Talking about dependencies: one thing we did *not* reimplement in #GPUSPH is rigid body motion. GPUSPH is intended to be code for #CFD, and while I do dream about making it a general-purpose code for #ContinuumMechanics, at the moment anything pertaining solids is “delegated”.

When a (solid) object is added to a test case in GPUSPH, it can be classified as either a “moving” or a “floating” object. The main difference is that a “moving” object is assumed to have a prescribed motion, which effectively means the user has to also define how the object moves, while a “floating” object is assumed to move according to the standard equations of motion, with the forces and torques exerted on the body by the fluid provided by GPUSPH.

For floating objects, we delegate the rigid body motion computation to the well-established simulation engine #ProjectChrono
https://projectchrono.org/

Chrono is a “soft dependency” of GPUSPH: you do not need it to build a generic test case, but you do need it if you want floating objects without having to write the entire rigid body solver yourself.

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#SmoothedParticleHydrodynamics #SPH #ComputationalFluidDynamics

Point 1. (non-trivial geometries) is one of the reasons why most CFD systems have a separate, heavy-duty preprocessing stage dedicated to help users design said geometries and make them “accessible” to the method. The problem for us is that the vast majority of the “tools of the trade” are dedicated to mesh-based methods (especially the finite elements method, FEM) and are thus not useful for particle methods such as #SPH.

There's still a lot of ongoing research on how to “optimally” fill arbtirary geometries with particles for these applications (see for example a recent work by the #SPHinXsys team on the topic <https://doi.org/10.1016/j.cpc.2023.108744>): although superficially one could think that this is a simple extension of what is used for the standard meshes (which is almost true as long as one sticks to a single layer of boundary particles) things devolve pretty quickly when multiple layers are needed (which is the case for many solid boundary models in #SmoothedParticleHydrodynamics) or a complete fill to be achieved in a way that respect a number of equilibrium conditions that should be satisfied at the beginning of the simulation. (And remember: you might need to do both an “outer” and an “inner” fill for the same geometry, putting fluid particles on one side, and boundary particles on the other).

2/

Hello all! This will be the official #GPUSPH account on the Fediverse going forward. What is GPUSPH, you ask? It's a software for #ComputationalFluidDynamics using the #SmoothedParticleHydrodynamics method, accelerated by running entirely* on GPU. In fact, it was the first to do so, leveraging the new GPGPU capabilities offered by NVIDIA CUDA.

(These days we have wider hardware support, but for a long time CUDA was all we supported.)

#introduction #newHere #CFD #HPC

*conditions apply

Jokes aside, I think this is actually one of the powerful aspects of federation. On the corporate sites, the single namespace meant that for #SmoothedParticleHydrodynamics we had to use the #SPH_ tag (with the underscore) to avoid confusion with, shall we say, other uses of the same #SPH acronym.
On the #Fediverse, the experience is more “local”, something that I already observed with the Page42 game (<https://fediscience.org/@giuseppebilotta/113554443204685599>).

This means that, at least within the confines of the servers more focused on science, the unmodified tag has a better chance to work for the numerical method.

(Still, if I browse the tag, aside from feeling a bit “vox clamantis in deserto”, I do see a couple of posts with that other meaning.)

Apparenty we weren't having enough issues of context collapse for #SPH as an acronym of #SmoothedParticleHydrodynamics, since I'm now seeing #STI as an acronym for #SymplecticTimeIntegrator. And of course these article are more often than not written with #LaTeX.

(No, Mastodon, I really do not want you to normalize the case of *that* tag.)

One of these I'm going to create a quiz game: #kink #fetish or #numericalAnalysis?

When this post https://mastodon.social/@coreyspowell/113807316007617909 by @coreyspowell popped up in my feed just now my first thought was: «wait, I'm pretty sure I saw something similar at a recent #SPHERIC conference» so of course I checked the linked paper (<https://www.nature.com/articles/s41561-024-01612-0.epdf?sharing_token=9Q4L9YJs0dXIOXIb7dJ9F9RgN0jAjWel9jnR3ZoTv0NvCuY-CCmAUDS-e_nTUnvNU1gexpN1yz5LgFWb6OYeZtFJos0bQQeDtkY5TswjWh9TsZvZ6a44fcxf1Kw-c1KkueYZqv6G1Lx7wrnS7EBY4v1kIZ-srQuT1Md7nJKtojM%3D>) and lo and behold, they do use #SPH #SmoothedParticleHydrodynamics

However, I had a feeling it wasn't exactly the same, and by digging deeper in my memory, I realized that indeed what I had seen wasn't (a preview of) this work, but a #SPHERIC2019 contribution about simulating impacts on planetary giants with #SWIFT (a well-known SPH code for #astrophysics, the field SPH was originally designed for, available from <https://www.swiftsim.com>) with Uranus as a test case. You can read the full article here:
https://doi.org/10.1093/mnras/stz1606
and see a high-resolution animation of the Uranus impact, as well as other simulations, at https://icc.dur.ac.uk/giant_impacts/

A heads-up for anyone interested in #SPH #SmoothedParticleHydrodynamics: the #SPHERIC2025 abstract submission deadline has been moved to January 20.

https://spheric2025.upc.edu/

#CFD

There will also be 4 special sessions,

https://spheric2025.upc.edu/index.php/call-for-special-sessions/

for #Aerospace and maritime applications, #SolidMechanics, #CoastalEngineering (an #SPH classic), and one focused on #RenewableEnergy modelling and innovations through #SPH

#SPH_ #SmoothedParticleHydrodynamics

3/

There's something to be said about #Fediverse weirdness, that we all see different things. I discovered the Page42 hashtag game on my "unprofessional" profile, but since I'm at work now and taking a break, I participated by grabbing the closest book I have on hand, which is unsurprising a (somewhat dated, but still valid) reference on #SPH #SmoothedParticleHydrodynamics —and that seems to actually be quite characteristic of _this_ corner of the Fediverse

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Tomorrow I go to #Berlin for #SPHERIC2024. See you there if you're coming.

P.S. I hate #traveling. The day we invent teleportation can't come too soon.

#SPHERIC #SmoothedParticleHydrodynamics

I also want to explore more #GeometricAlgebra applied to #physics and #ComputationalPhysics (not necessarily for #FluidDynamics and #CFD, but that would be preferable as it's obviously our primary topic of relevance). I can't seem to find anything that combines #SPH and GA, so it might even lead to some new interesting venues to explore.

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#ComputationalFluidDynamics #SmoothedParticleHydrodynamics

One of the nice things about #SPH (as in #SmoothedParticleHydrodynamics —the acronym has some other meanings) is that its standard formulation is “weakly compressible” (pressure is derived from an equation of state, but for the most part the compressibility can be ignored), which makes the method itself “embarrassingly parallel” with trivial implementations: there's a natural map from particle to work-item that fits GPUs really well (or does it? https://www.youtube.com/watch?v=zxV846HIKP)

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Does anybody know of #Lemmy communities/magazines centered around any of these topics:

#CFD aka #ComputationalFluidDynamics

#SPH aka #SmoothedParticleHydrodynamics

The closest I can find is @fluidmechanics

#SPHERIC2024 abstract submission deadline has been extended to Friday, January 26th. If you or someone you know have a result that may be of interested to the #SmoothedParticleHydrodynamics community, consider submitting it at the upcoming #SPHERIC International #Workshop in #Berlin
More information at
https://www.spheric2024.com
https://www.dive-solutions.de/spheric2024

Although the focus of the paper is on #SmoothedParticleHydrodynamics, and the simulation of viscous fluids, the key finding is of more general interest: the numerical stability of #BiCGSTAB can be improved by rewriting the standard formulation https://en.wikipedia.org/wiki/Biconjugate_gradient_stabilized_method to avoid catastrophic cancellations in the computation of some important coefficients. Anyone interested in solving large linear systems would benefit from adopting the proposed alternative form of the method.

I'm still preparing my post series on #GPGPU, but in the mean time you can read some about in our most recent published paper:
“A numerically robust, parallel-friendly variant of #BiCGSTAB for the semi-implicit integration of the viscous term in #SmoothedParticleHydrodynamics”, freely accessible for the next 50 days from this link:
https://authors.elsevier.com/a/1fN8C508HsZiG

How does it look like when smoothed particles in a hydrodynamic simulation are doing nothing? Like this.. There is a small amount of initial energy and as you can see, no energy is lost 😆
#SmoothedParticleHydrodynamics #NumericalMethods

There's a lot to learn, and a lot to research, on #SmoothedParticleHydrodynamics. The #SPHERIC Global Seminars <https://www.spheric-sph.org/global-seminars> cover many interesting aspects of the method and its applications, and are an excellent way to whet your appetite and pique your interest.

For a more hands-on learning experience, the upcoming 16th #SPHERIC International Workshop <https://www.spheric2022.it> offers a #TrainingDay fully dedicated to learning the basics of #SmoothedParticleHydrodynamics, from the theory to practical examples with a #FreeSoftware #OpenSource implementation.

The community of researchers and industrial users of #SmoothedParticleHydrodynamics is represented by #SPHERIC, an #ERCOFTAC #SIG with the objective of fostering the development of the method and its adoption <https://spheric-sph.org>.
#SPHERIC defined 5 #GrandChallenges for #SPH:
GC1: #convergence, #consistency and #stability
GC2: #BoundaryConditions
GC3: #adaptivity
GC4: Coupling to other models
GC5: Applicability to #industry