lheea / cn-stream

Computation of nonlinear regular ocean waves using stream function

CN-Stream

Computation of nonlinear regular ocean waves using stream function

Installation/Compilation

The code can be compiled on any computer architecture. One only needs a Fortran compiler (for instance gfortran, the GNU Fortran compiler, part of GCC). A makefile is provided but the recommended procedure is to use cmake. The following commands can be executed in the root folder where CMakeLists.txt is located, to compile the dependency, the executable and the shared library:

• cmake -H. -Bbuild
• cmake --build build

Compilation has been tested with gfortran on different Unix/Linux platforms as well as in Windows environment.

For Windows environment, compilation using Intel Visual Studio has also been tested. The program is provided with the corresponding project file CN_Stream.vfproj allowing a straightforward compilation of the code.

Execution

Use of CN-Stream as a stand-alone program

CN-Stream has been developed for command-line run with an input file located in the input folder containing all specifications needed. All output files will be created in the directory output, but other specifications can be given. Details of inputs and outputs are provided hereafter. The executable can be run with the command ./mainCNS. The name of the dictionary can be specified as an argument.

CN-Stream - library

There are two ways to use CN-Stream as a library.

• Use the declarations of the variables of the variables_CN_Stream.h and variables_output_CN_Stream.h and call the functions described in the source file lib_CN_Stream.f90.
• Use the subroutines indicated in the communication module mod_CN_Stream.f90.

CN-Stream source files

Project organisation and dependency

The main folder consists in:

• CMakeLists.txt
• example Folder with examples of using the library through the communication module from Fortran and C++
• src Folder with source files (include also the sources of libFyMc)
• input Folder with input file example
• output Default folder output

The code use the library libFyMc to read the “dictionary” input file. The library is provided with the sources.

CN-Stream - variables and types

The different Fortran types (RF_type, option_type, output_type) are defined explicitely in variables_CN_Stream.h and variables_output_CN_Stream.h and are included when needed in CN-Stream. It allows the user to include them easily into CN-Stream but also in another code, which makes use of the CN-Stream library.

In more details, those types include:

• RF_type
  • definition of the parameters of the wave, corresponding to the input parameters specified in the input file.
  • Modal amplitudes of the free surface elevation η and of the velocity potential φ (or equivalently the stream function ψ).
  • If needed, free surface elevation and slope in the spatial domain.
• option_type: all options relative to the solution method, specified in input file. This type also includes the optimal number of points N1 and N2 resulting from the dedicated procedure.
• output_type: defines for one location (X, Y, Z) the free surface elevation, the pressure and velocity components together with the necessary time and/or spatial derivatives of those components. The possible existence of a Y -component is associated to the definition of an angle of propagation as input, referenced as θ.

CN-Stream - main program

The set of Fortran files needed in order to compile CN-Stream is listed hereafter with a brief description of the purpose of each of the source file.

• mod_CN_Stream.f90: Module allowing communication without using complex datatypes (C++)
• main_CN_Stream.f90: Main program for CN-Stream computations
• modSolve.f90: Solves the equation of the problem described above
• modCNinitialize.f90: Initialization of CN-Stream computation
• modUtils.f90: Useful functions
• modMatrix.f90: Computes the inverse matrix from the least square method
• modType.f90: Definition of types and useful constants
• modModal.f90: Useful functions used in modSolve.f90
• HOS_modlinear_wave.f90: Computation of linear dispersion relation
• HOS_modmaths.f90: Useful mathematical functions
• modSetupNameList.f90: Read the input NML file
• modReconstrucVol.f90: Evaluate wave elevation, pressure, velocity and its derivatives
• modReconstruction.f90: Recompute wave elevation, pressure, velocity and wave slope from Fourier coefficients and the other way around
• modOutputs.f90: Write outputs on files
• variables_CN_Stream.h: Definition of Fortran types: RF_type and option_type
• variables_output_CN_Stream.h: Definition of Fortran type: output_type

Inputs and Outputs

CN-Stream needs as input the characteristics of the wave, together with some informations relative to the numerical solution of the problem (target accuracy, etc.). The wave can be described in dimensional or non-dimensional form. As a matter of clarity, the wave parameters to provide as input are detailed in the next paragraphs depending on the need of the user. Note that those parameters are provided within an input file which content is also detailed.

In CN-Stream, the non-linear regular water wave is characterized by:

• the water depth h, possibly infinite,
• the wave length λ or the wave period T,
• the wave height H (distance from crest to trough),
• the constant current superimposed to the wave (under the form of a Eulerian current or a given transport of mass).

Input file

The input file is assumed to be named CN_Stream_input.dict. An example is provided in the input folder and details are provided hereafter. The Options_solver parameters are useful for an advanced user, in order to obtain solutions with a controlled accuracy and/or to look for waves close to the wave breaking limit.

---

waveInput: Label (waveStream in example file) and Definition of the characteristics of the simulated wave

---

GeneralDimension: Dimensional (=1) or Non-dimensional (=0)

GeneralDepth: h if GeneralDimension=1 / h’ if GeneralDimension=0

GeneralModes: Number of modes for first evaluation

WaveInput: Period / Wavelength (if GeneralDimension=0 only Wavelengthis possible)

Period: period value if WaveInput set to Period

Wavelength: Wavelength value if WaveInput set accordingly

WaveHeight: H if GeneralDimension=1 / H’ if GeneralDimension=0

CurrentValue: value of current ; dimensional if input: GeneralDimension=1 / non-dimensional if input: GeneralDimension=1

CurrentType: type of current ; 1 mass transport / 0 eulerian current

---

Options for the numerical solution of the problem

---

n_H: Number of steps in wave height

err_type: Error type: 0 absolute ; 1 relative

eps_err: Tolerance on the equations

err_max: Error value over which computation is considered divergent

eps_inc: Convergence criteria on the unknowns

eps_N1: Decision criteria on the modes for the automatic adjustmentof N1

itermax: Maximum number of iterations

increment_type: choose between a linear or exponential incrementation: Increment type for wave height / 0 linear ; 1 exponential

printonscreen: print the intermediate results of the simulation on the command prompt: Print on screen =1 / do not print on screen = 0

writeoutput: Write output files =1 / do not Write output files = 0

subdict: Standard way to include dictionnary (here “Output” in another using libFyMc)

---

Outputs: supplementary info for outputs

---

Path: Specify output path (default: “./output/”)

x/y/z/time: Specify position to evaluate quantities for local outputs (default:“0.0”)

theta: Incident angle of waves (default:“0.0”)

Output files

Depending on the choices made in the input file, different output files are created. They are located at the root of the folder. Input file also defines if outputs are dimensional or non-dimensional quantities. Following files may be created:

• waverf.cof gives the main important parameters of the simulation, namely λ, H, k, T, c, cS, cE, N1 + 1, N2 + 1, R, h (in dimensional or non-dimensional form depending on the value of input: GeneralDimension in the input file) as well as the modal amplitudes an and bn,
• waverf.dat gives the modal amplitudes an and bn. In complement, different subroutines may be called to write the necessary outputs needed by the user. They are available inside the source files and a simple call in the main program will enable the corresponding outputs:
• WriteOutput: this subroutine creates the file resultsOutput.txt containing at a given location and time all spatial quantities computed by CN-Stream (free surface elevation, velocities, pressures, derivaitves, etc.).
• TecplotOutput_Modes: this subroutine creates the file Modes_CN_Stream.dat containing the modal description of the free surface elevation and velocity potential, for use with Tecplot.
• TecplotOutput_VelocityPressure: this subroutine creates the file VP_card_fitted.dat containing the velocity and pressure field under the simulated wave, for use with Tecplot.
• TecplotOutput_FreeSurface: this subroutine creates the file FreeSurface_CN_Stream.dat, which provides the free surface elevation and slope.

cn-stream's Issues

gfortran 9.3 failed to compile

I got an error while compiling CN-stream on Ubuntu 20.04, with compiler Gfortran 9.3.0: I got an internal compiler error.
Compiling with an intel compiler worked.

Here is the error:

cmake --build build
Scanning dependencies of target fymc
[  2%] Building Fortran object src/libFyMc/CMakeFiles/fymc.dir/src/mfpGlobal.f90.o
[  5%] Building Fortran object src/libFyMc/CMakeFiles/fymc.dir/src/general/mfpGeneral.f90.o
string/string.inc:165:0:

Warning: '__builtin_memset' specified bound 18446744073709551615 exceeds maximum object size 9223372036854775807 [-Wstringop-overflow=]
[  8%] Building Fortran object src/libFyMc/CMakeFiles/fymc.dir/src/geometry/mfpGeometry.f90.o
f951: internal compiler error: in generate_finalization_wrapper, at fortran/class.c:2027
Please submit a full bug report,
with preprocessed source if appropriate.
See <file:///usr/share/doc/gcc-9/README.Bugs> for instructions.
make[2]: *** [src/libFyMc/CMakeFiles/fymc.dir/build.make:101: src/libFyMc/CMakeFiles/fymc.dir/src/geometry/mfpGeometry.f90.o] Error 1
make[1]: *** [CMakeFiles/Makefile2:118: src/libFyMc/CMakeFiles/fymc.dir/all] Error 2
make: *** [Makefile:136: all] Error 2

Current Speed

Hello, your code is very valuable and has helped me a lot.
I have a question: the initial wave height estimation is estimated without current velocity. If the initial wave height estimation without current velocity is used, it will easily lead to failure to solve. How should the initial wave height estimate with current velocity be calculated?
Hope to get your help