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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 307 records · Page 17
All sourcesNASA NTRSDOE OSTI
NASA NTRS2023

Thermomechanical Real-Time Hybrid Simulation: Conceptual Framework and Control Requirements

Real-time hybrid simulation (RTHS) is an enabling technology that has transformed engineering experimentation and helped researchers expand modeling capabilities. However, breakthroughs are necessary to expand the range of hybrid simulation methods and, thus, enable experiments with loading conditions representing multiple hazards. This paper discusses the development of a new thermomechanical RTHS framework and a systematic approach to determining RTHS control requirements. First, the framework is established using a representative finite element model of a layered structural system subjected to thermal loading. A complete two-layer system model serves as the reference system, and it is then partitioned into a numerical layer and an experimental layer that share interface conditions. Next, a thermal actuator is introduced to impose dynamic thermal loading on the experimental subsystem, serving as a transfer system. Finally, control and performance metrics are defined to evaluate the realization of interface boundary conditions and map this to the RTHS execution. Through an illustrative example considering the influence of temperature on a lunar habitat, we demonstrate how to establish controller requirements for RTHS and demonstrate that this approach can be used to conduct RTHS on structures with thermomechanical loading.

Herta Montoya↗
NASA NTRS1999

Mass Transport in Global Geophysical Fluids

Mass transports occurring in the atmosphere-hydrosphere-solid Earth-core system (the "global geophysical fluids") are important geophysical phenomena. They occur on all temporal and spatial scales. Examples include air mass and ocean circulations, tides, hydrological water redistribution, mantle processes such as post-glacial rebound, earthquakes and tectonic motions, and core geodynamo activities. With only a few exceptions on the Earth surface, the temporal history and spatial pattern of such mass transport are often not amenable to direct observations. Space geodesy techniques, however, have the capability of monitoring certain direct consequences of the mass transport, including Earth's rotation variations, gravitational field variations, and the geocenter motion. These techniques include the very-long-baseline interferometry, satellite laser ranging and Doppler tracking, and the Global Positioning System, all entail global observational networks. While considerable advances have been made in observing and understanding of the dynamics of Earth's rotation, only the lowest-degree gravitational variations have been observed and limited knowledge of geocenter motion obtained. New space missions, projects and initiatives promise to further improve the measurements and hence our knowledge about the global mass transports. The latter contributes to our understanding and modeling capability of the geophysical processes that produce and regulate the mass transports, as well as the solid Earth's response to such changes in constraining the modeling of Earth's mechanical properties.

Chao, B. F.↗
NASA NTRS1985

Turbine Vane External Heat Transfer. Volume 1: Analytical and Experimental Evaluation of Surface Heat Transfer Distributions with Leading Edge Showerhead Film Cooling

Progress in predictive design capabilities for external heat transfer to turbine vanes was summarized. A two dimensional linear cascade (previously used to obtain vane surface heat transfer distributions on nonfilm cooled airfoils) was used to examine the effect of leading edge shower head film cooling on downstream heat transfer. The data were used to develop and evaluate analytical models. Modifications to the two dimensional boundary layer model are described. The results were used to formulate and test an effective viscosity model capable of predicting heat transfer phenomena downstream of the leading edge film cooling array on both the suction and pressure surfaces, with and without mass injection.

Turner, E. R.↗
NASA NTRS2009

A Computational Approach for Probabilistic Analysis of Water Impact Simulations

NASA's development of new concepts for the Crew Exploration Vehicle Orion presents many similar challenges to those worked in the sixties during the Apollo program. However, with improved modeling capabilities, new challenges arise. For example, the use of the commercial code LS-DYNA, although widely used and accepted in the technical community, often involves high-dimensional, time consuming, and computationally intensive simulations. The challenge is to capture what is learned from a limited number of LS-DYNA simulations to develop models that allow users to conduct interpolation of solutions at a fraction of the computational time. This paper presents a description of the LS-DYNA model, a brief summary of the response surface techniques, the analysis of variance approach used in the sensitivity studies, equations used to estimate impact parameters, results showing conditions that might cause injuries, and concluding remarks.

Horta, Lucas G.↗
NASA NTRS1991

Seals Flow Code Development

In recognition of a deficiency in the current modeling capability for seals, an effort was established by NASA to develop verified computational fluid dynamic concepts, codes, and analyses for seals. The objectives were to develop advanced concepts for the design and analysis of seals, to effectively disseminate the information to potential users by way of annual workshops, and to provide experimental verification for the models and codes under a wide range of operating conditions.

Source record↗
NASA NTRS2003

Effect of Resonator Axis Skew on Normal Incidence Impedance

High by-pass turbofan engines have fewer fan blades and lower rotation speeds than their predecessors. Consequently, the noise suppression at the low frequency end of the noise spectra has become an increasing concern. This has led to a renewed emphasis on improving noise suppression efficiency of passive, duct liner treatments at the lower frequencies. For a variety of reasons, passive liners are comprised of locally-reacting, resonant absorbers. One reason for this design choice is to satisfy operational and economic requirements. The simplest liner design consists of a single layer of honeycomb core sandwiched between a porous facesheet and an impervious backing plate. These resonant absorbing structures are integrated into the nacelle wall and are very ef- ficient over a limited bandwidth centered on their resonance frequency. Increased noise suppression bandwidth and greater suppression at lower frequencies is typically achieved for conventional liners by increasing the liner depth and incorporating thin porous septa into the honeycomb core. However, constraints on liner depth in modern high by-pass engine nacelles severely limit the suppression bandwidth extension to lower frequencies. Also, current honeycomb core liners may not be suitable for irregular geometric volumes heretofore not considered. It is of interest, therefore, to find ways to circumvent liner depth restrictions and resonator cavity shape constraints. One way to increase effective liner depth is to skew the honeycomb core axis relative to the porous facesheet surface. Other possibilities are to alter resonator cavity shape, e.g. high aspect ratio, narrow channels that possibly include right angle bends, 180. channel fold-backs, and splayed channel walls to conform to irregular geometric constraints. These possibilities constitute the practical motivation for expanding impedance modeling capability to include unconventional resonator orientations and shapes. The work reported in this paper is in the nature of a progress report and is limited to examining the implications of resonator axis skew on the composite normal incidence impedance of an array of resonator channels. Specifically, experimental results are compared with a modified impedance prediction model for highaspect- ratio, rectangular, resonator channels with varying amounts of skew relative to the incident particle velocity. It is shown that for resonator channel widths of 1 to 2 mm, aspect ratios of 25 to 50, and skew angles of zero to sixty degrees, the surface impedance of test models can be predicted with good accuracy. Predicted resistances and reactances are particularly well correlated through the first resonance and first anti-resonance for all six test models investigated. Beyond the first anti-resonance, the impedance prediction model loses the ability to predict details of resistance and reactance but still predicts the mean trends very well.

Parrott, Tony L.↗
NASA NTRS2013

PowderSim: Lagrangian Discrete and Mesh-Free Continuum Simulation Code for Cohesive Soils

PowderSim is a calculation tool that combines a discrete-element method (DEM) module, including calibrated interparticle-interaction relationships, with a mesh-free, continuum, SPH (smoothed-particle hydrodynamics) based module that utilizes enhanced, calibrated, constitutive models capable of mimicking both large deformations and the flow behavior of regolith simulants and lunar regolith under conditions anticipated during in situ resource utilization (ISRU) operations. The major innovation introduced in PowderSim is to use a mesh-free method (SPH-based) with a calibrated and slightly modified critical-state soil mechanics constitutive model to extend the ability of the simulation tool to also address full-scale engineering systems in the continuum sense. The PowderSim software maintains the ability to address particle-scale problems, like size segregation, in selected regions with a traditional DEM module, which has improved contact physics and electrostatic interaction models.

Johnson, Scott↗
NASA NTRS2019

Scale-Resolving Simulations of Laminar-to-Turbulent Transition in Swept-Wing Flow

Aerodynamic shape optimization of swept Natural Laminar Flow (NLF) wing design plays an important role for the development of future energy-efficient commercial transport aircraft. Lack of predictive laminar-to-turbulent transition modeling capabilities is still limiting the extent to which design can rely on computational tools, while making costly wind tunnel and flight tests a necessity. Prediction of transition on practical 3D wing geometries using the e (sup N) method coupled with laminar boundary layer and linear stability codes or local statistical correlation CFD (Computational Fluid Dynamics) models such as the gamma - Re (sub theta) Langtry-Menter model have proven challenging, whereas transitional hybrid RANS-LES solvers have shown encouraging but still mitigated results.

Scale-resolving↗
NASA NTRS1981

Measurement of forces due to liquid motion in a propellant tank

This paper presents the results of a study to develop an analytical model capable of predicting the forces acting on a tank caused by large-amplitude propellant motion. This effort contributed to an analysis of the influence of propellant dynamics on separation of the External Tank from the space shuttle orbiter. This paper is concerned with an experimental investigation that aided in development and verification of the analytical model. A scaling approach was developed that allowed the liquid motion to be simulated in subscale tanks. Liquid reorientation forces were measured using two test systems. One operated in the low-gravity environment produced in a drop tower and the second operated aboard the KC-135 'zero-g' test aircraft. The manner of liquid motion, influence of various factors, and the measured forces are discussed.

Tegart, J. R.↗
NASA NTRS1984

Multidimensional Modeling of Atmospheric Effects and Surface Heterogeneities on Remote Sensing

A modeling capability that allows a quantitative determination of atmospheric effects on remote sensing including the effects of surface heterogeneities is established. The objectives include: (1) the adaptation of existing radiative transfer codes to remote sensing applications, (2) the implementation of a realistic atmospheric data base, (3) the definition and verification against field measurements of a coupled atmosphere/canopy model, and (4) the quantitative characterization of the effects of some biophysical canopy parameters and soil surface boundary conditions on satellite-sensed Multispectral Scanner System (MSS) data. Substantial progress was also made in quantifying the effects of varying atmospheric turbidity and different non-Lambertian and specular ground reflectances on MSS data and its transforms like greenness and brightness.

Gerstl, S. A.↗
NASA NTRS2003

Thermal Response of Cooled Silicon Nitride Plate Due to Thermal Conductivity Effects Analyzed

Lightweight, strong, tough high-temperature materials are required to complement efficiency improvements for next-generation gas turbine engines that can operate with minimum cooling. Because of their low density, high-temperature strength, and high thermal conductivity, ceramics are being investigated as materials to replace the nickelbase superalloys that are currently used for engine hot-section components. Ceramic structures can withstand higher operating temperatures and a harsh combustion environment. In addition, their low densities relative to metals help reduce component mass (ref. 1). To complement the effectiveness of the ceramics and their applicability for turbine engine applications, a parametric study using the finite element method is being carried out. The NASA Glenn Research Center remains very active in conducting and supporting a variety of research activities related to ceramic matrix composites through both experimental and analytical efforts (ref. 1). The objectives of this work are to develop manufacturing technology, develop a thermal and environmental barrier coating (TBC/EBC), develop an analytical modeling capability to predict thermomechanical stresses, and perform a minimal burner rig test on silicon nitride (Si3N4) and SiC/SiC turbine nozzle vanes under simulated engine conditions. Moreover, we intend to generate a detailed database of the material s property characteristics and their effects on structural response. We expect to offer a wide range of data since the modeling will account for other variables, such as cooling channel geometry and spacing. Comprehensive analyses have begun on a plate specimen with Si3N4 cooling holes.

Baaklini, George Y.↗
NASA NTRS2008

Utilizing Mars Global Reference Atmospheric Model (Mars-GRAM 2005) to Evaluate Entry Probe Mission Sites

Engineering-level atmospheric model widely used for diverse mission applications. Mars-GRAM s perturbation modeling capability is commonly used, in a Monte-Carlo mode, to perform high fidelity engineering end-to-end simulations for entry, descent, and landing (EDL)1. Traditional Mars-GRAM options for representing the mean atmosphere along entry corridors include: a) TES Mapping Years 1 and 2, with Mars-GRAM data coming from MGCM model results driven by observed TES dust optical depth; and b) TES Mapping Year 0, with user-controlled dust optical depth and Mars-GRAM data interpolated from MGCM model results driven by selected values of globally-uniform dust optical depth. From the surface to 80 km altitude, Mars-GRAM is based on NASA Ames Mars General Circulation Model (MGCM). Mars-GRAM and MGCM use surface topography from Mars Global Surveyor Mars Orbiter Laser Altimeter (MOLA), with altitudes referenced to the MOLA areoid, or constant potential surface. Mars-GRAM 2005 has been validated2 against Radio Science data, and both nadir and limb data from the Thermal Emission Spectrometer (TES)

Justh, Hilary L.↗
NASA NTRS2014

Recent Developments and Challenges Implementing New and Improved Stress Intensity Factor (K) Solutions in NASGRO for Damage Tolerance Analyses

Fatigue crack growth analysis software has been available to damage tolerance analysts for many years in either commercial products or via proprietary in-house codes. The NASGRO software has been publicly available since the mid-80s (known as NASA/FLAGRO up to 1999) and since 2000 has been sustained and further developed by a collaborative effort between Southwest Research Institute® (SwRI®), the NASA Johnson Space Center (JSC), and the members of the NASGRO Industrial Consortium. Since the stress intensity factor (K) is the foundation of fracture mechanics and damage tolerance analysis of aircraft structures, a significant focus of development efforts in the past fifteen years has been geared towards enhancing legacy K solutions and developing new and efficient numerical K solutions that can handle the complicated stress gradients computed by today’s analysts using detailed finite element models of fatigue critical locations. This paper provides an overview of K solutions that have been recently implemented or improved for the analysis of geometries such as two unequal through cracks at a hole and two unequal corner cracks at a hole, as well as state-of-the-art weight function models capable of computing K in the presence of univariant and/or bivariant stress gradients and complicated residual stress distributions. Some historical background is provided to review how common K solutions have evolved over the years, including selective examples from the literature and from new research. Challenges and progress in rectifying discrepancies between older legacy solutions and newer models are reviewed as well as approaches and challenges for verification and validation of K solutions. Finally, a summary of current challenges and future research and development needs is presented. A key theme throughout the presentation of this paper will be how members of the aerospace industry have collaborated with software developers to develop a practical analysis tool that is used world-wide to support new design as well as the ongoing sustainment and airworthiness of commercial and military aircraft.

Cardinal, Joseph W.↗
NASA NTRS1993

Berthing of Space Station Freedom using the shuttle remote manipulator system

A large-angle, flexible, multi-body, dynamic modeling capability was developed to help validate analytical simulations of the dynamic motion and control forces which occur while berthing of Space Station Freedom to the Shuttle Orbiter during early assembly flights. The dynamics and control of the station, the attached Shuttle Remote Manipulator System, and the Orbiter during a berthing maneuver are described. Emphasis is placed on the modeling of the Shuttle Remote Manipulator System in the multi-body simulation. The influence of the elastic behavior of the station and of the Remote Manipulator System on the attitude control of the station/Orbiter system during the maneuver is investigated.

Cooper, Paul↗
NASA NTRS2001

The NASA Seasonal-to-Interannual Prediction Project (NSIPP)

The goal of the project is to develop an assimilation and forecast system based on a coupled atmosphere-ocean-land-surface-sea-ice model capable of using a combination of satellite and in situ data sources to improve the prediction of ENSO and other major S-I signals and their global teleconnections. The objectives of this annual report are to: (1) demonstrate the utility of satellite data, especially surface height surface winds, air-sea fluxes and soil moisture, in a coupled model prediction system; and (2) aid in the design of the observing system for short-term climate prediction by conducting OSSE's and predictability studies.

Rienecker, Michele↗
NASA NTRS2000

Fully Three-Dimensional Helical RF Field Effects on TWT Interaction

The phenomenal growth of the satellite communications industry has created a large demand for traveling wave-tubes (TWTs) operating with unprecedented specifications requiring design and production of many novel devices in record time. To achieve this, the TWT industry heavily relies upon computational modeling. However, there is a need for improvement in the TWT industry's computational modeling capabilities as there are often discrepancies between measured TWT data and that predicted by conventional two-dimensional helical TWT interaction codes. This severely limits the analysis and design of novel devices or TWTs with parameters differing from what is conventionally manufactured. In addition, the inaccuracy of current computational tools limits achievable TWT performance because optimized designs require highly accurate models. In particular, collector efficiency, which significantly affects overall TWT efficiency, is difficult to optimize unless extremely accurate spent beam data is predicted by the interaction code.

Kory, Carol L.↗
NASA NTRS2019

Technology Development and Infusion by NASA's Entry Systems Modeling Project

This paper describes recent development of modeling and simulation technologies for entry systems and their infusion into NASA's exploration missions. Technology development is organized and prioritized using a system-level perspective, resulting in four broad technical areas of investment: (1) Thermal protection material modeling, (2) Shock layer kinetics and radiation, (3) Computational and experimental aerosciences, and (4) Guidance, navigation, and control. The paper will highlight key contributions from each of these areas, their impacts from a spacecraft and mission design perspective, and discuss planned future investment. Aspects of each technical area are only briefly summarized here. Thermal protection material modeling is geared toward high-fidelity, predictive models capable of optimizing design performance, post-flight reconstruction, and quantifying thermal protection system reliability. New computational tools and experimental techniques have been applied to Orion, MSL/Mars 2020, Mars InSight, and Mars Sample Return missions. Research and development in the area of shock layer kinetics has focused on air and CO2-based atmospheres. In both cases, substantial improvements in model uncertainty have directly impacted the development of mission margin policies, flight instrumentation design and analysis (Orion and Mars 2020), and have even revealed the importance of neglected phenomena like mid-wave infrared radiation of CO2. Aerosciences is a very broad area of interest in entry systems, yet a number of important challenges are being addressed: Coupled fluid-structure simulations of parachute inflation and dynamics affecting Orion, Commercial Crew, and Mars programs; Experimental and computational studies of vehicle dynamics; Multi-phase flow with dust particles to simulate augmentation of aerothermal environments at Mars during dust storms; and studies of roughness-induced heating augmentation relevant to tiled (Orion, Mars 2020) and woven (Mars Sample Return) thermal protection systems. Guidance and control in the context of entry systems has focused on development of methods for multi-axis control (i.e. pitch and yaw, rather than bank angle alone) of spacecraft during entry and descent, with precision landing requirements driven by Mars human exploration goals.

Barnhardt, Michael D.↗
NASA NTRS1994

Understanding the Biosphere From Space: Strategies to Exploit Remote Sensing Data

The quantitative interpretation of satellite observations requires the use of mathematical tools to extract the desired information on terrestrial environments from the radiation data collected in space. A whole range of approaches can be pursued, from the development of models capable of explaining the nature of the physical signal being measured and of characterizing the state of the system under observation, to the empirical correlations between the variables of interest and the space measurements. The premises and implications of these approaches are outlined, paying special attention to the mathematical and numerical requirements. The role and specific applications of empirical bidirectional reflectance models is also discussed, even though these models do not contribute to the understanding of the theory of radiation transfer or to the assessment of the variables of interest. The advantages and drawbacks of these various approaches and the research priorities for the next few years are discussed in the context of the planned availability of new sensors.

Michel M Verstraete↗