I have an interesting question relating to coupled analysis in OrcaFlex with respect to the vessel lateral degree of freedom.
Using the OC3 Hywind model as an example I created my own model of the floater and I successfully performed the analysis when I only had Wind and Waves acting on the vessel. Now I have added Current to the model as well. My forces are uni-directional in the x-direction. The displacement of the vessel in the x-direction is much larger now than it used to be (understandably so). The problem is that my simulation crashes 112s after the start giving either: a supersonic blade error or that my wind field has been exhausted.
When I looked at the visualisation of the 112s simulation in OrcaFlex, I noticed that my model proceeds to drift in the x-direction up to 29.8m and at roughly 30m away from the origin it appears to be literally yanked back to the origin instantly, which I assume gives the supersonic error for the blades. Conversely, when my turbine drifts away out of the range of the wind field, I assume it is considered exhausted.
The “face” or front plane of my turbine is located in the YZ plane. That is the plane in OrcaFlex where the wind is being applied to the hub in the x-direction
My question to you is: Does AeroDyn or any other of the FAST modules have a specific distance restriction? Given that we can specify the width and height of the front plane, in which the wind field is acting, via the grid, can we specify the depth of the field, i.e. if my SPAR drifts too far back, how can I tell the software not to realign the vessel at the origin?
The reason I suspect that the issue lies with AeroDyn is because I checked the Wind field (which I have been running successfully for the past 3 months with different alterations), I checked the controller and then I adjusted some of the values in the AeroDyn module, which delayed the crash by 40s, from 78s to 112s into the simulation.
Have you encountered such an issue before? Where does the fault lie in your opinion? Is it even possible to specify a high current and wave force without the crash occurring? When I say “high” I mean a 50-year extreme return case.