Hello everyone,
I would like to run the standalone version of Hydrodyn, and impose an oscillatory movement to the platform, to adjust the damping coefficients based on CFD simulation.
However, I have had problems reading the WAMIT Inputs Time-Series Data File. I have used the format specefied in the HydroDyn User Guide (I have specified in each data row the time step, the displacements, velocities and accelerations of the platform: 19 floats per row, separated by space or commas), and I get the following message:
“Opening HydroDyn Driver input file: NRELOffshrBsline5MW_ITIBarge4_HydroDyn.dvr
Error reading the WAMIT input time-series file.”
Do you have any sample case? What format should have the file?
Many thanks in advance,
Nicolas
Dear Deza,
Which version of FAST or OpenFAST are you using?
I’m not aware that we had a sample WAMIT time-series input file from FAST v8 or older versions of OpenFAST, but you could always review the standalone HydroDyn driver source code to figure out what exact format was required.
However, it may be preferable to upgrade to OpenFAST v2.6, if you have not already. The HydroDyn driver was redeveloped in OpenFAST v2.6, with examples provided in the OpenFAST r-test.
Best regards,
Dear Jason,
Do you have a precompiled binary of the latest version of Hydrodyn?
Thanks in advance,
Nicolas
Dear Nicolas,
NREL has not provided precompiled binaries for the standalone drivers of OpenFAST modules, but you can compile these yourselves using the available scripts, e.g. CMake for Mac or Linux and Visual Studio for Windows.
Best regards,
Dear Jason,
Thank you for the response. I have one more question regarding Hydrodyn.
If I wanted to analyze a platform with variable hydrostatic stiffness, is there a way to do it in Hydrodyn using the Potential Flow model?
Thank you in advance.
Best regards,
Nicolas
Dear Nicolas,
The potential flow solution of HydroDyn only supports a linear stiffness matrix.
In OpenFAST v2.6 and newer, the strip-theory solution computes the hydrostatic loads on the strip-theory members based on the time-dependent position/orientation of the floater, and so, this solution can include hydrostatic nonlinearities. But the potential-flow solution is still limited in this regard.
Best regards,