Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “variable conductance”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 721 records · Page 40
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

VAINE: Visualization and AI for Natural Experiments

Natural experiments are observational studies where the assignment of treatment conditions to different populations occur by chance ``in the wild''. Researchers from fields such as economics, healthcare, and the social sciences leverage natural experiments to conduct hypothesis testing and causal effect estimation for treatment and outcome variables that would otherwise be costly, infeasible, or unethical. In this paper, we introduce VAINE (Visualization and AI for Natural Experiments), a visual analytics tool for identifying and understanding natural experiments from observational data. We then demonstrate how VAINE can be used to validate causal relationships, estimate average treatment effects, and identify statistical phenomena such as Simpson’s paradox through two use cases.

Guo, Grace↗
DOE OSTI2024

TAMU TRACER: Targeted Mobile Measurements to Isolate the Impacts of Aerosols and Meteorology on Deep Convection

Difficulty in using observations to isolate the impacts of aerosols from meteorology on deep convection often stems from inability to resolve the spatiotemporal variations in the environment serving as the storm’s inflow region. During the DOE TRacking Aerosol Convection interactions ExpeRiment (TRACER) in June-September 2022, a Texas A&M University (TAMU) team conducted a mobile field campaign to characterize the meteorological and aerosol variability in airmasses that serve as inflow to convection across the ubiquitous mesoscale boundaries associated with the sea- and bay-breezes in the Houston, Texas, region. These boundaries propagate inland over the fixed DOE Atmospheric Radiation Measurement (ARM) sites. However, convection occurs on either or both the continental or maritime sides or along the boundary. The maritime and continental airmasses serving as convection inflow may be quite distinct, with different meteorological and aerosol characteristics that fixed-site measurements cannot simultaneously sample. Thus, a primary objective of TAMU TRACER was to provide mobile measurements similar to those at the fixed sites, but in the opposite airmass across these moving mesoscale boundaries. TAMU TRACER collected radiosonde, lidar, aerosol, cloud condensation nuclei (CCN), and ice nucleating particle (INP) measurements on 29 enhanced operations days covering a variety of maritime, continental, outflow, and pre-frontal airmasses. This paper summarizes the TAMU TRACER deployment and measurement strategy, instruments, available datasets, and provides sample cases highlighting differences between these mobile measurements and those made at the ARM sites. We also highlight the exceptional TAMU TRACER undergraduate student participation in high impact learning activities through forecasting and field deployment opportunities.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2023

Statistical Analysis of the Limiting Dynamics of Two dimensional Boussinesq Turbulent Systems

In the current study, we investigate rotational and stratified turbulent systems within the framework of the Boussinesq equations. The effects of rotation and stratification give rise to a variety of dynamical regimes in atmospheric and oceanic turbulence. To develop a better understanding of the fundamental flow properties through a more straightforward mathematical framework, we commence our research with a simplified two-dimensional Boussinesq model that incorporates rotation and stratification effects. We explore two distinct limiting dynamics, considering pure rotation and pure stratification separately. We examine these intriguing dynamics through numerical investigations, applying the exact solution theory of Boussinesq equations and examining small-scale perturbations to the exact solution under rotation and stratification. We conduct an analysis of statistical quantities associated with the turbulent state variables. The results indicate that, under weak rotation at the equilibrium statistical state, the flow field exhibits vortex flow. However, strong rotation transforms the flow into vertical shear flow. We observe both downscale and upscale energy transfers with a decay rate of k −3 in the absence of external forcing and dissipation. Furthermore, we delve into the study of internal gravity wave mode interactions in the simplified two-dimensional Boussinesq system, which is a crucial aspect of geophysical turbulence due to gravity. Our findings reveal that the time series of the mode coefficients exhibit wave-like interactions between wave modes.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2024

Wholesale Electricity Analysis via Simulation & Learning Experiments (WEASLE): Platform Development and Pilot Competition

This document reports the development of the Wholesale Electricity Analysis via Simulation and Learning Experiments (WEASLE) platform and the pilot competition that was conducted to test the platform. Due to the increasing reliance on variable renewable energy resources for bulk power, the pilot competition, called the Energy Storage Participation Algorithm Competition (ESPA-Comp), was used to test the effect of various market designs on storage utilization and market efficiency. Basic details of the platform are provided, including an overview of the market clearing engine, the battery dispatch and degradation models, electric grid topology and resource mix, and software architecture. Two market designs were tested: a two-settlement market analogous to typical ISO design today, and a multi-settlement market that allows additional forward-trading periods during the real-time market. Results from the pilot competition show that the storage bidding problem is nontrivial and is well suited for future challenges. We find that: 1) all four teams utilized different approaches to the bidding problem, 2) different methodological approaches led to substantially different offer behaviors, 3) resource profits are clustered by team and methodological approach, 4) simulated offers reduced market surplus by about 0.5%, 5) substantially different prices between two-settlement and multi-settlement markets albeit minimal difference in overall market surplus.

24 POWER TRANSMISSION AND DISTRIBUTION↗
NASA NTRS1969

Predicting lunar temperatures.

Lunar temperature prediction with emphasis on variable property models, noting assumptions about physical properties appearing in heat conduction equations

Jones, B. P.↗
NASA NTRS1973

Water quality parameters of harbors of Charlotte Amalie, St. Thomas, Virgin Islands: Acquisition of in situ water data, intercorrelation of selected water parameters, and initial correlation of these in situ biological, chemical and physical data with ERTS-1 bulk CCT MSS band 5 data

The author has identified the following significant results. Remote sensing by the ERTS-1 satellite was compared with selected water quality parameters including pH, salinity, conductivity, dissolved oxygen, water depth, water temperature, turbidity, plankton concentration, current variables, chlorophylla, total carotenoids, and species diversity of the benthic community. Strong correlation between turbidity and MSS-sensed radiance was recorded and less strong correlations between the two plankton pigments and radiance. Turbidity and benthic species diversity were highly correlated furnishing an inferential tie between an easily sensed water quality variable and a sensitive indicator of average water quality conditions.

Coulbourn, W. C.↗
NASA NTRS1980

Low frequency sound absorption of orifice plates, perforated plates and nozzles

Analyses of impulse time history data from acoustic transmission tests for conical nozzles attached to a pipe show internal reflections from the solid contraction and open area tend to cancel. To gain understanding of the opposing reflections, tests were conducted by replacing the conical nozzles with orifice plates. The primary variable was the open to solid area ratio. Internal reflection coefficient data reveal that, at an area ratio of 10-12%, the low frequency internal reflection is reduced from unity to about 0.2. Based on comparisons of far-field and internal data, acoustic energy is not conserved. Results are presented for complex reflection coefficient and far-field noise for a series of orifice and perforated plate configurations.

Salikuddin, M.↗
NASA NTRS1980

Supersonic cruise vehicle research/business jet

A comparison study of a GE-21 variable propulsion system with a Multimode Integrated Propulsion System (MMIPS) was conducted while installed in small M = 2.7 supersonic cruise vehicles with military and business jet possibilities. The 1984 state of the art vehicles were sized to the same transatlantic range, takeoff distance, and sideline noise. The results indicate the MMIPS would result in a heavier vehicle with better subsonic cruise performance. The MMIPS arrangement with one fan engine and two satellite turbojet engines would not be appropriate for a small supersonic business jet because of design integration penalties and lack of redundancy.

Kelly, R. J.↗
NASA NTRS1981

A flight investigation of static stability, control augmentation, and flight director influences on helicopter IFR handling qualities

A flight experiment was conducted using the NASA-Army V/STOLAND UH-1H variable-stability helicopter to investigate the influence of several longitudinal-static-stability, control-augmentation, and flight-director parameters on helicopter flying qualities during terminal area operations in instrument conditions. This experiment, which was part of a joint NASA/FAA program pertaining to helicopter IFR airworthiness, was designed to corroborate and extend previous ground simulation results obtained in this program. Variations examined included stable and neutral longitudinal control position gradients, rate-damping and attitude-command augmentation, and raw data versus flight-director displays. Pilot rating results agreed excellently with the ground simulation data, indicating an adequate instrument capability with rate-damping augmentation and neutral statics and the need for pitch-roll attitude augmentation to achieve a satisfactory system.

Lebacqz, J. V.↗
NASA NTRS1981

Pre-design study for a modern four-bladed rotor for the Rotor System Research Aircraft (RSRA)

Various candidate rotor systems were compared in an effort to select a modern four-bladed rotor for the RSRA. The YAH-64 rotor system was chosen as the candidate rotor system for further development for the RSRA. The process used to select the rotor system, studies conducted to mate the rotor with the RSRA and provide parametric variability, and the development plan which would be used to implement these studies are presented. Drawings are included.

Hughes, C. W.↗
NASA NTRS1983

NASA/FAA experiments concerning helicopter IFR airworthiness criteria

A sequence of ground and flight simulation experiments was conducted as part of a joint NASA/FAA program to investigate helicopter instrument flight rules (IFR) airworthiness criteria. The first six of these experiments are described and the results summarized. Five of the experiments were conducted on large amplitude motion base simulators; V/STOLAND UH-1H variable stability helicopter was used in the flight experiment. Airworthiness implications of selected variables that were investigated across all of the experiments are discussed, including the level of longitudinal static stability, the type of stability and control augmentation, the addition of flight director displays, and the type of instrument approach task. Among the specific results reviewed are the adequacy of neutral longitudinal statics for dual pilot approaches and the requirement for pitch and roll attitude stabilization in the stability and control augmentation system to achieve flying qualities evaluated as satisfactory.

Lebacqz, J. V.↗
NASA NTRS1984

Ground-simulation investigation of VTOL instrument flight rules airworthiness criteria

A two-part ground-simulation investigation of VTOL terminal-area operations, conducted as part of a joint NASA/FAA program to develop airworthiness criteria for this class of vehicle, is described. The baseline vehicle selected for the simulations was a generalized version of the XV-15 tilt-rotor mathematical model, which was modified to permit generic variations in forces or moments or both with power or configuration changes. Additionally, changes to wing area and rotor-blade chord were considered as a means of modifying the allowable thrust-angle versus speed relationships (the conversion corridor). The Vertical Motion Simulator at Ames Research Center was used in the experiment. Four engineering test pilots conducted over 200 piloted evaluations examining the influence of the experimental variables on their ability to perform terminal-area operations.

Lebacqz, J. V.↗
NASA NTRS1987

Quantifying uncertainties in the structural response of SSME blades

To quantify the uncertainties associated with the geometry and material properties of a Space Shuttle Main Engine (SSME) turbopump blade, a computer code known as STAEBL was used. A finite element model of the blade used 80 triangular shell elements with 55 nodes and five degrees of freedom per node. The whole study was simulated on the computer and no real experiments were conducted. The structural response has been evaluated in terms of three variables which are natural frequencies, root (maximum) stress, and blade tip displacements. The results of the study indicate that only the geometric uncertainties have significant effects on the response. Uncertainties in material properties have insignificant effects.

Nagpal, Vinod K.↗
NASA NTRS1986

Morphology of large valleys on Hawaii - Evidence for groundwater sapping and comparisons with Martian valleys

Morphometric data on the runoff and sapping valleys on the slopes of Hawaii and Molokai in Hawaii are analyzed. The analysis reveals a clear distinction between the runoff valleys and sapping valleys. The Hawaiian sapping valleys are characterized by: (1) steep valley walls and flat floors, (2) amphitheater heads, (3) low drainage density, (4) paucity of downstream tributaries, (5) low frequency of up-dip tributaries, and (6) structural and stratigraphic control on valley patterns. The characteristics of the Hawaiian sapping valleys are compared to Martian valleys and experimental systems, and good correlation between the data is detected. Flume experiments were also conducted to study the evolution of sapping valleys in response to variable structure and stratigraphy.

Kochel, R. Craig↗
NASA NTRS1988

Microwave remote sensing of sea ice

The long term objectives are: (1) to understand the physics of the multispectral microwave radiative characteristics of sea ice as it goes through different phases; (2) to improve characterization of sea ice cover using satellite microwave sensors; and (3) to study ice/ocean physical and biological processes associated with polynya formations and variability of the marginal sea ice region. Two field experiments were conducted to pursue these objectives. One involved measurements of radiative and physical characteristics of sea ice from a ship during a 3-month long cruise through the Weddell Sea ice pack during the Austral winter of 1986. The other involved similar measurements from two aircrafts and a submarine over the Central Arctic and Greenland Sea region. Preliminary results have already led to an enhanced understanding of the microwave signatures of pancake ice, nilas, first year ice, multiyear ice and effects of snow cover. Coastal and deep ocean polynyas and their role in bottom water formation and ocean circulation were studied using a time series of ice images from SMMR. An unsupervised cluster analysis of Arctic sea ice using SMMR and THIR emissivity and brightness temperature data was implemented. The analysis indicates the existence of several unique and persistent clusters in the Central Arctic region during winter and that the sum of the area of these clusters excluding those of first year ice is about 20 percent less than minimum ice cover area inferred from a previous summer data. This result is consistent with saline surface for some multiyear ice floes as observed during MIZEZ and suggests that a significant fraction of multiyear ice floes in the Arctic have first year ice signatures.

Comiso, J. C.↗
NASA NTRS1990

Probabilistic failure assessment with application to solid rocket motors

A quantitative methodology is being developed for assessment of risk of failure of solid rocket motors. This probabilistic methodology employs best available engineering models and available information in a stochastic framework. The framework accounts for incomplete knowledge of governing parameters, intrinsic variability, and failure model specification error. Earlier case studies have been conducted on several failure modes of the Space Shuttle Main Engine. Work in progress on application of this probabilistic approach to large solid rocket boosters such as the Advanced Solid Rocket Motor for the Space Shuttle is described. Failure due to debonding has been selected as the first case study for large solid rocket motors (SRMs) since it accounts for a significant number of historical SRM failures. Impact of incomplete knowledge of governing parameters and failure model specification errors is expected to be important.

Jan, Darrell L.↗
NASA NTRS1989

An evaluation of the liquid oxygen mechanical impact test

This study was conducted to evaluate the repeatability of the ambient LO2 mechanical impact test used by NASA to screen materials for oxygen service (NHB 8060.1B Test 12 Part 1, which is based on the ASTM method). Four materials were tested: Teflon, Vespel SP-21, Viton A, and nylon 6/6. Each test material was subjected to several series of tests that were conducted at different impact energy levels. The results show that the variability from series to series in the reaction threshold energy level is within the precision statement of the ASTM method. However, this precision is considerably broader than the reaction threshold implied by the NHB 8060.1B test criteria.

Moffett, Gary E.↗
NASA NTRS1991

Simulation of extra-vehicular activity (EVA) self-rescue

Self-rescue during EVA is examined in terms of the use of a hand-held thruster that is similar to the hand-held maneuvering units HHMU developed for earlier programs. The problem of assessing velocity-increment requirements is addressed by means of examples of simulation technologies for studying EVA. The technologies evaluated include virtual reality systems such as the Virtual Interactive Environment Workstation (VIEW) and the Space Operations Simulator, and standard approaches like the air-bearing floor and the space shuttle. The VIEW is employed for a study of five trained NASA subjects that conduct a simulated return to a spacecraft with an HMMU under variable conditions. The study demonstrates the efficacy of VIEW for obtaining fuel-consumption values, and separation velocity is identified as the most significant determinant of the fuel and time requirements for a self-rescue operation.

Brody, Adam R.↗