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At least 865 records · Page 48

All sources NASA NTRS DOE OSTI

DOE OSTI2018

A Fast Solver for Implicit Integration of the Vlasov--Poisson System in the Eulerian Framework

In this paper, we present a domain decomposition algorithm to accelerate the solution of Eulerian-type discretizations of the linear, steady-state Vlasov equation. The steady-state solver then forms a key component in the implementation of fully implicit or nearly fully implicit temporal integrators for the nonlinear Vlasov--Poisson system. The solver relies on a particular decomposition of phase space that enables the use of sweeping techniques commonly used in radiation transport applications. The original linear system for the phase space unknowns is then replaced by a smaller linear system involving only unknowns on the boundary between subdomains, which can then be solved efficiently with Krylov methods such as GMRES. Steady-state solves are combined to form an implicit Runge--Kutta time integrator, and the Vlasov equation is coupled self-consistently to the Poisson equation via a linearized procedure or a nonlinear fixed-point method for the electric field. Finally, numerical results for standard test problems demonstrate the efficiency of the domain decomposition approach when compared to the direct application of an iterative solver to the original linear system.

97 MATHEMATICS AND COMPUTING↗

DOE OSTI2014

Measurement of the transmission magnetic circular dichroism of Ga{sub 1−x}Mn{sub x}As epilayers using a built-in p-i-n photodiode

By constructing a GaMnAs epilayer/semi-insulating In{sub 0.2}Ga{sub 0.8}As/(001) n{sup +}-GaAs substrate layer structure as a built-in p-i-n photodiode, we developed a scheme for on-chip measurements of transmission magnetic circular dichroism (T-MCD). Both the hysteresis loops in the magnetic field sweeps and the wavelength scans at saturated magnetic fields measured using the new T-MCD scheme, illustrated the same features as those previously measured on the freestanding GaMnAs thin films by conventional T-MCD. Because a large group of epitaxially grown magnetic film/semiconductor heterostructures, such as Fe, NiFe, CoFeAl, and MnGa films on semiconductor substrates, are becoming important new building blocks for semiconductor-based spin field-effect transistor, perpendicular magnetic tunnel junction (p-MTJ) and lateral MTJ devices, the new T-MCD scheme can be applied to tests of their magnetic properties by forming either p-i-n or Schottky photodiodes.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

NASA NTRS1992

Reynolds number and cowl position effects for a generic sidewall compression scramjet inlet at Mach 10 - A computational and experimental investigation

Reynolds number and cowl position effects on the internal shock structure and the resulting performance of a generic three-dimensional sidewall compression scramjet inlet with a leading edge sweep of 45 degrees at Mach 10 have been examined both computationally and experimentally. Prior to the experiment, a three-dimensional Navier-Stokes code was adapted to perform preliminary parametric studies leading to the design of the present configuration. Following this design phase, the code was then utilized as an analysis tool to provide a better understanding of the flow field and the experimental static pressure data for the final experimental configuration. The wind tunnel model possessed 240 static pressure orifices distributed on the forebody plane, sidewalls, and cowl and was tested in the NASA Langley 31 Inch Mach 10 Tunnel.

Holland, Scott D.↗

NASA NTRS1992

Reynolds Number and Cowl Position Effects for a Generic Sidewall Compression Scramjet Inlet at Mach 10: A Computational and Experimental Investigation

Holland, Scott D.↗

NASA NTRS2012

Improved Finite-Volume Method for Radiative Hydrodynamics

Fully coupled simulations of hydrodynamics and radiative transfer are essential to a number of fields ranging from astrophysics to engineering applications. Of particular interest in this work are hypersonic atmospheric entries and associated experimental apparatus, e.g., shock tubes and high enthalpy testing facilities. The radiative transfer calculations must supply to the CFD a heating term in the energy equation in the form of the divergence of the radiative heat flux and the radiative heat fluxes to bounding surfaces. It is most efficient to solve the radiative transfer equation on the same grid as the CFD solution, and this work presents an algorithm with improved accuracy for such simulations on structured and unstructured grids compared to more conventional approaches. Results will be shown for shock radiation during hypersonic reentry. Issues of parallelization within a radiation sweep will also be discussed.

Wray, Alan↗

NASA NTRS1997

F/A-18A Inlet Flow Characteristics During Maneuvers with Rapidly Changing Angle of Attack

The performance and distortion levels of the right inlet of the F/A-18A High Alpha Research Vehicle were assessed during maneuvers with rapidly changing angle-of-attack at the NASA Dryden Flight Research Center, Edwards, California. The distortion levels were compared with those produced by current inlet-engine compatibility evaluation techniques. The objective of these analyses was to determine whether the results obtained for steady aerodynamic conditions were adequate to describe the inlet-generated distortion levels that occur during rapid aircraft maneuvers. The test data were obtained during 46 dynamic maneuvers at Mach numbers of 0.3 and 0.4. Levels of inlet recovery, peak dynamic circumferential distortion, and peak dynamic radial distortion of dynamic maneuvers for a General Electric F404-GE-400 turbofan engine were compared with estimations based on steady aerodynamic conditions. The comparisons were performed at equivalent angle-of-attack, angle-of-sideslip, and Mach number. Results showed no evidence of peak inlet distortion levels being elevated by dynamic maneuver conditions at high angle-of-attack compared with steady aerodynamic estimations. During sweeps into high angle-of-attack, the peak distortion levels of the dynamic maneuvers rarely rose to steady aerodynamic estimations. The dynamic maneuvers were shown to be effective at identifying conditions when discrete changes in inlet behavior occur.

Yuhas, Andrew J.↗

NASA NTRS1961

Heat-Transfer Measurements at a Mach Number of 4.95 on Two 60 deg Swept Delta Wings with Blunt Leading Edges and Dihedral Angles of 0 deg and 45 deg

An experimental investigation was conducted to evaluate the heat-transfer characteristics of two 60 deg swept delta wings with cylindrical leading edges of 0.25-inch radii and dihedral angles of 0 deg and 45 deg. The tests were conducted at a Mach number of 4.95 and a stagnation temperature of 400 F. The The test-section unit Reynolds number was varied from 1.95 x 10(exp 6) to 12.24 x 10(exp 6) per foot. The results of the investigation indicated that, in a plane normal to the leading edge, the laminar-flow heat-transfer distribution was in good agreement with two-dimensional blunt-body theory. The stagnation-line heat-transfer level could be predicted from two-dimensional blunt-body theory provided the stagnation-line heat-transfer coefficient was assumed to vary as the cosine of the effective sweep. A comparison of the heating rates to the 0 deg dihedral wing (planform sweep of 60 deg) and the 45 deg dihedral wing (planform sweep of 69.3 deg) with equal panel sweep and panel area indicated that the stagnation-line heat-transfer coefficient for the 45 deg dihedral wing could be as much as 40 percent less than the stagnation-line heat-transfer coefficient for the 0 deg dihedral wing at both equal angles of attack and equal lifts. The laminar-flow heat-transfer rate to both wings outside the vicinity of the stagnation line was essentially equal.

Stainback, P. Calvin↗

DOE OSTI2013

Analysis of fission gas release in LWR fuel using the BISON code

Recent advances in the development of the finite-element based, multidimensional fuel performance code BISON of Idaho National Laboratory are presented. Specifically, the development, implementation and testing of a new model for the analysis of fission gas behavior in LWR-UO2 fuel during irradiation are summarized. While retaining a physics-based description of the relevant mechanisms, the model is characterized by a level of complexity suitable for application to engineering-scale nuclear fuel analysis and consistent with the uncertainties pertaining to some parameters. The treatment includes the fundamental features of fission gas behavior, among which are gas diffusion and precipitation in fuel grains, growth and coalescence of gas bubbles at grain faces, grain growth and grain boundary sweeping effects, thermal, athermal, and transient gas release. The BISON code incorporating the new model is applied to the simulation of irradiation experiments from the OECD/NEA International Fuel Performance Experiments database, also included in the IAEA coordinated research projects FUMEX-II and FUMEX-III. The comparison of the results with the available experimental data at moderate burn-up is presented, pointing out an encouraging predictive accuracy, without any fitting applied to the model parameters.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗

DOE OSTI2019

First Ever Polymer Flood Field Pilot to Enhance the Recovery of Heavy Oils on Alaska’s North Slope – Polymer Injection Performance

Alaska North Slope (ANS) holds an estimated 20-30+ billion barrel heavy oil resources, yet the development pace has been very slow due to high development costs and low oil recovery using conventional waterflood and EOR methods. The objective of this pilot is to perform a field experiment to validate the use of an advanced polymer flooding technology to unlock the vast heavy oil resources on ANS. The advanced polymer flooding technology combines polymer flooding, low salinity water flooding, horizontal wells, and if necessary, injection conformance control treatments into one integrated process to significantly improve oil recovery from heavy oil reservoirs. Two pairs of horizontal injection and production wells have been deployed in an isolated fault block of the Schrader Bluff heavy oil reservoir at the Milne Point Field to conduct a polymer flood pilot. The pilot will acquire scientific knowledge and field performance data to optimize polymer flood design in the Schrader Bluff heavy oil reservoirs on ANS. Polymer injection started on August 28, 2018 using a custom made polymer blending and pumping unit. This paper focuses on the facility setup and polymer injection performance into the horizontal injectors drilled and completed in the Schrader Bluff heavy oil reservoir. Partially hydrolyzed polyacrylamide (HPAM) polymer was selected and the initial target viscosity was set at 45 centipoise. Polymer injection rate was set at 2200 bbl/day for one injector (J-23A) and 1200 bbl/day for the other (J-24A) based on production voidage. Injection pressure was controlled at below fracture pressure to prevent fracturing the reservoir and causing fast breakthroughs. Step rate and pressure falloff tests indicate that short term polymer injectivity is similar to water injectivity, which means that injectivity is mostly controlled by fluid mobility deep in the reservoir rather than that in the vicinity of the injection wellbore. Long term injection data indicate that polymer injectivity has been decreasing in both injectors as the reservoir is filled by polymer. No polymer has been observed in the production stream 7 months after the start of polymer injection compared with a 3-month breakthrough time with waterflood. This indicates that polymer significantly delays breakthrough time which will lead to increased sweep efficiency.

Ning, Samson↗

NASA NTRS1992

Flight test results from a supercritical mission adaptive wing with smooth variable camber

The mission adaptive wing (MAW) consisted of leading- and trailing-edge variable-camber surfaces that could be deflected in flight to provide a near-ideal wing camber shape for any flight condition. These surfaces featured smooth, flexible upper surfaces and fully enclosed lower surfaces, distinguishing them from conventional flaps that have discontinuous surfaces and exposed or semiexposed mechanisms. Camber shape was controlled by either a manual or automatic flight control system. The wing and aircraft were extensively instrumented to evaluate the local flow characteristics and the total aircraft performance. This paper discusses the interrelationships between the wing pressure, buffet, boundary-layer and flight deflection measurement system analyses and describes the flight maneuvers used to obtain the data. The results are for a wing sweep of 26 deg, a Mach number of 0.85, leading and trailing-edge cambers (delta(sub LE/TE)) of 0/2 and 5/10, and angles of attack from 3.0 deg to 14.0 deg. For the well-behaved flow of the delta(sub LE/TE) = 0/2 camber, a typical cruise camber shape, the local and global data are in good agreement with respect to the flow properties of the wing. For the delta(sub LE/TE) = 5/10 camber, a maneuvering camber shape, the local and global data have similar trends and conclusions, but not the clear-cut agreement observed for cruise camber.

Powers, Sheryll Goecke↗

DOE OSTI2017

A new approach to three-dimensional neutron transport solution based on the method of characteristics and linear axial approximation

A new approach based on the method of characteristics (MOC) is proposed to solve the neutron transport equation. A new three-dimensional (3D) spatial discretization is applied to avoid the instability issue of the transverse leakage iteration of the traditional 2D/1D approach. In this new approach, the axial and radial variables are discretized in two different ways: the linear expansion is performed in the axial direction, then, the 3D solution of the angular flux is transformed to be the planar solution of 2D angular expansion moments, which are solved by the planar MOC sweeping. Based on the boundary and interface continuity conditions, the 2D expansion moment solution is equivalently transformed to be the solution of the axially averaged angular flux. Using the piecewise averaged angular flux at the top and bottom surfaces of 3D meshes, the planes are coupled to give the 3D angular flux distribution. The 3D CMFD linear system is established from the surface net current of every 3D pin-mesh to accelerate the convergence of power iteration. The STREAM code is extended to be capable of handling 3D problems based on the new approach. Several benchmarks are tested to verify its feasibility and accuracy, including the 3D homogeneous benchmarks and heterogeneous benchmarks. The computational sensitivity is discussed. The results show good accuracy in all tests. With the CMFD acceleration, the convergence is stable. In addition, a pin-cell problem with void gap is calculated. This shows the advantage compared to the traditional 2D/1D MOC methods.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

DOE OSTI2025

Experimental investigation of air-fuel equivalence ratio effects on advanced dual-fuel ammonia/diesel combustion on a single-cylinder medium-duty diesel engine at high load

Ammonia (NH 3 ) has garnered significant interest as an alternative fuel for meeting international emissions reduction mandates in sectors with high weight and distance requirements, such as shipping. Technical barriers and unanswered questions remain on the combustion strategies that can maximize ammonia utilization and minimize emissions. Prior research studies at the US Department of Energy’s Oak Ridge National Laboratory have shown strong performance with NH 3 under dual-fuel mode using conventional diesel combustion (CDC) manifold air pressure settings. Diesel airflow was initially used to simplify retrofitting (no turbocharger modification), which resulted in air-fuel equivalence ratios (λ) greater than 1.5. To characterize potential improvements in dual-fuel NH 3 combustion performance at richer in-cylinder conditions, a global λ sweep compared the use of early (E-pilot) and late (L-pilot) single diesel injections. The experiments were conducted at 1200 RPM and 12.8 ± 0.2 bar (75 % load), and λ was varied by decreasing the commanded air flow to the engine at greater than 90 % ammonia energy substitution level. A diesel injection timing sweep was conducted for both the injection strategies at fixed λ, and the timing with the lowest engine-out N 2 O emissions was identified. The results indicated an optimal balance between CO 2,eq and thermal efficiency benefits both E-pilot and l-pilot injection strategy cases compared with CDC at a λ of 1.4. In conclusion, the indicated nitrogen-based emissions exhibited a strong correlation to the ratio of CA5–50 and ignition delay for l-pilot, but no apparent trend emerged for the E-pilot injection strategy at the tested boundary conditions.

Ammonia↗

DOE OSTI2017

Infrared Photometric Properties of 709 Candidate Stellar Bowshock Nebulae

Arcuate infrared nebulae are ubiquitous throughout the Galactic Plane and are candidates for partial shells, bubbles, or bowshocks produced by massive runaway stars. We tabulate infrared photometry for 709 such objects using images from the Spitzer Space Telescope, the Wide-field Infrared Explorer, and the Herschel Space Observatory (HSO). Of the 709 objects identified at 24 or 22 μm, 422 are detected at the HSO 70 μm bandpass. Of these, only 39 are detected at HSO 160 μm. The 70 μm peak surface brightnesses are 0.5–2.5 Jy arcmin{sup −2}. Color temperatures calculated from the 24 to 70 μm ratios range from 80 to 400 K. Color temperatures from 70 to 160 μm ratios are systematically lower, 40–200 K. Both of these temperature are, on average, 75% higher than the nominal temperatures derived by assuming that dust is in steady-state radiative equilibrium. This may be evidence of stellar wind bowshocks sweeping up and heating—possibly fragmenting but not destroying—interstellar dust. Infrared luminosity correlates with standoff distance, R {sub 0}, as predicted by published hydrodynamical models. Infrared spectral energy distributions are consistent with interstellar dust exposed to either single radiant energy density, U=10{sup 3}--10{sup 5} (in more than half of the objects) or a range of radiant energy densities U {sub min} = 25 to U {sub max} = 10{sup 3}–10{sup 5} times the mean interstellar value for the remainder. Hence, the central OB stars dominate the energetics, making these enticing laboratories for testing dust models in constrained radiation environments. The spectral energy densities are consistent with polycyclic aromatic hydrocarbon fractions q{sub PAH}≲1% in most objects.

79 ASTRONOMY AND ASTROPHYSICS↗

NASA NTRS1973

Misalignment studies on space shuttle integrated vehicle (IA31FC)

The effects of test model element misalignments on test results were investigated. Transonic wind tunnel-573 was designed to study these misalignment effects in detail by purposely misaligning model elements a known amount. Misalignments in TWT-573 were achieved by use of special off-set spacers and mounting hardware to change, yaw, pitch and roll on various elements of a 0.004-Scale PRR Baseline space shuttle configuration model. By comparing the misalignment runs to the nominal configuration with no misalignment, relative effects of the misalignment could be seen. This data was obtained over a Mach range of .9 to 1.46 using an angle of attack sweep of minus 10 deg to plus 10 deg in 2 deg increments.

Ramsey, P.↗

NASA NTRS2006

Flight Acoustic Testing and For the Rotorcraft Noise Data Acquisition Model (RNM)

Two acoustic flight tests have been conducted on a remote test range at Eglin Air Force Base in the panhandle of Florida. The first was the "Acoustics Week" flight test conducted in September 2003. The second was the NASA Heavy Lift Rotorcraft Acoustics Flight Test conducted in October-November 2005. Benchmark acoustic databases were obtained for a number of rotorcraft and limited fixed wing vehicles for a variety of flight conditions. The databases are important for validation of acoustic prediction programs such as the Rotorcraft Noise Model (RNM), as well as for the development of low noise flight procedures and for environmental impact assessments. An overview of RNM capabilities and a detailed description of the RNM/ART (Acoustic Repropagation Technique) process are presented. The RNM/ART process is demonstrated using measured acoustic data for the MD600N. The RNM predictions for a level flyover speed sweep show the highest SEL noise levels on the flight track centerline occurred at the slowest vehicle speeds. At these slower speeds, broadband noise content is elevated compared to noise levels obtained at the higher speeds. A descent angle sweep shows that, in general, ground noise levels increased with increasing descent rates. Vehicle orientation in addition to vehicle position was found to significantly affect the RNM/ART creation of source noise semi-spheres for vehicles with highly directional noise characteristics and only mildly affect those with weak acoustic directionality. Based on these findings, modifications are proposed for RNM/ART to more accurately define vehicle and rotor orientation.

Burley, Casey L.↗

NASA NTRS2006

Flight Acoustic Testing and Data Acquisition For the Rotor Noise Model (RNM)

Two acoustic flight tests have been conducted on a remote test range at Eglin Air Force Base in the panhandle of Florida. The first was the Acoustics Week flight test conducted in September 2003. The second was the NASA Heavy Lift Rotorcraft Acoustics Flight Test conducted in October-November 2005. Benchmark acoustic databases were obtained for a number of rotorcraft and limited fixed wing vehicles for a variety of flight conditions. The databases are important for validation of acoustic prediction programs such as the Rotorcraft Noise Model (RNM), as well as for the development of low noise flight procedures and for environmental impact assessments. An overview of RNM capabilities and a detailed description of the RNM/ART (Acoustic Repropagation Technique) process are presented. The RNM/ART process is demonstrated using measured acoustic data for the MD600N. The RNM predictions for a level flyover speed sweep show the highest SEL noise levels on the flight track centerline occurred at the slowest vehicle speeds. At these slower speeds, broadband noise content is elevated compared to noise levels obtained at the higher speeds. A descent angle sweep shows that, in general, ground noise levels increased with increasing descent rates. Vehicle orientation in addition to vehicle position was found to significantly affect the RNM/ART creation of source noise semi-spheres for vehicles with highly directional noise characteristics and only mildly affect those with weak acoustic directionality. Based on these findings, modifications are proposed for RNM/ART to more accurately define vehicle and rotor orientation.

Conner, David A.↗

NASA NTRS1988

Sensitivity of F-106B Leading-Edge-Vortex Images to Flight and Vapor-Screen Parameters

A flight test was undertaken at NASA Langley Research Center with vapor-screen and image-enhancement techniques to obtain qualitative and quantitative information about near-field vortex flows above the wings of fighter aircraft. In particular, the effects of Reynolds and Mach numbers on the vortex system over an angle-of-attack range were sought. The relevance of these flows stems from their present and future use at many points in the flight envelope, especially during transonic maneuvers. The aircraft used in this flight program was the F-106B because it was available and had sufficient wing sweep (60 deg) to generate a significant leading-edge vortex system. The sensitivity of the visual results to vapor screen hardware and to onset flow changes is discussed.

Lamar, John E.↗

DOE OSTI2020

Bench-Scale Development of a Hybrid Membrane-Absorption CO 2 Capture Process

This final technical report describes work conducted for the Department of Energy (DOE) on the development of a bench-scale hybrid membrane-absorption carbon dioxide (CO 2 ) capture system for coal-fired power plant applications (Cooperative Agreement number DE-FE0013118). The work was conducted by Membrane Technology and Research, Inc. (MTR) with major support from the University of Texas at Austin (UT Austin) from April 1, 2013 through September 30, 2018. The overall goal of this project was to evaluate two variations of a hybrid membrane-absorption capture system combining the MTR air-swept Polaris TM membrane technology, which enriches flue gas to ~20% CO 2 , with UT Austin’s absorption-based advanced flash stripper (AFS) using piperazine (PZ), to determine the superior hybrid variant and to assess the potential of hybrid capture systems to achieve a lower cost-of-capture, compared to NETL’s reference amine-based capture plant. This project included the evaluation, development and testing of a hybrid membrane-absorption CO 2 capture system for coal-fired power plant applications using the MTR high-gas-flow, lowpressure- drop membrane contactor. The ability of the membrane contactor to enrich coal-fired flue gas from its normal content of ~13% CO 2 into a smaller volume of gas containing 20-25% CO 2 – with minimal energy input – could reduce the cost of the final concentration process, regardless of whether it is absorption, adsorption, cryogenic, or membrane-based. In this project, we are evaluating the feasibility of a hybrid system combining the MTR sweep membrane technology with the UT Austin piperazine-based advanced flash stripper (PZAS) capture system.

99 GENERAL AND MISCELLANEOUS↗