Sunday, August 25, 2013

SU2 Now on Git: Build and Install Latest on Fedora

As I wrote previously the Stanford University Unstructured (SU2) code is now available on git hub. Here's the steps to get the latest code, build and install it.
  • Use the git client to clone the repo:

    git clone

  • Follow the 'from source' install instructions for your system. It is should look something like:

    make install

    This will give you (after a little help from the kindly devs) a plain-Jane version of SU2 for serial computations, without CGNS or Metis (graph partitioning) support.
Happy number crunching!

Wednesday, August 21, 2013

3-D Printing in DoD: Who's Dragging Their Feet?

I found this article, Why is the Pentagon Dragging Its Feet on 3D Printing, by way of Small Wars Journal. It has some interesting information. The Army is deploying mobile Fab Labs, which seems like a mini MIT FabLab in a shipping container. I think this is a really neat idea. How this can be characterized as feet dragging, I'm not sure. The feet dragging accusation is based on some hand-waving from an article on Disruptive Thinkers, and another article that seems to be worried that there is no Pentagon overlord in charge of an additive manufacturing strategy:
With possible dwindling budgets on the horizon, a clear strategy and cohesive approach is essential to create efficiencies in the area of research and development as well as eliminating duplicative efforts. In order for DoD to take advantage of what is anticipated to be an explosion in the commercial sector within the next ten years, the Department must take an active approach, partnering with the private sector to keep up with this relatively nascent technology and shaping/guiding it towards the desired end state the department has in mind.

One step towards a clear strategy and cohesive approach is for DoD to designate an AM Czar within the Department. They could serve as a single point for all things AM and not the myriad of technical advisory boards that currently exist. This office could then work with policy makers to execute and monitor a strategy which will allow DoD to take full advantage of this technology. Logically, this office would interface directly with the National Additive Manufacturing and Innovation Institute (NAMII) as DoD's representative
3-D Printing Revolution in Military Logistics
I think an "additive manufacturing Czar" sounds like a terrible idea (so I'm sure it will secure funding for some beltway bandits to do a study). I know my recent success with qualifying a particular additive manufacturing process and supplier for use in 3D printing wind tunnel models did not need a Pentagon king-pin to tell me about DoD's strategy for additive manufacturing. Using this technology just made sense as a way to solve my problem: get a complex wind-tunnel model rapidly, and at an affordable cost. I did not receive top-down direction or guidance to use AM, I simply took the initiative to solve my problem. After reading that article I'm left wondering, just how exactly is waiting on direction from the very heights of the bureaucracy supposed to lead to innovation?

Monday, August 19, 2013

UberCloud HPC Experiment

I think I originally saw a link for the UberCloud HPC Experiment on one of the "This week in CFD" posts on Another Fine Mesh. It is a market research exercise to see how people would use cloud computing (platform as a service, software as a service) for their high performance computing workloads. The focus of the experiment is on the difference between enterprise work-loads and high-performance or scientific computing work-loads. Here's some of the introduction describing the research:

We found that, in particular, small- and medium-sized enterprises in digital manufacturing would strongly benefit from HPC in the Cloud (or HPC as a Service). The major benefits they would realize by having access to additional remote compute resources are: the agility gained by speeding up product design cycles through shorter simulation run times; the superior quality achieved by simulating more sophisticated geometries or physics; and the discovery of the best product design by running many more iterations. These are benefits that increase a company’s competitiveness.

Tangible benefits like these make HPC, and more specifically HPC as a Service, quite attractive. But how far away are we from an ideal HPC cloud model? At this point, we don’t know. However, in the course of this experiment as we followed each team closely and monitored its challenges and progress, we gained an excellent insight into these roadblocks and how our teams have tackled them.
UberCloud HPC Experiment: Compendium of Cases
Each of their teams has an industry user, a resource provider, a software provider, and an HPC expert.

This part on applications is interesting:
By far, computational fluid dynamics (CFD) was the main application run in the cloud by the Round 1 and Round 2 teams – 11 of the 25 teams presented here concentrated their efforts in this area.
I think this really helps make the case for open source CFD codes:
In addition to unpredictable costs associated with pay-per-use billing, incompatible software licensing models are a major headache. Fortunately many of the software vendors, especially those participating in the Experiment, are working on creating more flexible, compatible licensing models, including on-demand licensing in the cloud.
Paying a per-core license makes no sense for these large jobs.

One of the interesting use cases was from Team 30 who used an open source stack (Elmer, CAELinux) on top of Amazon Web Services Elastic Compute Cloud.

Saturday, August 17, 2013

UAVs Aquiline and Axillary in Declassified U2 Documents

The National Security Archive has an extensive page up on a previously released CIA report on the U2 program that has now been released with significantly less redaction. One of the interesting un-redacted sections has to do with two CIA UAV programs, Aquiline and Axillary. 

According to an interview conducted by Thomas P. Ehrhard,
Aquiline was a stealthy propeller-driven, low altitude, anhedral-tailed UAV called Aquiline and designed for low-level electronic
surveillance of the Chinese nuclear program. Aquiline was designed by McDonnell Douglas in the late 1960s and advanced to flight testing, but never saw operational use due to reliability problems. The aircraft was to be controlled by data link from a high-flying U-2.
Air Force UAVs: The Secret History
Axillary was a radar-homing drone by Melpar.

The UAV section is in Appendix E.

Wednesday, August 14, 2013

ITAR Public Domain: DIYDrones and Defense Distributed

What is public domain for ITAR compliance purposes? Apparently, being available on a NASA website for years and widely available to the public without restriction is insufficient (and frustrating for aero engineers like me!).

This question has raised discussion on the DIYDrones site:
By and large, open-source qualifies as public domain, so the active technology being created free by the Internet and shared by the Internet means it's exempted.
--Chris Anderson, DIYDrones founder
5 steps to cutting costs: Open-source leads to regulatory breaks
Anderson goes in to more detail,
Autopilots are export controlled by the International Traffic in Arms Regulations (ITAR), which is why it's very difficult for US manufacturers to sell abroad without incredibly complicated guarantees about security procedures put in place by the buyer. That doesn't just apply to autopilot hardware; it also covers autopilot software, groundstation code and other technology in digital form such as schematics. And "export" doesn't just mean physically sending boxes abroad, it also covers "export by electronic means" such as over the Internet.

So why haven't we been arrested? We publish autopilot code, schematics and PCB design files here, and nearly half of our user base is outside the US. The answer is the "public domain exclusion" in ITAR. Because we're open source and release everything to the general public, it's no longer subject to export control.

Why haven't we been arrested?

The argument Anderson is making is the same one that Cody Wilson made about his Wiki Weapons project. Wilson took a "belt and suspenders" approach to getting his files into the public domain,
Wilson argues that he’s also legally protected. He says Defense Distributed is excluded from the ITAR regulations under an exemption for non-profit public domain releases of technical files designed to create a safe harbor for research and other public interest activities. That exemption, he says, would require Defense Distributed’s files to be stored in a library or sold in a bookstore. Wilson argues that Internet access at a library should qualify under ITAR’s statutes, and says that Defcad’s files have also been made available for sale in an Austin, Texas bookstore that he declined to name in order to protect the bookstore’s owner from scrutiny.

State Department Demands Takedown Of 3D-Printable Gun Files For Possible Export Control Violations

However we see two very different trajectories in each case. DIYDrones is merrily turning out hardware and software, and publishing it all online, while Defense Distributed recieves take-down letters from the State Department. I can't see in the ITAR definition of public domain how the two situations should recieve different treatment.
§ 120.11
Public domain.
(a) Public domain means information which is published and which is generally accessible or available to the public:
(1) Through sales at newsstands and bookstores;
(2) Through subscriptions which are available without restriction to any individual who desires to obtain or purchase the published information;
(3) Through second class mailing privileges granted by the U.S. Government;
(4) At libraries open to the public or from which the public can obtain documents;
(5) Through patents available at any patent office;
(6) Through unlimited distribution at a conference, meeting, seminar, trade show or exhibition, generally accessible to the public, in the United States;
(7) Through public release (i.e., unlimited distribution) in any form (e.g., not necessarily in published form) after approval by the cognizant U.S. government department or agency (see also § 125.4(b)(13) of this subchapter);
(8) Through fundamental research in science and engineering at accredited institutions of higher learning in the U.S. where the resulting information is ordinarily published and shared broadly in the scientific community. Fundamental research is defined to mean basic and applied research in science and engineering where the resulting information is ordinarily published and shared broadly within the scientific community, as distinguished from research the results of which are restricted for proprietary reasons or specific U.S. Government access and dissemination controls. University research will not be considered fundamental research if:
(i) The University or its researchers accept other restrictions on publication of scientific and technical information resulting from the project or activity, or
(ii) The research is funded by the U.S. Government and specific access and dissemination controls protecting information resulting from the research are applicable.

Previous cases have shown that the restrictions on publishing source code for cryptography violate the First Amendment, why wouldn't restrictions on publishing gcode for 3d printing a drone or a pistol? I think the First Amendment problems around the Defense Distributed case are the real interesting part of this. Wilson's provocations are not really about the 2nd Amendment, the gun is just a clever marketing hook. His focus is on political speech and freedom of the means of production,
PCMag: Are freely available guns the core of your political beliefs or a part of that larger ideology?

Wilson: No, I think it's a very clever way of unpacking the ideology for people. A lot of people get there and stop at the gun. And that's great, like some of the Second Amendment people who are like, "Alright, this is great for guns." No, I think it's more importantly a signal of the future and it helps through just getting at some of these bigger ideas.
Dismantle the State: Q&A with 3D Gun Printer Cody Wilson
In another article,
Wilson said we’re not so much dealing with firearms regulation as “what can be put into the public domain and how.”

“It’s a demonstration of claiming everything in the national security interest,” he said. “They say, ‘well, your useless plastic gun can’t be shared with other people. It’s important to national security.’ In the end, everything will be claimed…”

It seems to be “consistent [with] the total bureaucratization of social space itself,” Wilson continued.
'In the End, Everything will be Claimed'

Probably the biggest reason for the difference in treatment between DIYDrones' Chris Anderson and Defense Distributed's Cody Wilson is that Anderson wanted to build toys for his kids, while Wilson wants to take on the Leviathan. Lesson: be careful what you wish for.

Monday, August 12, 2013

SU2 Now on Git

Good news for Open Source Computational Fluid Dynamics from the SU2 team:
The Stanford University Unstructured (SU2) development team is proud to announce that the open-source SU2 suite has moved to GitHub!

This change makes it much easier for individuals and groups to use and modify the code for their own purposes. It also means that now SU2 is more open than ever. Moving to GitHub is an important and exciting step for SU2, and we are looking forward new contributions from the community in the true spirit of open-source software.

Users who wish to work with the code will now find that all of the capabilities they require to track modifications are already in place. Copying the code and submitting revisions is easier than ever with GitHub's "fork" and "pull request" features.

In the year and a half since our initial release, SU2 has been downloaded over 5,700 times, and the main SU2 website has received over 45,000 visits from around the world. Our forum hosted by CFD online sees an abundance of activity from many of our users.

SU2 is under active development in the Aerospace Design Lab (ADL) in the Department of Aeronautics and Astronautics at Stanford University and is released under an open-source license.

More information can be found at:
Thank you for your interest and support! The SU2 team
I think this is a really good thing (see previous discussion about SU2 being more open). You may say, why do we need another open source CFD code, don't we already have OpenFOAM? Yes we do, but OpenFOAM is focused on industrial CFD applications that tend to have incompressible formulations and methods. SU2 is a compressible flow finite-volume code (with lots of neat design optimization capabilities too). If you come from the compressible flow world, then you'll find the schemes and methods (upwind/flux splitting, TVD limiters, etc) in SU2 are right in your comfort zone. The beauty of open source is that we can have all these complimentary options to fill different niches.

Sunday, August 4, 2013

A Defense of Computational Physics

This is a defense a long time in the making (h/t Dan Hughes). Patrick Roache has done short articles along a similar vein defending the Computational Physics enterprise against what amounts to an empty nihilism that seems to be popular among academics.

Here is the publisher's description,
Karl Popper is often considered the most influential philosopher of science of the first half (at least) of the 20th century. His assertion that true science theories are characterized by falsifiability has been used to discriminate between science and pseudo-science, and his assertion that science theories cannot be verified but only falsified have been used to categorically and pre-emptively reject claims of realistic Validation of computational physics models. Both of these assertions are challenged, as well as the applicability of the second assertion to modern computational physics models such as climate models, even if it were considered to be correct for scientific theories. Patrick J. Roache has been active in the broad area of computational physics for over four decades. He wrote the first textbooks in Computational Fluid Dynamics and in Verification and Validation in Computational Science and Engineering, and has been a pioneer in the V&V area since 1985. He is well qualified to confront the mis-application of Popper's philosophy to computational physics from the vantage of one actively engaged and thoroughly familiar with both the genuine problems and normative practice.
Here is a short excerpt from one of Roache's papers that gives a flavor of the argument he is addressing,
In a widely quoted paper that has been recently described as brilliant in an otherwise excellent Scientific American article (Horgan 1995), Oreskes et al (1994) think that we can find the real meaning of a technical term by inquiring about its common meaning. They make much of supposed intrinsic meaning in the words verify and validate and, as in a Greek morality play, agonize over truth. They come to the remarkable conclusion that it is impossible to verify or validate a numerical model of a natural system. Now most of their concern is with groundwater flow codes, and indeed, in geophysics problems, validation is very difficult. But they extend this to all physical sciences. They clearly have no intuitive concept of error tolerance, or of range of applicability, or of common sense. My impression is that they, like most lay readers, actually think Newton’s law of gravity was proven wrong by Einstein, rather than that Einstein defined the limits of applicability of Newton. But Oreskes et al (1994) go much further, quoting with approval (in their footnote 36) various modern philosophers who question not only whether we can prove any hypothesis true, but also “whether we can in fact prove a hypothesis false.” They are talking about physical laws—not just codes but any physical law. Specifically, we can neither validate nor invalidate Newton’s Law of Gravity. (What shall we do? No hazardous waste disposals, no bridges, no airplanes, no...) See also Konikow & Bredehoeft (1992) and a rebuttal discussion by Leijnse & Hassanizadeh (1994). Clearly, we are not interested in such worthless semantics and effete philosophizing, but in practical definitions, applied in the context of engineering and science accuracy.
Quantification of Uncertainty in Computational Fluid Dynamics, Annu. Rev. Fluid. Mech. 1997. 29:123–60

Saturday, August 3, 2013

Navier Stokes 12 Step Program

By way of another fine mesh, Boston University’s Prof. Lorena Barba has released a 12 Step Program for Navier-Stokes. It is a self-paced introductory CFD course presented based on IPython Notebooks. From the site:
We announce the public release of online educational materials for self-learners of CFD using IPython Notebooks: the CFD Python Class on Bitbucket
The course starts with simple one dimensional toy problems and progresses through Burger's equation, then to two dimensions and then finally to Navier-Stokes in 2D. Looks neat, can't wait to try out the notebooks.