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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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All sourcesNASA NTRSDOE OSTI
DOE OSTI2016

TU-FG-201-12: Designing a Risk-Based Quality Assurance Program for a Newly Implemented Y-90 Microspheres Procedure

Purpose: To create a quality assurance program based upon a risk-based assessment of a newly implemented SirSpheres Y-90 procedure. Methods: A process map was created for a newly implemented SirSpheres procedure at a community hospital. The process map documented each step of this collaborative procedure, as well as the roles and responsibilities of each member. From the process map, different potential failure modes were determined as well as any current controls in place. From this list, a full failure mode and effects analysis (FMEA) was performed by grading each failure mode’s likelihood of occurrence, likelihood of detection, and potential severity. These numbers were then multiplied to compute the risk priority number (RPN) for each potential failure mode. Failure modes were then ranked based on their RPN. Additional controls were then added, with failure modes corresponding to the highest RPNs taking priority. Results: A process map was created that succinctly outlined each step in the SirSpheres procedure in its current implementation. From this, 72 potential failure modes were identified and ranked according to their associated RPN. Quality assurance controls and safety barriers were then added for failure modes associated with the highest risk being addressed first. Conclusion: A quality assurance program was created from a risk-based assessment of the SirSpheres process. Process mapping and FMEA were effective in identifying potential high-risk failure modes for this new procedure, which were prioritized for new quality assurance controls. TG 100 recommends the fault tree analysis methodology to design a comprehensive and effective QC/QM program, yet we found that by simply introducing additional safety barriers to address high RPN failure modes makes the whole process simpler and safer.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2016

WE-DE-209-00: Practical Implementation of Deep Inspiration Breath Hold Techniques for Breast Radiation Therapy

Breast radiation therapy is associated with some risk of lung toxicity as well as cardiac toxicity for left-sided cases. Radiation doses to the lung and heart can be reduced by using the deep inspiration breath hold (DIBH) technique, in which the patient is simulated and treated during the deep inspiration phase of the breathing cycle. During DIBH, the heart is usually displaced posteriorly, inferiorly, and to the right, effectively expanding the distance between the heart and the breast/chest wall. As a result, the distance between the medial treatment field border and heart/lung is increased. Also, in a majority of DIBH patients, the air drawn into the thoracic cavity increases the total lung volume. The DIBH was discussed by an AAPM Task Group 10 years ago in the AAPM TG 76 report. However, DIBH is still not the standard of care in many clinics, which may be partially due to challenges associated with its implementation. Therefore, this seccion will focus primarily on how to clinically implement four different DIBH techniques: (1) Active Breathing Control, (2) Spirometric Motion Management, (3) 3D Surface Image-Guided, and (4) Self-held Breath Control with Respiratory Monitoring and Feedback Guidance. Learning Objectives: Describe the physical displacement of the heart and the change in lung volume during DIBH and discuss dosimetric consequences of those changes. Provide an overview of the technical aspects. Describe work flow for patient simulation and treatment. Give an overview of commissioning and routine. Provide practical tips for clinical implementation.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2016

Continuous Energy Photon Transport Implementation in MCATK

The Monte Carlo Application ToolKit (MCATK) code development team has implemented Monte Carlo photon transport into the MCATK software suite. The current particle transport capabilities in MCATK, which process the tracking and collision physics, have been extended to enable tracking of photons using the same continuous energy approximation. We describe the four photoatomic processes implemented, which are coherent scattering, incoherent scattering, pair-production, and photoelectric absorption. The accompanying background, implementation, and verification of these processes will be presented.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2016

Photon Next-Event Estimator Implementation in MCATK

A photon next-event fluence estimator at a point has been implemented in the Monte Carlo Application Toolkit (MCATK). The next-event estimator provides an expected value estimator for the flux at a point due to all source and collision events. An advantage of the next-event estimator over track-length estimators, which are normally employed in MCATK, is that flux estimates can be made in locations that have no random walk particle tracks. The next-event estimator allows users to calculate radiographs and estimate response for detectors outside of the modeled geometry. The next-event estimator is not yet accessable through the MCATK FlatAPI for C and Fortran. The next-event estimator in MCATK has been tested against MCNP6 using 5 suites of test problems. No issues were found in the MCATK implementation. One issue was found in the exclusion radius approximation in MCNP6. The theory, implementation, and testing are described in this document.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2018

The Role of Technical Guidance and Analysis Tools in Remedy Decisions, Implementation, and Closure - 18307

Selection, design, and implementation of environmental remedies are conducted under regulatory frameworks that define the activities, communication, and documentation requirements for the remediation process. However, there are site situations that are not well described in the basic regulatory frameworks, and technical guidance and analysis tools can help facilitate remedy decisions and actions. An example where technical guidance and analysis tools are helpful is in the transition from pump-and-treat (P and T) remediation to monitored natural attenuation (MNA). Standard MNA regulatory guidance does not account for a plume initially controlled by P and T hydraulic conditions rather than natural-gradient conditions. For instance, MNA guidance discusses demonstrating plume stability as a means to evaluate the suitability of MNA. However, plume stability under long-term natural gradient conditions cannot be directly demonstrated while the plume is being contained by a P and T system. Thus, additional guidance is needed to describe other measures that can be used to support transition from P and T to MNA. As an additional example, standard MNA regulatory guidance is not written to provide suitable information for application to vadose-zone contamination; discussion and examples in the regulatory guidance are predominantly for groundwater. Use of contaminant transport assessments is an important component of vadose-zone remedy decisions where technical guidance and analysis tools can facilitate these decisions. For volatile compounds, the assessment may need to also consider flux to the surface and constraints associated with vapor intrusion. Recent technical guidance and associated analysis tools provide sites with approaches to support remedy decisions for the above conditions. In particular, these recent approaches target developing and implementing P and T and soil vapor extraction remediation exit strategies and facilitating assessment and implementation of remedies for coupled vadose-zone/groundwater contamination. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2018

Safety Requirement Management System (SRMS) - Improved Documented Safety Analyses Implementation - 18476

Savannah River Remediation (SRR) developed a new software application, Safety Requirement Management System (SRMS), to improve Documented Safety Analysis (DSA) safety requirement implementation in the Savannah River Site's Liquid Waste facilities. Technical Safety Requirement (TSR) Limited Conditions of Operations (LCOs) and related surveillances were previously tracked using four different applications. Due to their differences and their age, the applications introduced a number of operational challenges and vulnerabilities, including outdated platforms, usage demands beyond original design, and different organizational work processes. SRMS was developed to resolve these issues by using a single web-based approach that provides consistency, wider accessibility, simpler maintenance, and a platform for additional functionality. Other SRS facilities are evaluating the application for its applicability as a standard practice across the site. The new SRMS application decreased the administrative overhead for application maintenance, provided the needed TSR change management functionality, and reduced error precursors with the following advantages: - Consistent process/application across all SRR facilities - More efficient way to track and communicate compliance with DSA time-related requirements (i.e., TSR LCOs and surveillances). - Web-based search capability for LCO entries/exits and a record of surveillance performances. - TSR change management and independent reviews through electronic approvals. For example, the application provides the ability to bundle and stage LCO and surveillance changes associated with a TSR revision. The approval process involves multiple roles from the facility to ensure validity. - Formal configuration management program, fully supported by software life cycle documents. SRMS was implemented at Defense Waste Processing Facility (DWPF) in June 2017, with implementation in all Liquid Waste facilities expected by the end of 2017. Next, SRR plans to expand SRMS functionality to include a linking document database (LDD) to support the DSA requirements. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2018

Leakage Rate Testing Considerations and Implementation of ANSI N 14.5-2014 Standard within EnergySolutions Type (B) cask fleet - 18629

In March 2016, Nuclear Regulatory Commission (NRC) staff issued Information Notice 2016-04: 'ANSI N14.5-2014 Revision and leakage rate testing considerations'. American National Standards Institute (ANSI) N14.5, 'American National Standard for Radioactive Materials-Leakage Tests on Packages for Shipment', applies to leakage rate testing of Low Level Radioactive Waste (LLRW) Type B packages operated under 10CFR71. In their information notice NRC is encouraging Type B cask license holders and licensees (cask users) to adapt a new version of ANSI N 14.5 standard. Typically, leakage rate testing for Type B packages (or casks) is performed at different stages of cask development (design and fabrication leak tests) and operations (periodic/maintenance and pre-shipment leak tests) with the purpose to reasonably assure that the packaging will contain radioactive material under both normal and hypothetical accident conditions of transport described in 10CFR71. The standard was updated to provide a modern, robust and standardized approach for performance of leak rate testing on Type B casks by the industry stakeholders. Although implementation of new version of the leak testing standard may not be problematic for a modern Type B package designs, it may be extremely challenging to apply its principles to the existing legacy Type B casks which were designed/fabricated more then 20-30 years ago based on older requirements. Majority of such casks are not 'leak test' friendly. Some of legacy Type B packages may not readily available to meet newer ANSI N 14.5 standard requirements and will require implementation of alternative compensatory measures in lieu of the standard's requirements. In addition, the new standard mandates implementation of additional requirements for leak rate testing performance and personnel qualifications during routine maintenance of Type B casks by owner and during operations of casks by users. The focus of the paper will be to discuss ANSI N 14.5-2014 requirements and provide specific examples on how these requirements will impact the current leak rate test practices. This will be illustrated based on several Type B cask models operated within EnergySolutions fleet (both newer and legacy cask designs). Finally, the paper will cover considerations of the cask closure design features that have to be considered by Type B cask designers in order to ensure robustness of leak testing during design, fabrication and, most importantly, operation of a package. This information shall benefit both owners and users of Type B casks with respect to improvement of the cask designs and Type B cask operational experience. (author)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2020

Opportunities to Implement Solutions to Achieve Remedial Action Objectives in Consideration of Stakeholder Interests - 20365

A case study in the implementation of a soils excavation and removal project conducted at a Formerly Utilized Sites Remedial Action Program (FUSRAP) Maywood Superfund Site (FMSS) vicinity property; an active commercial business, in a densely populated area, with significant operational, technical and, logistical constraints that were expected to limit areas that could be remediated. The United States Army Corps of Engineers-led (USACE) team successfully navigated complex overlapping stakeholder interests to achieve a more efficient and complete removal of contaminated soils and debris while minimizing unnecessary excess costs to the Government. This paper centers on FUSRAP activities at the FMSS vicinity property located at 149-151 Maywood Avenue, Maywood, Bergen County, New Jersey. For most of its FUSRAP history, this ∼109,000 square meter (27-acre) property housed a now-demolished ∼26,000 square meter (6.5-acre) warehouse operated by Sears Logistics Services, a unit of the Sears Roebuck Company (Figure 2). Sears ended its property lease and vacated the warehouse in December 2016. Given that long history and for the purposes of this paper, the property will be referred to as the 'Sears property' or simply 'the property.' The Sears property is approximately 109,000 square meters (27-acres) and is currently zoned for commercial use. The property is bound to the north and northwest by 100 West Hunter Avenue (the Stepan Company), to the northeast by 205 Maywood Avenue, to the east by Maywood Avenue, to the south by 23 West Howcroft Road, and to the west by businesses on NJ Route 17 and the NJ Route 17 roadway. Until December 2016, the property housed a warehouse and distribution center operated by Sears Logistical Services. On-site structures were demolished by the property owner in 2017. The warehouse covered the north section of the property along the Stepan Company property line. A railroad spur from the adjacent property now known as the Maywood Interim Storage Site (MISS) ended at the northeast corner of the warehouse. Wetlands were located east of the warehouse; the rest of the property was covered with paved parking lots and grassed areas. During remediation at the property, opportunities frequently arose where the project team was able to coordinate effectively with stakeholders to sequence remediation activities to facilitate removal of otherwise inaccessible soils and identify opportunities for materials reuse when supported by residual radiological and chemical levels. Some specific opportunities include: - remediating individual truck loading dock bays to maintain tenant operations; - working along a busy highway and in a utility corridor containing a 30-inch high pressure gas main; - remediating Lodi Brook and associated wetlands requiring bypass pumping and other diversionary structures to maintain local community stormwater drainage; - protecting during remediation and supporting access to facilitate tenant/owner maintenance of critical fire protection and water supply system service lines buried in contaminated soils and necessary for safe warehouse operations; and - coordinating with stakeholders to ensure non-radiological contaminants of concern for the site (unaffiliated with FUSRAP) were addressed by the responsible party in a manner that maximized benefit to all parties while supporting an efficient overall site remediation program. Once the property was vacant and the warehouse structure and radiologically non-impacted above-grade structures were demolished, the project identified an opportunity to significantly reduce the volume of waste associated with the foundation of the former warehouse, a foundation suspected of being partially constructed in radiologically contaminated soils. The project developed and implemented supplemental radiological verification survey and sampling strategies based on radiological cross-contamination risk potential with process flow-charts and screening-level based decision points; a program that classified saw-cut sections of concrete based on observed residual surface radioactivity conditions using a combination of gamma sensitive sodium-iodide scans and beta sensitive Geiger-Muller direct measurements. The proposed approach was reviewed with stakeholders with feedback, including consideration of applicable State of New Jersey Site Remediation Program criteria and guidance before implementation. Once classified, additional sampling was performed at frequencies driven by screening. The sampling methods, stockpile sampling frequencies, criteria and, approach to data evaluation were developed in consideration of existing site cleanup standards, regional background ranges, State of New Jersey radiological remediation program guidance, and specific stakeholder input With the property remediation and survey efforts nearly completed, it is relevant to examine retrospectively the objectives, assumptions and limitations in the remedial design (i.e., what was planned) versus what was able to be accomplished through effective teaming. Benefits to other environmental remediation site programs include better understanding of how to work effectively with stakeholders to achieve win-win outcomes, and approaches to site remediation, waste minimization and materials reuse that were successful in their overall outcomes. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2017

Real-time supervisory control implementation of SmAHTR power plant - 143

This paper discusses an implementation of a supervisory control system for a nuclear power plant model using Small modular Advanced High Temperature Reactors (SmAHTR). The simulation operates in real-time using a network of computer agents, implemented on Raspberry Pi's (RPi's), where each major task is performed by one or more RPi's running calculations in parallel. The system architecture contains local, module, master, and operator actions to automate all aspects of the plant. Local level controllers run individual control loops to ensure the desired reference signals are met. The module level controllers set the local level reference signals within each SMR unit and detect sensor and actuator failures to adjust those reference signals as needed. Master level controllers balance plant power by calculating required heat power from each reactor and electric power from each generator and sending that data to the module controllers. Finally, the operator level contains an operator interface to summarize data and faults gathered through the controller levels, with options to review plant and reactor details as desired. This control implementation allows the plant to run autonomously, load follow a desired electrical power curve, and detect a growing number of fault scenarios. Ultimately, this type of supervisory control system will reduce labor-intensive surveillance and testing and allow fewer operators to more safely monitor an entire plant. (authors)

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗
DOE OSTI2017

Implementing computer-based procedures: thinking outside the paper margins - 236

In the past year there has been increased interest from the nuclear industry in adopting the use of electronic work packages and computer-based procedures (CBPs) in the field. The goal is to incorporate the use of technology in order to meet the Nuclear Promise requirements of reducing costs, and improving efficiency and decreasing human error rates in plant operations. Researchers, together with the nuclear industry, have been investigating the benefits of an electronic work package system and specifically CBPs would have over current paper-based procedure practices. There are several classifications of CBPs ranging from a straight copy of the paper-based procedure in PDF format to a more intelligent dynamic CBP. A CBP system offers a vast variety of potential improvements, such as context driven job aids, integrated human performance tools (e.g., place-keeping and correct component verification), and dynamic step presentation. However, the implementation of a CBP system does not automatically improve the quality of procedures. Utilities should review, standardize format and update current procedure content before transitioning to a computerized process. Implementation of a CBP system can be a time to break out of traditional procedure writing processes and create new processes and procedures that take advantage of the capabilities a CBP system. This paper summarizes INL research findings related to challenges with implementing a CBP system and provides suggestions to take into consideration. (authors)

22 GENERAL STUDIES OF NUCLEAR REACTORS↗
DOE OSTI2022

Implementation of real‐time TDDFT for periodic systems in the open‐source PySCF software package

Abstract We present a new implementation of real‐time time‐dependent density functional theory (RT‐TDDFT) for calculating excited‐state dynamics of periodic systems in the open‐source Python‐based PySCF software package. Our implementation uses Gaussian basis functions in a velocity gauge formalism and can be applied to periodic surfaces, condensed‐phase, and molecular systems. As representative benchmark applications, we present optical absorption calculations of various molecular and bulk systems and a real‐time simulation of field‐induced dynamics of a (ZnO) 4 molecular cluster on a periodic graphene sheet. We present representative calculations on optical response of solids to infinitesimal external fields as well as real‐time charge‐transfer dynamics induced by strong pulsed laser fields. Due to the widespread use of the Python language, our RT‐TDDFT implementation can be easily modified and provides a new capability in the PySCF code for real‐time excited‐state calculations of chemical and material systems.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Investigation of Main Bearing Fatigue Estimate Sensitivity to Synthetic Turbulence Models Using a Novel Drivetrain Model Implemented in OpenFAST

ABSTRACT A coupled medium‐fidelity drivetrain model is developed and implemented in OpenFAST for a 10‐MW land‐based reference turbine. The implementation is verified against a fully coupled multibody wind turbine model, including a detailed drivetrain. The new model can simultaneously and accurately estimate main bearing loads and represent elastic bending of the drivetrain. It has low computational cost and is useful for early design phases, sensitivity analyses and complex systems like wind farms (where computational expense must be expended elsewhere). Here, the model is implemented for a monopile offshore wind turbine and used to investigate the sensitivity of main bearing basic rating life to different synthetic turbulence models. Large‐eddy simulations (LES) targeting stable, neutral, and unstable atmospheric conditions at below‐, near‐ and above‐rated wind speeds are used as a reference. The turbulence models recommended by the International Electrotechnical Commission, the Mann spectral tensor model, and the Kaimal spectral model with exponential coherence are fitted to the LES data. Additionally, a constrained turbulence generator, PyConTurb (short for Python Constrained Turbulence ), based on LES data, is applied in the aero‐hydro‐servo‐elastic simulations. Taking PyConTurb as the baseline, the Kaimal model significantly underestimates fatigue of the downwind main bearing, with between 10% and 40% less damage. The Mann model also underestimates the downwind main bearing fatigue by up to 30%. The upwind main bearing damage is driven by mean loads, and differences between models are less significant, although the trends are similar. Reasons for these discrepancies are investigated and attributed to differences in spatial and temporal variations among the turbulence models.

17 WIND ENERGY↗
DOE OSTI2016

Using Hybrid Model OpenSHMEM + CUDA to Implement the SHOC Benchmark Suite

This work describes the process of porting the Scalable HeterOgeneous Computing (SHOC) benchmark suite from the hybrid MPI + CUDA implementation to OpenSHMEM + CUDA. SHOC includes a wide variety of benchmark kernels used to measure accelerator performance in both single node and cluster configurations. The hybrid model implementation attempts to place all major computation on accelerator devices, and uses MPI to synchronize and aggregate results. In some cases, MPI Groups are used to gradually reduce the number of accelerators used for computation as the problem size drops. Porting this behavior to OpenSHMEM required implementing several synchronizing collective operations, and using SHMEM teams to replace MPI Group functionality. Benchmark results on a Cray XK7 system with one GPU per compute node show that SHMEM performance is equal to MPI performance in these hybrid tasks. These results and porting experience show that using OpenSHMEM for accelerator devices benefits from adding functionality for synchronization and teams, and would further benefit from adding support for communication within accelerator kernels.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2022

Implementing the three-particle quantization condition for π + π + K + and related systems

Recently, the formalism needed to relate the finite-volume spectrum of systems of nondegenerate spinless particles has been derived. In this work we discuss a range of issues that arise when implementing this formalism in practice, provide further theoretical results that can be used to check the implementation, and make available codes for implementing the three-particle quantization condition. Specifically, we discuss the need to modify the upper limit of the cutoff function due to the fact that the left-hand cut in the scattering amplitudes for two nondegenerate particles moves closer to threshold; we describe the decomposition of the three-particle amplitude K df,3 into the matrix basis used in the quantization condition, including both s and p waves, with the latter arising in the amplitude for two nondegenerate particles; we derive the threshold expansion for the lightest three-particle state in the rest frame up to O(1/L 5 ); and we calculate the leading-order predictions in chiral perturbation theory for K df,3 in the π + π + K + and π + K + K + systems. We focus mainly on systems with two identical particles plus a third that is different (“2+1” systems). We describe the formalism in full detail, and present numerical explorations in toy models, in particular checking that the results agree with the threshold expansion, and making a prediction for the spectrum of π + π + K + levels using the two- and three-particle interactions predicted by chiral perturbation theory.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2019

Implementing the three-particle quantization condition including higher partial waves

We present an implementation of the relativistic three-particle quantization condition including both s - and d -wave two-particle channels. For this, we develop a systematic expansion of the three-particle K matrix, \( \mathcal{K} \) df,3 , about threshold, which is the generalization of the effective range expansion of the two-particle K matrix, \( \mathcal{K} \) 2 . Relativistic invariance plays an important role in this expansion. We find that d -wave two-particle channels enter first at quadratic order. We explain how to implement the resulting multichannel quantization condition, and present several examples of its application. We derive the leading dependence of the threshold three-particle state on the two-particle d -wave scattering amplitude, and use this to test our implementation. We show how strong two-particle d -wave interactions can lead to significant effects on the finite-volume three-particle spectrum, including the possibility of a generalized three-particle Efimov-like bound state. We also explore the application to the 3 π + system, which is accessible to lattice QCD simulations, where we study the sensitivity of the spectrum to the components of \( \mathcal{K} \) df,3 . Finally, we investigate the circumstances under which the quantization condition has unphysical solutions.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2016

Numerical implementation, verification and validation of two-phase flow four-equation drift flux model with Jacobian-free Newton–Krylov method

This study presents a numerical investigation on using the Jacobian-free Newton–Krylov (JFNK) method to solve the two-phase flow four-equation drift flux model with realistic constitutive correlations (‘closure models’). The drift flux model is based on Isshi and his collaborators’ work. Additional constitutive correlations for vertical channel flow, such as two-phase flow pressure drop, flow regime map, wall boiling and interfacial heat transfer models, were taken from the RELAP5-3D Code Manual and included to complete the model. The staggered grid finite volume method and fully implicit backward Euler method was used for the spatial discretization and time integration schemes, respectively. The Jacobian-free Newton–Krylov method shows no difficulty in solving the two-phase flow drift flux model with a discrete flow regime map. In addition to the Jacobian-free approach, the preconditioning matrix is obtained by using the default finite differencing method provided in the PETSc package, and consequently the labor-intensive implementation of complex analytical Jacobian matrix is avoided. Extensive and successful numerical verification and validation have been performed to prove the correct implementation of the models and methods. Code-to-code comparison with RELAP5-3D has further demonstrated the successful implementation of the drift flux model.

42 ENGINEERING↗
DOE OSTI2020

Efficient discontinuous Galerkin implementations and preconditioners for implicit unsteady compressible flow simulations

This work presents and compares efficient implementations of high-order discontinuous Galerkin methods: a modal matrix-free discontinuous Galerkin (DG) method, a hybridizable discontinuous Galerkin (HDG) method, and a primal formulation of HDG, applied to the implicit solution of unsteady compressible flows. The matrix-free implementation allows for a reduction of the memory footprint of the solver when dealing with implicit time-accurate discretizations. HDG reduces the number of globally-coupled degrees of freedom relative to DG, at high order, by statically condensing element-interior degrees of freedom from the system in favor of face unknowns. The primal formulation further reduces the element-interior degrees of freedom by eliminating the gradient as a separate unknown. This paper introduces a p-multigrid preconditioner implementation for these discretizations and presents results for various flow problems. Benefits of the p-multigrid strategy relative to simpler, less expensive, preconditioners are observed for stiff systems, such as those arising from low-Mach number flows at high-order approximation. The p-multigrid preconditioner also shows excellent scalability for parallel computations. Finally, additional savings in both speed and memory occur with a matrix-free/reduced version of the preconditioner.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2018

Implementation of replica-exchange umbrella sampling in GAMESS

In GAMESS-US quantum chemistry package, both replica-exchange molecular dynamics (REMD) and the umbrella sampling (US) methods are available. However, prior to this work, the replica-exchange umbrella sampling (REUS) method, combining REMD and US, was not implemented. Here, REUS affords a more efficient conformational sampling than the conventional US method and is often used in MD simulations. We implemented REUS in GAMESS-US and improved some routines of the existing REMD code. A density-functional tight-binding REMD (DFTB-REMD) simulation of alanine deca-peptide and a DFTB-MD REUS simulation of proton transfer in malonaldehyde were performed. The results of DFTB-MD REUS simulations performed with three different simulation packages were compared to validate our GAMESS-US implementation.

97 MATHEMATICS AND COMPUTING↗