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Tag: Numerical analysis
  • Simulated Barge Impacts on Fiber-Reinforced Polymers (FRP) Composite Sandwich Panels: Dynamic Finite Element Analysis (FEA) to Develop Force Time Histories to Be Used on Experimental Testing

    Abstract: The purpose of this study is to evaluate the dynamic response of fiber-reinforced polymer (FRP) composite sandwich panels subjected to typical barge impact masses and velocities to develop force time histories that can be used in controlled experimental testing. Dynamic analyses were performed on FRP composite sandwich panels using the finite element method software Abaqus/Explicit. The “traction-separation” law in the Abaqus software is used to define the cohesive surface interaction properties to evaluate the damage between FRP composite laminate layers as well as the core separation within the sandwich panels. Numerical models were developed to better under-stand the damage caused by barge impacts and the effects of impacts on the dynamic response of composite structures. Force, displacement, and velocity time histories were obtained with finite element modeling for several mass and velocity cases to develop experimental testing procedures for these types of structures.
  • Foundational Principles in the Development of AdH-SW3, the Three-Dimensional Shallow Water Hydrodynamics and Transport Module within the Adaptive Hydraulics/Hydrology Model

    Abstract: This report details the design and development of the three-dimensional shallow water hydrodynamics formulation within the Adaptive Hydraulics/Hydrology model (AdH-SW3) for simulation of flow and transport in rivers, estuaries, reservoirs, and other similar hydrologic environments. The report is intended to communicate principles of the model design for the interested and diligent user. The design relies upon several layers of consistency to produce a stable, accurate, and conservative model. The mesh design can handle rapid changes in bathymetry (e.g., steep-sided navigation channels in estuaries) and maintain accuracy in density-driven transport phenomena (e.g., thermal, or saline stratification and intrusion of salinity).
  • In Situ Visualization with Temporal Caching

    Abstract: In situ visualization is a technique in which plots and other visual analyses are performed in tandem with numerical simulation processes in order to better utilize HPC machine resources. Especially with unattended exploratory engineering simulation analyses, events may occur during the run, which justify supplemental processing. Sometimes though, when the events do occur, the phenomena of interest includes the physics that precipitated the events and this may be the key insight into understanding the phenomena that is being simulated. In situ temporal caching is the temporary storing of produced data in memory for possible later analysis including time varying visualization. The later analysis and visualization still occurs during the simulation run but not until after the significant events have been detected. In this article, we demonstrate how temporal caching can be used with in-line in situ visualization to reduce simulation run-time while still capturing essential simulation results.
  • Publication Notification: Distribution of the Two-Point Product of Complex Amplitudes in the Fully Saturated Scattering Regime

    Abstract:  This Letter considers probability density functions (pdfs) involving products of the complex amplitudes observed at two points (which may, in general, involve separations in space, time, or frequency) in conditions of fully saturated scattering. First, the pdf is derived for the product of the complex amplitude at one point with the conjugate of the complex amplitude at another point. It is shown that the real and imaginary parts of this product each have a variance gamma pdf. Second, expressions are derived for several joint pdfs involving complex amplitude products and powers at two points.
  • PUBLICATION NOTICE: New York/New Jersey Harbor Sedimentation Study: Numerical Modeling of Hydrodynamics and Sediment Transport

    Abstract: The New York/New Jersey Harbor (NYNJH) is a vital economic resource for both the local economy and the entire US economy due to the vast quantity of imports and exports handled by the numerous ports in this waterway. As with most ports, there is a significant, recurring expense associated with dredging the navigation channels to the authorized depths. In an effort to determine the impact of channel enlargements (“the project”) on dredging volumes, a numerical model study was performed. The advantage of a numerical model study is the ability to isolate individual system modifications and associated impacts in terms of dredging volumes. Five years (1985, 1995, 1996, 2011, and 2012) were simulated for both the with- and without-project conditions to determine the impact of the channel deepening on the dredging requirements for a wide range of meteorological conditions including storm events. The numerical model results were analyzed to provide insight into which locations will experience increased/decreased deposition and quantify the amount of increase/decrease for a given channel reach. The model results indicate a relatively minor increase in the total dredge volumes for the NYNJH with the increase being insignificant in comparison to the natural variability in dredge volumes across years.
  • PUBLICATION NOTICE: Hydraulic Analysis and Modeling of Navigation Conditions near the Mississippi River Bridges in Vicksburg, Mississippi

    Abstract: The River and Estuarine Engineering Branch of the Coastal and Hydraulics Laboratory developed a two-dimensional numerical model of the Mississippi River near Vicksburg, MS, using Adaptive Hydraulics to investigate navigation conditions through the Interstate 20 and Old Highway 80 Bridges reach. A focus of the study was determining the Marshall Brown Dikes impact to velocities and navigation through the reach. Proposed dikes, focused on improving currents, were also tested to determine if they are a feasible option to improve navigability through the bridges. A second proposed alternative, a levee to protect the articulated concrete mattress (ACM) field, was also simulated to determine if flood damage to the ACM field could be successfully reduced without negatively impacting navigation. Velocity data from 2008 throughout the reach of concern were used for validation along with water surface elevation data from 2008, 2011, 2016, and 2018. The Marshall Brown Dikes were shown to have a localized impact on velocities near the dikes, but the changes to the velocity downstream near the bridge were negligible for all tested flow rates. Simulations of the proposed dikes did not result in an improvement to navigation conditions, but the proposed levee was successful in decreasing velocities and depths over the ACM field.
  • PUBLICATION NOTICE: Theory, Formulation, and Implementation of The Cartesian and Spherical Coordinate Two-Dimensional Depth-Averaged Module of the Adaptive Hydraulics (AdH) Finite Element Numerical Code

    Abstract: The US Army Engineer Research and Development Center, Coastal and Hydraulics Laboratory, has undertaken the development of the multi-module Adaptive Hydraulics (AdH) hydrodynamic, sediment, water quality, and transport numerical code. This report documents the mathematical formulation and numerical implementation of the two-dimensional depth-averaged module of AdH.
  • PUBLICATION NOTICE: A Practical Two-Phase Approach to Improve the Reliability and Efficiency of Markov Chain Monte Carlo Directed Hydrologic Model Calibration

    ABSTRACT: Markov chain Monte Carlo (MCMC) methods are widely used in hydrology and other fields for posterior inference in a Bayesian framework. A properly constructed MCMC sampler is guaranteed to converge to the correct limiting distribution, but convergence can be very slow. While most research is focused on improving the proposal distribution used to generate trial moves in the Markov chain, this work instead focuses on efficiently finding an initial population for population-based MCMC samplers that will expedite convergence. Four case studies, including two hydrological models, are used to demonstrate that using multi-level single linkage implicit filtering stochastic global optimization to initialize the population both reduces the overall computational cost and significantly increases the chance of finding the correct limiting distribution within the constraint of a fixed computational budget.