26 research outputs found
PyClaw: Accessible, Extensible, Scalable Tools for Wave Propagation Problems
No full textDevelopment of scientific software involves tradeoffs between ease of use, generality, and performance. We describe the design of a general hyperbolic PDE solver that can be operated with the convenience of MATLAB yet achieves efficiency near that of hand-coded Fortran and scales to the largest supercomputers. This is achieved by using Python for most of the code while employing automatically wrapped Fortran kernels for computationally intensive routines, and using Python bindings to interface with a parallel computing library and other numerical packages. The software described here is PyClaw, a Python-based structured grid solver for general systems of hyperbolic PDEs [K. T. Mandli et al., PyClaw Software, Version 1.0, http://numerics.kaust.edu.sa/pyclaw/ (2011)]. PyClaw provides a powerful and intuitive interface to the algorithms of the existing Fortran codes Clawpack and SharpClaw, simplifying code development and use while providing massive parallelism and scalable solvers via the PETSc library. The package is further augmented by use of PyWENO for generation of efficient high-order weighted essentially nonoscillatory reconstruction code. The simplicity, capability, and performance of this approach are demonstrated through application to example problems in shallow water flow, compressible flow, and elasticity
ForestClaw: Hybrid forest-of-octrees AMR for hyperbolic conservation laws
No full textWe present a new hybrid paradigm for parallel adaptive mesh refinement (AMR) that combines the scalability and lightweight architecture of tree-based AMR with the computational efficiency of patch-based solvers for hyperbolic conservation laws. The key idea is to interpret each leaf of the AMR hierarchy as one uniform compute patch in Rd with md degrees of freedom, where m is customarily between 8 and 32. Thus, computation on each patch can be optimized for speed, while we inherit the flexibility of adaptive meshes. In our work we choose to integrate with the p4est AMR library since it allows us to compose the mesh from multiple mapped octrees and enables the cubed sphere and other nontrivial multiblock geometries. We describe aspects of the parallel implementation and close with scalings for both MPI-only and OpenMP/MPI hybrid runs, where the largest MPI run executes on 16,384 CPU cores. © 2014 The authors and IOS Press.We would like to thank the Texas Advanced Computing Center (TACC) for access to the Stampede supercomputer under allocations TG-DPP130002 and TG-ASC130001 granted by the NSF XSEDE program. The authors acknowledge valuable discussion with Randy LeVeque, Marsha Berger, and Hans-Petter Langtangen. We also acknowledge David Ketcheson and the KAUST sponsored HPC3 numerics workshop at which the initial phases of this project were first discussed. The second author would like to also acknowledge the Isaac Newton Institute (Cambridge, UK), where much of the preliminary development work for ForestClaw was done. The fourth author recognizes Simula Research Lab, Norway, for funding. The leaf/patch paradigm was independently presented by B. as part of a talk at the SCI Institute, Salt Lake City, Utah, USA in July 2011
Impacts of barrier-island breaching on mainland flooding during storm events applied to Moriches, New York
No full textBarrier islands can protect the mainland from flooding during storms through reduction of storm surge and dissipation of storm-generated wave energy. However, the protective capability is reduced when barrier islands breach and a direct hydrodynamic connection between the water bodies on both sides of the barrier island is established. Breaching of barrier islands during large storm events is complicated, involving nonlinear processes that connect water, sediment transport, dune height, and island width, among other factors. In order to assess how barrier-island breaching impacts flooding on the mainland, we used a statistical approach to analyze the sensitivity of mainland storm surge to barrier-island breaching by randomizing the location, time, and extent of a breach event. We created a framework that allows breaching to develop during the course of a simulation and imposes a breach in an approximation of a Gaussian bell curve that deepens over time. We show that simulating a storm event and varying the size, location, and number of breaches in the barrier island that mainland storm surge and horizontal inundation is affected by breaching; total inundation has a logarithmic relationship with total breach area which tapers off after the entire island is removed. Breach location is also an important predictor of inundation and bay surge. The insights we have gleaned from this study can help prepare shoreline communities for the differing ways that breaching affects the mainland coastline. Understanding which mainland locations are vulnerable to breaching, planners and coastal engineers can design interventions to reduce the likelihood of a breach occurring in areas adjacent to high flood risk.</p
A new tropical cyclone surge index incorporating the effects of coastal geometry bathymetry and storm information
No full textRobust Adaptive Estimator Using Evolutional Algorithm for Noise Cancellation in Multichannel System
No full textSolving the Serre-Green-Naghdi equations to add dispersive corrections to the shallow water wave equations
No full textThe depth-averaged shallow water wave equations are commonly used to model flows arising from natural hazards. The GeoClaw code, developed by D. George, R. J. LeVeque, M. J. Berger, K. Mandli and others is one example of a depth-averaged flow solver now widely used for modeling tsunamis, overland flooding, debris flows, storm surges and so on. Generally, depth averaged flow models show excellent large scale agreement with observations and can thus be reliably used to predict whether tsunamis will reach distant coast lines, and if, so can give vital information about arrival times. However, for other types of flows, dispersive effects missing from the SWE model can play an important role in determining localized effects such as whether waves will overtop seawalls, or whether a landslide entering a lake will trigger tsunami-like behavior on the opposite shore. Because of the importance of these dispersive effects, several depth averaged codes include dispersive corrections to the SWE. One set of equations commonly used to model these dispersive effects are the Serre-Green-Naghdi (SGN) equations.
I will present my work to include dispersive correction terms into the GeoClaw extension of ForestClaw, a parallel adaptive library for Cartesian grid methods. One formulation of the SGN equations stabilizes higher order derivatives by treating them implicitly. As a result, a key component of an SGN solver is a variable coefficient Poisson solver. We will describe the SGN equations and provide an overview of their derivation, and then show preliminary results on uniform Cartesian meshes. Comparisons with the SGN solver in Basilisk (S. Popinet) and BoussClaw (J. Kim et al) will also be shown to verify our model. Preliminary results using the Hierarchical-Poincar\'e-Steklov (HPS) method developed by Gillman and Martinsson (2014) to solve the Poisson problem on adaptive meshes will also be shown.Non UBCUnreviewedAuthor affiliation: Boise StateResearche
New results from the antarctic muon and neutrino detector array
No full textWe present recent results from the Antarctic Muon And Neutrino Detector Array (AMANDA) on searches for high-energy neutrinos of extraterrestrial origin. We have searched for a diffuse flux of neutrinos, neutrino point sources and neutrinos from GRBs and from WIMP annihilations in the Sun or the center of the Earth. We also present a preliminary result on the first energy spectrum above a few TeV for atmospheric neutrinos. © 2005 Published by Elsevier B.V.0SCOPUS: ar.jinfo:eu-repo/semantics/publishe
Results from the AMANDA detector
No full textThe Antarctic Muon And Neutrino Detector Array (AMANDA) is a high-energy neutrino telescope based at the geographic South Pole. It is a lattice of photo-multiplier tubes buried deep in the polar ice, which is used as interaction and detection medium. The primary goal of this detector is the observation of astronomical sources of high-energy neutrinos. This paper shows the latest results of the search for a diffuse flux of extraterrestrial νμs with energies between 1011 eV and 10 18 eV, νμs emitted from point sources and νμs from dark matter annihilation in the Earth and the Sun
Journal of Waterway, Port, Coastal, and Ocean Engineering
No full textAs scientific understanding of barrier morphodynamics has improved, so has the ability to reproduce observed phenomena and predict future barrier states using mathematical models. To use existing models effectively and improve them, it is important to understand the current state of morphodynamic modeling and the progress that has been made in the field. This manuscript offers a review of the literature regarding advancements in morphodynamic modeling of coastal barrier systems and summarizes current modeling abilities and limitations. Broadly, this review covers both event-scale and long-term morphodynamics. Each of these sections begins with an overview of commonly modeled phenomena and processes, followed by a review of modeling developments. After summarizing the advancements toward the stated modeling goals, we identify research gaps and suggestions for future research under the broad categories of improving our abilities to acquire and access data, furthering our scientific understanding of relevant processes, and advancing our modeling frameworks and approaches.This material is based upon work that is primarily supported by the U.S. Army Corps of Engineers through the U.S. Coastal Research Program (under Grant No. W912HZ-20-2-0005) and partially supported by the National Science Foundation (under Grant No. 1735139). Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of these organizations. This publication was also prepared in part by Steven Hoagland using Federal funds under award NA18OAR4170083, Virginia Sea Grant College Program Project R/72155T, from the National Oceanic and Atmospheric Administration’s (NOAA) National Sea Grant College Program, U.S. Department of Commerce. The statements, findings, conclusions, and recommendations are those of the author(s) and do not necessarily reflect the views of Virginia Sea Grant, NOAA, or the U.S. Department of Commerce.Published versio
Flux limits on ultra high energy neutrinos with AMANDA-B10
No full textData taken during 1997 with the AMANDA-B10 detector are searched for a diffuse flux of neutrinos of all flavors with energies above 1016eV. At these energies the Earth is opaque to neutrinos, and thus neutrino induced events are concentrated at the horizon. The background are large muon bundles from down-going atmospheric air shower events. No excess events above the background expectation are observed and a neutrino flux following E-2, with an equal mix of all flavors, is limited to E2φ(1015eV < E < 3 × 1018eV) ≤ 0.99 × 10-6GeV cm-2 s-1 sr-1 at 90% confidence level. This is the most restrictive experimental bound placed by any neutrino detector at these energies. Bounds to specific extra-terrestrial eutrino flux predictions are also presented. © 2004 Elsevier B.V. All rights reserved.0SCOPUS: ar.jinfo:eu-repo/semantics/publishe
