# AQWA Stuff

Discussion in 'Software' started by CWTeebs, Oct 13, 2011.

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### CWTeebsAnomalyGenerator

Rename it to "aqwawave.dat" and see what happens.

CWTeebs

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### CWTeebsAnomalyGenerator

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### usmani13220Junior Member

Dear CW Teebs,
I am using aqwa lin
but there is a problem in calculating the moment of inertia of submerged body whose axis are not in mid of the object
i made a solid cylinder of length 12 meter and of dia 4 meter
i set the water surface at the level of 4 meter (means 8 meter cylinder is in water or in -ve z direction and 4 meter is in +ve z direction)
please guide me how can i calculate its moment of inertia

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### CWTeebsAnomalyGenerator

5. Joined: Apr 2011
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Location: Maine

### CWTeebsAnomalyGenerator

This is not exactly AQWA, but rather a CFD experiment I did to get an idea of the magnitude of damping due to wave making, viscous drag and boundary layer growth. This can be turned into coefficients that can be used on roll damping in AQWA.

http://youtu.be/63bnrhWKi1o

#### Attached Files:

• ###### RollDampScreenie.jpg
File size:
19.9 KB
Views:
500
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### CweoNew Member

Hi everyone.
I´m new using Aqwa.
Do you know how to estimate the resistance force on an structure. I´m trying to tow a floating object, so i think ,in aqwa i could use a current to simulate the towing speed, fix the structure and solve forces on it. But the fixing details is my problem.
thanks

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### khabiranJunior Member

Hi
Resistance calculated by Morrison Drag, while hull drag loads are only included if Current Force Coefficients are defined for the part.

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### CweoNew Member

Thanks
But is necessary fix the structure?
i´m not using tube elements, im using a big structure, so morrison is not applied.
for the drag coefficient is necessary multiply by 0.5*rho, true?

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### khabiranJunior Member

Morrison has 3 terms, third one is drag force =1/2 p(Cd.....)...so you need Cd (drag coefficient) invariant. Morrison focus on wave load (first and second term).. So Cd calculated with some other software such as Fluent or CFX....

khabiran@gmail.com

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### CWTeebsAnomalyGenerator

AQWA isn't really the best tool to use for this type of analysis. It assumes you are either using tube elements, which follow Morison's equation as Khab. stated, or, you know the drag coefficients of the structure. It'd be easier to just do this in Excel quite frankly.

If you're adamant about doing it in AQWA you can supply the drag force coefficients, current profile and then fix the structure using a fixed constraint.

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### CweoNew Member

That is what I'm trying to do. When I use a fixed constrain (only one point is possible, using a fixed point, and a rigid joint connection) the structure needs to be classified as fixed and results are very strange. Maybe due to the Cd, stiffeners or damping values.
thanks for the help, if you have any recommendations on these points ...
I´ll keep trying!

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### CWTeebsAnomalyGenerator

Sorry for the delayed response. I would probably need to see your setup.

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### Wang YangmingNew Member

Hi Everyone

I'm a freshman in AQWA. These day I am working on a project name Spar-type floating offshore wind turbines. I am interested in the dynamic behaviors in multiple-DOFs (Surge,Heave and Pitch). The Spar are 8 meters in diameter and the total draft is 65 meters.The upper structure, including tower and nacelle and turbine, remains the same as the fixed-bottom ones. We are required to take all of the environmental loads (current, wind and wave) into account. We noticed that AQWA-Drift may be a proper solution for us. But in the input file of AQWA-Drift, Deck 10 requires information of current forces coefficients and wind force coefficient. How to calculate these coefficients ?

Is there someone who can help me ?

Thanks!

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### khabiranJunior Member

Spar

Hi Wang
Aqwa is a BEM code based on panel method. In this condition, these types of code are not capable to find drag coefficient, which also found based on Navier-Stocks codes such as Fluent or CFX.
I prefer to you, calculate Cd for upper and submerged parts of your structures under air flow and water flow in CFX.
hope be useful.

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### AhsanJunior Member

How to extract or transfer Pressure Real component using AQWA Wave

Hi everyone! Specially MR CWTeebs

My work is related to spectral fatigue analysis, which requires separate pressure laod files(real and imaginary) for a combination of heading and frequency. Well as per my knowledge, AQWAWAVE generates a single load file containing total pressure(hydrostatic+ real +img pressure component).

Howto obtain or transfer real and imaginary pressure components separatelyin two differnt load files