Evaluation of bubble-induced turbulence using direct numerical simulation
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Feng, Jinyong↗
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Results for “simulation evaluation”
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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Evaluation of Clouds in Version 1 of E3SM Atmosphere Model with Satellite and Simulators
This study systematically evaluates clouds simulated by the Energy Exascale Earth System Model (E3SM) Atmosphere Model version one (EAMv1) against satellite and ground-based cloud observations. Both low (1°) and high (0.25°) resolution EAMv1 configurations generally underestimate clouds in low and midlatitutes and overestimate clouds in the Arctic although the error is smaller in the high-resolution model. The underestimate of clouds is due to the underestimate of optically thin to intermediate clouds. EAMv1 overestimates the optically intermediate to thick clouds. Other model errors include the largely under-predicted stratocumulus along the coasts and high clouds over the tropical deep convection regions. The underestimate of thin clouds results in too much LW radiation being emitted to space and too little SW radiation being reflected back to space while the overestimate of optically intermediate and thick clouds leads to too little LW radiation being emitted to space and too much SW radiation being reflected back to space. EAMv1 shows better skill in reproducing the observed distribution of clouds and their properties and has smaller radiatively relevant errors in the distribution of clouds than most of the CFMIP2 models. It produces more supercooled liquid cloud fraction than CAM5 and most CMIP5 models owing to a new ice nucleation scheme and a reduction of ice deposition growth rate. It simulates the diurnal variation of clouds during the summer season at SGP qualitatively well, with both the evolution of shallow clouds and the nocturnal peak in high clouds well captured, however, it largely overestimates the observed magnitude.
Zhang, Yuying↗
A Real2Sim Digital Twin Pipeline for Photorealistic Robot Simulation: Evaluating VLA Policy Deployment on a Bimanual Mobile Robot
Digital twins that are automatically constructed from robot sensor data offer a promising pathway for scalable Real2Sim and Sim2Real transfer. However, it remains an open question whether photorealistic reconstruction alone is sufficient to support reliable deployment of vision-language-action (VLA) policies. We present a generative-AI-assisted Real2Sim pipeline that generates simulation-ready digital twins from real-world RGB observations with minimal manual intervention. The pipeline uses prompted segmentation to isolate scene components and a generative 3D model to directly produce simulation assets, eliminating the need for traditional multi-view reconstruction or manual 3D modeling.\r\nTo evaluate simulation fidelity, we deploy and compare policies from two VLA models in both the real robot and the reconstructed\r\nsimulation under identical tasks and initial conditions. We compare joint-level action trajectories and analyze how divergence evolves over time in closed-loop execution. Although the reconstructed environments are visually accurate, we observe increasing trajectory divergence during closedloop operation. These results indicate that photorealistic reconstruction alone is insufficient to preserve closed-loop control behavior\r\nin VLA policies, particularly in contact-rich manipulation settings where small perceptual errors compound over time.
97 MATHEMATICS AND COMPUTING↗
Simulation evaluation of NIST air-kerma rate calibration standard for electronic brachytherapy: Simulation of NIST air-kerma rate eBT calibration standard
Purpose: Dosimetry for the model S700 50 kV electronic brachytherapy (eBT) source (Xoft, Inc., a subsidiary of iCAD, San Jose, CA) was simulated using Monte Carlo (MC) methods by Rivard et al. [“Calculated and measured brachytherapy dosimetry parameters in water for the Xoft Axxent x-ray source: An electronic brachytherapy source,” Med. Phys. 33, 4020–4032 (2006)] and recently by Hiatt et al. [“A revised dosimetric characterization of the model S700 electronic brachytherapy source containing an anode-centering plastic insert and other components not included in the 2006 model,” Med. Phys. 42, 2764–2776 (2015)] with improved geometric characterization. Additionally, while these studies examined the dose distribution in water, there have not previously been reports of the eBT source calibration methods beyond that recently reported by Seltzer et al. [“New national air-kerma standard for low-energy electronic brachytherapy sources,” J. Res. Natl. Inst. Stand. Technol. 119, 554–574 (2014)]. Therefore, the motivation for the current study was to provide an independent determination of air-kerma rate at 50 cm in air K air (d = 50 cm) using MC methods for the model S700 eBT source. Methods: Using CAD information provided by the vendor and disassembled sources, an MC model was created for the S700 eBT source. Simulations were run using the mcnp6 radiation transport code for the NIST Lamperti air ionization chamber according to specifications by Boutillon et al. [“Comparison of exposure standards in the 10-50 kV x-ray region,” Metrologia 5, 1–11 (1969)], in air without the Lamperti chamber, and in vacuum without the Lamperti chamber. K air (d = 50 cm) was determined using the *F4 tally with NIST values for the mass energy-absorption coefficients for air. Photon spectra were evaluated over 2π azimuthal sampling for polar angles of 0° ≤ θ ≤ 180° every 1°. Volume averaging was averted through tight radial binning. Photon energy spectra were determined over all polar angles in both air and vacuum using the F4 tally with 0.1 keV resolution. A total of 10 11 simulated histories were run for the Lamperti chamber geometry (statistical uncertainty of 0.14%), with 10 10 histories for the in-air and in-vacuum simulations (statistical uncertainty of 0.04%). The total standard uncertainty in the calculated air-kerma rate determination amounted to 6.8%. Results: MC simulations determined the air-kerma rate at 50 cm from the source with the modeled Lamperti chamber to be (1.850 ± 0.126) × 10 -4 Gy/s, which was within the range of K air (d = 50 cm) values (1.67–2.11) × 10 -4 Gy/s measured by NIST. The ratio of the photon spectra in air and in vacuum were in good agreement above 13 keV, and for θ < 150° where the influence of the Kovar sleeve and the Ag epoxy components caused increased scatter in air. Below 13 keV, the ratio of the photon spectra in air to vacuum exhibited a decrease that was attributed to increased attenuation of the photons in air. Across most of the energy range on the source transverse plane, there was good agreement between the authors' simulated spectra and that measured by NIST. Discrepancies were observed above 40 keV where the NIST spectrum had a steeper fall-off towards 50 keV. Conclusions: Through MC simulations of radiation transport, this study provided an independent validation of the measured air-kerma rate at 50 cm in air at NIST for the model S700 eBT source, with mean results in agreement within 3.3%. Lastly, this difference was smaller than the range (i.e., 23%) of the measured values.
61 RADIATION PROTECTION AND DOSIMETRY↗
Simulation Evaluation of a Large-Scale Implementation of Virtual-Phase Link-Based Model Predictive Control
Traffic congestion is a serious problem in the US, and traffic signal control is one of the effective solutions to congestion. Previous research on model predictive control (MPC)-based traffic signal control showed substantial benefits over conventional methods. This study focused on implementing MPC over a large-scale network with complex intersections and the impact of cycle length, network size, and imperfect state estimation on performances. This study implemented a virtual phase link (VPL)-based model predictive control method which used the number of vehicles in each VPL as input state variables and was suitable for National Electrical Manufacturing Association (NEMA) ring-barrier control. To test the impact of network size, the performance of distributed MPC (36 intersections in the network are divided into five subnetworks) was compared with that of MPC over the full network for a set of cycle lengths. To test the impact of imperfect state estimation, we synthetically infused estimation error and developed two scenarios, MPC-error and MPC-error narrow, which had higher and lower estimation errors, respectively. The performance of these MPC methods was compared with that of the existing time-of-day (TOD) method and an offline method that used Webster's method for split and MULTIBAND for cycle length and offset optimization. Trajectory and linkwise signal performance measures were collected from the simulation to evaluate performance. The distributed MPC method with perfect state estimation had the lowest delay and highest energy efficiency of all the methods. The performance of MPC decreased as the prediction inaccuracy increased. MPC-error had 7% and 11% more delay than MPC-error narrow in the morning and evening peaks, respectively. Overall, simulation results suggest that even with imperfect state estimation, MPC methods will outperform offline methods significantly.
large-scale simulation↗
gdess: A framework for evaluating simulated atmospheric CO 2 in Earth System Models
Atmospheric carbon dioxide (CO 2 ) plays a key role in the global carbon cycle and global warming. Climate-carbon feedbacks are often studied and estimated using Earth System Models (ESMs), which couple together multiple model components—including the atmosphere, ocean, terrestrial biosphere, and cryosphere—to jointly simulate mass and energy exchanges within and between these components. Despite tremendous advances, model intercomparisons and benchmarking are aspects of ESMs that warrant further improvement (Fer et al., 2021; Smith et al., 2014). Such benchmarking is critical because comparing the value of state variables in these simulations against observed values provides evidence for appropriately refining model components; moreover, researchers can learn much about Earth system dynamics in the process (Randall et al., 2019). We introduce `gdess` (a.k.a., Greenhouse gas Diagnostics for Earth System Simulations), which parses observational datasets and ESM simulation output, combines them to be in a consistent structure, computes statistical metrics, and generates diagnostic visualizations. In its current incarnation, `gdess` facilitates evaluating a model's ability to reproduce observed temporal and spatial variations of atmospheric CO 2 . The diagnostics implemented modularly in `gdess` support more rapid assessment and improvement of model-simulated global CO 2 sources and sinks associated with land and ocean ecosystem processes. We intend for this set of automated diagnostics to form an extensible, open source framework for future comparisons of simulated and observed concentrations of various greenhouse gases across Earth system models.
97 MATHEMATICS AND COMPUTING↗
Field test and simulation evaluation of variable refrigerant flow systems performance
Our study aims to compare the performance of a Variable Refrigerant Flow (VRF) system with a Roof Top Unit, (RTU) and a variable-air-volume (VAV) system through field tests and energy simulations. The field test was conducted in as similar conditions as possible between the two systems, such as the installation and operating environments of heating, the ventilation and air conditioning (HVAC) system, including internal heat gain and outdoor conditions, including buildings to compare the performance of the two systems accurately. A VRF system and RTU were installed at the test building located in Oak Ridge, Tennessee, in the USA. The same internal heat gain was generated at the same operating time of the two systems using lighting, electric heaters, and humidifiers inside the building. The HVAC system was alternately operated between cooling and heating operations to acquire energy performance data and to compare energy usage. Furthermore, an hourly building energy simulation model was developed with regard to the VRF system and RTU, and then the model was calibrated using actual measured data. Then, annual energy consumption of the two systems were compared and analyzed using the calibrated model. Moreover, additional analysis was conducted when the controlled discharge air temperature in the RTU was changed. The field test result showed that when energy consumptions of two systems were compared at the same outdoor conditions, using the weather-normalized model, the VRF system exhibited an energy reduction of approximately 17% during cooling operation and of approximately 74% during heating operations. A comparison on the annual energy consumption using simulations showed that the VRF system reduced energy consumption more than that of the RTU by 60%. Furthermore, when the discharge air temperature in the RTU was controlled according to the outdoor air temperature, energy consumption of the RTU was reduced by 6% in cooling operations and by 18% in heating operation. As a result, energy consumption of the VRF system was reduced by more than that of the RTU by 55% approximately.
32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
Quantum Networks for Resilient Power Grids: Theory and Simulated Evaluation
Quantum networks are considered the future of secure communication in the coming quantum era. Yet there lack significant efforts on developing practical quantum networks for power grids. Here, in this paper, we establish a quantum network-based power grid (QNetGrid) framework and develops a real-time, reliable, flexible, programmable, and cost-effective QNetGrid software testbed containing repeater-based quantum communication, quantum routing, real software-defined networking (SDN) switches, and real-time networked microgrids (NMs) operations. It makes the following contributions: 1) a repeater and routing based quantum network simulator (QNSim) is developed, 2) repeaters with and without quantum memories are respectively simulated in QNSim, 3) different routing scenarios in QNetGrid are investigated, 4) a real-time QNetGrid software testbed is built in RTDS incorporating QNSim and real SDN switches, and 5) various test cases are designed, and experimental results produced with the QNetGrid testbed provide valuable insights for building quantum networks in power grids.
24 POWER TRANSMISSION AND DISTRIBUTION↗
A Simulated Evaluation of Powder Flowability Through a Partially Obstructed Consumable in Blown Powder Directed Energy Deposition Systems
Abstract In the interest of continued industrialization of metal additive manufacturing in modern production environments, cost is often referenced as a primary deterrent to new adopters. Conventional economic models for additive systems, processes, and supply chains often focus on specific process applications with little generalizability, or they neglect significant costs associated with production such as machine maintenance and consumable part replacement. Compounding the latter issue are substantial knowledge gaps in consumable part wear characterization for additive and other convergent manufacturing systems. In coaxial blown powder directed energy deposition systems, gas atomized metal powder is wasted during material deposition at a rate that is partly dependent on present wear phenomena in a consumable nozzle housed in the cladding head assembly. The price and lead time required to replace the nozzle incentivizes its reuse even when visibly worn. Often this initiates a process quality decline in the form of underbuilt geometry and internal defects due to losses in powder catchment efficiency. While depositing H13 steel using a hybrid manufacturing machine tool equipped with such a deposition system, a unique partial clog with a bridge-like structure formed at the consumable nozzle exit when supporting argon gas flows failed mid-process. To further understand coaxial multi-phase powder flow in the event of support gas failure, a computational fluid dynamics simulation is tailored to relevant process parameters, H13 powder material profile, and machine operator observations collected after the incident. The resulting differences in powder flow compared to control gas flow parameters is presented and discussed. The powder flowability and performance of the clogged nozzle is then assessed by using an optical profilometer to extract the profile of the clog and recreate the clog geometry within the simulation environment. In past work this simulation has been experimentally validated for a 316L steel powder material profile and used specifically for analyzing powder stream geometry and catchment efficiency. After the initial powder flow characterization, the clog is removed, and the nozzle is reprofiled. After removing the obstructing clog, the newly unobstructed nozzle geometry, the original off the shelf nozzle geometry, and additional nozzle profiles exploring different consumable refurbishment strategies are reevaluated in the simulation. Powder catchment efficiency for all variant nozzle geometries and relevant flow variables are compared and discussed, along with potential mitigation strategies for optimizing powder flowability with worn consumables. This work expands on the known morphology of blown powder obstructions and wear defects present in consumable coaxial nozzles while discussing pragmatic simulation driven responses to unanticipated subsystem failure in hybrid manufacturing machining platforms.
DeWitte, Lisa↗
Performance Evaluation of Distributed Energy Resource Management via Advanced Hardware-in-the-Loop Simulation
This poster provides an overview of the performance evaluation of distributed energy resource management via advanced hardware-in-the-loop simulation.
DER↗
MLEC-Sim: A Simulator for Evaluating Multi-Level Erasure Coding
We present MLEC-Sim, a sophisticated simulator for Multi-Level Erasure Coding (MLEC), developed in approximately 13 KLOC. The simulator is engineered to analyze the impact of various system configurations and erasure coding policies on system durability and network overhead. It supports a comprehensive range of parameters including disk capacity, disk I/O bandwidth, failure rates, network bandwidth, and system scale, accommodating various erasure coding approaches such as Single-Level Erasure Coding (SLEC), Multi-Level Erasure Coding (MLEC), and Local Reconstruction Codes (LRC). MLEC-Sim provides support for multiple chunk placement policies, including clustered parity and declustered parity, and encompasses a variety of repair methods like Repair-ALL, Repair-FCO, Repair-HYB, and Repair-MIN. It is capable of simulating disk failures through a variety of means, including distribution-based or trace-based mechanisms, and can handle complex multi-level (de)clustered placements and repair processes. A key feature of MLEC-Sim is its adoption of the splitting simulation method for evaluating system durabilities at extremely high levels, which are challenging to assess with traditional simulation approaches. This feature allows for a detailed evaluation of system resilience under a range of conditions, aiding in the selection of appropriate erasure coding solutions for enhancing system durability. MLEC-Sim contributes to the field of data storage and reliability by providing a tool for the detailed evaluation of the durability and efficiency of erasure coding configurations, intended for use by researchers and practitioners in the design and optimization of storage systems.
Wang, Meng↗
Evaluating EAMv2 Simulated High Latitude Clouds Using ARM Measurements in the Northern and Southern Hemispheres
Here, this study evaluates high latitude stratiform mixed-phase clouds (SMPC) in the atmosphere model of the Energy Exascale Earth System Model version 2 (EAMv2) by utilizing one-year-long ground-based remote sensing measurements from the Atmospheric Radiation and Measurement (ARM) program. A nudging approach is applied to model simulations for a constrained comparison with the ARM observations. Observed and modeled SMPCs are sampled and collocated to address the difference in data resolution, so that we can consistently evaluate their macrophysical properties at the North Slope of Alaska (NSA) site in the Arctic and the McMurdo (AWR) site in the Antarctic. We found that EAMv2 overestimates SMPC frequency of occurrence at both sites. However, the model captures the observed larger cloud frequency of occurrence at the NSA site. For collocated SMPCs, the annual statistics of observed cloud macrophysics are generally reproduced at the NSA site, while at the AWR site, there are larger biases. Compared to the AWR site, the lower cloud top and cloud base and the warmer cloud top temperature observed at NSA are well simulated. On the other hand, simulated cloud phase is substantially biased. The model largely overestimates liquid water path, and the ice water path is underestimated at NSA, but at AWR, the liquid water path is frequently underestimated due to the dominance of snow in Antarctic SMPCs. As a result, the observed hemispheric difference in cloud phase partitioning is misrepresented in EAMv2. This study implies that additional model development is needed for high latitude mixed-phase clouds.
54 ENVIRONMENTAL SCIENCES↗
Advanced Modeling and Simulation Methods for Evaluation of Thermal Neutron Scattering Materials
With the rise of interest in thermal neutron scattering data for advanced reactor, criticality safety, and shielding applications, new experimental data are required for evaluation of new materials or for re-evaluation (or validations) of previously evaluated materials. New experimental data are evaluated in a three-step process: (1) computing the phonon characteristics, (2) computing the dynamic structure factor (DSF) from the data, and (3) using the experimental setup to simulate the experimental data. All three steps have challenges, ranging from the need for a sufficiently general material simulation code—a processing code that can compute the corresponding DSF—to having a detailed layout of the instrument/beamline/facility where the data were measured. Whereas phonon characteristics of materials can be computed using various methods (molecular dynamics, density functional theory, etc.), a high-fidelity computation of the DSF and the simulation of the experiment based on the DSF is vital to the accuracy of the evaluation. The latter two steps can be achieved by using the two corresponding code systems developed by instrument scientists at the Spallation Neutron Source (SNS) at Oak Ridge National Laboratory: (1) OCLIMAX, a program that calculates the dynamic structure factor from DFT and MD simulation results, and (2) MCViNE, a Monte Carlo neutron ray-tracing program designed to simulate neutron scattering experiments. Recently, polyethylene and yttrium hydride were measured at the Wide Angular-Range Chopper (ARCS) and SEQUOIA instrument stations of the SNS. These experiments are simulated using the density functional theory code, the Cambridge Serial Total Energy Package (CASTEP), to compute its phonon characteristics (eigenvalues/vectors and PDOS), which is then processed using OCLIMAX to yield the DSF, and finally the data at each instrument station are simulated by the MCViNE for comparison to the measured data for evaluation. For comparison to conventional evaluation methods, the scattering data processed from OCLIMAX are compared against those processed from the LEAPR module of NJOY, and the results from MCViNE simulations are compared against previously used simplified beamline models implemented in the Monte Carlo N-Particle (MCNP) code.
73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
Advanced Modeling and Simulations for Evaluation of Thermal Neutron Scattering Materials [Slides]
In this presentation, researchers detail tradeoffs between two simulation suites for thermal neutron scattering data. OXLIMAX + MCViNE provide a more accurate elastic peak shape and NJOY + MCNP have more accurate spectra between phonon mode peaks (most likely due to multiple neutron scattering). Additionally, some outstanding issues with MCViNE are noted, including multiple neutron scattering and non-uniform (Q,E) grid for data.
73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
Simulation-based Performance Evaluation of Model Predictive Control for Building Energy Systems
The performance of model predictive control (MPC) can be significantly affected by different choices of controller parameters such as the time intervals for model discretization and control sampling. Due to the lack of a systematic understanding on how these parameters affect control performance, they are usually selected arbitrarily in practice.In this paper, the combined impacts of selected time intervals for model discretization and control sampling on the performance of MPC are comprehensively investigated for the first time through detailed simulations. Specifically, a typical MPC strategy is first designed to improve building operations based on a reduced-order model of building dynamics. Then, the performance of the designed MPC is evaluated against different choices of time intervals for model discretization and control sampling on a simulated office building. The detailed simulation results reveal that the time interval for model discretization has a much greater influence on the performance of MPC than the time interval for control sampling. Although the time interval for control sampling usually receives more attentions in practice, it turns out that the time interval for model discretization affects the prediction performance, cost saving, and computation time simultaneously and more significantly. Therefore, the simulation-based performance evaluation presented here sheds light on the impacts of different time intervals and facilitates their selection for practical applications of MPC to building operations
Huang, Sen↗
QASMBench: A Low-Level Quantum Benchmark Suite for NISQ Evaluation and Simulation
The rapid development of quantum computing (QC) in the NISQ era urgently demands a low-level benchmark suite and insightful evaluation metrics for characterizing the properties of prototype NISQ devices, the efficiency of QC programming compilers, schedulers and assemblers, and the capability of quantum system simulators in a classical computer. In this work, we fill this gap by proposing a low-level, easy-to-use benchmark suite called QASMBench based on the OpenQASM assembly representation. It consolidates commonly used quantum routines and kernels from a variety of domains including chemistry, simulation, linear algebra, searching, optimization, arithmetic, machine learning, fault tolerance, cryptography, and so on, trading-off between generality and usability. To analyze these kernels in terms of NISQ device execution, in addition to circuit width and depth, we propose four circuit metrics including gate density, retention lifespan, measurement density, and entanglement variance, to extract more insights about the execution efficiency, the susceptibility to NISQ error, and the potential gain from machine-specific optimizations. Applications in QASMBench can be launched and verified on several NISQ platforms, including IBM-Q, Rigetti, IonQ and Quantinuum. For evaluation, we measure the execution fidelity of a subset of QASMBench applications on 12 IBM-Q machines through density matrix state tomography, comprising 25K circuit evaluations. In addition we also compare the fidelity of executions among the IBM-Q machines, the IonQ QPU and the Rigetti Aspen M-1 system.
97 MATHEMATICS AND COMPUTING↗