Learning Forum

[adeodatoarthur]

Dear friends,

I am trying to simulate a float cylinder submitted to harmonic wave excitation to obtain the added mass, damping coefficient and exiting force.

I am following some basic tutorials in YouTube and having some problems with mesh generation. First of all ANSYS aqwa does not accept solid bodies. However, I see on the internet many solid bodies being simulated in this way.

Second, I see on the tutorials people separating the solid in 2 parts (don't understand why).

Third, if I try to use a surface geometry, I still even get the solution.

Does any one can explain those doubts or recommend me a beginner tutorial for floating bodies in ANSYS aqwa ?

thanks a lot

[Mike Pettit]

Aqwa performs hydrodynamics calculations only on surface and line bodies, so you should not try to use solid geometry.
For some parts of the Aqwa calculation, it is required that there are mesh nodes at the waterline of the structure. In Release 2022 R1 and earlier, you have to use the Geometry editor to split the structure at the waterline (Z = 0 in the XY plane) so that there are separate 'wet' and 'dry' surface bodies in the part. This ensures that the mesher creates the required waterline nodes.
In SpaceClaim, create an XY plane at Z = 0. The easiest way to do this is to click on the Design tab, then click the Plane tool (in Create section). Click on the blue Z arrow on the axes in the centre of the screen, and this will add a plane in the correct location.
Next, click on the Split Body tool (Design > Intersect > Split Body). Select your solid body, then select the plane you just created to use as the cutter. This will split the solid into two parts, above and below Z = 0.
To turn these solids into surface bodies, select the interior faces (the ones that were created when you split the solid), then right-click and Detach, and finally right-click and Delete these surfaces.
I hope this helps.
Cheers, Mike

[adeodatoarthur]

Hey Mike, thanks a lot for your answer. I followed yours recommendations and think I could move forward some steps. However, I still get some erro during the meshing process. The following picture show the erro I get. I was thinking if it is because the automatic meshing process is using both tri and quad elements but it makes no sense.

[adeodatoarthur]

[Mike Pettit]

I think the error messages in the Output window are from the previous meshing attempt with solid bodies. At the moment you cannot generate a mesh because the Mesh Parameters are invalid: the Defeaturing Tolerance must be less than 0.6 times the Maximum Element Size, which is why these fields are shown in yellow. Reduce the Defeaturing Tolerance to 0,002 m (for example) and then you should be able to generate a mesh.
Mike

[Marzi Rjb]

Dear friends, I really need your help now! 

i am modelling a FPSO in Ansys Aqwa and i need to simulate some roll stabilizers

i have done this for Bilge Keel

and now i need to simulate U-Tube tank and Gyro Stabilizer.

because im running out if time, can you help me with modelling the u-tube?

- should i draw it first and then connect it or no? because i have done this and i prefaced some error

- how should i model the Gyro?

 

and if i have an external turret that is non-diffracting

should i put the solid mass or wet surface mass?

thank you for your time and kindness! 

[Marzi Rjb]

Dear friends, I really need your URGENT help now! 

i am modelling a FPSO in Ansys Aqwa and i need to simulate some roll stabilizers

i have done this for Bilge Keel

and now i need to simulate U-Tube tank and Gyro Stabilizer.

because im running out if time, can you help me with modelling the u-tube?

- should i draw it first and then connect it or no? because i have done this and i prefaced some error

- how should i model the Gyro?

 

and if i have an external turret that is non-diffracting

should i put the solid mass or wet surface mass?

thank you for your time and kindness!