OUxSBLI

OUxSBLI is a GPU-accelerated CFD solver for compressible flows written in CUDA Fortran, with a Python API for parametric simulation runs.

It solves the compressible Euler / Navier-Stokes / LES equations on structured grids using explicit high-order finite-difference schemes, and runs on NVIDIA GPUs via the HPC SDK with MPI parallelisation.

Quick Start

# Install fypp (required at build time)
pip install fypp

# Build the NS Taylor-Green vortex case
cd 3D_solver/NSTGV
cmake -B build && cmake --build build -j

# Run with 2 MPI ranks
cd build && mpirun -n 2 ./a.out

Or use the Python API:

from ouxsbli import Case

case = Case(
    source   = "3D_solver/NSTGV",
    workdir  = "/tmp/my_run",
    visc     = "NS",
    scheme   = "SLAU",
    accuracy = 6,
    nx = 128, ny = 128, nz = 128,
)
case.build()
case.run(nranks=2)

Key Features

Feature	Description
KEEP scheme	Kinetic energy and entropy preserving — ideal for smooth vortical flows
SLAU / HRSLAU2	Low-dissipation AUSM — robust for compressible turbulence with shocks
Hybrid scheme	KEEP ↔ SLAU blending via Ducros dilatation sensor
High-order stencils	2nd, 4th, and 6th-order spatial discretisation
TVD reconstruction	tvd and hybrid limiters
TVD-RK3 / RK4	3-stage and 4-stage time integration
MPI decomposition	z-direction with overlapped communication
Curvilinear solver	O-grid for wing/airfoil cases (NACA 0012, compression corner)
Python API	`Case` class for parametric runs and convergence studies

Solvers and Cases

3D Cartesian (`3D_solver/`)

Case	Physics	Description
DHIT	NS	Decaying homogeneous isotropic turbulence
ETGV	Euler	Entropy-preserving Taylor-Green vortex
IVST	Euler	Inviscid vortex smooth test case
KHI	Euler	Kelvin-Helmholtz instability
NSTGV	NS	NS Taylor-Green vortex (Re=1600, M=1.25)
SBLI	NS	Shock-boundary layer interaction
STZ	NS	z-direction MPI halo exchange validation
TBL	LES	Turbulent boundary layer

2D Solver (`2D_solver/`)

Case	Physics	Description
BL	NS	Supersonic laminar boundary layer
DSL	Euler	Double shear layer
EVC	Euler	Euler vortex convection
OS	Euler	Oblique shock (M=2, θ=8°)
SBLI	NS	2D shock-boundary layer interaction
ST	Euler	Sod shock tube

Curvilinear (`3D_solver_curv/`)

Case	Physics	Description
NACA	NS	NACA 0012 airfoil on an O-grid
CORN	NS	Compression corner (M=2, θ=8°)

Validations

Supersonic Taylor-Green Vortex

Results are consistent with Lusher & Sandham (2021). Setup: Re=1600, M=1.25, 512³ grid.

Shock-Boundary Layer Interaction (SBLI)

NACA 0012 Airfoil

Jun Hatayama, Kento Tanaka, and Toshinori Kouchi. "Nonlinear causal relationship between separation bubbles and reflected shock wave in shock wave/turbulent boundary layer interaction based on information theory." Computers & Fluids (2026): 107016.

@article{hatayama2026nonlinear,
  title={Nonlinear causal relationship between separation bubbles and reflected shock wave
         in shock wave/turbulent boundary layer interaction based on information theory},
  author={Hatayama, Jun and Tanaka, Kento and Kouchi, Toshinori},
  journal={Computers \& Fluids},
  pages={107016},
  year={2026},
  publisher={Elsevier}
}

License

BSD 3-Clause License.