Channel3d

 Channel3d is an efficient second- /fourth-order finite-difference direct numerical simulation (DNS) solver with versatile viscous treatments, also with the ability to handle different boundary conditions:

• Versatile viscous treatments. The viscous term can be handled full implicitly, full explicitly, or partial implicitly
• Have the ability to handle periodic, no-slip and free-slip boundary conditions
• Second-order spatial accuracy in non-periodic directions, and fourth-order scheme is also available for periodic directions
• FFT-based (FFTW used here) method is used for Pressure Poisson Equation (PPE)
• Alternating Direction Implicit (ADI) method is adopted for Helmholtz equations
• MPI parallelization by means of pencil distributed decomposition, using 2DECOMP&FFT

How to cite Channel3d?

 Z. Gong and X. Fu, A pencil distributed direct numerical simulation solver with versatile treatments for viscous term, Computers and Mathematics with Applications, 2021;100:141-151, https://doi.org/10.1016/j.camwa.2021.09.003.

Notice 📰

 Channel3d has been integrated into the CFD-DEM sovler CP3d as a sub-solver.

Installation 💼

 During developing this solver, I often try my best to make it easy-to-understand and easy-to-use. As for compilation, present solver only has the following two prerequisites:

• MPI
• Gfortran/Intel Fortran (Supporting Fortran 2003 or higher version)

 FFTW-3.3.9 library has been explicitly included in the directory ./src/ThirdParty/fftw/, but it is strongly recommended to recomplied FFTW-3.3.9 for the first use. After entering the folder Channel3d-master/ in terminal, you can compile the code as follows:

1. chmod a+x ./mymake.sh
2. ./mymake.sh
3. choose the correct compiler you use, and the executable you want to compile, following guidances printed in the terminal

 Yon can also compile the interpolateField code in the folder ./Tool/interpolateField/ by typing:

1. cd ./Tool/interpolateField
2. chmod a+x ./makeInterp.sh
3. ./makeInterp.sh
4. choose the correct compiler you use, and the executable you want to compile, following guidances printed in the terminal
5. cd ../..

 If the compiling process successfully, the executable file(s) channel2nd/channel4th will be appeared in the folder Channe3d-master/, and interpolateField will be included in the folder ./Tool/interpolateField/.

Usage 📖

 After compiling the code successfully, you can run the executable file like that:

mpirun -n [np] [exeName] [inputFile]

 Here:

• np denotes the number of processors you use
• exeName stands for specific executable file name, namely channel2nd or channel4th
• inputFile is the name string for the input parameter file

 For instance, if you want to run the lid-driven cavity case, you can type the following words in your terminal:

mpirun -n 4 ./channel2nd ./Input/LidDrivenCavity.prm

Input file

 The input file examples are stored in the folder ./Input/. See ./doc/channel2nd_prm.md and ./doc/channel4th_prm.md for detailed descriptions to the input file for second-order and fourth-order scheme respectively.

A complete example

 See ./doc/Toturial_for_channel_turbulence_4th.pdf for a complete example to the wall-bounded turbulence at Re_tau =180 using fourth-order scheme, including the postprocessing, and verification.

To do list 💪

• Fourth-order scheme options for non-periodic directions
• Hybrid MPI/OpenMP parallelization and GPU acceleration
• Channel3d presented here is a part of my integral project: CP3d, Channnel-Particle 3d, which is still under development, and will be open-source in the coming future. My ultimate aim for CP3d project is to develop an efficient and easy-to-use particle-laden flow solver, including one-way, two-way, and full four-way coupling methods, by combination with Basset history force model, discrete element method (DEM), and immersed boundary method (IBM).

Contact and Feedback 📧

 If you have any question, or want to contribute to the code, please don't hesitate to contact me: Zheng Gong (gongzheng_justin@outlook.com)

Showcase

 Following picture shows the transition process from laminar to turbulent flow for open-channel case (Re_tau =180). The top half of the picture presents the normalized streamwise velocity field, and the bottom half shows the isosurface for Q vortex criterion value at Q+ = 1/80, colored by streamwise velocity.