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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 199 records · Page 11
All sourcesNASA NTRSDOE OSTI
NASA NTRSDate not supplied

Effect of Water Droplets Crossing the Boundary Layer in a Stagnation Point Configuration

An experimental study was conducted in the Vertical Icing Studies Tunnel at the Icing Physics Flow Laboratory of NASA Glenn Research Center to study the effect of water droplets crossing the boundary layer in a stagnation point configuration. The objective of the experiment was to determine if water droplets crossing a boundary layer create turbulent spots that accelerate the boundary layer transition from laminar to turbulent. Water droplets that crossed the boundary layer were generated with a nozzle installed in the plenum. The turbulence level in the boundary layer was measured with a hot wire system when the nozzle was off, air on, and air and water on. The results indicate that the presence of the nozzle alone did not affect the boundary layer. The activation of the nozzle to eject air only or to generate water droplets affected the turbulence level in the boundary layer. The continued study of this effect is needed because of its implications in the development of heat transfer models for icing codes.

Icing↗
NASA NTRS1984

Experimental and analytical investigation of a freezing point depressant fluid ice protection system

A glycol-exuding porous leading edge ice protection system was tested in the NASA Icing Research Tunnel. Stainless steel mesh, laser drilled titanium, and composite panels were tested on two general aviation wing sections. Two different glycol-water solutions were evaluated. Minimum glycol flow rates required for anti-icing were obtained as a function of angle of attack, liquid water content, volume median drop diameter, temperature, and velocity. Ice accretions formed after five minutes of icing were shed in three minutes or less using a glycol fluid flow equal to the anti-ice flow rate. Two methods of predicting anti-ice flow rates are presented and compared with a large experimental data base of anti-ice flow rates over a wide range of icing conditions. The first method presented in the ADS-4 document typically predicts flow rates lower than the experimental flow rates. The second method, originally published in 1983, typically predicts flow rates up to 25 percent higher than the experimental flow rates. This method proved to be more consistent between wing-panel configurations. Significant correlation coefficients between the predicted flow rates and the experimental flow rates ranged from .867 to .947.

Albright, A. E.↗
DOE OSTI2026

Rates of Sea‐Level Rise Are Highly Sensitive to Ice Viscosity Parameters in Model Benchmarks

Glacier flow plays a major role in current and future rates of globally averaged sea-level rise. The viscosity of glacial ice, controlling the rate of flow, decreases as stress increases and is highly sensitive to the value of the stress exponent, $n$, in the constitutive equation for viscous flow. Glaciologists and climate modelers almost exclusively assume $n=3$ when modeling ice flow and projecting sea-level rise through forward modeling. However, recent work suggests that $n\approx 4$ better fits observations, prompting the question: How sensitive are projections of sea-level rise to the value of $n$? We use an established community ice flow model and standard benchmark experiments designed as an idealized representation of Pine Island Glacier, West Antarctica. While initializing an $n=3$ model to match observations of an $n=4$ ice sheet is possible, we find that incorrectly assuming $n=3$ when in fact $n=4$ dramatically underestimates rates of sea-level rise. The scale of this error grows nonlinearly with the magnitude of the climate forcing, acting to increase projection uncertainties. Additionally, we find that models often account for this stress-dependent rheology mismatch during model initialization in a way that masks this rheological effect in the short term while leaving model outputs vulnerable to larger biases in longer-term projections. Initializations to observations of Pine Island Glacier display similar rheology-mismatch fingerprints to our idealized example.

climate sensitivity↗
NASA NTRS1973

Sea-surface circulation, sediment transport, and marine mammal distribution, Alaska continental shelf

The author has identified the following significant results. Even though nonsynchronous, the ERTS-1 imagery of November 4, 1972, showed a striking similarity to the ground truth data obtained in late August and September, 1972. The comparison of the images with ground truth data revealed that the general water circulation pattern in Lower Cook Inlet is consistent through the Fall season and that ERTS-1 images in MSS bands 4 and 5 are capable of delineating water masses with a suspended load as low as 1 mg/liter. The ERTS-1 data and the ground truth data demonstrate clearly that the coriolis effect dominates circulation in Lower Cook Inlet. The configuration of plumes in Nushagak and Kuskokwim bays further indicates the influence of the coriolis effect on the movement of sea water at high latitudes. Comparison of MSS bands 4, 5, 6, and 7 suggest MSS-1 penetration of several meters into the water column. Sea ice analysis of available imagery was exceptionally rewarding. The imagery provided a rapid method to delineate and describe the ice types apparent in the photos. The ice types ranged from newly formed grease ice to heavy flows of disintegrating shore-fast ice. Sea ice maps showing the extent of different ice zones in the Chukchi Sea are being compiled.

Wright, F. F.↗
NASA NTRS1989

The low frequency oscillation in the flow over a NACA0012 airfoil with an iced leading edge

The unusually low frequency oscillation in the wake of an airfoil is explored experimentally as well as computationally for a NACA0012 airfoil with a glaze ice accretion at the leading edge. Experimentally, flow oscillations were observed at low frequencies that correspond to a Strouhal number of about 0.02. This occurred in the angle of attack range of 8 to 9 deg, near the onset of static stall for this airfoil. With a Navier-Stokes computation, limit-cycle oscillations in the flow and in the aerodynamic forces were also observed at low Strouhal numbers. However, the occurrence of the oscillation is found to depend on the turbulence model in use as well as the Reynolds number.

Zaman, K. B. M. Q.↗
NASA NTRS1989

The low frequency oscillation in the flow over a NACA0012 airfoil with an 'iced' leading edge

The unusually low frequency oscillation in the wake of an airfoil is explored experimentally as well as computationally for a NACA0012 airfoil with a glaze ice accretion at the leading edge. Experimentally, flow oscillations were observed at low frequencies that correspond to a Strouhal number of about 0.02. This occurred in the angle of attack range of 8 to 9 deg, near the onset of static stall for this airfoil. With a Navier-Stokes computation, limit-cycle oscillations in the flow and in the aerodynamic forces were also observed at low Strouhal numbers. However, the occurrence of the oscillation is found to depend on the turbulence model in use as well as the Reynolds number.

Zaman, K. B. M. Q.↗
NASA NTRS1993

Global geologic applications of the Space Shuttle earth observations photography database

The advantages of the astronaut photography during Space Shuttle missions are briefly examined, and the scope and applications of the Space Shuttle earth observations photography database are discussed. The global and multidisciplinary nature of the data base is illustrated by several examples of geologic applications. These include the eruption of Mount Pinatubo (Philippine Islands), heat flow and ice cover on Lake Baikal in Siberia (Russia), and windblown dust in South America. It is noted that hand-held photography from the U.S. Space Shuttle provides unique remotely-sensed data for geologic applications because of the combination of varying perspectives, look angles, and illumination, and changing resolution resulting from different lenses and altitudes.

Lulla, Kamlesh↗
NASA NTRS1996

Active Microwave Radar Observations of Weddell Sea Ice

From Intro.: This paper first introduces the C-band(5.3 GHz) sensor systems used in this study, together with some of the important and relevant sampling issues and limitations of satellite radar. Second, a broad description of the backscatter characteristics of Weddell Sea ice, together with its regional and seasonal variations is provided...

Weddell Sea sea ice weddell sea ice dynamics sea i↗
NASA NTRS2017

Comparisons of Mixed-Phase Icing Cloud Simulations with Experiments Conducted at the NASA Propulsion Systems Laboratory

This paper builds on previous work that compares numerical simulations of mixed-phase icing clouds with experimental data. The model couples the thermal interaction between ice particles and water droplets of the icing cloud with the flowing air of an icing wind tunnel for simulation of NASA Glenn Research Centers (GRC) Propulsion Systems Laboratory (PSL). Measurements were taken during the Fundamentals of Ice Crystal Icing Physics Tests at the PSL tunnel in March 2016. The tests simulated ice-crystal and mixed-phase icing that relate to ice accretions within turbofan engines.

Bartkus, Tadas↗
NASA NTRS2017

Comparisons of Mixed-Phase Icing Cloud Simulations with Experiments Conducted at the NASA Propulsion Systems Laboratory

This paper builds on previous work that compares numerical simulations of mixed-phase icing clouds with experimental data. The model couples the thermal interaction between ice particles and water droplets of the icing cloud with the flowing air of an icing wind tunnel for simulation of NASA Glenn Research Centers (GRC) Propulsion Systems Laboratory (PSL). Measurements were taken during the Fundamentals of Ice Crystal Icing Physics Tests at the PSL tunnel in March 2016. The tests simulated ice-crystal and mixed-phase icing that relate to ice accretions within turbofan engines. Experimentally measured air temperature, humidity, total water content, liquid and ice water content, as well as cloud particle size, are compared with model predictions. The model showed good trend agreement with experimentally measured values, but often over-predicted aero-thermodynamic changes. This discrepancy is likely attributed to radial variations that this one-dimensional model does not address. One of the key findings of this work is that greater aero-thermodynamic changes occur when humidity conditions are low. In addition a range of mixed-phase clouds can be achieved by varying only the tunnel humidity conditions, but the range of humidities to generate a mixed-phase cloud becomes smaller when clouds are composed of smaller particles. In general, the model predicted melt fraction well, in particular with clouds composed of larger particle sizes.

Thermal model↗