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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 1,315 records · Page 73
All sourcesNASA NTRSDOE OSTI
NASA NTRS2016

Analysis and Prediction of Ice Shedding for a Full-Scale Heated Tail Rotor

When helicopters are to fly in icing conditions, it is necessary to consider the possibility of ice shed from the rotor blades. In 2013, a series of tests were conducted on a heated tail rotor at NASA Glenn's Icing Research Tunnel (IRT). The tests produced several shed events that were captured on camera. Three of these shed events were captured at a sufficiently high frame rate to obtain multiple images of the shed ice in flight that had a sufficiently long section of shed ice for analysis. Analysis of these shed events is presented and compared to an analytical Shedding Trajectory Model (STM). The STM is developed and assumes that the ice breaks off instantly as it reaches the end of the blade, while frictional and viscous forces are used as parameters to fit the STM. The trajectory of each shed is compared to that predicted by the STM, where the STM provides information of the shed group of ice as a whole. The limitations of the model's underlying assumptions are discussed in comparison to experimental shed events.

icing↗
NASA NTRS2018

Collaborative Experiments and Computations in Aircraft Icing

The formation of ice over lifting surfaces can affect aerodynamic performance. The ability to predict ice accumulation and the resulting degradation in vehicle performance is essential to determine the limitations of aircraft in icing encounters. The consequences of underestimating performance degradation can be serious and so it is important to produce accurate predictions, particularly for severe icing conditions. The simulation of ice accretion is a challenging multidisciplinary problem that requires close collaboration between the computational and ground test communities. This paper describes three recent case studies and the lessons learned through collaborative experiments and computations in aircraft icing- one for large commercial transports, one for rotorcraft, and one dealing with icing on regional jets.

and rotorcraft↗
NASA NTRS2018

Organic Ices in Titan’s Stratosphere

Titan’s stratospheric ice clouds are by far the most complex of any observed in the solar system, with over a dozen organic vapors condensing out to form a suite of pure and co-condensed ices, typically observed at high winter polar latitudes. Once these stratospheric ices are formed, they will diffuse throughout Titan’s lower atmosphere and most will eventually precipitate to the surface, where they are expected to contribute to Titan’s regolith. Early and important contributions were first made by the InfraRed Interferometer Spectrometer (IRIS) on Voyager 1, followed by notable contributions from IRIS’ successor, the Cassini Composite InfraRed Spectrometer (CIRS), and to a lesser extent, from Cassini’s Visible and Infrared Mapping Spectrometer (VIMS) and the Imaging Science Subsystem (ISS) instruments. All three remote sensing instruments made new ice cloud discoveries, combined with monitoring the seasonal behaviors and time evolution throughout Cassini’s 13-year mission tenure. A significant advance by CIRS was the realization that co-condensing chemical compounds can account for many of the CIRS-observed stratospheric ice cloud spectral features, especially for some that were previously puzzling, even though some of the observed spectral features are still not well understood. Relevant laboratory transmission spectroscopy efforts began just after the Voyager encounters, and have accelerated in the last few years due to new experimental efforts aimed at simulating co-condensed ices in Titan’s stratosphere. This review details the current state of knowledge regarding the organic ice clouds in Titan’s stratosphere, with perspectives from both an observational and experimental standpoint.

Ices↗
NASA NTRS2020

Damage Accelerates Ice Shelf Instability and Mass Loss in Amundsen Sea Embayment

Pine Island Glacier and Thwaites Glacier in the Amundsen Sea Embayment are among the fastest changing outlet glaciers in West Antarctica with large consequences for global sea level. Yet, assessing how much and how fast both glaciers will weaken if these changes continue remains a major uncertainty as many of the processes that control their ice shelf weakening and grounding line retreat are not well understood. Here, we combine multisource satellite imagery with modeling to uncover the rapid development of damage areas in the shear zones of Pine Island and Thwaites ice shelves. These damage areas consist of highly crevassed areas and open fractures and are first signs that the shear zones of both ice shelves have structurally weakened over the past decade. Idealized model results reveal moreover that the damage initiates a feedback process where initial ice shelf weakening triggers the development of damage in their shear zones, which results in further speedup, shearing, and weakening, hence promoting additional damage development. This damage feedback potentially preconditions these ice shelves for disintegration and enhances grounding line retreat. The results of this study suggest that damage feedback processes are key to future ice shelf stability, grounding line retreat, and sea level contributions from Antarctica. Moreover, they underline the need for incorporating these feedback processes, which are currently not accounted for in most ice sheet models, to improve sea level rise projections.

glaciology↗
NASA NTRS2020

Arctic Snow Depth and Sea Ice Thickness From ICESat‐2 and CryoSat‐2 Freeboards: A First Examination

We present a first examination of Arctic sea ice snow depth estimates from differencing satellite lidar (ICESat‐2) and radar (CryoSat‐2) freeboards. These estimates cover the period between 14 October 2018 and the end of April 2019. Snow depth is related to freeboard differences by the refractive index/bulk density of the snow layer—the only free parameter in the approach. Area‐averaged snow depth ranges from 9 cm (on first‐year ice: 5 cm, multiyear ice: 14 cm) in late October to 19 cm (first‐year ice: 17 cm, multiyear ice: 27 cm) in April; on average, this snow is thinner over FYI. Spatial patterns and gradients of snow depth estimates compare well with reconstructions using snowfall from ERA‐Interim and ERA5, although snowfall from ERA5 is systematically higher. For all months, the results suggest that ~50% of the total freeboard is comprised of snow. Retrievals are within a few centimeters of snow depth data acquired by Operation IceBridge in April 2019. Sources of uncertainties associated with this freeboard‐differencing approach are discussed. Further, sea ice thicknesses calculated using the retrieved snow depth and a modified climatology are contrasted. Comparatively, the snow depth and calculated ice thickness using a modified climatology are higher by ~5 cm and 0.33 m, although these differences are not uniform throughout the season. Snow accumulation was slower between October and December but increased between December and January, unlike the modified climatology, which exhibited a monotonic accumulation for all months. Future opportunities for assessment and improvement of these estimates are discussed.

Arctic Ocean↗
NASA NTRS2018

Enhanced Firn Densification in High‐Accumulation Shear Margins of the NE Greenland Ice Stream

Firn thickness across the NE Greenland Ice Stream is a function of accumulated strain, with thinner firn in the high‐strain margins of the ice stream. We present a novel technique for extracting firn density from previously collected seismic reflection profiles and apply this technique across both shear margins of NE Greenland Ice Stream. Firn is up to 30 m thinner in the vicinity of the ice stream shear margins. Snow accumulation rates across the ice stream were calculated from airborne ice‐penetrating radar data, calibrated with ground‐based firn density measurements from a shallow core. We find that accumulation is ~20% higher in the shear margins compared to the surroundings. The higher density firn adjacent to shear margins is due to high along‐flow stresses that accelerate firn densification and develops despite the higher accumulation rate favoring lower density. These firn density variations influence subglacial hydropotential by changing the ice surface slope and overburden pressure and may influence subglacial water flow. These results demonstrate the importance of high‐resolution firn surveys in studies of shear‐margin dynamics.

ice stream↗
NASA NTRS2022

Experimental and Computational Icing Simulation for Large Swept Wings

The purpose of this final report is to summarize the key results, findings and contributions of a large, multi-organization, multi-year effort focused on swept wing icing and aerodynamics. This research effort was jointly sponsored by NASA, FAA and ONERA and was supported by Boeing and the Universities of Illinois, Virginia, and Washington. The overall goal of this research was to improve the experimental and computational simulation capability for icing on large swept wings typical of commercial transports. This research included both ice accretion and aerodynamic studies using the NASA Common Research Model (CRM) as the reference geometry. For this work, a 65% scaled version—CRM65—was used as the full-scale baseline airplane geometry. This program marks the first non-proprietary research to generate and document full-scale swept wing ice accretions in an icing tunnel and then conduct semispan wing aerodynamic testing on scaled ice accretions at high Reynolds number (i.e., up to 11.9×106). During this work, several new experimental and computational techniques were developed or documented and new knowledge about swept wing icing aerodynamics was identified. All are documented in this report.

Aircraft icing↗
NASA NTRSDate not supplied

Introduction to Aircraft Icing and NASA’s Approach to Understanding It

This presentation provides a brief introduction to aircraft icing and NASA’s approach to understanding it. Specific topics that will be discussed include ice formation on an aircraft, the different types of ice, parameters that influence icing, engine and rotorcraft icing, and NASA’s approach to understanding icing through flight tests, wind tunnels tests, and computational tools. The presentation concludes with a look into the future of aviation and how it will be affected by icing.

Icing↗
NASA NTRSDate not supplied

Simulated Ice Shapes on the High Lift Common Research Model Using LEWICE3D

Computational icing tools consist of predicting two distinct problems, the dry air aerodynamics around the iced or uniced vehicle and the accretion of ice due to inclement weather. A desire exists to advance these tools such that they can be reliably used earlier in the design process to limit the need for more costly flight and wind tunnel testing. To achieve these goals the computational tools need to be benchmarked and validated against high quality experimental data sets to raise the software’s Technology Readiness Level. An ongoing collaborative effort between NASA and Boeing Commercial Airplanes is focused on obtaining this required experimental data and subsequently benchmarking and/or validating the tools that predict the aerodynamics around the iced and uniced vehicle. Currently the scope of this effort is focused on the usage of simulated ice shapes to be representative of the iced vehicle. This presentation discusses the generation of those simulated ice shapes.

Icing↗
NASA NTRSDate not supplied

Summary of Additional In-situ Cloud Data in High Ice Water Content Conditions from Three Recent Flight Campaigns

In-situ measurements of cloud Total Water Content and ice particle Median Mass Diameter have been previously collected during the High Altitude Ice Crystal – High Ice Water Content (HAIC-HIWC) and HIWC RADAR I flight campaigns. These measurements have been provided to an Ice Crystal Icing Aviation Rulemaking Advisory Committee to assess Title 14 Code of Federal Regulations (14CFR) Part 33 Appendix D, and recommend possible changes to the envelopes contained therein. Since then, NASA and the FAA have completed three additional flight campaigns in similar clouds. This article examines these new measurements and any impact they might have on Appendix D assessment. The addition of the new flight campaign data had little effect on previous estimates of the properties of high total water content regions of clouds. Some new information on the occurrence of graupel particles may be important to some ice crystal icing applications.

Aircraft Icing, Aircraft Instrumentation, Airspeed↗
DOE OSTI2023

Arctic Mixed-Phase Cloud Base Ice Precipitation Properties Over the NSA Site

Cloud-climate feedbacks are still the greatest source of uncertainty in current climate projections. Arctic clouds, which are predominantly stratiform and supercooled, often long-lived, and nearly continuously precipitate ice particles, contribute roughly 10% of the uncertainty attributed to the global cloud feedback. This arctic cloud uncertainty is driven by incomplete observational and theoretical knowledge required to estimate and explain the state and active processes occurring in those clouds. A focus on ice precipitation properties at arctic cloud base rather than the surface deconfounds the product of cloud condensate sink processes from the influence of the atmospheric thermodynamic state below cloud base, rendering cloud-base properties a more appealing target for inference and evaluation of model simulations. This data set provides more than 1800 samples of cloud-base ice precipitation properties over Utqiagvik, North Slope of Alaska, all of which were retrieved using the synthesis of ARM radar and lidar measurements. The retrieved ice precipitation variables in this data set include, among others, the ice number concentration, water content, PSD parameters, precipitation rate, mass-weighted fall velocity, vertical air motion, and effective radius, all of which are highly valuable for model evaluation and a general understanding of polar cloud sink processes. Each variable sample includes its mean value and associated uncertainty. Additional variables based on ARM measurements (liquid layer statistics, etc.) are included in this data set. The retrieval algorithm and analysis of this data set are described in Silber (JGR, 2023, https://doi.org/10.1029/2022JD038202).

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2023

Beyond the Stokes approximation: shallow visco-elastic ice-sheet models

Abstract The hypothesis that ice-sheet evolution is only controlled by the long-term non-Newtonian viscous behavior of ice has been challenged by observations indicating that effects like brittle failure, stick-slip sliding, tides and wave action may affect ice-sheet evolution on sub-daily timescales. Over these timescales, the quasi-static-creep approximation is no longer appropriate and elastic effects become important. Simulating elastic effects in ice-sheet models over relevant timescales, however, remains challenging. Here, we show that by including a visco-elastic rheology and reintroducing the oft neglected acceleration term back into the ice-sheet stress balance, we can create a visco-elastic system where the velocity is locally determined and information propagates at the elastic wave speed. Crucially, the elastic wave speed can be treated like an adjustable parameter and set to any value to reproduce a range of phenomena, provided the wave speed is large compared to the viscous velocity. We illustrate the system using three examples. The first two examples demonstrate that the system converges to the steady-state viscous and elastic limits. The third example examines ice-shelf rifting and iceberg calving. This final example hints at the utility of the visco-elastic formulation in treating both long-term evolution and short-term environmental effects.

58 GEOSCIENCES↗
NASA NTRS2013

A Study of the Effects of Altitude on Thermal Ice Protection System Performance

Thermal ice protection systems use heat energy to prevent a dangerous buildup of ice on an aircraft. As aircraft become more efficient, less heat energy is available to operate a thermal ice protections system. This requires that thermal ice protection systems be designed to more exacting standards so as to more efficiently prevent a dangerous ice buildup without adversely affecting aircraft safety. While the effects of altitude have always beeing taked into account in the design of thermal ice protection systems, a better understanding of these effects is needed so as to enable more exact design, testing, and evaluation of these systems.

thermal ice protection system↗
DOE OSTI2023

A hybrid deep neural operator/finite element method for ice-sheet modeling

One of the most challenging and consequential problems in climate modeling is to provide probabilistic projections of sea level rise. A large part of the uncertainty of sea level projections is due to uncertainty in ice sheet dynamics. At the moment, accurate quantification of the uncertainty is hindered by the cost of ice sheet computational models. In this work we develop a hybrid approach to approximate existing ice sheet models at a fraction of their cost. Our approach consists of replacing the finite element model for the momentum equations for the ice velocity, the most expensive part of an ice sheet model, with a Deep Operator Network, while we retain a classic finite element discretization for the evolution of the ice thickness. We show that the resulting hybrid model is very accurate and it is an order of magnitude faster than the traditional finite element model. Further, a distinctive feature of the proposed model, compared to other neural network approaches, is that it can handle high-dimensional parameter spaces (parameter fields) such as the basal friction at the bed of the glacier and can therefore be used for generating samples for uncertainty quantification. Further, we study the impact of hyper-parameters, number of unknowns and correlation length of the parameter distribution on the training and accuracy of the Deep Operator Network on a synthetic ice sheet model. We then target the evolution of the Humboldt glacier in Greenland and show that our hybrid model can provide accurate statistics of the glacier mass loss and can be effectively used to accelerate the quantification of uncertainty.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2022

Near-surface seismic anisotropy in Antarctic glacial snow and ice revealed by high-frequency ambient noise

Ambient seismic recordings taken at broad locations across Ross Ice Shelf and a dense array near West Antarctic Ice Sheet (WAIS) Divide, Antarctica, show pervasive temporally variable resonance peaks associated with trapped seismic waves in near-surface firn layers. These resonance peaks feature splitting on the horizontal components, here interpreted as frequency-dependent anisotropy in the firn and underlying ice due to several overlapping mechanisms driven by ice flow. Frequency peak splitting magnitudes and fast/slow axes were systematically estimated at single stations using a novel algorithm and compared with good agreement with active source anisotropy measurements at WAIS Divide determined via active sources recorded on a 1 km circular array. The approach was further applied to the broad Ross Ice Shelf (RIS) array, where anisotropy axes were directly compared with visible surface features and ice shelf flow lines. The near-surface firn, depicted by anisotropy above 30 Hz, was shown to exhibit a novel plastic stretching mechanism of anisotropy, whereby the fast direction in snow aligns with accelerating ice shelf flow.

58 GEOSCIENCES↗
DOE OSTI2026

Engineering Antifreeze Proteins to Optimally Resist Engulfment by Ice

Antifreeze proteins (AFPs) facilitate the survival of organisms in cold climates by inhibiting the growth and/or recrystallization of ice. To function, AFPs must first bind to ice crystals; bound AFPs must then resist engulfment by using their nonbinding side (NBS) to pin the ice–water interface. Here, we seek to understand how the molecular characteristics of an NBS, such as its ice-phobicity or shape, influence its ability to resist engulfment. By characterizing the free energy barriers that impede the engulfment of model AFPs, we find that the critical supercooling ΔT*, above which an AFP is engulfed, is dictated by an optimal pinning site on the NBS. We further find that the optimal pinning site is determined by an interplay between the contact line perimeter P and a pinning efficiency η, with ΔT* ∝ ηP at the optimal pinning site. For a hemispherical AFP, which displays progressively inward tapering, we find that η increases during engulfment, whereas P decreases; conversely, an NBS with outward tapering can achieve high P, but it suffers from low η. Because the product of η and P determines ΔT*, the inverse correlation between them limits ΔT. To circumvent such limiting behavior, we propose an NBS shape with an outward bulge; by initially tapering outward, a bulged NBS permits higher P, and by subsequently tapering inward, it promotes high η as well. Importantly, we find that ΔT* is enhanced by more than a factor of 2 with an outward bulge of only 1 nm. We also find that the more ice-phobic an NBS is, the more efficiently it pins the ice–water interface, resulting in a higher ΔT. Furthermore, our findings shed light on how the NBS molecular characteristics influence ΔT* and suggest strategies for engineering the NBS to optimally resist engulfment by ice.

Antifreeze↗
DOE OSTI2021

Global Importance of Secondary Ice Production

Measured ice crystal number concentrations are often orders of magnitude higher than the number concentrations of ice nucleating particles, indicating the existence of secondary ice production (SIP) in clouds. Here, we present the first study to examine the global importance of SIP through the droplet shattering during freezing of rain, ice-ice collision fragmentation, and rime splintering, using a global climate model. Our results show that SIP happens quite uniformly in the two hemispheres and dominates the ice formation in the moderately cold clouds with temperatures warmer than –15°C. SIP decreases the global annual average liquid water path by –14.6 g m –2 (–22%), increases the ice water path by 8.7 g m –2 (23%), improving the model agreement with observations. SIP changes the global annual average shortwave, longwave, and net cloud forcing by 2.1, –1.0, and 1.1 W m –2 , respectively, highlighting the importance of SIP on cloud properties on the global scale.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2023

Impact of Ural Blocking on Early Winter Climate Variability Under Different Barents‐Kara Sea Ice Conditions

Abstract Ural blocking (UB) is a prominent mode of variability of the Northern Hemisphere atmospheric circulation, particularly in fall. It can persist for several days and exert a lagged influence on the wintertime NH circulation, providing predictability at the subseasonal time scale. Using two atmospheric models, we explore how the early winter atmospheric circulation responds to a 2‐week persistent UB anomaly imposed in early November. Experiments are carried out with two different configurations of Barents‐Kara (BK) sea‐ice concentration to examine whether it plays a role in how UB impacts atmospheric variability. In both models, the UB anomaly is followed by a weakening of the stratospheric polar vortex and a negative phase of the North Atlantic Oscillation (NAO), which lasts up to 2 months after the forcing is released. Interestingly, the response is more persistent under low BK sea‐ice conditions, that is, BK sea ice modulates the atmospheric response to UB. Additional experiments with prescribed sea ice concentration anomalies alone suggest that BK sea ice exerts a limited influence on early winter NH atmospheric variability. The response to UB involves a weakening of the polar vortex that persists longer under low BK sea ice, which explains the more persistent response in that configuration. Our study highlights that UB variability in November is a robust precursor for early winter NAO/polar stratosphere anomalies, and this may be more relevant in the context of declining Arctic sea‐ice extent. Provided that climate models accurately capture this teleconnection, it has the potential to improve subseasonal predictions of the NH wintertime climate.

Meteorology & Atmospheric Sciences↗