CP3d (Channel-Particle 3d) is a comprehensive Euler-Lagrange solver for the direct numerical simulations of particle-laden flows.

• Have the ability to perform one-way, two-way, interface-unresolved four-way, and interface-resovled four-way coupling regime.
• For the fluid sub-solver, both the second-order and four-order finite difference discretization are available, in company with three viscous term treatment approaches: i.e., fully-implicit, partial-implicit, and fully-explicit.
• Four boundary conditions (BCs) are available in CP3d for the velocity terms, including the periodic, no-slip, slip, and convective outflow conditions. However, only two types of boundary condition are needed for the pressure term: periodic or Neumann BCs (∂p/∂xi=0 for non-periodic directions).
• For the discrete-element-method (DEM) solver, both linear and non-linear contact force models can be used, and the collision time can be also adaptive.
• The immersed boundary method (IBM) is used in interface-resolved simulation, and totally three IBM coupling approaches are included.
• In order to improve the numerical accuracy of the computational Basset history force, a third-order exponential approximation method is proposed in interface-unresolved four-way regime.
• An averaged lubrication force model is proposed for the short-range hydrodynamic interaction.
• The volume integration approach is also modified to adapt the staggered mesh configuration.
• The resulting solver is able to simulate large scale cases of billions of grid points with millions of moving particles in interface-resolved four-way regime using only hundreds of computational cores.
• MPI parallelization by means of pencil distributed decomposition. In order to improve the parallel efficiency, we propose a new 2D pencil-like parallel configuration with totally 6 different pencil arrangements.
  

• Z. Gong, Z. Wu, C. An, B. Zhang, X. Fu, CP3d: A comprehensive Euler-Lagrange solver for direct numerical simulation of particle-laden flows, Computer Physics Communications, 286 (2023) 108666. https://doi.org/10.1016/j.cpc.2023.108666.
• Z. Gong, G. Deng, C. An, Z. Wu, X. Fu, A high order finite difference solver for simulations of turbidity currents with high parallel efficiency, Computers and Mathematics with Applications, 128 (2022) 21–33. https://doi.org/10.1016/j.camwa.2022.09.024.
• Z. Gong, X. Fu, A pencil distributed direct numerical simulation solver with versatile treatments for viscous term, Computers and Mathematics with Applications, 100 (2021) 141–151. https://doi.org/10.1016/j.camwa.2021.09.003.

 There are totally 6 solvers in CP3d:

 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-3.3.10 library has been explicitly included in the directory ./src/ThirdParty/fftw/, but it is strongly recommended to recompile FFTW-3.3.10 for the first use. After entering the folder CP3d-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

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

mpirun -n [np] [exeName] [inputFile1] [inputFile2]

 Here:

• np denotes the number of processors you use
• exeName stands for specific executable file name, namely channel2nd or channel4th
• inputFile1 is the name string for the 1st input parameter file
• inputFile2 is the name string for the 2nd input parameter file, if any

 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/CFD_2nd/LidDrivenCavity.prm

The following table provides examples to run CP3d after compilation:

 The input file examples are stored in the folder ./Input/.

• Particle dispersion in wall-bounded turbulence
  

• Modification of particle-laden near-wall turbulence

• Free falling of single particle under gravity

• Drag coefficient of uniform flow past a spherical particle
• Wet head-on particle-wall collision
  
  

 Since Sep 2019, when I finally decided to develop my own CFD-DEM code from scratch, I have learnt quite a lot from the following really kind researchers (in alphabetical sequence):

• Dr. Costa from University of Iceland, and his second-order DNS code CaNS, also his papers on IBM approach.
• Dr. He from Iowa State University, and his fourth-order DNS solver HercuLES.
• Prof. Ji from Tianjin University, on the fruitful discussion about the particle IBM method, and on the access to their in-house DNS/LES-Solid interaction code cgLES.
• Dr. Laizet from Imperial College London, and their compact FD code Incompact3d.
• Prof. Marchioli from University of Udine, on the fruitful and continuous discussion about one-way CFD-Particle coupling benchmark and on the access to their benckmark data.
• Prof. Meiburg from University of California, Santa Barbara.
• Dr. Norouzi from University of Tehran, and his book Coupled CFD‐DEM Modeling: Formulation, Implementation and Applimation to Multiphase Flows, besides the attached DEM code.
• Prof. Orlandi from Sapienza University of Rome, and his book Fluid flow phenomena: a numerical toolkit, besides the attached CFD code.
• Dr. Tschisgale from Institute of Air Handling and Refrigeration, on the fruitful and continuous discussion about their IBM approach.
• Prof. Zhao from Tsinghua university, on the one-way CFD-Particle coupling benchmark.
• ......

 Without those researchers' help, I might do nothing but sleep in the dormitory all the days!!!:joy::joy::joy:
 Thanks so much again and again !!!

 If you have any question, or want to contribute to the code, please don't hesitate to contact me: Zheng Gong ([email protected])