Multi-r Topological-Dynamics Notes
(incl. new radial step-tow variant)

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Yes, Max, we should start with the most powerful multi-physics solver available.

Los Alamos Lab is under US DOE. Joe and I will make requests to mobilize them for AWE R&D. 

NREL developed KiteFast CFD Solver with GoogleX-Makani, but it is poorly documented and supported.

Two early non-CFD analytic calculations would be golden:

1) scalability of an AWES network to GW "extreme-scale"

2) effective aerodynamic scale-invariance, based on non-dimensional low-velocity at extreme-scale

Unit-kites within a lattice can be most-efficiently modeled by a state-machine-automata look-up table. This would cover lattice units at various wind velocities and load-demands. The overall "metakite" (kite of kites) is what needs careful CFD solving. At mega-scale, given constant most-probable-wind-velocity, Euler Equations are increasingly realistic CFD approximations. 

Suggesting a lattice will support multiple bulk harmonic modes to ranging over the IO dimensions, to be processed mechanically by the PTO (power take-off) network at the legs, or under the lattice. Upwind vectors of an iso-lattice are mostly static load and PTO vectors are crosswind aligned. Turbulence can in principle be harvested by local opportunistic response of the mesh, with a sufficiently granular PTO network. Analog Phonon view of bulk field energy packets is the most advanced representation. These packets are coupled wind-field and LSM waves.

A highest-value LSM multi-r prediction is any compelling >10GW scale CFD or analytical validation. Comparative vetting of competing AWES architectures is more complex and less urgent. Most architectures do not even scale to 1MW well. Early numeric evidence of GW-scale AWES meta-units will be revolutionary.

Both CFD solvers that you refer to seem to be quite capable. SU2 indeed looks very solid with extensive capabilities. I suppose that seamless operation with mesh deformations should be quite useful when considering kite membrane structures. However, I'm not sure if dynamic mesh topology changes are needed in the case of testing the behaviour / motion of airborne structures (unless perhaps the possibility of structural element detachment needs to be considered). I assume that OpenFOAM should also be quite sufficient to serve as a simulation testbed for evaluating AWE structure performance at least on a level of preliminary form-finding studies.

Your suggestion to consider particle-based CFD solvers is quite interesting. I was only aware of such use mainly in CGI (e.g. metaballs to visualise liquid behaviour), but after your suggestion, I came across the Smoothed-particle hydrodynamics method. It seems that it could offer advantages for the AWE kite-lattice case as it is a meshless method with no boundary condition requirements and could therefore be more suited for free standing airborne structures that can be modelled as mass-spring systems. Also, a particle-based method could prove to be more "elegant" and efficient as potentially a common solver could be used for simulating both wind and AWE structure behaviour. If there is an impact to precision when compared to traditional Navier-Strokes-based CFD methods, this may not be of consequence in cases where a preliminary evaluation mechanism is needed to test diverse AWE lattice structure configurations.

I also looked into the Discrete Element Method (DEM) which is a general formalisation of particle systems (and of course particle-spring systems). It seems that there has been substantial work in the coupling of DEM with CFD, which, to my understanding, should be the closest thing I have seen to the discussion we have been having (look for the term CFD-DEM). In fact, there seem to be a lot of initiatives that couple OpenFOAM with DEM solvers (e.g. LIGGGHTS and CFDEM project, some videos here and here). Might be worth looking into.

Best regards,

Tassos

Sept. 23, 2020, post by Dave Santos
Re: Open-Source CFD Solutions

Great to see Prof.Dr. Gauger's Group's role in SU2 CFD development. AWE is a wonderful challenge to show its potential. Nothing is currently hotter than SU2 promises to become. Maybe everyone in AWE should migrate to SU2, to take the "in-house" advantage.

Thank you for your feedback. Happy to hear you found the work in the video I shared to be interesting and relevant. Just to note that this was an early experiment with spring-mass simulations and it was tuned to accommodate the particular use case. In principle, a mass-spring simulation model can be elaborated to incorporate more accurate physical properties and quantities, including drag, material elasticity/rigidness, etc. Simple external forces can be modelled fairly easily (e.g. in that example there was a "reverse gravity" force applied to give the dome its shape and also spherical objects were used to locally "repel" nodes to form local cavities). Of course, any network topology can be implemented in such simplified models, either "hard-coded" (manually designed and specified) or potentially rule-based generative models can be applied to yield multiple variations. However, simulating wind dynamics and how this affects load-bearing surfaces (e.g. kite membranes) in a spring-mass simulation is another matter and unless very simplified models are sufficient, coupling with a CFD model may be necessary.

Regarding your discussion on coupling mass-spring simulations with CFD in the separate email threads, commercial-grade CFD packages can of course be used (like Ansys that you mention). However, I think that the customisation of such software and its integration is not trivial and would require the involvement of experts in the field, while generally, relying on third-party software may also present certain limitations in terms of possibilities, integration and configuration. Perhaps it may be worth to consider involving the actual developers of CFD software that would allow greater flexibility and can lead to more customised and efficient solutions (are there any people working with CFD at Kaiserslautern?). For example, at my lab, we have collaborated with a Greek company that develop their proprietary CFD solution and in the projects we've worked on, a CFD simulation is used to simulate fire and volatile product development and this is integrated to operate in realtime with a agent-based simulation of human crowd behaviour that is developed by my lab. This company have also used CFD for calculating wind load bearing on buildings (http://www.sofistik.gr/index.php?id=94) among other use cases. This is a paper from a previous collaborative project https://www.spiedigitallibrary.org/conference-proceedings-of-spie/9842/984216/PYRONES-pyro-modeling-and-evacuation-simulation-system/10.1117/12.2223162.short) and this is the website of an ongoing project  https://www.estia-project.gr/  (sorry it's in Greek only! maybe your browser can provide translation?)

Best regards,

Tassos

Dynamic Model of a Pumping Kite Power System                [d]  
Uwe Fechner, Rolf van der Vlugt, Edwin Schreuder, Roland Schmehl
Delft University of Technology, Faculty of Aerospace Engineering, Kluyverweg 1, 2629HS Delft, Netherlands

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Embryology- pin (mushroom) and bookend (seahorse) poloidal vortex forms, seen early in embryonic progressions.

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A major design option is to harvest wind energy by bulk motion of a lattice, or independent sub-motion of cells.

SubCell and Bulk-Lattice motions can be classed- SLK iso-pivot, iso-AoA-tilt, shunting, etc. Bulk and SubCell options correspond to each other.

In the flowering model, the general principle seems to be that the heavy-air rig (state) is the septal ring, and the petals open and close in large volume changes, as the light-air rig. Thus the petals are more centrally mounted, yet fully deployed they overhang farthest.

In the new radial-motion AWES model, multi-r better fills the airspace cylinder over its footprint in light air, for levelized output.