4.11.2. Output Files

SeaState produces five types of output files: echo files, a wave-elevation file, wave-kinematics files, a summary file, and a time-series file. The following sections detail the purpose and contents of these files.

4.11.2.1. Echo Files

If you set the Echo flag to TRUE in the SeaState driver file or the SeaState primary input file, the contents of those files will be echoed to a file with the naming conventions, OutRootName.dvr.ech for the driver input file and OutRootName.SeaSt.ech for the SeaState primary input file. OutRootName is either specified in the SEASTATE section of the driver input file, or by the OpenFAST program. The echo files are helpful for debugging your input files. The contents of an echo file will be truncated if SeaState encounters an error while parsing an input file. The error usually corresponds to the line after the last successfully echoed line.

4.11.2.2. Wave-Elevation File

Setting WaveElevSeriesFlag in the driver file to TRUE enables the output of the wave elevation across the entire SeaState wave grid to a text-based file with the name OutRootName.WaveElev.out. The output wave grid is controlled by the SPATIAL DISCRETIZATION section of the primary SeaState input file. These wave elevations are distinct and output separately from the wave elevations determined by NWaveElev in the SeaState primary input file, which are instead recorded in the time-series output file. The wave-elevation output file OutRootName.WaveElev.out contains the total wave elevation, which is the sum of the first- and second-order terms (when the second-order wave kinematics are optionally enabled). The wave-elevation file described here is useful for visualization purposes.

4.11.2.3. Wave-Kinematics Files

WrWvKinMod controls the wave kinematics output from the SeaState driver. The driver will output the wave-elevation time series at the global origin (0,0) in a separate .Elev file if WrWvKinMod = 1. This file also serves as a valid WvKinFile for WaveMod = 5 (externally generated wave-elevation time series) in the primary SeaState input file. This is a separate wave- elevation output independent from the wave-field output obtained with WaveElevSeriesFlag = TRUE and the wave-elevation time series obtained with NWaveElev in the SeaState primary input file.

If WrWvKinMod = 2, SeaState will output the full wave kinematics (velocity, acceleration, dynamic pressure, and wave elevation) at all wave grid points in eight output files with the extensions .Vxi, .Vyi, .Vzi, .Axi, .Ayi, .Azi, .DynP, and .Elev. The velocity and acceleration outputs are all in the global earth-fixed coordinate system. These files are also valid as WvKinFile for WaveMod = 6 (externally generated full wave-kinematics time series) and can be used as templates if users would like to build their own input files for WaveMod = 6.

4.11.2.4. Summary File

SeaState generates a summary file with the naming convention, OutRootName.SeaSt.sum if the SeaStSum parameter is set to TRUE. This file summarizes key information about your sea-state model, including water density, water depth, still-water level, the wave grid, first-order wave frequency components, and any user-requested time-series outputs.

4.11.2.4.1. Summary of User-Requested Outputs

The summary file includes information about all user-requested wave-elevation and wave-kinematics time-series output channels.

4.11.2.4.1.1. Wave-Kinematics Output Locations

The first column lists the index of the wave-kinematics output locations, as entered in the OUTPUT CHANNELS section of the SeaState input file. Xi, Yi, and Zi provide the spatial coordinates of the wave-kinematics output locations in the global inertial-frame coordinate system.

4.11.2.4.1.2. Wave-Elevation Output Locations

The first column lists the index of the wave-elevation output locations, as entered in the OUTPUT CHANNELS section of the SeaState input file. Xi and Yi provide the spatial coordinates of the wave-elevation output locations in the global inertial-frame coordinate system.

4.11.2.4.1.3. Requested Output Channels

The string labels of all requested time-series output channels, as entered in the OUTPUT CHANNELS section of the SeaState input file, are summarized here.

4.11.2.4.2. Wave Frequency Components

This section provides the frequency-domain description (in terms of a Discrete Fourier Transform or DFT) of the first-order wave elevation at (0,0) on the free surface, but is not written when WaveMod = 0 or 6. The first column, index, identifies the index of each wave frequency component. The finite-depth wave number, angular frequency, and direction of the wave components are given by k, Omega, and Direction, respectively. The last two columns provide the real (REAL(DFT{WaveElev})) and imaginary (IMAG(DFT{WaveElev})) parts of the first-order DFT wave amplitudes. The DFT produces both negative- and positive-frequency components. The negative-frequency components are complex conjugates of the positive-frequency components because the time-domain wave elevation is real-valued. The relationships between the negative- and positive-frequency components of the DFT are given by \(k\left( - \omega \right) = - k\left( \omega \right)\) and \(H\left( - \omega \right) = {H\left( \omega \right)}^{*}\), where H is the DFT of the wave elevation and * denotes the complex conjugate.

4.11.2.5. Results File

The SeaState time-series results are written to a text-based file with the naming convention OutRootName.SeaSt.out when OutSwtch is set to either 1 or 3. If SeaState is coupled to OpenFAST and OutSwtch is set to 2 or 3, then OpenFAST will generate a master results file that includes the SeaState results. The results are in table format, where each column is a data channel (the first column is always the simulation time), and each row corresponds to a simulation output time step. The data channels are specified in the OUTPUT CHANNELS section of the SeaState primary input file. The column format of the SeaState-generated file is specified using the OutFmt and OutSFmt parameter of the primary input file.