Repository explanation: RBVMS CFD application overview

[Copilot]

Addressed request to explain what this repository is about.

RBVMS is a computational fluid dynamics application for incompressible flow simulation using the Residual-Based Variational Multiscale formulation.

Key characteristics:

• Method: VMS formulation with LES turbulence modeling for high Reynolds number flows
• Discretization: Tetrahedral meshes and isogeometric (NURBS) analysis
• Dependencies: Built on MFEM (FEM library), HYPRE (linear solvers), MPI
• Boundary conditions: Strong/weak Dirichlet, outflow, suction/blowing, periodic
• Test cases: Poiseuille, lid-driven cavity, Von Karman vortex street, NACA foils

Based on: Bazilevs & Akkerman, "Large eddy simulation of turbulent Taylor–Couette flow using isogeometric analysis and the residual-based variational multiscale method," J. Comp. Physics (2010).

No code changes required—this was an explanatory request.

Original prompt

can u explain what this repo is?

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[Csh0917]

@copilot my focus is on rbvms and supg, so ignore the rbvms-ls

[Copilot]

@copilot my focus is on rbvms and supg, so ignore the rbvms-ls

Understood. The focus is on the rbvms (incompressible Navier-Stokes with RBVMS formulation) and supg (Streamline Upwind Petrov-Galerkin for convection-diffusion) modules. I'll exclude rbvms-ls from any future analysis or work.

[Csh0917]

@copilot what I confused is the workflow, what is the connection between mesh, condif, supg, rbvms,util folders and i am using linnux VM with info: Welcome to Ubuntu 22.04.5 LTS (GNU/Linux 6.8.12-11-pve x86_64)

• Documentation: https://help.ubuntu.com
• Management: https://landscape.canonical.com
• Support: https://ubuntu.com/pro
  New release '24.04.3 LTS' available.
  Run 'do-release-upgrade' to upgrade to it.

Last login: Fri Dec 5 08:08:30 2025 from 145.94.226.168
root@Sun:~# what should I do, how should make the command, how can I visualize it?

[Copilot]

@copilot what I confused is the workflow, what is the connection between mesh, condif, supg, rbvms,util folders and i am using linnux VM with info: Welcome to Ubuntu 22.04.5 LTS (GNU/Linux 6.8.12-11-...

Here's the workflow and folder connections:

Folder Structure:

• rbvms/ - Main Navier-Stokes solver (incompressible flow)
• supg/ - Convection-diffusion solver (SUPG method)
• util/ - Shared utilities (coefficients, solvers, print functions) used by both rbvms and supg
• cases/ - Test cases with meshes and boundary condition files
  • cases/condif/ - Uses supg executable for convection-diffusion problems
  • Other cases (poiseuille, lid-driven-cavity, etc.) - Use rbvms executable

Workflow:

1. Mesh file (.mesh) defines geometry
2. C file (e.g., poiseuille.c) defines boundary/initial conditions → compiled to libfun.so
3. Executable (rbvms or supg) reads mesh + library to run simulation

Ubuntu 22.04 Setup:

# Install dependencies
sudo apt-get update
sudo apt-get install cmake git build-essential openmpi-common libopenmpi-dev libmetis5 libmetis-dev

# Clone and build
git clone https://github.com/IdoAkkerman/rbvms.git
cd rbvms && mkdir build && cd build
cmake .. && make -j 4

# Run a test case
cd ../cases/poiseuille
bash run-nurbs

Visualization:
Install VisIt: https://visit-dav.github.io/visit-website/
Open the files in solution/ directory generated after running a simulation.

[Csh0917]

@copilot root@Sun:~/Minor_Project/build/bin# this is where I am at now, tell me what to do nex, btw, there is a new condif called condif3 in the branch minor2025

[Copilot]

@copilot root@Sun:~/Minor_Project/build/bin# this is where I am at now, tell me what to do nex, btw, there is a new condif called condif3 in the branch minor2025

From ~/Minor_Project/build/bin#, here's what to do next:

To run the condif case (convection-diffusion with SUPG):

cd ../../cases/condif
bash run-nurbs

To run rbvms cases (Navier-Stokes):

cd ../../cases/poiseuille
bash run-nurbs

For the condif3 case on minor2025 branch:

cd ~/Minor_Project
git fetch origin
git checkout minor2025
# Then rebuild if needed:
cd build && make -j 4
# Navigate to the new condif3 case and run it

Check available executables in your build:

ls -la ~/Minor_Project/build/bin/
# You should see: rbvms, supg (and possibly rbvms-ls)

The supg executable is for convection-diffusion problems (condif cases), while rbvms is for incompressible Navier-Stokes flow cases.

[Csh0917]

@copilot i keep getting this error: esh Characteristics:
Dimension : 2
Space dimension : 2
Number of vertices : 10
Number of edges : 13
Number of elements : 4 -- 4 Square(s)
Number of bdr elem : 10
Euler Number : 1
h_min : 1
h_max : 1
kappa_min : 1
kappa_max : 1

Strong = 1

Verification failed: (bnd_flag[b]) is false:
--> Not all boundaries have a boundary condition set.
... in function: int main(int, char**)
... in file: /root/Minor_Project/Minor_project/supg/supg.cpp:186

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MPI_ABORT was invoked on rank 0 in communicator MPI_COMM_WORLD
with errorcode 1.

NOTE: invoking MPI_ABORT causes Open MPI to kill all MPI processes.
You may or may not see output from other processes, depending on
exactly when Open MPI kills them.

[Copilot]

@copilot i keep getting this error: esh Characteristics:
Dimension : 2
Space dimension : 2...

The error indicates you need to specify boundary conditions for ALL boundaries in your mesh. Your mesh has multiple boundary attributes, but only boundary 1 is set.

To fix: Update your run command to include all boundary attributes. Check your mesh file to see which boundary IDs exist, then specify them all:

# For the original condif case with square.mesh (boundaries 1,2,3,4):
mpirun -n 1 ./supg -m square.mesh -o 2 -r 1 --strong-bdr "1 2 3 4" -l libfun.so

# For condif3 or other meshes, check boundary attributes:
grep -A 20 "boundary" your_mesh_file.mesh

The mesh info shows 10 boundary elements - you need to identify all unique boundary attribute numbers and include them in --strong-bdr or --weak-bdr.

Example if boundaries are 1-5:

--strong-bdr "1 2 3 4 5"

Check the run-nurbs script in your condif3 case folder - it should have the correct boundary settings for that specific mesh.