ParaTC is a high order finite difference solver for direct numerical simulations of turbidity currents with high parallel efficiency:

• 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.
• A parallel Thomas algorithm is included to further reduce the communication overhead when solving tridiagonal equations.
• An optimal search method is performed in the initializing stage to find the fast Poisson solver scheme among four alternatives for specific mesh configuration. The runtime ratio between traditional pencil-like Poisson solver and present solver is about 1.5.
  An example of the optimal PPE method search. Corresponding grid number is 9216×140×1400.

  Auto-tuning mode for Poisson Solver......
    Choice-1, time= 4350.00035871624
    Choice-2, time= 4099.76840879989
    Choice-3, time= 3699.08386557852
    Choice-4, time= 4507.20634813479
  The best Poisson Solver choice is probably Choice-3

• Periodic conditions are imposed in streamwise (x) and spanwise (z) directions.
• Navier-Stokes equations, coupled with an active passive scalar transport equation, are simulated.
  
• Fourth-order spatial scheme is used for periodic directions, i.e., streamwise and spanwise directions. Second-order scheme is used in wall-normal direction.The partially semi-implicit time advancement scheme is used, where all the convective terms, besides and streamwise and spanwise viscous terms are treated explicitly, while vertical viscous term is treated implicitly.
• The resulting statistical data are compared with those extracted from the simulations of spectral method, and very good agreements are achieved, even when we use the same grid resolution.
• An approximate linear strong scaling performance is achieved, and the weak scaling performance is also improved.

 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, 2022;128:21-33, https://doi.org/10.1016/j.camwa.2022.09.024.

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

 As for compilation, present solver 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/, so compiling and additional linking to external FFTW are avoided. (Note: Recompiling FFTW for first use is strongly recommended.)  After entering the folder ParaTC-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, following guidances printed in the terminal
5. cd ../..

 If the compiling process successfully, the executable file ParaTC will be appeared in the folder ParaTC-master/, and interpolateField will be included in the folder ./Tool/interpolateField/.

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

mpirun -n [np] ./ParaTC [inputFile]

 Here:

• np denotes the number of processors you use
• inputFile is the name string for the input parameter file

 For instance, if you want to run the canonical closed-channel case at Re\tau = 180, you can type the following words in your terminal:

mpirun -n 8 ./ParaTC ./Input/TurbCha0180_4th.standard

 The input file examples are stored in the folder ./Input/. See ./doc/ParaTC_prm.md for detailed descriptions to the input file.

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