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DOE OSTI2024

Heat transfer and transport property contrast effects on the compressible Rayleigh-Taylor instability

In extreme environments, the Rayleigh-Taylor instability (RTI) may occur under large variations in density and temperature and with fluid transport properties strongly dependent on temperature. Direct numerical simulations of the 3D fully compressible RTI are conducted, examining the idealized configuration of a hotter, less dense fluid pushing against a colder, denser fluid. Various temperature ratios and transport property configurations are explored to examine how heat conduction, large variations in transport properties, and sudden changes in transport properties can affect the evolution of the mixing layer. Nonuniform fluid expansion and contraction induced by heat transfer can significantly affect local density differences and overall instability growth, causing profile asymmetries about the initial interface for flow and mixing statistics. The departures from classical self-similar development of the instability along with misalignment between regions of mixing and regions of most intense turbulent activity caused by both heat transfer and transport property contrasts are examined. After sudden changes in fluid transport properties, which may occur as a result of rapid heating (e.g., in inertial confinement fusion), the flow quickly responds and begins to relax towards quasi-self-similar late-time evolution. For many dynamical quantities such as vorticity and dissipation, this late-time evolution resembles that of the configuration that already started with the final transport property magnitudes, suggesting that these quantities depend only on the transport properties and not on past flow history, provided that the density field distributions for the flows remain similar. On the other hand, the mixing evolution after the transport property change is unique, implying that both property magnitudes and previous history are impactful on the mixing. In conclusion, these simulations demonstrate how various temperature-related effects are extremely important to consider in compressible RTI flows with large temperature variations.

42 ENGINEERING↗

DOE OSTI2020

Mitigation of Motor Stalling and FIDVR via Energy Storage Systems with Temporal Logic Specifications

The fault-induced delayed voltage recovery (FIDVR) phenomenon has been very common from the distribution system through the transmission system. It causes a delay on recovering significantly depressed local voltage after the fault is cleared, and it can also lead to more widespread cascading system failures. Mitigating this event with current control approaches is challenging and becoming a crucial issue. Here, a model predictive control-based strategy employing signal temporal logic specifications is proposed to help mitigate FIDVR. To this end, it investigates and extends a dynamic performance model allowing analytic insights into the system-wide impact of motor stalling and FIDVR. The proposed controller provides richer descriptions of voltage specifications addressing both magnitude and time simultaneously. We consider different control specifications with reactive power support from energy storage systems to prevent the voltage during/after the fault from dropping too low, and reduce the delay time of voltage recovery. The simulation results conducted with the IEEE 57 bus test network validate the proposed method and demonstrate the effectiveness of the mitigation strategy on FIDVR.

25 ENERGY STORAGE↗

DOE OSTI2025

Exercise alters molecular profiles of inflammation and substrate metabolism in human white adipose tissue

White adipose tissue (WAT) plays a significant role in whole body energy homeostasis, and its excess typifies obesity. In addition to WAT quantity, perturbations in the basic cellular processes of WAT (i.e., quality) are also associated with obesity and metabolic disease. Exercise training alleviates metabolic perturbations associated with obesity; however, the underlying molecular mechanisms that drive these metabolic adaptations in WAT are not well described. For this work, abdominal subcutaneous WAT biopsies were collected after an acute bout of exercise (1 day after) at baseline and following 3 wk of supervised aerobic training in sedentary overweight women (n = 6) without alterations in body weight and fat mass. RNA-seq, global proteomics, and phosphoproteomics in WAT revealed training-induced changes in 1,527 transcripts, 154 proteins, and 144 phosphosites, respectively. Training decreased abundance of transcripts and proteins involved in inflammation and components of the extracellular matrix and increased abundance of transcripts and proteins related to fatty acid esterification and lipolysis. In summary, short-term aerobic training significantly reduces local inflammation and increases lipid metabolism in WAT of sedentary overweight women—independent of alterations in body and fat mass. As such, some of the health benefits of aerobic training may occur through molecular alterations in WAT (i.e., enhanced quality) rather than a sheer reduction in WAT quantity.

60 APPLIED LIFE SCIENCES↗

DOE OSTI2025

Distinctive Pattern of Global Warming in Ocean Heat Content

Abstract Huge heat anomalies in the atmosphere and ocean in recent years are not yet explained. Strong characteristic patterns in temperatures for upper layers of the ocean occurred from 2000 to 2023 in the presence of global warming from increasing atmospheric greenhouse gases. Here, we show that the deep tropics are warming, although sharply modulated by El Niño–Southern Oscillation events, with strong heating in the extratropics near 40°N and 40°–45°S but little heating near 20°N and 25°–30°S. The heating is most clearly manifested in zonal-mean ocean heat content and is evident in sea surface temperatures. The strongest heating is in the Southern Hemisphere, where aerosol effects are small. Estimates are made of the contributions to heating of top-of-atmosphere (TOA) radiation, atmospheric energy transports, surface fluxes of energy, and redistribution of energy by surface winds and ocean currents. The patterns of change are not directly related to TOA radiation but are evident in net surface energy fluxes and inferred ocean heat transports, underscoring their coupled origin. Changes in the atmospheric circulation through a poleward shift in ocean jet streams and storm tracks are reflected in surface wind-driven ocean Ekman transports. As well as human-induced climate change, internal natural variability is likely in play. Hence, the atmosphere and ocean currents are systematically redistributing heat from global warming, profoundly affecting local climates. Significance Statement As the climate changes, it has been difficult to discern meaningful patterns. Distinctive patterns of change have occurred in the ocean when examined as zonal averages around latitude bands. Most excess heat from global warming resides in the ocean and, since 2005, has become focused into bands near 40°N and 40°S, with little net warming in the subtropics. The strongest warming is in the Southern Hemisphere, although sea surface temperatures have increased more in the Northern Hemisphere. Changes in the atmospheric circulation through a poleward shift in the jet stream and storm tracks are primarily responsible along with corresponding changes in ocean currents. These changes are linked through surface exchanges of energy via heat, moisture, and wind stress.

Trenberth, Kevin E. [National Center for Atmospher↗

NASA NTRS1980

The formation of arcs in the dynamic spectra of Jovian decameter bursts

A model is presented that can account for several features of the dynamic spectral arcs observed at decameter wavelengths by the planetary radio astronomy experiment on Voyagers 1 and 2. It is shown that refraction of an extraordinary mode wave initially excited nearly orthogonal to the local magnetic field is significantly influenced by the local plasma density, being greater the higher the density. It is assumed that the source of the decameter radiation lies along the L = 6 flux tube and that the highest frequencies are produced at the lowest altitudes, where both the plasma density and magnetic field gradients are largest. It is further assumed that the decameter radiation is emitted into a thin conical sheet, consistent with both observation and theory. In the model the emission cone angle of the sheet is chosen to vary with frequency so that it is relatively small at both high and low frequencies, but approximately 80 deg at intermediate frequencies. The resulting emission pattern as seen by a distant observer is shown to resemble the observed arc pattern. The model is compared and contrasted with examples of Voyager radio data.

Goldstein, M. L.↗

NASA NTRS1981

The formation of arcs in the dynamic spectra of Jovian decameter bursts

A model is presented that accounts for several features of the dynamic spectral arcs observed at decameter wavelengths by the planetary radio astronomy experiment on Voyagers 1 and 2. It is shown that refraction of an extraordinary mode wave initially excited and nearly orthogonal to the local magnetic field is significantly influenced by the local plasma density. The source of the radiation is on the L = 6 flux, and the emission cone angle of the sheet is chosen to vary with frequency so that it is relatively small at both high and low frequencies while about 80 deg at intermediate frequencies. This functional dependence of cone angle on frequency appears to be consistent with estimates of refraction of the ordinary mode in a source region where the electron density is greater than a few hundred per cu cm.

Goldstein, M. L.↗

NASA NTRS1983

Leeward centerline and side fuselage entry heating predictions for the space shuttle orbiter

Heat transfer data measured along the leeward centerline and on the side fuselage of the Space Shuttle orbiter during STS-2 and STS-3 are compared with predictions of empirical heating techniques derived from wind tunnel tests. Steps required to extrapolate an existing leeward centerline theory to flight conditions are described. Generally favorable comparisons from Mach 24 down to approximately Mach 7 for both flights are presented. The side fuselage impingement heating method is currently under development, but some preliminary results are available. The method is briefly described and compared with wind tunnel and flight measurements. Side heating predictions are given for an STS-3 trajectory point near Mach 10 showing good agreement with flight data. There is evidence of embedded vortices emanating from the side fuselage impingement line which significantly enhance local heating rates at both wind tunnel and flight conditions.

Helms, V. T., III↗

NASA NTRS1987

Periodic extinction of families and genera

Eight major episodes of biological extinction of marine families over the past 250 million years stand significantly above local background (P less than 0.05). These events are more pronounced when analyzed at the level of genus, and generic data exhibit additional apparent extinction events in the Aptian (Cretaceous) and Pliocene (Tertiary) Stages. Time-series analysis of these records strongly suggests a 26-million-year periodicity. This conclusion is robust even when adjusted for simultaneous testing of many trial periods. When the time series is limited to the four best-dated events (Cenomanian, Maestrichtian, upper Eocene, and middle Miocene), the hypothesis of randomness is also rejected for the 26-million-year period (P less than 0.0002).

Raup, David M.↗

NASA NTRS1987

The impact of domain partitioning on the performance of a shared memory multiprocessor

The impact of the choice of domain partition/stencil pairs in solving elliptic partial differential equations on a multiprocessor system with both global shared memory and local memory is considered. A parallel execution time model is given for square and hexagonal partitions using both five-point and nine-point star discretizations. Results from the model for a particular multiprocessor system show that keeping copies of partition boundaries in local memory significantly improves performance.

Patrick, Merrell L.↗

NASA NTRS1991

Damage and fracture in composite thin shells

The effect of fiber fracture on the load carrying capability and structural behavior of a composite cylindrical shell under internal pressure is investigated. An integrated computer code is utilized for the simulation of composite structural degradation under loading. Damage initiation, damage growth, fracture progression, and global structural fracture are included in the simulation. Results demonstrate the significance of local damage on the structural durability of pressurized composite cylindrical shells.

Minnetyan, Levon↗

NASA NTRS1991

Damage and fracture in composite thin shells

Minnetyan, Levon↗

NASA NTRS1992

Design for progressive fracture in composite shell structures

The load carrying capability and structural behavior of composite shell structures and stiffened curved panels are investigated to provide accurate early design loads. An integrated computer code is utilized for the computational simulation of composite structural degradation under practical loading for realistic design. Damage initiation, growth, accumulation, and propagation to structural fracture are included in the simulation. Progressive fracture investigations providing design insight for several classes of composite shells are presented. Results demonstrate the significance of local defects, interfacial regions, and stress concentrations on the structural durability of composite shells.

Minnetyan, Levon↗

NASA NTRS1997

Novel Highly Parallel and Systolic Architectures Using Quantum Dot-Based Hardware

VLSI technology has made possible the integration of massive number of components (processors, memory, etc.) into a single chip. In VLSI design, memory and processing power are relatively cheap and the main emphasis of the design is on reducing the overall interconnection complexity since data routing costs dominate the power, time, and area required to implement a computation. Communication is costly because wires occupy the most space on a circuit and it can also degrade clock time. In fact, much of the complexity (and hence the cost) of VLSI design results from minimization of data routing. The main difficulty in VLSI routing is due to the fact that crossing of the lines carrying data, instruction, control, etc. is not possible in a plane. Thus, in order to meet this constraint, the VLSI design aims at keeping the architecture highly regular with local and short interconnection. As a result, while the high level of integration has opened the way for massively parallel computation, practical and full exploitation of such a capability in many applications of interest has been hindered by the constraints on interconnection pattern. More precisely. the use of only localized communication significantly simplifies the design of interconnection architecture but at the expense of somewhat restricted class of applications. For example, there are currently commercially available products integrating; hundreds of simple processor elements within a single chip. However, the lack of adequate interconnection pattern among these processing elements make them inefficient for exploiting a large degree of parallelism in many applications.

Fijany, Amir↗

NASA NTRS2000

A Solid Case for Microgravity Processing

Solidification of metals, particularly alloys, is a complicated process. At some sufficiently high temperature, the components comprising an alloy fully mix, producing a single homogeneous liquid. Unfortunately, after this liquid is cast into a mold and allowed to freeze, the resulting solid is usually very inhomogeneous. In most cases the first solid to "freeze out" of the liquid has a composition very close to one of the pure metals. This initially solidifying metal usually comprises microscopic, pine-tree shaped components, collectively referred to as a dendritic array, whose distribution, alignment, and scale directly influence a materials strength and docility. During dendrite growth the adjacent liquid becomes enriched, and consequently, solidifies a much lower temperature and considerably later time. Thus, in the course of solidification, both the solid and the enriched liquid can have compositions (and local temperatures) significantly different from those of the bulk liquid. Different compositions and temperatures imply different densities that, in Earth's gravity, induce motion in the liquid. Such motion promotes formation of a casting that is denser at the bottom and lighter at the top. This condition known as macrosegregation, precludes optimized, uniform material properties.

Grugel, Richard N.↗

NASA NTRS2002

Batse Triggered Observations of Galactic Superluminal Sources GROJ1655-40

We have analyzed multiwavelength data of galactic superluminal sources including GROJ1655-40. Currently there are thirteen X-ray binaries, in which the masses of the invisible and compact objects have been determined to be much higher than three solar masses, the well-known upper limit to the mass of a neutron star. Because no stable and compact objects are believed to exist above this limit, these compact objects are consequently considered as stellar mass black holes, though clean evidence of strong gravity effects around the assumed black holes is very rare. From optical and radio observations, their system inclination angles have been determined to range between 25 degrees and 80 degrees, but peaked between 60-70 degrees. This peak is not explained in the frame work of Newtonian gravity in these systems. However, this peak is reproduced naturally if we model the observed X-ray radiation as being produced in the accretion disks very close to the black hole horizons, where the extremely strong general and special relativistic effects, caused by the extremely strong gravity near the black hole horizons, modify the local radiation significantly as the X-rays propagate to the remote observer.

Zhang, Shuang Nan↗

NASA NTRS2003

Analysis and Design of Rotors at Ultra-Low Reynolds Numbers

Design tools have been developed for ultra-low Reynolds number rotors, combining enhanced actuator-ring / blade-element theory with airfoil section data based on two-dimensional Navier-Stokes calculations. This performance prediction method is coupled with an optimizer for both design and analysis applications. Performance predictions from these tools have been compared with three-dimensional Navier Stokes analyses and experimental data for a 2.5 cm diameter rotor with chord Reynolds numbers below 10,000. Comparisons among the analyses and experimental data show reasonable agreement both in the global thrust and power required, but the spanwise distributions of these quantities exhibit significant deviations. The study also reveals that three-dimensional and rotational effects significantly change local airfoil section performance. The magnitude of this issue, unique to this operating regime, may limit the applicability of blade-element type methods for detailed rotor design at ultra-low Reynolds numbers, but these methods are still useful for evaluating concept feasibility and rapidly generating initial designs for further analysis and optimization using more advanced tools.

Kunz, Peter J.↗

NASA NTRS2002

Inclination Angles of Black Hole X-Ray Binaries Manifest Strong Gravity around Black Holes

System inclination angles have been determined for about 15 X-ray binaries, in which stellar mass black holes are considered to exist. These inclination angles range between 25 degrees and 80 degrees, but peaked between 60-70 degrees. This peak is not explained in the frame work of Newtonian gravity. However, this peak is reproduced naturally if we model the observed X-ray radiations as being produced in the accretion disks very close to the black hole horizons, where the extremely strong general and special relativistic effects, caused by the extremely strong gravity near the black hole horizons, modify the local radiation significantly as the X-rays propagate to the remote observer. Therefore the peak of the inclination angle distribution provides evidence or strong gravity around stellar mass black holes.

Zhang, S. N.↗

NASA NTRS1986

Periodic extinction of families and genera

Eight major episodes of biological extinction of marine families over the past 250 million years stand significantly above local background (P < 0.05). These events are more pronounced when analyzed at the level of genus, and generic data exhibit additional apparent extinction events in the Aptian (Cretaceous) and Pliocene (Tertiary) Stages. Time-series analysis of these records strongly suggests a 26-million-year periodicity. This conclusion is robust even when adjusted for simultaneous testing of many trial periods. When the time series is limited to the four best-dated events (Cenomanian, Maestrichtian, upper Eocene, and middle Miocene), the hypothesis of randomness is also rejected for the 26-million-year period (P < 0.0002).

Non-NASA Center↗