The Seasteading Institute

Reply To: Wayne Gramlich

[quote=Wayne Gramlich]

[quote=Borodog]

WAMIT is a competitor of AQWA. WaSim is a similar type of code. All are so-called "wave interaction" codes rather than full CFD codes. ...

Flow-3d is a full CFD code that specializes in free surface modeling (e.g. the ocean surface is a "free surface"). They compete with our FLUENT and CFX products. ....

I'm not familiar with Accusolve (I've never heard of it, actually).

[/quote]

I don't know much about AccuSolve either. Here's a URL: www.redwingengineering.com/ocean_engineering.html .

In summary, AQWA, WAMIT, and WaSim are "wave interaction codes" and not full up Navier-Stokes CFD codes. Flow-3d is similar to CFX and FLUENT but without FEA. Could I ask you to dig in a little on AccuSolve to figure out whether it is more like AQWA or more like CFX? (I simply do not know how to figure something like that out.)[/quote]

From the pictures in the link that is definitely a full CFD code. If it's specifically for ocean engineering, though, it may be a hybrid code (i.e. can do both full CFD and wave only).

[quote]

To reiterate, my goal is to have a modest sized team of TSI volunteers who can take a design from the larger TSI community and run it through one or more of these CFD codes to figure out its response to various wave conditions. It sounds like AQWA, WAMIT and WaSim would be adequate for this task.

Do you know how structures are intput into AQWA? For WAMIT, the Rhino 3D program has an output module that will generate WAMIT files. Thus, people can use Rhino for input, press a button and have the hard part of WAMIT file generation done by Rhino.[/quote]

AQWA is integrated into the ANSYS Workbench environment, which has geometry interfaces for most major CAD applications (Pro Engineer, Solidworks, etc.), and can import neutral files like step, parasolid, iges, etc. Or you can build the geometry in ANSYS Design Modeler, which is a CAD-lite application for creating and preparing geometry for FEA and CFD.

[quote]]Could you give me an idea what the licensing fees are for AQWA?

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Not cheap. $30k minimum, and that's just for the basic diffraction code, which is probably inadequate. $60k for AQWA Suite, which is probably a bare minimum, and $75k total to include cable modeling. That's before the 20% annual maintenance fees. There are annual leases available, and we can in fact finance the price tag for paid up licenses over 4 or 5 years.

Reply To: Wayne Gramlich

[quote=Wayne Gramlich]

[quote=Borodog]

Mainy I use general purpose CFD (ANSYS CFX) and FEA (ANSYS) codes. There's a possibility that I could get ahold of AQWA, which is a general purpose spectral radiation code used for offshore oil & gas, seakeeping, tidal design, etc., but that would take some finagling at work, and obviously the time involved to come up to speed on that code is non-trivial. Such a code is obviously better suited to a lot of marine design that a full CFD code because of the overhead involved in the latter, but there are still contributions to be made from a full CFD code. In particular CFX & ANSYS play nicely together for fluid-structure interaction modeling.

[/quote]

I do not know enough about CFD/FEA to understand the pros and cons of the various CFD codes that are out there. AQWA is a new one for me. I've heard of WAMIT, Flow-3D, AccuSolve, and WaSim. The people who engineered ClubStead use WAMIT.

We have a lot of people in this community who would like to try out their ideas. I think doing a software simulation is the best way to examine a bunch of different designs and converge on some of the better designs. My current thoughts are that TSI (The Seasteading Institute) picks one of these codes and attempts to develop a team of people who enter such designs into one of the codes and runs the designs through the paces. The ideal soluton would be to use some sort of free CFD code, but I do not know of any such. Lacking that, we need to find an inexpensive CFD code that we run models through.

I started with WAMIT, since that is what Marine Innovation & Technology uses. The costs for WAMIT are 1) $700/month, 2) $6000/year, 3) $10,000/machine, 4) $20,000/site (i.e. multiple machines.)

I'm sure that finding the licensing costs of the other machines is quite easy. Figuring out the capabilites of the CFD code itself requires someone who is pretty familiar with issues. Could I ask you to do a quick technical comparison of Aqwa, Flow-3d, Accusolve, WaSim, and WAMIT? That would be a huge help in trying to standardize on a common CFD code for TSI.

[/quote]

WAMIT is a competitor of AQWA. WaSim is a similar type of code. All are so-called "wave interaction" codes rather than full CFD codes. CFD codes discretize and solve the full Navier-Stokes equations (the equations of fluid dynamics) throughout the volume of interest, whereas wave interaction codes discretize and solve a set of surface wave equations and the velocity and pressure potentials on submerged surfaces of structures. Because a full CFD code solves more complex equations on a volume rather than simpler equations on surfaces, they are much, much, much more computationally intensive. An analysis that might take seconds with a wave interaction code may take hours (even days) with full CFD. However, there are important features that cannot be modeled well with wave interaction codes that can be modeled with full CFD, such as wave cresting, topping, hydrodynamic interactions (for example part of the submerged structure is shedding vortices that then affect other parts of the structure), high speed flows (not too important with seasteads, admittedly), submerged currents, etc. AQWA is integrated with the ANSYS structural solver to compute the structural response (deformations and stresses) of platforms, ships, etc. I don't believe that WAMIT or WaSim can do this, but I am not certain.

Flow-3d is a full CFD code that specializes in free surface modeling (e.g. the ocean surface is a "free surface"). They compete with our FLUENT and CFX products. They use a rectangular meshing scheme, whereas FLUENT and CFX use unstructured meshes. Flow-3d typically requires less user-interaction setting up problems, but is more computationally intensive, so there is a trade-off in terms of time spent setting up problems vs. time to solution. In terms of free surface applications, I don't think either code is technically superior, but FLUENT and CFX are far more advanced in terms of the other kinds of advanced physics that can be modeled (rotating frames of reference for turbomachinery, reacting & combusting flows, radiation modeling, electromagnetics, particle tracking, advanced turbulence models, etc). Flow-3d allows for modeling moving structures in the flow, but to my knowledge does not talk to any actual structural codes, so the structural response (deformations and stresses) cannot be calculated. CFX is integrated with the ANSYS structural solver for full two way fluid structure interaction modeling.

I'm not familiar with Accusolve (I've never heard of it, actually).