Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “computer experiment”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 865 records · Page 48
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Computational study of inertial migration of prolate particles in a straight rectangular channel

Inertial migration of spherical particles has been investigated extensively using experiments, theory, and computational modeling. Yet, a systematic investigation of the effect of particle shape on inertial migration is still lacking. Herein, we numerically mapped the migration dynamics of a prolate particle in a straight rectangular microchannel using smoothed particle hydrodynamics at moderate Reynolds number flows. After validation, we applied our model to 2:1 and 3:1 shape aspect ratio particles at multiple confinement ratios. Their effects on the final focusing position, rotational behavior, and transitional dynamics were studied. In addition to the commonly reported tumbling motion, for the first time, we identified a new logrolling behavior of a prolate ellipsoidal particle in the confined channel. This new behavior occurs when the confinement ratio is above an approximate threshold value of K = 0.72. Our microfluidic experiments using cell aggregates with similar shape aspect ratio and confinement ratio confirmed this new predicted logrolling motion. In this study, we also found that the same particle can undergo different rotational modes, including kayaking behavior, depending on its initial cross-sectional position and orientation. Furthermore, we examined the migration speed, angular velocity, and rotation period as well as their dependence on both particle shape aspect ratio and confinement ratio. Our findings are especially relevant to the applications where particle shape and alignment are used for sorting and analysis, such as the use of barcoded particles for biochemical assays through optical reading, or the shape-based enrichment of microalgae, bacteria, and chromosomes.

42 ENGINEERING↗
NASA NTRS2001

Flight Computer Processing Avionics for Space Station Microgravity Experiments: A Risk Assessment of Commercial Off-the-Shelf Utilization

NASA/Marshall Space Flight Center (MSFC) is continually looking for ways to reduce the costs and schedule and minimize the technical risks during the development of microgravity programs. One of the more prominent ways to minimize the cost and schedule is to use off-the-shelf hardware (OTS). However, the use of OTS often increases the risk. This paper addresses relevant factors considered during the selection and utilization of commercial off-the-shelf (COTS) flight computer processing equipment for the control of space station microgravity experiments. The paper will also discuss how to minimize the technical risks when using COTS processing hardware. Two microgravity experiments for which the COTS processing equipment is being evaluated for are the Equiaxed Dendritic Solidification Experiment (EDSE) and the Self-diffusion in Liquid Elements (SDLE) experiment. Since MSFC is the lead center for Microgravity research, EDSE and SDLE processor selection will be closely watched by other experiments that are being designed to meet payload carrier requirements. This includes the payload carriers planned for the International Space Station (ISS). The purpose of EDSE is to continue to investigate microstructural evolution of, and thermal interactions between multiple dendrites growing under diffusion controlled conditions. The purpose of SDLE is to determine accurate self-diffusivity data as a function of temperature for liquid elements selected as representative of class-like structures. In 1999 MSFC initiated a Center Director's Discretionary Fund (CDDF) effort to investigate and determine the optimal commercial data bus architecture that could lead to faster, better, and lower cost data acquisition systems for the control of microgravity experiments. As part of this effort various commercial data acquisition systems were acquired and evaluated. This included equipment with various form factors, (3U, 6U, others) and equipment that utilized various bus structures, (VME, PC104, STD bus). This evaluation of hardware was performed in conjunction with a trade study that considered over twenty (20) different factors relevant to the selection of an optimum design approach. These factors included; safety, sizing and timing, radiation hardness and single event upset, power consumption, heat dissipation, size and volume, expected service life, maintainability, heritage, operating systems, requirements for software reuse, availability of compatible interface boards, relative cost, schedule, reliability, EMI/EMC factors, "hot swap" capability, standards for conduction cooling, I/O capabilities, unique carrier requirements and operating system considerations. The approach to evaluate Safety as part of this study included a review of the Preliminary Hazard Analysis (PHA) for each of the experiment designs and a determination of how each hazard could be addressed and eliminated when different processors were selected. This included evaluating various design approaches and trade-offs between fault tolerant designs and fail-safe designs in accordance with NSTS 1700.7B. This will include the results of radiation testing where available. Various operating systems, such as VxWorks, Linux, QNX, and Embedded NT are evaluated and the advantages and disadvantages of their utilization are also addressed. Design implementation strategies for the various operating systems are considered and discussed. This paper presents the results and recommendations from this trade study. Preliminary conclusions from this study are that safety concerns from lack or radiation testing on COTS equipment can be addressed by additional testing and design considerations, the PC104 bus provided adequate I/O for the SDLE and EDSE microgravity experiments, and PC104 bus components offered significant advantages over VME and cPCI for weight and space reductions.

Estes, Howard↗
NASA NTRS1984

Investigations of flowfields found in typical combustor geometries

Studies are concerned with experimental and theoretical research on 2-D axisymmetric geometries under low speed, nonreacting, turbulent, swirling flow conditions. The flow enters the test section and proceeds into a larger chamber (the linear expansion ratio D/d = 2, 1.5 and 1) via a sudden or gradual expansion (side wall angle alpha = 90 and 45 degrees). A weak or strong nozzle (of area ratio A/a = 2 and 4) may be positioned downstream at x/D = 2 to form a contraction exit to the test section. Inlet swirl vanes are adjustable to a variety of vane angles with values of theta = 0, 38, 45, 60 and 70 degrees being emphasized. The objective is to determine the effect of these parameters on isothermal flow field patterns, time mean velocities and turbulence quantities, and to establish an improved simulation in the form of a computer prediction code equipped with a suitable turbulence model. The goal of the on going research is to perform experiments and complementary computations with the idea of doing the necessary type of research that will yield improved calculation capability. This involves performing experiments where time mean turbulence quantities are measured and taking input conditions and running an existing prediction code for a variety of test cases so as to compare predictions against experiment.

Lilley, D. G.↗
NASA NTRS2016

The Low-Lying Electronic States of MgO

The low-lying singlet and triplet states of MgO have been studied using a SA-CASCF/ICMRCI approach using the aug-cc-pV5Z basis set. The spectroscopic constants (r(sub e), W(sub e), and T(sub e)) are in good agreement with the available experimental data. The computed lifetime for the B state is in excellent agreement with two of the three experimental results. The d state lifetime is in good agreement with experiment, while the computed D state lifetime is about twice as long as experiment.

Charles W Bauschlicher↗
NASA NTRS1979

Computation of supersonic viscous flows over ogive-cylinders at angle of attack

The parabolic Navier-Stokes (PNS) marching finite-difference method is applied to 3-D viscous flow over pointed ogive-cylinders, and to turbulent flow over a cone. Ogive computations were performed using the new technique recently reported by Vigneron, Rakich, and Tannehill. Comparison is made with experiment and inviscid computations. The present results show that this method, which neglects part of the pressure gradient in the x-momentum equation, is nevertheless valid for flows with a strong favorable pressure gradient. In addition, turbulent separated flow over a cone has been computed using the older PNS code due to Lubard and Helliwell. It is found that one must freeze the turbulent eddy-viscosity model upstream of 3-D separation to get agreement with experiment.

Rakich, J. V.↗
NASA NTRS1985

Overset grids in compressible flow

Numerical experiments have been performed to investigate the importance of boundary data handling with overset grids in computational fluid dynamics. Experience in using embedded grid techniques in compressible flow has shown that shock waves which cross grid boundaries become ill defined and convergence is generally degraded. Numerical boundary schemes were studied to investigate the cause of these problems and a viable solution was generated using the method of characteristics to define a boundary scheme. The model test problem investigated consisted of a detached shock wave on a 2-dimensional Mach 2 blunt, cylindrical body.

Eberhardt, S.↗
DOE OSTI2023

Reactivity Coefficient Measurements to Aid in Reducing Compensating Errors in Plutonium Nuclear Data

Compensating errors between several nuclear data observables in a nuclear data library can adversely impact application simulations. The primary goal of the EUCLID project (Experiments Underpinned by Computational Learning for Improvements in Nuclear Data) is to reduce compensating errors between fast (0.1–5 MeV) 239Pu nuclear data for prompt fission neutron spectra (PFNS), average prompt fission neutron multiplicities, and neutron induced fission, capture, elastic, and inelastic cross sections. This work will focus on the design and execution of void reactivity coefficient measurements in the EUCLID experiment, performed on the Planet vertical lift critical assembly machine at the National Criticality Experiments Research Center (NCERC). Two different base configurations were designed and measured, one with high neutron leakage, and one with low neutron leakage. Both were primarily made up of plutonium metal (Zero Power Physics Reactor plates) without interstitial moderators and reflected by half-inch aluminum. Design optimization showed that void reactivity coefficient measurements in three locations per configuration was most impactful to reduce nuclear data uncertainties due to the varying impacts from elastic and inelastic scattering, as well as fission and capture. The locations for measurements were chosen based on preliminary studies which balanced measurement uncertainty and measurement practicality. The measurements were also selected to have sensitivities maximally complementary to previous arrangements. Comparisons across nuclear data libraries highlight the potential impact.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
NASA NTRS1980

Advanced control techniques for teleoperation in earth orbit

Emerging teleoperation tasks in space invite advancements in teleoperator control technology. This paper briefly summarizes the generic issues related to earth orbital applications of teleoperators, and describes teleoperator control technology development work including visual and non-visual sensors and displays, kinesthetic feedback and computer-aided controls. Performance experiments were carried out using sensor and computer aided controls with promising results which are briefly summarized.

Bejczy, A. K.↗
NASA NTRS1981

Sound propagation through a variable area duct - Experiment and theory

A comparison of experiment and theory has been made for the propagation of sound through a variable area axisymmetric duct with zero mean flow. Measurement of the acoustic pressure field on both sides of the constricted test section was resolved on a modal basis for various spinning mode sources. Transmitted and reflected modal amplitudes and phase angles were compared with finite element computations. Good agreement between experiment and computation was obtained over a wide range of frequencies and modal transmission variations. The study suggests that modal transmission through a variable area duct is governed by the throat modal cut-off ratio.

Silcox, R. J.↗
DOE OSTI2026

Sensitivity of a closed dielectric haloscope to axion dark matter

We present a method to determine the sensitivity of a closed dielectric haloscope to axiondark matter. Dielectric haloscopes aim to probe the theoretically well-motivated axion mass rangeof ∼ 26 µeV to ∼ 500 µeV by utilizing a stack of dielectric disksand a mirror to enhance the axion-photon conversion within an external magnetic field. Theirconversion volume is nearly axion-mass independent, thereby favoring large-scale designs toincrease sensitivity. The large volume causes simulations to be computationally expensive andtime-consuming. This paper presents a simple model that can be used to determine the sensitivityof the experiment with minimal computational resources. The model is able to describe theelectromagnetic response of a closed dielectric haloscope, accounting for realistic geometricimperfections, as well as the noise introduced by the receiver system. It is applied to datataken with a MAgnetized Disk and Mirror Axion Experiment (MADMAX) prototype within the 1.6 TMorpurgo magnet at CERN. This work underpins the first axion dark matter search using adielectric haloscope and provides the foundation for future dark matter searches with MADMAX.

Ivanov, A. [Munich, Max Planck Inst. Quantenopt.]↗
NASA NTRS1989

Finite element computations and experimental studies of flow past an array of plates

Finite element computations and laboratory experiments were carried out to study the mutual wake interaction behind two plates placed side by side. The computations are based on the vorticity-stream function formation of the two-dimensional incompressible Navier-Stokes equations. The flow visualization studies indicate independent vortex sheddings at large gap sizes and metastable biased flow at smaller gap sizes. The computational results exhibit a similar behavior.

Higuchi, H.↗
NASA NTRSDate not supplied

Computational Fluid Dynamics Simulation of Methane Slosh and Drain Experiments

NASA possesses a wealth of historical cryogenic experiments that provide valuable insights into the design, troubleshooting, and understanding involved in the complex fluid and thermodynamics of managing cryogenic propellants. One approach to leveraging these historical datasets is by simulating these experiments to validate the accuracy of simulation environments and constituent models. This study focused on simulating a selection of the K site test series for both static and sloshing pressurized liquid methane draining experiments conducted at NASA in the 1970’s, utilizing computational fluid dynamics. The simulations were performed in the ANSYS FLUENT environment using the Volume of Fluid (VOF) numerical approach. A k-omega turbulence model was used with interfacial turbulence damping, and accurately predicted the amount of pressurant needed to maintain the required tank pressure throughout the static drain. The static simulation predicted the temperature stratification in the ullage observed at the end of the drain. During the methane expulsion with sloshing test, many features were successfully captured using the k-omega turbulence model with interfacial turbulence damping included. The rate of phase change and liquid temperature was overpredicted compared to the experimental measurements. The overprediction may be attributed to uncertainties in the vessel geometry, methane pressurant temperature and composition, and methodological differences in how the sloshing frequency was adjusted during the expulsion.

Cryogenic Propellants↗
DOE OSTI2023

Criticality Experiments to Reduce Compensating Errors in Plutonium Nuclear Data

Compensating errors between nuclear data observables in a library can adversely impact application simulations. The primary goal of the EUCLID project (Experiments Underpinned by Computational Learning for Improvements in Nuclear Data) is to reduce compensating errors in nuclear data. A new criticality experiment, described in this work, was designed with the specific target nuclear data of 239 Pu fission, inelastic scattering, elastic scattering, capture, nu-bar, and prompt fission neutron spectrum (PFNS). This work will focus on the design and execution of the EUCLID experiment, performed on the Planet vertical lift critical assembly machine at the National Criticality Experiments Research Center (NCERC). The criticality experiment includes two different configurations with very different geometries: one is cube-like to minimize neutron leakage while the other is slab-like to maximize leakage. Having these two widely varying configurations allows the scattering sensitivities of 239 Pu to the neutron multiplication factor to be greatly changed while minimally impacting the other cross section sensitivities. Both configurations utilize the Pu ZPPR (Zero Power Physics Reactor) plates as fuel. The experiments were designed using a D-Optimality criteria, which is an optimization method minimizing the log-determinant of the adjusted nuclear data covariance for the target reactions. These experiments include not only inference of k eff , as done in all critical benchmark experiments, but several other responses as well, such as neutron multiplication measurements and reaction rate ratios. After analysis of the measured data is complete, adjustment of nuclear data will be performed to assess whether the new experimental data successfully reduced compensating errors.

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗
DOE OSTI2025

Exploring transport-enabled gates with integrated optical addressing to demonstrate high fidelity control of trapped ion qubits in a scalable quantum computer

In recent years, experiments involving micofabricated surface ion traps have grown in complexity, and as this complexity grows, a common design has emerged in the form of quantum charge-coupled device architecture. This architecture, already utilized on multiple systems, supports multiple zones on a device for areas such as memory or computation. The shutting process between these zones is a process often seen to be minimized. An additional component to scalable surface trapped-ion experiments includes some form of integrated photonics, as free space lasers have difficulty scaling to many ions. Here, we discuss recent results in utilizing the shuttling process with integrated photonics to perform a specific type of gate, as well as demonstrating state preparation. Furthermore, we show that these gates can be utilized as a type of optical modulator as the Doppler shift that occurs during shuttling will make the light seen by shuttled ions different than that seen by stationary ions. Furthermore, we show that the shuttling operation can be utilized as an optical modulator, where the Doppler shift changes the frequency from that of a stationary ion.

42 ENGINEERING↗
NASA NTRS2014

Comparison of the Results of MISSE 6 Atomic Oxygen Erosion Yields of Layered Kapton H Films with Monte Carlo Computational Predictions

A space experiment flown as part of the Materials International Space Station Experiment 6B (MISSE 6B) was designed to compare the atomic oxygen erosion yield (Ey) of layers of Kapton H polyimide with no spacers between layers with that of layers of Kapton H with spacers between layers. The results were compared to a solid Kapton H (DuPont, Wilmington, DE) sample. Monte Carlo computational modeling was performed to optimize atomic oxygen interaction parameter values to match the results of both the MISSE 6B multilayer experiment and the undercut erosion profile from a crack defect in an aluminized Kapton H sample flown on the Long Duration Exposure Facility (LDEF). The Monte Carlo modeling produced credible agreement with space results of increased Ey for all samples with spacers as well as predicting the space-observed enhancement in erosion near the edges of samples due to scattering from the beveled edges of the sample holders.

Oxygen atoms↗
DOE OSTI2023

Computing rank‐revealing factorizations of matrices stored out‐of‐core

This paper describes efficient algorithms for computing rank-revealing factorizations of matrices that are too large to fit in main memory (RAM), and must instead be stored on slow external memory devices such as disks (out-of-core or out-of-memory). Traditional algorithms for computing rank-revealing factorizations (such as the column pivoted QR factorization and the singular value decomposition) are very communication intensive as they require many vector-vector and matrix-vector operations, which become prohibitively expensive when data is not in RAM. Randomization allows to reformulate new methods so that large contiguous blocks of the matrix are processed in bulk. The paper describes two distinct methods. The first is a blocked version of column pivoted Householder QR, organized as a “left-looking” method to minimize the number of the expensive write operations. The second method results employs a UTV factorization. It is organized as an algorithm-by-blocks to overlap computations and I/O operations. As it incorporates power iterations, it is much better at revealing the numerical rank. Numerical experiments on several computers demonstrate that the new algorithms are almost as fast when processing data stored on slow memory devices as traditional algorithms are for data stored in RAM.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2025

Structurally Driven Selective Adsorption of Hydrocarbons by Metal Substitution in Isostructural Rare-Earth Metal–Organic Frameworks

The design and realization of highly selective nanoporous materials are necessary to target critical separations across industries. By leveraging pore size, pore shape, and linker functionalization, the design of nanoporous solid adsorbents will enable the rapid production of energy efficient separation materials for high-value gas mixtures. This study uses a combination of modeling, synthesis, and gas adsorption testing to investigate a new class of small-pore isostructural rare-earth (RE) 2,5-dihydroxyterephthalic acid (DOBDC) metal–organic frameworks (MOFs) (RE: Pr-, Gd-, Er-, Yb; DOBDC = 2,5-dihydroxyterephthalic acid) and their adsorption selectivity for acetylene/ethylene mixtures. Density functional theory simulations identified that selective binding of acetylene over ethylene in the Gd-, Er-, and Yb-DOBDC MOFs was due to hydrogen-bonding between acetylene and the linker hydroxyl. Adsorption experiments validated the computational results by identifying mechanisms that control the acetylene/ethylene adsorption selectivity and high acetylene adsorption. Furthermore, dynamic column breakthrough experiments with the Gd-DOBDC MOF validated the simulations and indicated that ethylene can be separated from acetylene in a mixture containing 1 vol % acetylene and 39 vol % ethylene (balance argon). In conclusion, the results highlight the complexity of gas binding in functional porous materials and how combining modeling and experiment enables a fundamental understanding of gas–framework interactions that can be leveraged for the design of future separation materials.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1988

Computer-Graphical Simulation Of Robotic Welding

Computer program ROBOSIM, developed to simulate operations of robots, applied to preliminary design of robotic arc-welding operation. Limitations on equipment investigated in advance to prevent expensive mistakes. Computer makes drawing of robotic welder and workpiece on positioning table. Such numerical simulation used to perform rapid, safe experiments in computer-aided design or manufacturing.

Fernandez, Ken↗