AQWA Stuff

[Buddychichi]

thank you saeideros

[Buddychichi]

Hi everyone
Is there anyone still talking in this forum?
Pls guys I have a question, can someone pls tell me how to model TLP tether in aqwa workbench
Pls urgent
I need to figure this out
Thanks in advance

[CWTeebs]

We're still here, but, your question is too vague and doesn't really warrant an answer (unless you're willing to pay someone to write a huge step-by-step tutorial on how to model a TLP in AQWA).

Do you need help solving a particular problem in AQWA, e.g. are you stuck on meshing? Or perhaps you've got a strange modeling error you don't know how to fix?

You need to help us help you.

[Buddychichi]

Hi everyone
do anyone know how to get the values to use for 'wind force coefficients and current force coefficient' suggested in the aqwa user manual to account for the viscous drag of current and wind computation.
I am designing Tension leg Platform for academic THESIS
thanks

[CWTeebs]

You must supply those coefficients and they only apply in AQWA-FER, AQWA-NAUT or AQWA-DRIFT. If you're modeling a TLP you're going to want to calculate the quadratic transfer functions including sum-frequency values. You also probably want to use the near-field solution as the vertical plane motions tend to have a resonant sub-harmonic period (for a TLP).

CWTeebs

[Buddychichi]

ok thanks for the reply
Is the force coefficient in question mathematically F/u^2 =1/2 ρCA (if correct) Where the ( F/u^2 ) is the force coefficient in question and (A) is the instantaneous wetted surface area in that direction of the whole structure in consideration. In that case we will need a drag coefficient of the whole structure in the various directions which is the problem.

Will I need a cfd analysis of the whole structure, what do you suggest.

[Buddychichi]

sorry (A) is the area in contact with the force

[CWTeebs]

The force coefficients given to AQWA are per unit velocity squared. You must remember to include the 0.5 * rho * area in the number you supply to AQWA.

EDIT:

CFD wouldn't be a bad way to go. Alternately you can use data from Hoerner from simple shapes. You might be able to find standards from DNV, ABS or API regarding accepted methods for calculating such coefficients.

[Buddychichi]

hi CWTeebs
I am trying to describe Morrison elements in wb-14 so I can do a coupled analysis in aqwa fer.
I have modeled line bodies total of 42 tubes, 44 body (ie 1 diffracting surface, 1 non-diffracting surface, 42 tubes (representing 12 tendons and 9 risers with two cross section each tube).
I want to visualize my impute in wb before going to the gambit part after running diffraction and time response hydrodynamics. I also want to add articulations in workbench as required for tether and riser analysis.
I have tried putting the whole surface and line body as a part and I am having problem with connection articulation of individual tubes then I try separating the line body from the surface body i am still having problems running the diffraction system. what should I do?

[CWTeebs]

Hmm, I'm not immediately sure what the problem is without seeing your project. Also, you must know this already, but you can't run AQWA-FER from Workbench. You might be using the wrong articulation type (fixed point and structure vs structure and structure), or the articulation axes could be wrong.

Also, what are you using gambit for? Meshing?

[Buddychichi]

Hi CWTeebs
my mistake, i thought gambit is used for systems that do not run from workbench, you know I am a new user. i mean aqwa gs.
i know i cannot run aqwa fer from wb. but when i run hydrodynamic diffraction and time response system i get analysis files i can open in gs. then from there i can continue my investigation on aqwa fer (is that not ok?). that was what i did earlier with the hull alone and just linear connections.
i will look into it again tomorrow. can i send you the file.

[CWTeebs]

Sure, you can post it here or e-mail me the archived project:

cthibault@mainemarinecomposites.com

Good luck regardless

[Buddychichi]

before I send you the project let me try sorting out something first so i dont waste your time.
i am trying to model Morison elements to interact with the TLP hull. I am getting non-diffracting structure cannot be in an interacting set.
if I make the Morison element one structure with the hull (multi-body part), then i can not add articulation b/w the Morison and the hull or fixed point on the sea bed.
you know i cannot see ahead of me in the software pls what can i do?

[CWTeebs]

I am not 100% sure of the proper way to model the legs of a TLP. Perhaps you should contact ANSYS help to see if they have a demo. they can send you. Regardless, I'll try to take a look at your project if you want.

What version of Workbench are you using?

CWTeebs

[usmani13220]

hi CW Teebs,
dear i am facing a problem while creating file in aqwa wave for ansys apdl
the error which i encountered is attached here in the form of image
please check it and guide me what to do for successful completion of load transfer