Mooring in AQWA

[Mikhail]

Dear AQWA users,
I try to use mooring line connection in AQWA at ANSYS 13 interface (Hydrodynamic Diffraction).
Has anybody known how I can pick out a Single Vertex for End Vertex in Details of Cable?

[CWTeebs]

I realize you posted this quite some time ago, but, you may need to either a) enter a construction point in Design Modeler for the connection point, or, if that fails, you can enter a small primitive geometry such as a cone.

[Mikhail]

Yes I've done this problem by using the polygonal prism (approximation to cylinder), but any way thank you for your answer

[CWTeebs]

I am curious to see how your project is progressing. Pretty hard to find a user community for AQWA. My company has been using it for the past few months, but we're thinking of switching back to WAMIT.

[Mikhail]

Honestly I am not familiar with AQWA in ANSYS 13 so not sure that it's the best way to solve my problem.
I used to work with traditional AQWA + prep7(ANSYS preprocessor) and did not have any troubles with additional nodes, elements, etc.
It's difficult to say what better WAMIT or AQWA, unfortunately I have not got an opportunity to work at WAMIT, but all depends on objects some objects easer for WAMIT, some for AQWA.

[CWTeebs]

Hi Mikhail,

Seems like your project is going along quite well. I am unfamiliar with Prep7, but it looks like it's actually a part of the Mechanical package. What were the steps you took to start Prep7 and create the geometry you've shown above.

Also, have you managed to mesh more complex geometries, e.g. boat hulls?

Good luck and keep up the good work.

EDIT:

Would there be any way you could share your project files and describe the steps you took? I discovered that in the Mechanical APDL there's a command that does in fact write out your mesh to an AQWA-LINE job file. Did you run native AQWA (e.g., AQWA-GRAPHICAL SUPERVISOR) once the AQWA-LINE project file was created from Prep7/Mechanical APDL?

[Mikhail]

Dear CWTeebs,

You are right the Prep7 it is a preprocessor for Ansys APDL were you can create shell model, mesh it and then import it to AQWA-Line by command anstoaqwa. Such way you just avoid using AGS so you can safe your time.
>have you managed to mesh more complex geometries, e.g. boat hulls?
Yes I have, actually the shape dose not meter, but Aqwa has some limits on quantity and quality of shell elements.
> Did you run native AQWA (e.g., AQWA-GRAPHICAL SUPERVISOR) once the AQWA-LINE project file was created from Prep7/Mechanical APDL?
Yes I did, and I suppose it is much easier way than create the boat hull in AGS.
>Would there be any way you could share your project files and describe the steps you took?
For some reason I cannot share my project file right here, so if you are interested please send me your e-mail.

[CWTeebs]

Hi Mikhail,

you can send it to:

cthibault@mainemarinecomposites.com

Thanks a bunch!

[mehdibaghaee]

To model a floating structure, I want to link msc Adams with AQWA. But I dont know how to do so. Is there any body knows this?
Help me please.

M. Baghaee

[CWTeebs]

I can help you get started. Do you have a CAD model of it? I can help with the AQWA side anyway, I don't have MSC Adams for dynamics.

[mehdibaghaee]

Dear CWTeebs
I have modeled the land based wind turbine in MSC ADAMS, and now I want to drift it on the water using floating spar type platform support with mooring lines. In this way I must do hydrodynamic analysis, as well. For this purpose I want to use AQWA package and link it with MSC ADAMS. But I do not know how to do so.
I read in ANSYS 13.0 help that there is linking capability between ADAMS and MSC ADAMS. But don’t know what about AQWA. As you know, AQWA is one of the ANSYS 13.0 modules that work in ANSYS workbench.
I have good knowledge working with both MSC ADAMS and ANSYS software, but no knowledge about AQWA software. So needs help who knows this software well.
How you can help me? I have not worked with AQWA at all. How start to learn it then use in my project (link with ADAMS).
This my email address: mehdi.bgh@gmail.com
Can I have your email, as well.

Many Thanks

[CWTeebs]

Hi mehdibaghaee,

Fully dynamic mooring analysis requires AQWA plus cable dynamics, which is a separate cost. The cable dynamics package can be a bit finnicky, in that great care must be taken with respect to starting conditions and cable properties. I guess this isn't unique to numerical modeling, but I recently did a mooring analysis for a type of underwater structure and had some difficulty getting it to work.

I created the surfaces in Rhino, imported into ANSYS Design Modeler to create the modifications required by AQWA. I ran AQWA-LINE which does radiation and diffraction frequency domain calculations.

Next I ran AQWA-LIBRIUM with cable dynamics and dynamic stability option to find a suitable starting location to run AQWA-DRIFT (to limit the transients at the start of the simulation).

Finally, I ran a time domain simulation with the object immersed in a specified current profile to give first order estimations of mooring line tensions and anchor uplift, etc.

Note that all of this was rather tedious and requires a great deal of working knowledge on how to use AQWA. For example, I only actually used the ANSYS front-end, Workbench, for doing the AQWA-LINE analysis (mesh can be created by using Mechanical APDL as well). You then have to switch to using 'native' AQWA, which ultimately comes down to editing text files and writing control scripts to generate job data files.

I'm an experienced AQWA user and the above job took several days to get working to an acceptable degree of fidelity. I do mean that as a warning if you plan on taking the AQWA work in-house with no prior experience.

[CWTeebs]

I have been having trouble sending you e-mail, they are all bouncing back, but I will keep trying to send you those files.

[mehdibaghaee]

Dear CWteebs
Thanks to your attempt to sending me those files.
I have another email you can try it.
mehdi_bg_53@yahoo.com

Thanks again.

[giovanna.bevila]

Dear AQWA users,
I'm an Italian researcher on floating wave energy converters and I recently start to perform some simulations with AQWA but I found this quite difficult and problematic. I'm new with this kind of software and I hoped in some advices because the User's manual seems to be quite unuseless for non-experts like me and the ANSYS technical support as well.
Let me explain.
Performing the simple analysis in workbanch seems that the program cannot calculate properly the initial cable position. I try with all the available kind of cable but it never works.
Moreover, using a catenary cable, it seems quite impossible to define accurately the request parameters "negative dz range" and "positive dz range" in the way that the program can calculate finally the initial cable tension and run the analysis. The User's Manual has no answer. I try everything. So, I was thinking: maybe I don't understand the meaning of this parameters and thus I put wrong values. Can someone please explain me what have I to do to analize the cable's effects on the system. Is there something missing?

Thanks
Giovanna