DP and density

lkaluzi

Hi, I have a question concerning the density of a floating object. How does the relative weight of the floating object compare to the number of particles in the simulation. I ask because I ran the CASEFLOATING example with the block a block of relative weight 1.2 and got two different solutions for dp=.15 and dp=.3. When the dp=.15 the block sank more than in the dp=.3 simulation. Are there other parameters that need to be changed along with dp to get physically accurate results (artificial viscosity, speed of sound, density correction, etc.)?

Alex

You can also indicate the mass and density of the object.
Different resolution can lead to different behaviour.
Note that, by default, the mass of the object M is computed using density or relativeweight and then the mass of each particle of the object is computed as m=M/Nfloat so depending on the resolution you can get different accuracy. To avoid that you should use high resolution and also impose the value M.

Regards

lkaluzi

Ok, that makes sense. How do you set the mass of the object?

Alex

You can check that in "CaseTemplate.xml"
massbody value="1300"

NWRichmond

Hello, I am also having issues with this. I have edited a floating object in an example of mine. I specified a massbody value of 1000, but when I tried to solve it gave me an error that rhopbody must be designated as well. This confuses me because if I've already specified a volume and a mass, why does it need density? Also are the units for mass in kg?

Alex

No worries, in that case you have to specify also rhopbody, but once massbody is given then that value will be used for the rest of computations:

*floatings*
*floating mkbound="51" rhopbody="700" *
*massbody value="1300" /*
*/floating*
*/floatings*

NWRichmond

Hello, I am still getting unphysical results. I have a block of 2x2x2 dimensions floating in water. If I set the rhopbody to 500, it should float so that half of the block is below the water and half is above. However, only about a fourth of the block is beneath the surface. I have also tried defining mass body to be 3200 and the same error occurs. Am I doing something wrong?

Alex

What resolusition are you using?
You can also send to us your XML file to check it.

Regards

mzbr1g12

Hi,

I notice that we can also insert moment of inertia of the floating body.

For a 3d long floating object, is that moment of inertia actually define/calculating the transverse BM and longitudinal BM for its stability?

regards

NWRichmond

I ran my simulation with a dp of .15. Where would be the best place to send the XML file? Copy and paste here or send to an email of some sort?
Thank you for your help