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Tomographic time-resolved laser-induced incandescence

AIAA Scitech 2020 Forum

Munz, Elise D.; Halls, Benjamin R.; Richardson, Daniel R.; Guildenbecher, Daniel R.; Cenker, Emre; Paciaroni, Megan E.

Three ultra-high-speed, 10 MHz, cameras imaged the time-resolved decay of laser-induced incandescence (LII) from soot in a turbulent non-premixed ethylene jet flame. Cameras were equipped with a stereoscope allowing each CMOS array to capture two separate views of the flame. The resulting six views were reconstructed into a volumetric soot decay series using commercially available DaVis tomographic software by LaVision. Primary soot particle sizes were estimated from the decay time history on a per voxel basis by comparing measured signals to an LII model. Experimentally quantified soot particle sizes agree with existing predictions and previous measurements.

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TYPE Conference Poster YEAR 2020
OSTIScopus

Spatially-resolved surface temperature measurements of a rocket motor nozzle using an acousto-optic modulator

AIAA Scitech 2020 Forum

Mazumdar, Yi C.; Wagner, Justin L.; Frederick, Donald J.; Guildenbecher, Daniel R.; Hendricks, Terry L.

Solid rocket motors operate at high temperatures that can potentially damage engineering materials used for motor nozzles or thrust vanes. In this work, surface temperature measurements were collected on solid rocket motor components of varying materials exposed to the combustion of ammonium perchlorate-based solid propellants. Spatially-resolved temperatures were measured using a novel two-color pyrometer built from an acousto-optic tunable filter (AOTF) coupled to a near IR camera. Temperatures were then verified using a single-point visible spectrometers. Experiments conducted in low pressure conditions inside a high altitude chamber at Sandia National Laboratories illustrate the temporal and spatial evolution of temperature gradients across the nozzle and vanes.

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TYPE Conference Poster YEAR 2020
DOIOSTIScopus

Multilevel uncertainty quantification using cfd and openfast simulations of the swift facility

AIAA Scitech 2020 Forum

Laros, James H.; Maniaci, David C.; Herges, Thomas H.; Geraci, Gianluca G.; Seidl, Daniel T.; Eldred, Michael S.; Blaylock, Myra L.; Houchens, Brent C.

Uncertainty is present in all wind energy problems of interest, but quantifying its impact for wind energy research, design and analysis applications often requires the collection of large ensembles of numerical simulations. These predictions require a range of model fidelity as predictive models, that include the interaction of atmospheric and wind turbine wake physics, can require weeks or months to solve on institutional high-performance computing systems. The need for these extremely expensive numerical simulations extends the computational resource requirements usually associated with uncertainty quantification analysis. To alleviate the computational burden, we propose here to adopt several Multilevel-Multifidelity sampling strategies that we compare for a realistic test case. A demonstration study was completed using simulations of a V27 turbine at Sandia National Laboratories’ SWiFT facility in a neutral atmospheric boundary layer. The flow was simulated with three models of disparate fidelity. OpenFAST with TurbSim was used stand-alone as the most computationally-efficient, lower-fidelity model. The computational fluid dynamics code Nalu-Wind was used for large eddy simulations with both medium-fidelity actuator disk and high-fidelity actuator line models, with various mesh resolutions. In an uncertainty quantification study, we considered five different turbine properties as random parameters: yaw offset, generator torque constant, collective blade pitch, gearbox efficiency and blade mass. For all quantities of interest, the Multilevel-Multifidelity estimators demonstrated greater efficiency compared to standard and multilevel Monte Carlo estimators.

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TYPE Conference Poster YEAR 2020
DOIOSTIScopus

A cfd validation challenge for transonic, shock-induced separated flow: Experimental characterization

AIAA Scitech 2020 Forum

Lynch, Kyle P.; Lance, Blake L.; Lee, Gyu S.; Naughton, Jonathan W.; Miller, Nathan M.; Barone, Matthew F.; Beresh, Steven J.; Spillers, Russell W.; Soehnel, Melissa M.

An experimental characterization of the flow environment for the Sandia Axisymmetric Transonic Hump is presented. This is an axisymmetric model with a circular hump tested at a transonic Mach number, similar to the classic Bachalo-Johnson configuration. The flow is turbulent approaching the hump and becomes locally supersonic at the apex. This leads to a shock-wave/boundary-layer interaction, an unsteady separation bubble, and flow reattachment downstream. The characterization focuses on the quantities required to set proper boundary conditions for computational efforts described in the companion paper, including: 1) stagnation and test section pressure and temperature; 2) turbulence intensity; and 3) tunnel wall boundary layer profiles. Model characterization upstream of the hump includes: 1) surface shear stress; and 2) boundary layer profiles. Note: Numerical values characterizing the experiment have been redacted from this version of the paper. Model geometry and boundary conditions will be withheld until the official start of the Validation Challenge, at which time a revised version of this paper will become available. Data surrounding the hump are considered final results and will be withheld until completion of the Validation Challenge.

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TYPE Conference Poster YEAR 2020
DOIOSTIScopus

Ensemble grammar induction for detecting anomalies in time series

Advances in Database Technology - EDBT

Gao, Yifeng; Lin, Jessica; Brif, Constantin B.

Time series anomaly detection is an important task, with applications in a broad variety of domains. Many approaches have been proposed in recent years, but often they require that the length of the anomalies be known in advance and provided as an input parameter. This limits the practicality of the algorithms, as such information is often unknown in advance, or anomalies with different lengths might co-exist in the data. To address this limitation, previously, a linear time anomaly detection algorithm based on grammar induction has been proposed. While the algorithm can find variable-length patterns, it still requires preselecting values for at least two parameters at the discretization step. How to choose these parameter values properly is still an open problem. In this paper, we introduce a grammar-induction-based anomaly detection method utilizing ensemble learning. Instead of using a particular choice of parameter values for anomaly detection, the method generates the final result based on a set of results obtained using different parameter values. We demonstrate that the proposed ensemble approach can outperform existing grammar-induction-based approaches with different criteria for selection of parameter values. We also show that the proposed approach can achieve performance similar to that of the state-of-the-art distance-based anomaly detection algorithm.

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TYPE Conference Poster YEAR 2020
OSTIScopus

Initial simulations of empty room collapse and reconsolidation at the waste isolation pilot plant

54th U.S. Rock Mechanics/Geomechanics Symposium

Reedlunn, Benjamin R.; Moutsanidis, Georgios; Baek, Jonghyuk; Huang, Tsung H.; Koester, Jacob K.; He, Xiaolong; Taneja, Karan; Wei, Haoyan; Bazilevs, Yuri; Chen, Jiun S.

Room ceilings and walls at the Waste Isolation Pilot Plant tend to collapse over time, causing rubble piles on floors of empty rooms. The surrounding rock formation will gradually compact these rubble piles until they eventually become solid salt, but the length of time for a rubble pile to reach a certain porosity and permeability is unknown. This paper details the initial model development to predict the porosity and fluid flow network of a closing empty room. Conventional geomechanical numerical methods would struggle to model empty room collapse and rubble pile consolidation, so three different meshless methods, the Immersed Isogeometric Analysis (IGA) Meshfree Method, Reproducing Kernel Particle Method (RKPM), and Conformal Reproducing Kernel (CRK) method, were assessed. First, each meshless method simulated gradual room closure, without ceiling or wall collapse. All methods produced equivalent predictions to a finite element method reference solution, with comparable computational speed. Second, the Immersed IGA Meshfree method and RKPM simulated two-dimensional empty room collapse and rubble pile consolidation. Both methods successfully simulated large viscoplastic deformations, fracture, and rubble pile rearrangement to produce qualitatively realistic results. Finally, the meshless simulation results helped identify a mechanism for empty room closure that had been previously overlooked.

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TYPE Conference Poster YEAR 2020
OSTIScopus

Full function sampling of uncertain correlations

ASME 2020 Verification and Validation Symposium, VVS 2020

Irick, Kevin W.; Engerer, Jeff; Lance, Blake; Roberts, Scott A.; Schroeder, Ben

Empirically-based correlations are commonly used in modeling and simulation but rarely have rigorous uncertainty quantification that captures the nature of the underlying data. In many applications, a mathematical description for a parameter response to some input stimulus is often either unknown, unable to be measured, or both. Likewise, the data used to observe a parameter response is often noisy, and correlations are derived to approximate the bulk response. Practitioners frequently treat the chosen correlation-sometimes referred to as the "surrogate"or "reduced-order"model of the response-as a constant mathematical description of the relationship between input and output. This assumption, as with any model, is incorrect to some degree, and the uncertainty in the correlation can potentially have significant impacts on system responses. Thus, proper treatment of correlation uncertainty is necessary. In this paper, a method is proposed for high-level abstract sampling of uncertain data correlations. Whereas uncertainty characterization is often assigned to scalar values for direct sampling, functional uncertainty is not always straightforward. A systematic approach for sampling univariable uncertain correlations was developed to perform more rigorous uncertainty analyses and more reliably sample the correlation space. This procedure implements pseudo-random sampling of a correlation with a bounded input range to maintain the correlation form, to respect variable uncertainty across the range, and to ensure function continuity with respect to the input variable.

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TYPE Conference Poster YEAR 2020
OSTIScopus

Six Degrees of Freedom (6DOF) Simulations of Supersonic Fragment Trajectories

Yeh, Peter D.

In this report a process using existing technologies at Sandia National Laboratories (SNL) to simulate the six degrees-of-freedom (6DOF) trajectories of explosive fragments is described and tested. First, aerodynamic forces and moments as functions of orientation are computed using the SIERRA/Aero supersonic flow solver. The forces and moments are normalized and tabulated in a database. Second, this the aerodynamic coefficient database is imported into a 6DOF rigid body dynamics solver in order to compute the resulting trajectories. The supersonic flow simulations are tested for simple geometries and show good agreement with literature values. The simulation procedure is then demonstrated for an example fragment. The results of the example fragment indicate that the distance traveled in the early ight (from 2.5 km/s until decreasing down to 1 km/s) varies widely depending on the initial orientations. The fragment trajectory distribution and steady tumbling rate is explored. The study indicates that a 6DOF analysis will yield information about a spread of possible trajectories, while using an average drag coefficient can only represent the most likely trajectory.

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TYPE SAND Report YEAR 2020
DOIOSTI

Light Water Reactor Sustainability Program: September 2019 Physical Security Stakeholder Working Group Meeting

Osborn, Douglas M.; Lord, Jodie L.; Werner, Hannah J.

The LWRS Program Physical Security Pathway held the first meeting of the Physical Security Stakeholder working group on September 10-12, 2019 at Sandia National Laboratories. This working group is comprised of nuclear enterprise physical security stakeholders and the meeting included over 10 Utilities representing roughly 60 nuclear power plants, two staff from the Nuclear Regulatory Commission, physical security vendors, the Nuclear Energy Institute, the Electric Power Research Institute, and staff from Sandia National Laboratories and Idaho National Laboratory. The working group was established with the objectives of providing stakeholder feedback to the LWRS Program on their research and development needs and priorities, socializing the progress of Physical Security Pathway initiatives, and identifying opportunities for additional engagement and participation of stakeholders in the pathway research activities. The working group also provided a forum for physical security professionals to share common experiences and recommend prioritized activities based on their common needs.

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TYPE SAND Report YEAR 2020
DOIOSTI

Tritium Pressure Enhancement on the TPBAR Cladding by Physical Processes at the Getter

Cowgill, D.F.

Tritium for the U.S. nuclear weapon stockpile is produced in tritium producing burnable absorber rods (TPBARs) inserted into Tennessee Valley Authoritys (TVA) light-water nuclear reactors. The rods are stainless steel tubes with a permeation barrier coating and internal components that generate and contain the tritium. The TPBAR incorporates a Ni-plated Zircoloy getter tube to capture tritium and prevent it from reaching the rod cladding and permeating into the environment. Under the conventional view of getter behavior, the tritium pressure outside the getter tube is expected to be limited to the equilibrium vapor pressure of Zr hydride at the temperature of the rod as long as the total hydrogen concentration remains below the capacity of the hydride. Since the tritium pressure is higher within the rod core, this behavior relies on the thin getters ability to hold off a differential tritium pressure. The effective tritium pressure on the cladding can also be enhanced by isotope exchange. Hydrogen ingress through the cladding from the reactor coolant creates a hydrogen pressure on the outer surface of the getter that can exchange with tritium, allowing the tritium partial pressure to increase toward this hydrogen gettering pressure. The goal of this work was to use laboratory-scale experiments to examine these mechanisms and create a model of getter behavior that describes tritium transport within the TPBAR. A third mechanism wherein the concentration at the outer surface of the getter is increased by the temperature gradient within the getter tube wall (the Soret effect) is not experimentally tested but is captured in the model. While not conclusively demonstrated by the experiments due to low pressure, high temperature, and small gap volume conditions, the model shows that when combined, the three mechanisms can explain both the magnitude and time dependence of the tritium release observed for reactor fuel assemblies with TPBARs. The model also shows how various modifications of the TPBAR design can reduce this tritium release into the environment.

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TYPE SAND Report YEAR 2020
DOIOSTI

Infrared absorption spectroscopy of dynamically compressed water

Proceedings of SPIE - The International Society for Optical Engineering

Ramsey, Darrell; Mance, Jason; La Lone, Brandon; Dolan, Dan

Streaked visible spectroscopy is well established in dynamic compression research. Infrared measurements remain problematic, however, due to the diminishing sensitivity of streak camera photocathodes beyond 800 nm. Time-stretch techniques offer an alternative method for probing infrared features during single-event experiments. This paper discusses the development of a time-stretch spectroscopy diagnostic using dispersed supercontinuum laser pulses. The technique is applied to near-infrared measurements of liquid water during multiple shock compression.

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TYPE Conference Poster YEAR 2020
DOIOSTIScopus

Process variation model and analysis for domain wall-magnetic tunnel junction logic

Proceedings - IEEE International Symposium on Circuits and Systems

Hu, Xuan; Edwards, Alexander J.; Xiao, Tianyao X.; Bennett, Christopher H.; Incorvia, Jean A.C.; Marinella, Matthew J.; Friedman, Joseph S.

The domain wall-magnetic tunnel junction (DW-MTJ) is a spintronic device that enables efficient logic circuit design because of its low energy consumption, small size, and non-volatility. Furthermore, the DW-MTJ is one of the few spintronic devices for which a direct cascading mechanism is experimentally demonstrated without any extra buffers; this enables potential design and fabrication of a large-scale DW-MTJ logic system. However, DW-MTJ logic relies on the conversion between electrical signals and magnetic states which is sensitive to process imperfection. Therefore, it is important to analyze the robustness of such DW-MTJ devices to anticipate the system reliability before fabrication. Here we propose a new DW-MTJ model that integrates the impacts of process variation to enable the analysis and optimization of DW-MTJ logic. This will allow circuit and device design that enhances the robustness of DW-MTJ logic and advances the development of energy-efficient spintronic computing systems.

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TYPE Conference Poster YEAR 2020
DOIOSTIScopus

The emergence of small-scale self-affine surface roughness from deformation

Science Advances

Hinkle, Adam H.; Author, No; Wolfram, Leute R.; Junge, Till; Pastewka, Lars

Most natural and man-made surfaces appear to be rough on many length scales. There is presently no unifying theory of the origin of roughness or the self-affine nature of surface topography. One likely contributor to the formation of roughness is deformation, which underlies many processes that shape surfaces such as machining, fracture, and wear. Using molecular dynamics, we simulate the biaxial compression of single-crystal Au, the high-entropy alloy Ni36.67Co30Fe16.67Ti16.67, and amorphous Cu50Zr50 and show that even surfaces of homogeneous materials develop a self-affine structure. By characterizing subsurface deformation, we connect the self-affinity of the surface to the spatial correlation of deformation events occurring within the bulk and present scaling relations for the evolution of roughness with strain. These results open routes toward interpreting and engineering roughness profiles.

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TYPE Journal Article YEAR 2020
DOIOSTIScopus
Results 17201–17400 of 96,771
Results 17201–17400 of 96,771