The formula using ViscoBoundFactor
In relation to
<parameter key="Visco" value="0.01" comment="Viscosity value" /> <parameter key="ViscoBoundFactor" value="1" comment="Multiply viscosity value with boundary (default=1)" />
beside the little glitch that one does not multiply a viscosity for a boundary,
- What is the formula using the product Visco * ViscoBoundFactor?
- If that formula is the conventional expression of the artificial viscous term (below), which fluid particles is that product applied to, as opposed to the conventional fluid particles?
- Which physics am I actually modelling when setting this ViscoBoundFactor to zero?
- And when ViscoBoundFactor is one?
Thanks in advance for addressing these questions. I could not spot an answer in the wiki, forum and some literature.
Comments
Brief explanation can be found in page 134 of the XML-GUIDE-v5.0.pdf in DualSPHysics_v5.0\doc\guides.
This value was introduced to mimic the roughness of some boundaries as we did in the study of runoff on real terrains in:
Barreiro A, Domínguez JM, Crespo AJC, González-Jorge H, Roca D, Gómez-Gesteira M. 2014. Integration of UAV photogrammetry and SPH modelling of fluids to study runoff on real terrains. PLoS ONE, 9(11): e111031. doi:10.1371/journal.pone.0111031.
Follow figure 6: https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0111031
Regards
Thanks @Alex
The article is, understandably, all about the effects of such a ViscoBoundFactor, which is not sufficient (for me) to understand how it has been implemented. I'd rather have a context to anticipate what ViscoBoundFactor does for me in other situations.
The figure, by the way, is also directly on-line: https://journals.plos.org/plosone/article/figure?id=10.1371/journal.pone.0111031.g006 As I understand it, it shows a calibration exercise, which is case-specific understandably. Fair enough, but magic for me (exaggerated).
Leaning on the slide of the XML guide,
Thanks for your helping out
When I tested in the past, I also found that it had an effect (using ViscoBoundFactor) when working with SPS-LES. That was quite confusing for me at the time. It makes sense that one can do it as well, but it is not documented in the wiki
Kind regards.
I would impart some buoyancy to this thread again. Distilling all questions above to the very essential:
Which physics I am modelling when setting either ViscoBoundFactor = 1 or ViscoBoundFactor = 0?
Thanks in advance for answering this.
I would also really like to know this. Especially when using SPS-LES I have a kinematic viscosity of 1e-6. Then if I use, viscobound factor, a_FB = 1e6, I suppose I get a friction factor of "1"?
What does this mean?
How do I interpret it physically?
Kind regards