Lethe 1.0: An open-source parallel high-order computational fluid dynamics software framework for single and multiphase flows
Bibliographic record
Abstract
Lethe is an open-source Computational Fluid Dynamics (CFD) software framework with extensive multiphase and multiphysics capabilities. By leveraging the deal.II open-source framework, Lethe finite element solvers scale well on modern high-performance computers while possessing advanced features such as dynamic mesh adaptation, load-balancing, isoparametric high-order capabilities, and a fully-fledged Discrete Element Method (DEM) module. To facilitate contributions from the community, Lethe is extensively tested with continuous integration using over 450 unit and functional tests. Furthermore, Lethe contains 74 fully documented examples with pre-processing and post-processing steps to allow users to learn how to rapidly use and modify the framework. In this article, we give an overview of the simulation models available within Lethe and illustrate these capabilities with a selected list of examples including turbulent and multiphase flows. Program summary Program Title: Lethe CPC Library link to program files: https://doi.org/10.17632/mc5trb4kd3.1 Developer's repository link: https://github.com/chaos-polymtl/lethe Licensing provisions: Apache-2.0 Programming language: C++ Nature of problem: Single-phase incompressible flows of Newtonian and generalized Newtonian fluids. Granular flows of cohesive or non-cohesive spherical particles. Multiphase flows, including particle-laden (solid-liquid and solid-gas) flows and fluid-fluid (gas-liquid and liquid-liquid) flows. Multiphysics coupling with heat transfer. Solution method: Lethe uses stabilized continuous Galerkin finite element formulations to solve the incompressible Navier-Stokes equations and other partial differential equations. Lethe utilizes the DEM to simulate granular flows. For particle-laden flow simulations, Lethe uses an unresolved CFD-DEM approach for flows containing numerous spherical particles ( > 10 3 ), while a resolved CFD-DEM approach is used for flows with few spherical or non-spherical particles (<100). For gas-liquid and liquid-liquid flows, Volume of Fluid (VOF) or Cahn–Hilliard (CH) models are used. Additional comments including restrictions and unusual features: Lethe possesses both matrix-based and matrix-free CFD solvers for incompressible flows. The matrix-free solver efficiently simulates larger problem sizes with more than 1B unknowns, but only supports hexahedral (structured or unstructured) meshes, whereas the matrix-based solver supports both tetrahedral and hexahedral meshes. Lethe also supports dynamic mesh adaptation and load-balancing for hexahedral meshes. The load-balancing capabilities can also be used within the DEM and CFD-DEM modules and the CFD-DEM coupling.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.002 | 0.003 |
| Meta-epidemiology (narrow) | 0.002 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 0.002 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.002 | 0.003 |
| Open science | 0.004 | 0.003 |
| Research integrity | 0.002 | 0.004 |
| Insufficient payload (model declined to judge) | 0.057 | 0.023 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".