Automatic grid refinement criterion for lattice Boltzmann method

In all kinds of engineering problems, and in particular in methods for computational fluid dynamics based on regular grids, local grid refinement is of crucial importance. To save on computational expense, many applications require to resolve a wide range of scales present in a numerical simulation by locally adding more mesh points. In general, the need for a higher (or a lower) resolution is not known a priori, and it is therefore difficult to locate areas for which local grid refinement is required. In this paper, we propose a novel algorithm for the lattice Boltzmann method, based on physical concepts, to automatically construct a pattern of local refinement. We apply the idea to the two-dimensional lid-driven cavity and show that the automatically refined grid can lead to results of equal quality with less grid points, thus sparing computational resources and time. The proposed automatic grid refinement strategy has been implemented in the parallel open-source library Palabos

Cybershake NZ v17.9: New Zealand simulation-based probabilistic seismic hazard analysis

This paper presents the computational workflow and preliminary results of probabilistic seismic hazard analysis (PSHA) in New Zealand based on physics-based ground motion simulations (‘Cybershake NZ’). In the current work completed to date, the Graves and Pitarka (2010, 2015) hybrid broadband ground motion simulation approach is utilized considering a transition frequency of 0.25 Hz, a detailed crustal model with a grid spacing of 0.4 km, and an empirically-calibrated local site response model. Variation in hypocentre location and slip distribution are considered to partially account for the variability in ground motion characteristics. Ruptures from the distributed seismicity model are considered in the total hazard via empirical ground motion models. Intensity measures for sample scenario ruptures and subsequently generated hazard curves are presented here. Treatment of uncertainty in the context of simulation-based PSHA is discussed. Lastly, improvements for future versions of the ongoing effort are outlined

SeisFinder: A web application for extraction of data from computationally-intensive earthquake resilience calculations

SeisFinder is an open-source web service developed by QuakeCoRE and the University of Canterbury, focused on enabling the extraction of output data from computationally intensive earthquake resilience calculations. Currently, SeisFinder allows users to select historical or future events and retrieve ground motion simulation outputs for requested geographical locations. This data can be used as input for other resilience calculations, such as dynamic response history analysis. SeisFinder was developed using Django, a high-level python web framework, and uses a postgreSQL database. Because our large-scale computationally-intensive numerical ground motion simulations produce big data, the actual data is stored in file systems, while the metadata is stored in the database

Vizualisation for scientific discovery and communication: Kaikoura earthquake as a case study

Ground Motion (GM) Simulation involves complex calculations that produce a large collection of numerical data, which needs a good visual presentation to help better understanding of the complex dynamics of the earthquake. In this poster, we present a visualisation workflow that we developed to produce a 3D animation from the simulation data of the 2016 M7.8 Kaikoura earthquake as a case study, and discuss how it facilitated scientific discovery and communication

Local mesh refinement sensor for the lattice Boltzmann method

A novel mesh refinement sensor is proposed for lattice Boltzmann methods (LBMs) applicable to either static or dynamic mesh refinement algorithms. The sensor exploits the kinetic nature of LBMs by evaluating the departure of distribution functions from their local equilibrium state. This sensor is first compared, in a qualitative manner, to three state-of-the-art sensors: (1) the vorticity norm, (2) the Q-criterion, and (3) spatial derivatives of the vorticity. This comparison shows that our kinetic sensor is the most adequate candidate to propose tailored mesh structures across a wide range of physical phenomena: incompressible, compressible subsonic/supersonic single phase, and weakly compressible multiphase flows. As a more quantitative validation, the sensor is then used to produce the computational mesh for two existing open-source LB solvers based on inhomogeneous, block-structured meshes with static and dynamic refinement algorithms, implemented in the Palabos and AMROC-LBM software, respectively. The sensor is first used to generate a static mesh to simulate the turbulent 3D lid-driven cavity flow using Palabos. AMROC-LBM is then adopted to confirm the ability of our sensor to dynamically adapt the mesh to reach the steady state of the 2D lid-driven cavity flow. Both configurations show that our sensor successfully produces meshes of high quality and allows to save computational time

QuakeCoRE and OpenSees (Year 1): Optimisation of Source Code, Pre- and Post-Processing Tools, and Community Development

The OpenSees finite element platform (Open System for Earthquake Engineering Simulation) developed through the University of California Berkeley is the principal collaborative software identified by QuakeCoRE Technology Platform 4 for use in detailed seismic response modelling of individual infrastructure components. OpenSees was selected for this purpose due to its capabilities as an open-source platform for sequential and parallel analysis of both geotechnical and structural systems. OpenSees is one of the few tools available with all of these attributes, and due to this unique combination of features it meets all three of the underlying principles identified for QuakeCoRE Technology Platform 4: it is open-source, it is scalable (able to make use of HPC resources), and it is flexible (works for variety of problem types and able to work with other QuakeCoRE software modules)

The Bolivian fauna of the genus Anastrepha Schiner (Diptera: Tephritidae)

Ramos, Elizabeth Quisberth, Norrbom, Allen L., Marinoni, Luciane, Sutton, Bruce D., Steck, Gary J., Sánchez, Juan José Lagrava (2021): The Bolivian fauna of the genus Anastrepha Schiner (Diptera: Tephritidae). Zootaxa 4926 (1): 43-64, DOI: https://doi.org/10.11646/zootaxa.4926.1.