I'm a computational mathematics researcher, with a focus on geophysical fluid dynamics, ocean modelling and planetary climate simulation. My research interests include: high-order accurate finite-volume/difference methods for computational fluid dynamics, general-circulation modelling and ocean dynamics, unstructured mesh-generation and computational geometry.

I'm a staff scientist in the Theoretical Division (T-3) at Los Alamos National Laboratory, contributing to the development of the Energy Exascale Earth System Model (E3SM), and ocean dynamics in the Model for Prediction Across Scales (MPAS).

Sometimes I also work with my wife, artist Sara Morawetz, on more philosophical projects.


Contact: dengwirda [at] lanl [dot] gov


PROJECTS


See my github profile for a full listing.

JIGSAW-GEO: a variant of my general-purpose meshing library JIGSAW, designed to generate high-quality grids for unstructured ocean/atmospheric models including MPAS, COMPAS, FESOM and PERISCOPE.

See JIGSAW-GEO(PYTHON) on github for more >>
See JIGSAW-GEO(MATLAB) on github for more >>

PERISCOPE: an unstructured, arbitrary lagrangian-eulerian ocean model.

PERISCOPE is still under development.

SWE-Sandbox: A Python environment for developing unstructured discretisation schemes for the spherical shallow-water equations.

See SWE-Python on github for more >>

JIGSAW: a computational library for unstructured mesh generation; designed to generate high-quality triangulations and polyhedral decompositions of general planar, surface and volumetric domains.

See JIGSAW on github for more >>
See JIGSAW(PYTHON) on github for more >>
See JIGSAW(MATLAB) on github for more >>

PPR: a Fortran library for high-order Piecewise Polynomial Reconstruction (PPR). This package forms the basis for our high-order finite-volume and arbitrary lagrangian-eulerian (ALE) transport algorithms.

See PPR on github for more >>

MESH2D: a MATLAB / OCTAVE-based unstructured mesh-generator for two-dimensional polygonal geometries, providing a range of relatively simple, yet effective two-dimensional meshing algorithms.

See MESH2D on github for more >>



PUBLICATIONS


A Conservative Flux-Form Semi-Lagrangian Method for Offline Scalar Transport on Unstructured Meshes (M. Herzfeld and D. Engwirda, 2020. Ocean Modelling, in preparation.)

A description of the conservative 'long time-step' scalar transport algorithm developed for COMPAS.

Australian tidal currents – assessment of a barotropic model (COMPAS v1.3.0 rev6631) with an unstructured grid (D. Griffin, M. Herzfeld, M. Hemer, D. Engwirda, in review, 2021.)
https://doi.org/10.5194/gmd-2021-51

Use of the unstructured COMPAS model to simulate tidal dynamics in the Australian coastal zone.

Fast Mapping onto Census Blocks (J. Kepner, A. Kipf, D. Engwirda, N. Vembar, M. Jones, L. Milechin, V. Gadepally, C. Hill, T. Kraska, W. Arcand, D. Bestor, W. Bergeron, C. Byun, M. Hubbell, M. Houle, A. Kirby, A. Klein, J. Mullen, A. Prout, A. Reuther, A. Rosa, S. Samsi, C. Yee, P. Michaleas, 2020. IEEE High Performance Extreme Computing)

Very large scale spatial indexing for tracking COVID-like epidemics.

A Coastal Unstructured Model using Voronoi Meshes and C-grid Staggering (M. Herzfeld, D. Engwirda and F. Rizwi, 2020. Ocean Modelling, 148, 101599)
https://doi.org/10.1016/j.ocemod.2020.101599

A description of COMPAS: an unstructured coastal ocean modelling framework developed at CSIRO, Australia.

MPAS-Ocean Simulation Quality for Variable-Resolution North American Coastal Meshes ( K. Hoch, M. Petersen, S. Brus, D. Engwirda, K. Rosa, P. Wolfram, A. Roberts, 2020. JAMES, 12(3), e2019MS001848)
https://doi.org/10.1029/2019MS001848

How robust is MPAS-Ocean wrt. aggressive variable resolution configurations refined in the US coastal zone?

Generalised primal-dual grids for unstructured co-volume schemes (D. Engwirda, 2018. J. Comp. Phys., 375, 155-176)
https://doi.org/10.1016/j.jcp.2018.07.025

An algorithm for the construction of 'weighted' Delaunay/Voronoi pairs (a.k.a. Laguerre/Power tessellations) to build 'optimal' orthogonal grids for staggered discretisations.

JIGSAW-GEO (1.0): locally-orthogonal staggered unstructured grid generation for general circulation modelling on the sphere (D. Engwirda, 2017, Geosci. Model Dev., 10, 2117-2140)
https://doi.org/10.5194/gmd-10-2117-2017

JIGSAW's spherical meshing algorithm; designed to generate high-quality unstructured grids for global ocean/atmospheric modelling.

High-order accurate finite-volume formulations for the pressure gradient force in layered ocean models. (D. Engwirda, M. Kelley, & J. Marshall, 2017, Ocean Modelling, 116, 1-15)
https://doi.org/10.1016/j.ocemod.2017.05.003

A finite-volume formulation for the pressure-gradient force in 'generalised' coordinate ocean models.

Conforming restricted Delaunay mesh generation for piecewise smooth complexes. (D. Engwirda, 2016, Procedia Engineering, 163, 84-96
http://dx.doi.org/10.1016/j.proeng.2016.11.024

A description of JIGSAW's 'restricted' Frontal-Delaunay algorithm for meshing surfaces/volumes with 'sharp-features'.

Voronoi-based point-placement for three-dimensional Delaunay-refinement. (D. Engwirda, 2015, Procedia Engineering, 124, 330-342
http://dx.doi.org/10.1016/j.proeng.2015.10.143

A description of JIGSAW's 'off-centre' Delaunay-refinement strategy for meshing three-dimensional volumes.

On the formulation of environmental fugacity models and their numerical solutions. (M. Bates, M. Bigot, R. Cropp, D. Engwirda, C. Friedman & D. Hawker, 2016, Environmental Toxicology and Chemistry, 35 (9), 2182-2191
http://dx.doi.org/10.1002/etc.3403

A analysis of fugacity models, focusing on consistent, mass-based fomulations.

Off-centre Steiner points for Delaunay-refinement on curved surfaces. (D. Engwirda & D. Ivers, 2016, Computer-Aided Design, 72, 157-171
https://doi.org/10.1016/j.cad.2015.10.007

A description of JIGSAW's 'off-centre' Delaunay-refinement strategy for meshing curved surfaces.

Face-centred Voronoi refinement for surface mesh generation. (D. Engwirda & D. Ivers, 2014, Procedia Engineering, 82, 8-20
http://dx.doi.org/10.1016/j.proeng.2014.10.364

A description of JIGSAW's 'off-centre' Delaunay-refinement algorithm for meshing curved surfaces.



REPORTS


Multi-resolution unstructured grid-generation for geospatial applications on the sphere, (D. Engwirda, Research Note, International Meshing Roundtable, 2015)
arXiv preprint arXiv:1512.00307

Initial exploration of spherical mesh generation using JIGSAW.

A WENO-type slope-limiter for a family of piecewise polynomial methods, (D. Engwirda and M. Kelley, NASA Tech. Report, 2015)
arXiv preprint arXiv:1606.08188

A description of the WENO-limited PQM/PPM reconstruction techniques used in our finite-volume and arbirary lagrangian-eulerian algorithms.

Locally-optimal Delaunay-refinement and optimisation-based mesh generation, (D. Engwirda, September 2014, Ph.D Thesis, School of Mathematics and Statistics, The University of Sydney)
http://hdl.handle.net/2123/13148

My Ph.D. thesis, introducing the various 'restricted' Frontal-Delaunay refinement algorithms and mesh-optimisation techniques used in JIGSAW.

Unstructured mesh methods for the Navier-Stokes equations, (D. Engwirda, November 2005, Undergraduate Honours Thesis, School of Aerospace, Mechanical and Mechatronic Engineering, The University of Sydney)

My undergraduate honours thesis, describing an unstructured finite-volume type solver for the unsteady Navier-Stokes equations.



ART/SCIENCE WORKS (WITH SARA MORAWETZ)


Metric Units for the Solar System: [a set of 'metric units' curated for each planetary body]. The original metric system was designed in accord with the Earth -- reflecting its size, its spin; the relationship between the mass and volume of its constituent elements. What if humanity had been born elsewhere though? Should other planets be denied the autonomy to determine their own systems? Is the metric system universal, or simply a kind of Earth-centric colonialism?

étalon: [A performative walk in search of the metre]. We measure only by measuring against; a self-reflexive act of standardisation through which we order society [and self as a consequence]. To measure is to run from chaos; to divest oneself of natural entropy; to know space, place and purpose with certainty. By surveying the Paris meridian, Sara and a team of female artists will measure the Earth's curvature and create a new 'metre' through physical action.

61/60: [A series of 1-second performances celebrating leap-seconds]. The leap-second is the 'force' by which the sun is held overhead at midday, and without it our time would become unfastened to the solar-cycles in which it is steeped. Through haphazard and listless drift, we would eventually find the passage of our star bore little relation to the movement of our clocks. Striking a pair of cymbals coincident with each event, Sara tracks this unfolding discontinuity.

How the Stars Stand: [An investigation of time as measured on Mars]. Our experience of time is not constant, rather, it flexes and yields to the nature of our passage through space. Bound to Earth, this concept seems imperceptible, for we know no time but our own. Yet as we chart our path around the sun, revolving on a familial axis, time operates differently elsewhere. Living in open-source gallery for 36 Martian 'sols', Sara charted the divergence of planetary 'time'.