Project Description

Context

Notus open source CFD code is an initiative of the Institut d'Ingénierie et de Mécanique de Bordeaux (I2M), started in 2015. It is dedicated to the modeling and simulation of incompressible fluid flows in a massively parallel context. Its numerical framework is based on 2D/3D Finite Volume methods on staggered grids.

Purposes

The objective of the project is to provide a code:

• for the mechanical community that is easy to use and adapt, based on proven state-of-the-art numerical methods;
• for the applied mathematics community to develop new numerical schemes without having to rewrite a complete code, offering a fast, efficient, and approved framework for comparative and qualitative tests on numerical and physical cases;
• that runs on massively parallel supercomputers (such as those available at PRACE and various French mesocenters), while masking parallelism complexities for easy programming;
• that offers numerical tools that can be easily used to solve novel mathematical and physical problems of your own;
• that is thoroughly validated and documented.

Technical Features List

To have a complete view of what Notus is capable of computing, we provide a comprehensive list of general, modeling, and numerical features of the code.

Domain Features / Grids

Module	Feature	Remarks and Limitations
Geometry / Grid	Rectangular domain (2D/3D); regular, Chebyshev, exponential, file, composite grids
Immersed Boundaries	Static geometries from surface mesh	Under development

Modeling Features

Module/Equation	Feature	Remarks and Limitations
Navier-Stokes	Boundary conditions: wall, inlet, moving, Neumann, slip, periodic
Navier-Stokes	Brinkman term	At user convenience
Navier-Stokes	Gravity term	Boussinesq approximation
Navier-Stokes	Surface tension term	Contact line not taken into account
Energy	Advection + diffusion
Species	Advection + diffusion	Passive scalars; solutal flows
Multiphase	One fluid model	Immiscible fluids
Turbulence	LES model (mixed scale) Synthetic inlet boundary conditions RANS: \(k-\omega~SST\), \(v^2-f\)	Under validation
Physical Properties	Temperature-dependent density	Other properties are constant per phase

For a detailed description of each modeling feature, refer to the Brief description of models and equations page.

Numerical Features

Module/Equation	Sub-topic	Feature	Remarks and Limitations
Navier-Stokes	Temporal discretization	1st or 2nd order
Navier-Stokes	Time splitting method	Goda or Timmermans	Dodd & Frantzis approximations also available
Navier-Stokes	Advection term	Implicit: order 1 (upwind), order 2 (upwind and centered), hybrid upwind/centered schemes Explicit: order 2 (upwind and centered), WENO3 & WENO5 schemes
Energy / Species	Advection term	Implicit: order 1 (upwind) and order 2 (upwind and centered) schemes Explicit: order 1 (upwind) and order 5 (WENO5) schemes
Phases	Advection	VOF-PLIC	2D/3D
Phases	Advection	MOF	2D. 3D is under development
Phases	Advection	Level Set	WENO5 scheme with Euler or RK2 temporal discretization
Phases	Surface tension	Level Set curvature computation VoF-PLIC, MoF	Standard or Closest Point methods Height function method
Solvers		HYPRE	Struct, SStruct interfaces
Solvers		MUMPS	Pord and Metis partitioners
Solvers		Lis

For a detailed description of each numerical feature, refer to the Discretization of PDE page.

System and Validation Features

Module	Feature	Remarks and Limitations
User Interface	Input file	Input parameters are read from a file
Input/Output	ADIOS, Ensight, ADIOS2, Pixie & Xdmf Checkpoint / restart	Parallel output (single files are written)
Diagnostic Quantities	Nusselt number, Sherwood number, mean velocity, etc.
V&V	Scripts	The code can be verified and validated through automatic scripts
V&V	Convergence scripts	Numerical spatial and temporal convergence rates can automatically be computed
Performance	Scripts to test code scalability	Available on several supercomputers

Requirements

The compilation and execution of Notus CFD require several third-party libraries. These are used for numerical calculus, output data writing, etc. The How to Build Notus Guide details how they can be compiled and installed on your particular platform, if needed.

We provide a list of required tools, libraries, and associated versions with which Notus CFD is guaranteed to compile and function.

Third-Party Libraries

The following third-party libraries can be automatically downloaded and compiled from our notus_third_party Git repository.

Library	Version	Remarks
ADIOS	1.13.1 (patched)	The Adaptable Input/Output System version 1
ADIOS2	2.10.1	The Adaptable Input/Output System version 2
HDF5	1.14.4-2	Hierarchical Data Format version 5
HYPRE	2.18.2	Scalable Linear Solvers and Multigrid Methods
METIS	5.1.0	Graph partitioning, required by MUMPS
MUMPS	5.7.2	MUltifrontal Massively Parallel Sparse Direct Solver
ScaLAPACK	2.0.2	Scalable Linear Algebra PACKage, required by MUMPS
Lis	2.2.0	Library of Iterative Solvers for Linear Systems
T3PIO	2.3.10	TACC's Terrific Tool for Parallel I/O

Compilation Tools

Depending on your system, you may choose one of the following options:

GNU

Tool / Library	Version	Remarks
GNU compilers	7.3
Open MPI	2.1.1

Intel

Tool / Library	Version	Remarks
Intel compilers	≥ 18
Intel OneAPI	≥ 24
Intel MPI