Particles leaking through bottom of stl domain

rhysomac

Hi,

I've made a three-dimensional circular wave pool outside of SPH and imported it in as an .stl file. When the model is run the fluid particles leak through the bottom, mostly around the edges but also in the middle. Has this happened to anyone else and if so what are some possible reasons/solutions? There was no leaking in the two-dimensional version of the same wave pool.

moh

Decrease the CFL number.

Alex

Perhaps your complex geometry and the way we create particles in the nodes of a 3D mesh allows to the presence of some holes in the created geometry. Increasing the coefsound(=10-20) can also solve the problem unless the gap is too large.

Regards

rhysomac

Hi moh and Alex,

Thanks for the advice, unfortunately I've tried varying both of those numbers but they don't appear to make a difference. What does work is lowering the coefh value to 0.9, in this case there is no leakage. The problem with this is that it's outside of the recommended range for wave simulations and therefore waves do not appear to propagate outwards, the fluid appears too viscous.

Also, just to clarify, the xml I'm using is based on the wavemaker case, originally using the same parameters. I also get leakage when I make geometry within the xml so it's not an issue with the stl file.

moh

A better solution is adding more rows of solid particles in the bottom. I am sure that it will work!

Alex

The parameters shown in the XML of CaseWavemaker and generally in all cases are only a combination of the different options you can use. Perhaps the ones in that case are not the best... that is why we then suggest values of wave tanks. Maybe we should change this in future releases and include only the best options for XML paramters in all testcases.

The leakage in your case comes from the bathymetry... I am pretty sure.
There is one option in GenCase (not properly explained in the online version) that allows you to create one row of particles close to the boundary that can then be replaced for boundaries, so that, you can fill the gaps....

If you are interested, please email us to dualsphysics@gmail.com and we will help you when we have time

Regards

NWRichmond

Hi Alex,

I've also been having gaps in my boundary particle lattice owing to complex surfaces (STL imports). You mentioned that, "There is one option in GenCase (not properly explained in the online version) that allows you to create one row of particles close to the boundary that can then be replaced for boundaries, so that, you can fill the gaps...."

Could you please elaborate on this GenCase option?

Many thanks,
Nick

NWRichmond

Maybe this wasn't the GenCase option you were referring to, but I think it might be: changing the lattice value for boundary particles from 1 to 2 seemed to achieve the desired effect in my case. For the curious among you, see the lattice documentation on Page 9 of XML_v4.0_GUIDE.pdf for more information about how the particle mesh is assembled.

Alex

It is more complicated than that
Please email us to dualsphysics@gmail.com and we will find time to reply with an example

Regards