Tolosa is an open-source research project for efficient free-surface flow simulation.
Tolosa is a research project developing open-source simulation software for free-surface flows, with a focus on coastal flooding, tides, storm surges, and nearshore wave dynamics.
The project is jointly developed at IMT / INSA Toulouse and SHOM (Service Hydrographique et Océanographique de la Marine). The shallow-water solver runs operationally at SHOM and Météo-France — a 5-day Atlantic storm surge forecast on a 640-CPU cluster completes in under 5 minutes.
All modules share a common infrastructure built around unstructured triangular meshes, making it straightforward to resolve complex coastlines and transition seamlessly between deep water, shelf, and intertidal zones within a single simulation.
The wave solver (Tolosa-lct) is built on a hyperbolized Green-Naghdi model — a dispersive extension of the shallow-water equations — with an original enstrophy-based wave breaking closure that tracks the onset and dissipation of surf-zone turbulence without ad hoc switches.
Schemes are designed with three constraints: entropy dissipation for global nonlinear stability, low numerical dissipation for accurate wave propagation, and asymptotic preservation of the low-Froude limit to remain well-behaved for tidal and surge flows where gravity waves are stiff.
The codebase follows the KISS principle with selective use of object-oriented features. MPI parallelism with Scotch-based domain decomposition scales to hundreds of CPUs. GPU acceleration (AMD MI300A) delivers roughly 11× speedup over a CPU node for the wave solver.
Shared infrastructure: unstructured meshes, MPI partitioning, I/O, numerics utilities.
Saint-Venant solver for tides, surges and coastal flooding — operational at SHOM.
Hyperbolized Green-Naghdi solver for phase-resolved dispersive wave propagation and breaking.
Two-phase Euler solver with ALE formulation — under active development.
The shared foundation used by all Tolosa modules. It handles everything below the physics layer:
A 2D Saint-Venant (shallow-water) solver on unstructured triangular meshes. It targets tidal, storm surge, and riverine flooding problems where phase-resolved wave dynamics are not needed.
(Leucothea) — a phase-resolved dispersive wave solver based on a hyperbolized Green-Naghdi model. Hyperbolicization removes the elliptic solve otherwise required at each time step, making the system amenable to explicit finite-volume discretization on unstructured meshes.
A two-phase (water/air) compressible Euler solver with an Arbitrary Lagrangian-Eulerian (ALE) formulation. It is intended to push beyond the depth-averaged approximation for problems where vertical dynamics or air entrainment matter.