## General Mechanical

#### Modeling of Floating Photovoltaics

• jaevin10
Subscriber

Hi,

I'm trying to model offshore floating solar panels for our research project. I've read from some materials that in hydrodynamic analysis, only the structures in contact with the water is essential and the upper structure can be ignored in modeling. I plan to only model the floaters to keep the number of elements as minimum as possible. Is there a way to connect the floaters to make them act as one structure (see attached image), like a rigid connection?

• Erik Kostson
Ansys Employee

As we (Ansys employees) can not download any attachments (see rules for this forum), can you please attach the image inline in your next post so we can view it without opening an attachment?

Our AQWA experts (), can then perhaps advice on this (assuming that you are using AQWA which would be one of the appropartie tools as far as we can see here).

Thank you

Erik
• Mike Pettit
Ansys Employee

It is true that you can perform a Hydrodynamic Diffraction calculation by modelling only the wet surfaces (i.e. parts of the structure under the mean water surface).
However, if you also want to perform Hydrodynamic Response calculations, we usually recommend including a Stability Analysis. This provides the initial conditions for any subsequent time response or frequency statistical analyses. During the Stability Analysis the structure is moved to its equilibrium position accounting for the external forces due to mooring lines etc. As the structure position/rotation changes in the Stability Analysis, the hydrostatic force is re-calculated under the instantaneous wetted surface - so if (for example) the weight of the mooring lines pulls the structure down in the water, and the cut water-plane shape changes significantly, then it may be important to also model the upper structure.
To model multiple separate parts as a single rigid structure you can use one of the following options:
Group the surfaces into a single Part in the geometry editor. Aqwa will consider them as a single rigid structure, even if there is no 'physical' connection between them in the geometry.
Model the surfaces as separate Parts in the geometry editor, but group them in an Interacting Structure Group for the Hydrodynamic Diffraction calculation, and set a Motion Lock for that group. Add rigid Joints between the structures if you are also going to perform Hydrodynamic Response analyses.
I hope this helps.
Best regards, Mike
• jaevin10
Subscriber
Thanks
Thanks for the insight, how do I add rigid joints between the structures? Is it done by modeling connecting elements in the geometry editor or added in the AQWA solver?
• Mike Pettit
Ansys Employee

Sorry for the delayed reply - our Learning Forum website didn't send me the usual notification, I've only just seen this.
Joints are added in the Aqwa Workbench editor. To create rigid joints, you first need to add Connection Points to the structures (right-click on the Part in the Outline tree, then Add > Connection Point). Next, right-click on Connections and Insert Connection > Joint. Set the joint Type to Rigid, and select the appropriate Connection Point on Structure A and Connection Point on Structure B. In the Graphical Window you will see the structures moved so that the selected Connection Points are coincident. You can use the Joint Axes objects to apply a rotation of the structures about the joint position, if necessary.
It is important to understand that Joints (as well as Cables, Fenders and Tethers) are only used in Hydrodynamic Response analyses - they will not affect a Hydrodynamic Diffraction analysis. Similarly, if a Joint is added which changes a structure's position, this change in position will not be included in the Hydrodynamic Diffraction analysis (i.e. the Hydrodynamic Diffraction analysis position will always be the position as defined in the geometry editor).
Cheers, Mike