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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 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRSDate not supplied

Adaptive Pressure Profile Method to Locate the Isolator Shock Train Leading Edge Given Limited Pressure Information

To maximize the performance of high-speed air-breathing engines, such as dual-mode scramjets, the streamwise location of the shock train leading edge (STLE) is ideally placed as far upstream in the isolator as possible while avoiding engine unstart. Thus, it is of interest to quantify and control the STLE location as the vehicle travels along its flight trajectory. The STLE location is typically quantified using wall static pressure measurements but there are often restrictions on the number and placement of transducers, thus reducing the accuracy and overall capability of STLE detection methods. In this work, the Adaptive Pressure Profile (APP) method is introduced to address such sparsity concerns. This method is data driven and does not heavily rely on prior information about the flow regime or engine model. Instead, the \mname method uses real-time pressure measurements from a small number of transducers to adaptively learn the isolator pressure profile. This adaptively-learned profile is fit to the pressure data at each time instance to estimate STLE location. The \mname method produces accurate estimates even when (1) the STLE location is not bounded by two or more transducers or (2) when the STLE location is between two transducers that are situated several duct heights apart. Data from two direct-connect isolator models are used to evaluate the accuracy of the \mname method and demonstrate its robustness for different back-pressure scenarios and transducer configurations.

Robin L Hunt↗
NASA NTRSDate not supplied

Adaptive Pressure Profile Method to Locate the Isolator Shock Train Leading Edge Given Limited Pressure Information

To maximize the performance of high-speed air-breathing engines, such as dual-mode scramjets, the streamwise location of the shock train leading edge (STLE) is ideally placed as far upstream in the isolator as possible while avoiding engine unstart. Thus, it is of interest to quantify and control the STLE location as the vehicle travels along its flight trajectory. The STLE location is typically quantified using wall static pressure measurements but there are often restrictions on the number and placement of transducers, thus reducing the accuracy and overall capability of STLE detection methods. In this work, the Adaptive Pressure Profile (APP) method is introduced to address such sparsity concerns. This method is data driven and does not heavily rely on prior information about the flow regime or engine model. Instead, the \mname method uses real-time pressure measurements from a small number of transducers to adaptively learn the isolator pressure profile. This adaptively-learned profile is fit to the pressure data at each time instance to estimate STLE location. The \mname method produces accurate estimates even when (1) the STLE location is not bounded by two or more transducers or (2) when the STLE location is between two transducers that are situated several duct heights apart. Data from two direct-connect isolator models are used to evaluate the accuracy of the \mname method and demonstrate its robustness for different back-pressure scenarios and transducer configurations.

Robin Hunt↗
NASA NTRS1974

Observation of a cosmic gamma-ray burst on Apollo 16. II - X-ray time profile and source location

A burst of X-rays was detected during the trans-earth coast phase of Apollo 16 on Apr. 27, 1972 at 10:68 UT, simultaneously with the observation of a transient event by a gamma-ray spectrometer aboard the same spacecraft. The two instruments provide a broad energy range of more than three orders of magnitude for describing the spectral distribution of this event. The conclusion that the incident flux was X-rays and not charged particles is based on the fact that the particle flux detectors in the Apollo gamma ray spectrometer and on the Vela 6A, which also observed the event, did not respond. The time variation of the total count rate in the X-ray range before and after corrections for detector geometry and the analysis for source direction is presented.

Trombka, J. I.↗
DOE OSTI2024

Investigation of core transport changes in DIII-D discharges with off-axis T e profile peaks

Abstract DIII-D discharges that transition to H-mode solely with off-axis electron cyclotron heating (ECH) often exhibit strong off-axis peaking of electron temperature profiles at the heating location. Electron heat transport properties near these off-axis temperature peaks have been studied using modulated ECH. The Fourier analyzed electron temperature data have been used to infer electron thermal diffusivity. Comparisons with numerical solutions of the time-dependent electron thermal equation find that the data are consistent with a narrow region with electron diffusivity χ e an order of magnitude lower than the average value across the plasma, suggesting an electron internal transport barrier (ITB) near the ECH heating location. Detailed profile analysis and equilibrium reconstructions suggest that the formation of these ITBs are correlated with off-axis values of the safety factor q being near 1. Furthermore, the ECH driven H-mode discharges demonstrate more rapid electron heating rate near the ECH deposition location than L-mode discharges with higher auxiliary ECH heating power. Additional modeling attributes this difference to the modification of electron heat transport in the core at the L-H transition, which also sustains the off-axis electron temperature peaks.

Physics↗
NASA NTRS2014

The GLAS Algorithm Theoretical Basis Document for Laser Footprint Location (Geolocation) and Surface Profiles

This ATBD summarizes (and links with other ATBDs) the elements used to obtain the geolocated GLAS laser spot location, with respect to the Earth Center of Mass. Because of the approach used, the reference frame used to express the geolocation is linked to the reference frame used for POD and PAD, which are related to the ITRF. The geolocated spot coordinates (which includes the elevation or height, with respect to an adopted reference ellipsoid) is the inferred position of the laser spot, since the spot location is not directly measured. This document also summarizes the GLAS operation time periods.

Shutz, Bob E.↗
DOE OSTI2021

Development of Mission Profiles for Humidity Models in the Reliability Testing of PV Inverters: Preprint

To understand the impacts of humidity on PV inverters, mission profiles were developed to accurately describe the different processes and rates based on the environmental factors of temperature, relative humidity, and irradiance. The operating environment of the device introduces stress factors dependent on component temperature, relative humidity, and component voltage. The development of profiles started from looking at historical climate conditions at Cocoa, Florida, a hot and humid location. The profile developed from field location was compared with existing humidity test profiles in industrial and military standards to determine acceleration factors. Prior to the evaluation of the mission profiles, critical components in the PV inverter were identified based on vendor discussions along with failure modes of interest. The profiles considered in this study was demonstrated using a 4-kVA string inverter. The measurements from the devices were substituted in device manufacturer specified equation to determine the severity of each test. The severity of each test was compared against the severity of the 24-hour result to determine the acceleration factor of each test. The acceleration factors were determined to be over a range of 1.2-6 for the existing humidity tests from standards, when compared against the mission profile developed from field data. This optimal humidity/thermal profile will be passed to the IEC standards development for inverter qualification testing.

humidity models↗
DOE OSTI2023

Evaluating wind profiles in a numerical weather prediction model with Doppler lidar

We use Doppler lidar wind profiles from six locations around the globe to evaluate the wind profile forecasts in the boundary layer generated by the operational global Integrated Forecast System (IFS) from the European Centre for Medium-range Weather Forecasts (ECMWF). The six locations selected cover a variety of surfaces with different characteristics (rural, marine, mountainous urban, and coastal urban). We first validated the Doppler lidar observations at four locations by comparison with co-located radiosonde profiles to ensure that the Doppler lidar observations were of sufficient quality. The two observation types agree well, with the mean absolute error (MAE) in wind speed almost always less than 1 m s –1 . Large deviations in the wind direction were usually only seen for low wind speeds and are due to the wind direction uncertainty increasing rapidly as the wind speed tends to zero. Time–height composites of the wind evaluation with 1 h resolution were generated, and evaluation of the model winds showed that the IFS model performs best over marine and coastal locations, where the mean absolute wind vector error was usually less than 3 m s –1 at all heights within the boundary layer. Larger errors were seen in locations where the surface was more complex, especially in the wind direction. For example, in Granada, which is near a high mountain range, the IFS model failed to capture a commonly occurring mountain breeze, which is highly dependent on the sub-grid-size terrain features that are not resolved by the model. The uncertainty in the wind forecasts increased with forecast lead time, but no increase in the bias was seen. At one location, we conditionally performed the wind evaluation based on the presence or absence of a low-level jet diagnosed from the Doppler lidar observations. The model was able to reproduce the presence of the low-level jet, but the wind speed maximum was about 2 m s –1 lower than observed. This is attributed to the effective vertical resolution of the model being too coarse to create the strong gradients in wind speed observed. Our results show that Doppler lidar is a suitable instrument for evaluating the boundary layer wind profiles in atmospheric models.

54 ENVIRONMENTAL SCIENCES↗
NASA NTRS1985

Doppler wind profile experiment

The data collection phase of a Doppler wind measurement experiment supported by high-resolution Jimsphere/FPS-16 wind data and Windsonde data was carried out at the Kennedy Space Center in February, March and early April of 1985. The Doppler wind measurements were made using a hybrid doppler profiler put in place by the Johnson Space Center and a SOUSY profiler operated by Radian Corporation. Both systems operated at 50 Mhz. Although the doppler profiler systems were located 10 km apart to enable concurrent operation of the systems for data comparison, little concurrent data were obtained due to set-up delays with the SOUSY system, and system problems with the WPL system during the last month of the test. During the test period, special serial Jimsphere soundings were taken at two-hour intervals on six days in March and April in addition to balloon soundings taken in support of the Shuttle launch operations. In addition, there is temperature, moisture and wind information available from the daily morning Radiosonde sounding taken at the Kennedy site. The balloon release point was at the same location as the SOUSY profiler. Vertical resolution of the SOUSY profiler was 150 M to approximately 20 km. The vertical resolution of the WPL profiler was 290 M to 10 km and 870 M to 17 km. Winds determined form the Jimsphere balloon have a vertical resolution of 30 M.

Arnold, J. E.↗
NASA NTRS1996

Experimental Study of Vane Heat Transfer and Film Cooling at Elevated Levels of Turbulence

This report documents the results of an experimental study on the influence of high level turbulence on vane film cooling and the influence of film cooling on vane heat transfer. Three different cooling configurations were investigated which included one row of film cooling on both pressure and suction surfaces, two staggered rows of film cooling on both suction and pressure surfaces, and a shower-head cooling array. The turbulence had a strong influence on film cooling effectiveness, particularly on the pressure surface where local turbulence levels were the highest. For the single row of holes, the spanwise mixing quickly reduced centerline effectiveness levels while mixing in the normal direction was more gradual. The film cooling had a strong influence on the heat transfer in the laminar regions of the vane. The effect of film cooling on heat transfer was noticeable in the turbulent regions but augmentation ratios were significantly lower. In addition to heat transfer and film cooling, velocity profiles were taken downstream of the film cooling rows at three spanwise locations. These profile comparisons documented the strong spanwise mixing due to the high turbulence. Total pressure exit measurements were also documented for the three configurations.

Ames, Forrest E.↗
NASA NTRS2013

Integrating Wind Profiling Radars and Radiosonde Observations with Model Point Data to Develop a Decision Support Tool to Assess Upper-Level Winds for Space Launch

On the day of launch, the 45th Weather Squadron (45 WS) Launch Weather Officers (LWOs) monitor the upper-level winds for their launch customers. During launch operations, the payload/launch team sometimes asks the LWOs if they expect the upper-level winds to change during the countdown. The LWOs used numerical weather prediction model point forecasts to provide the information, but did not have the capability to quickly retrieve or adequately display the upper-level observations and compare them directly in the same display to the model point forecasts to help them determine which model performed the best. The LWOs requested the Applied Meteorology Unit (AMU) develop a graphical user interface (GUI) that will plot upper-level wind speed and direction observations from the Cape Canaveral Air Force Station (CCAFS) Automated Meteorological Profiling System (AMPS) rawinsondes with point forecast wind profiles from the National Centers for Environmental Prediction (NCEP) North American Mesoscale (NAM), Rapid Refresh (RAP) and Global Forecast System (GFS) models to assess the performance of these models. The AMU suggested adding observations from the NASA 50 MHz wind profiler and one of the US Air Force 915 MHz wind profilers, both located near the Kennedy Space Center (KSC) Shuttle Landing Facility, to supplement the AMPS observations with more frequent upper-level profiles. Figure 1 shows a map of KSC/CCAFS with the locations of the observation sites and the model point forecasts.

Bauman, William H., III↗
NASA NTRS2004

Ozone Measurements and a 3D Chemical Transport Model

We have used our three-dimensional chemical transport model (CTM) to calculate the expected reponse of stratospheric composition over the past 30 years to forcing by chlorine and bromine compounds, solar ultraviolet, and volcanic aerosols. The CTM uses off-line winds and temperatures fiom a 50-year run of the finite volume general circulation model (FVGCM). We compare the total column ozone and the ozone profile fiom the CTM output to a variety of data sources. These include a merged total ozone data set from TOMS and SBUV using the new version 8 algorithm. Total ozone fiom the CTM are compared to ground-station measurements of total ozone at specific locations. Ozone profiles are compared to satellite meausrements fiom SBUV, SAGE, and HALOE. Profiles are also compared to ozonesondes over several locations. The results of the comparisons are quantified by using a time-series statistical analysis to determine trends, solar cycle, and volcanic reponse in both the model and in the data. Initial results indicate that the model responds to forcings in a way that is similar to the observed atmospheric response. The model does seem to be more sensitive to the chlorine and bromine perturbation ihan is the data. Further details and comparisons wiii be discussed.

Stolarski, Richard S.↗
NASA NTRS1986

Undersea volcano production versus lithospheric strength from satellite altimetry

All seamount signatures apparent in the SEASAT altimeter profiles were located and digitized. In addition to locating the seamount signatures, their amplitudes were also estimated. The second phase consisted of determining what basic characteristics of a seamount can be extracted from a single vertical deflection profile. Seven seamounts that had both good bathymetric coverage and good satellite altimeter coverage were used to test a simple flexural model. A method was developed to combine satellite altimeter profiles from several different satellites to construct a detailed and accurate geoid.

Tapley, B. D.↗
NASA NTRS1986

Need for a subtropical wind profiling system

The purpose is to point out the need for, and the benefit that can be derived from, a national wind profiling facility located in the subtropics. At present no such facility exists. There are several advantages associated with a low-latitude location. The first is that wave motions and large-scale circulations unique to the tropics can be studied. The second is that the relatively steady mean flows in the subtropical belt may provide a cleaner environment for studies of waves common at all latitudes. Researchers suggest the Arecibo Observatory as an ideal site for a wind profiling facility since the land and much of the computing, technical, and scientific support is already available.

Rottger, J.↗
NASA NTRS2015

Aerosol Properties From Combined Oxygen A Band Radiances and Lidar

We have developed a new aerosol retrieval technique based on combing high-resolution A band spectra with lidar profiles. Our goal is the development of a technique to retrieve aerosol absorption, one of the critical parameters affecting the global radiation budget and one which is currently poorly constrained by satellite measurements. Our approach relies on two key factors: 1) the use of high spectral resolution (17,000:1) measurements which resolve the A-band line structure, and 2) the use of co-located lidar profile measurements to constrain the vertical distribution of scatterers in the forward model. The algorithm has been developed to be applied to observations from the CALIPSO and OCO-2 satellites, flying in formation as part of the A-train constellation. We describe the approach and present simulated retrievals to illustrate performance potential.

Winker, Dave↗
DOE OSTI2023

GPU Profiling and Optimizing xRAGE (Final Report)

Our project’s objective is to increase the efficiency of GPU-enabled kernels in xRAGE. To do so, we conduct GPU profiling with NSight Systems on xRAGE tests unsplit_sod_1d and unsplit_sedov_2d to identify bottlenecks and understand the behavior of the GPU during code execution. Next, we analyze these generated GPU profiles to locate the lines of code whose optimization have the most potential for improving runtime. We replicate the structure of the code in smaller test problems that are easier to understand, edit, and run quickly. Within these test problems, we implement two different methods of improving performance: transformation of nested loops into a single MDRangePolicy and hierarchical parallelization using teams of threads. Both methods show speedups in the test code, and after transferring them to xRAGE, they both show up to 30x speedups on various computing platforms. Profiling the edited versions of xRAGE reveals that the GPU successfully executed the bottlenecks with greater efficiency

97 MATHEMATICS AND COMPUTING↗