osinco3d

This project is a Fortran90 Computational Fluid Dynamics (CFD) code designed to solve the 3D Navier-Stokes equations for incompressible flow using a high-order finite difference method.

Table of Contents

• Summary
• Installation
• Usage
• Contributing
• Parameters

Summary

• Prediction-correction method: Utilizes the Chorin method.
• Time integration schemes: Euler, Adams-Bashforth 2nd order (AB2), or Adams-Bashforth 3rd order (AB3).
• Spatial discretization schemes: Finite differences.
  • First derivatives: 6th order.
  • Second derivatives: 4th order.
• Poisson equation solver: Successive Over-Relaxation (SOR) method with a 2nd order finite differences scheme.
• Boundary conditions: Periodic or free-slip conditions in all directions and Dirichlet conditions in the x-direction only.
• Large Eddy Simulation: Standard Smagorinsky model
• Visualization:
  • 2D: Using Gnuplot.
  • 3D: Using ParaView (XDMF format).
• Programming language: Fortran90.
• Configuration: Single parameter file parameters.o3d.
• Executable: The executable file is named osinco3d.app.

Installation

Clone the repository:

git clone git@github.com:jojoledemago/osinco3d.git
cd src/
make

Use make clean to clean compilation directory

Usage

Got to the bin directory:

cd bin

Edit the paramters file: parameters.o3d

./osinco3d.app

Contributing

I am looking to parallelize the code using the MPI library and to implement a non-reflective outflow condition at $x=L_x$. If you're interested in contributing, please feel free to help with these tasks.

Parameters

The parameters.o3d file contains various parameters that control the simulation. Here's a description of each parameter group:

FlowParam

• typesim: type of simulation
  • 0: read data from fields.bin file
  • 1: Convected vortex
  • 2: Taylor-Green vortex
  • 3: Planar Jet
  • 4: Co-planar Jet
  • 5: Mixing Layer
  • 6: Vortex Merge
• l0: characteristic size of the flow field
• u0: characteristic velocity of the flow field
• re: Reynolds number of the flow, defined as $Re = \frac{u_0 \cdot l_0}{\nu}$ ($\nu$ is the kinematic viscosity)
• ratio: ratio between the maximum and minimum velocity in the domain. This parameter depends on the simulation type typesim

Domain

• nx, ny, nz: number of discretisation points in each direction ($x$, $y$, $z$)
• xlx, yly, zlz: sizes of the computational domain in each direction
• x0, y0, z0: origin of the computational domain in each direction

BoundaryConditions

• nbcx1, nbcxn: BC for x-direction at faces 1 $x(1)$ and nx $x(nx)$
• nbcy1, nbcyn: BC for y-direction at faces 1 $y(1)$ and ny $y(ny)$
• nbcz1, nbczn: BC for z-direction at faces 1 $z(1)$ and nz $z(nz)$
  • 0: Periodic
  • 1: Free Slip
  • 2: Dirichlet, only for x-direction
• sim2d: Set 1 to execute a 2D simulation

AdvanceTime

• itscheme: time integration scheme
  • 1: Euler
  • 2: second-order Adams-Bashforth
  • 3: third-order Adams-Bashforth
• cfl: Courant-Friedrichs-Lewy (CFL) number, a criterion for numerical stability, defined as $\text{CFL} = \frac{u_0 \cdot \Delta t}{\Delta x}$
• irestart
  • 1: restart simulation from fields.bin file (only valid for typesim = 0)
  • 0: start a new simulation
• itstart: Index of the first time step
• itstop: Index of the last time step

PoissonEq

• omega: relaxation coefficient for the Successive Over-Relaxation (SOR) method. The theoretical optimum is: $\omega = \frac{2}{1+\sin(\pi \cdot L_x/n_x)}$
• idyn: If 1, the relaxation coefficient $\omega$ is calculated dynamically at each iteration.
• eps: convergence criterion for the iterative solver
• kmax: maximum number of iterations allowed for the solver

Scalar (optional)

• nscr: flag to enable scalar equation resolution (set to 1)
• sc: Schmidt number, defined as $Sc = \frac{\nu}{D}$ (D is the scalar diffusivity)

VisuParameters

• nfre: frequency of saving data for visualization (XDMF format)
• nsve: frequency of saving data for post-processing
• initstat: time after which statistics are collected
• xpro, ypro, zpro: coordinates of the cut plane for 2D visualization (Gnuplot format)

InitInflow

• iin: inlet boundary condition type (0: classical, 1: turbulent)
• inflow_noise: turbulence intensity at the inlet boundary (0 to 1), representing a fraction of the characteristic velocity u0
• ici: initial condition type (0: classical, 1: oscillation, 2: noise, 3: both)
• init_noise: turbulence intensity for the initial condition (0 to 1), representing a fraction of the characteristic velocity u0

LES

• iles: If 1, Large Eddy Simulation is enabled
• cs: Samgorinsky constant to evaluate $\nu_{t}$