents craters smaller than about 2 km in daimater from forming and also causes formation of several crater fields and multiple-floored craters (collectively referred to as multiple impacts). A model has been constructed that simulates the behavior of a meteoroid in a dense planetary atmosphere. This model was then combined with an assumed flux of incoming meteoroids in an effort to reproduce the size-frequency distribution of impact craters and several aspects of the population of the crater fields and multiple-floored craters on Venus. The modeling indicates that it is plausible that the observed rollover in the size-frequency curve for Venus is due entirely to atmospheric effects on incoming meteoroids. However, there must be substantial variation in the density and behavior of incoming meteoroids in the atmosphere. Lower-density meteoroids must be less likely to survive atmospheric passage than simple density differences can account for. Consequently, it is likely that the percentage of craters formed by high-density meteoroids is very high at small crater diameters, and this percentage decreases substantially with increasing crater diameter. Overall, high-density meteoroids created a disproportionately large percentage of the impact craters on Venus. Also, our results indicate that a process such as meteoroid flattening or atmospheric explosion of meteoroids must be invoked to prevent craters smaller than the observed minimum diameter (2 km) from forming. In terms of using the size-frequency distribution to age-date the surface, the model indicates that the observed population has at least 75% of the craters over 32 km in diameter that would be expected on an atmosphereless Venus; thus, this part of the curve is most suitable for comparison with calibrated curves for the Moon.

Herrick, Robert R.↗
NASA NTRS1981

Effect of forest canopy closure on incoming solar radiance

In order to better understand the physical processes involved in defoliation assessment from remotely sensed data, a field study was designed to investigate the effect of forest canopy closure and other environmental variables on incoming solar radiation. Diffuse radiation measurements were recorded in red, infrared, and middle infrared wavelengths using the Mark 2 three band field radiometer. Results to date indicate that the percent canopy closure is the single most important variable affecting incoming solar radiation. In the visible and near infrared regions, interaction between time of day and date (defined later as solar zenith angle) also affect radiometric response. Aspect has only limited influence on radiance response. These same variables do not influence middle infrared response, however. Uniformity of the forest canopy appears to be more important. These results are compared to LANDSAT MSS classification results of gypsy moth defoliation.

Dottavio, C. L.↗
NASA NTRS1992

An experimental examination of the effects of incoming boundary layer modifications on the dynamics of a turbulent compression corner interaction

This experimental study examines the effects of modifications to the incoming turbulent boundary layer on the highly separated shock wave/boundary layer interaction generated by an unswept compression corner. Particular focus is placed on the motion of the unsteady separation shock wave. The flowfield was generated by a 28 deg ramp in a Mach 5 flow with a freestream Reynolds number of 50 x 10 exp 6/m. The incoming turbulent boundary layer transitioned naturally and developed under near-adiabatic wall conditions. Modification of the flow entering the interaction was effected through either a single plate boundary layer manipulator (BLM) or riblets. The BLM reduced the length of separation by 35-45 percent and reduced the streamwise extent of the separation shock motion by 36-74 percent. Examination of the flowfield downstream of the BLM showed this result to be due to the inviscid preturning of the flow by the BLM, and not by changes to the boundary layer dynamics. The riblets had no measurable effect on the compression corner interaction.

Mcclure, W. B.↗
NASA NTRS2004

Incoming Metrology of Segmented X-Ray Mandrels at MSFC

The Constellation-X Spectroscopy X-ray telescope (SXT) is designed to be built from X-ray optic segments. The X-ray segments will be fabricated from the segmented mandrels using a replication process. The purpose of the incoming metrology is to map the surface of the mandrels, so the performance of the X-ray optics produced can be predicted. Three Constellation-X segmented mandrels have been delivered to MSFC for incoming metrology. The segmented mandrels are 30-degree sections of a cylindrical surface and have diameters of 1.0 m, 1.2 m and 1.6 m. The maximum dimensions of the optical surface are 1.0 m axial length and 0.5 m azimuthal segment length. The metrology of the mandrels consists of the measurement of their slope differences, roundness, absolute radius, axial profile and microroughness. Accuracy goals for each type of measurement and the accuracy of the instruments used for the measurements will be discussed. The results of the mandrel metrology together with the performance predictions will be presented.

Gubarev, Mikhail↗
NASA NTRS2015

Unsteady Loss in the Stator Due to the Incoming Rotor Wake in a Highly-Loaded Transonic Compressor

The present paper reports an investigation of unsteady loss generation in the stator due to the incoming rotor wake in an advanced GE transonic compressor design with a high-fidelity numerical method. This advanced compressor with high reaction and high stage loading has been investigated both experimentally and analytically in the past. The measured efficiency in this advanced compressor is significantly lower than the design intention/goal. The general understanding is that the current generation of compressor design/analysis tools miss some important flow physics in this modern compressor design. To pinpoint the source of the efficiency miss, an advanced test with a detailed flow traverse was performed for the front one and a half stage at the NASA Glenn Research Center. Detailed data-match analysis by GE identified an unexpected high loss generation in the pressure side of the stator passage. Higher total temperature and lower total pressure are measured near the pressure side of the stator. Various analyses based on the RANS and URANS of the compressor stage do not calculate the measured higher total temperature and lower total pressure on the pressure side of the stator. In the present paper, a Large Eddy Simulation (LES) is applied to find the fundamental mechanism of this unsteady loss generation in the stator due to the incoming rotor wake. The results from the LES were first compared with the NASA test results and the GE interpretation of the test data. LES calculates lower total pressure and higher total temperature on the pressure side of the stator, as the measured data showed, resulting in large loss generation on the pressure side of the stator. Detailed examination of the unsteady flow field from LES shows that the rotor wake, which has higher total temperature and higher total pressure relative to the free stream, interacts quite differently with the pressure side of the blade compared to the suction side of the blade. The higher temperature in the wake remains high as the wake passes through the pressure side of the blade. On the other hand, the total temperature diffuses as it passes through near the suction surface. For the presently investigated compressor, the classical intra-stator wake transport to the pressure side of the blade by the slip velocity in the wake seems to be minor. The main causes of this phenomenon are three-dimensional unsteady vortex interactions near the blade surface. The stabilizing effect of the concave curvature on the suction side keeps the rotor wake thin. On the other hand, the destabilizing effect of the convex curvature of the pressure side makes the rotor wake thicker, which results in a higher total temperature measurement at the stator exit. Additionally, wake stretching through the stator seems to contribute to the redistribution of the total temperature and the loss generation.

Efficiency↗