Saturday, July 19, 2014

FreeFem++ Topology Optimization Scripts

There are lots of open source topology optimization options out there (e.g. 99 line code, ToPy) that I've written about before. One that I haven't posted about yet is a collection of FreeFem++ scripts by Allaire, et al. that illustrate a variety of topology optimization approaches and problems. FreeFem++ is a partial differential equation solver based on the finite element method. FreeFem++problems are defined in scripts that use a high level language. FreeFem++ itself is written in C++.

Tuesday, July 1, 2014

UAVs for Film and Profit

Yesterday's AIAA Daily Launch had a great round-up of some recent UAV news:
  • Wall Street Journal (6/27, Nicas, Subscription Publication) reported on the ongoing fight over U.S. unmanned aircraft rules, which is pitting high-tech entrepreneurs against major aerospace and defense companies.
  • Washington Post (6/28, Whitlock) reported that a majority of U.S. military UAV accidents occur abroad, but “at least 49 large drones have crashed during test or training flights near domestic bases since 2001, according to a yearlong Washington Post investigation.”
  • AP (6/28, Jelinek) reported that the Pentagon announced armed UAVs are “flying over Baghdad to protect U.S. troops that recently arrived to assess Iraq’s deteriorating security.”
  • South Florida Sun Sentinel (6/29, Anthony) reported that Boynton Beach is dropping plans to ban drones in order to boost its “fledgling image as a technological hot spot — a place that welcomes engineers and innovation.”
  • South Bend (IN) Tribune (6/29, Sheckler) reported that as UAVs become cheaper and more available to the public, and their popularity grows among hobbyists and entrepreneurs, “they will increasingly raise questions about how to best regulate them, and how to balance concerns about safety and privacy.”
  • Hollywood Reporter (6/27, Giardina) reported that Hollywood movie studios are interested in using UAVs in filming “because they hold the promise of new creative options, real cost savings and possibly even safer sets.” Federal law prohibits the commercial use of UAVs, so filmmakers choose to shoot in countries with lax UAV laws to get the shots needed for their films.
Most interesting are the petitions of the seven aerial photography companies for exemptions for commercial filming operations. As the FAA press release says, the seven Section 333 Exemption Applications for Commercial Operations of Unmanned Aircraft are available on I think it is interesting that these companies are taking this approach, because in some fillings by Pirker they specifically call out historical use of remote control aircraft for movies and TV (one of four broad categories of commercial use they cite). The applications have 18 "limitations and conditions" under which commercial operations will take place. They also make this interesting claim: "These limitations provide for at least an equivalent or even higher level of safety to operations under the current regulatory structure because the proposed operations represent a safety enhancement to the already safe movie and television filming operations conducted with conventional aircraft."
To drive that point home they show a couple pictures of a manned helicopter filming as it currently occurs.

Sunday, June 29, 2014

3-in Tack Strip Bracket TopOpt

I found a useful bracket on thingiverse for mounting things on a 3-in tack strip. Of course I thought this was a perfect opportunity for a bit of topology optimization. All of the design files and the stl (rendered above) are available on GitHub. The part is also on thingiverse.

Here's a video showing the progress of the optimization:

Rendered with a wave texture in Cycles to give the layered look it would have from an FDM machine, not quite right, but pretty close:

Thursday, June 26, 2014

HiFiLES v0.1 Release

The folks at the Stanford Aerospace Computing Lab have recently released version 0.1 of HiFiLES. "HiFiLES is a high-order Flux Reconstruction solver for the Euler and Navier Stokes equations, capable of simulating high Reynolds number turbulent flows and transonic/supersonic regimes on unstructured grids."

From the release notes:

High-order numerical methods for flow simulations capture complex phenomena like vortices and separation regions using fewer degrees of freedom than their low-order counterparts. The High Fidelity (HiFi) provided by the schemes, combined with turbulence models for small scales and wall interactions, gives rise to a powerful Large Eddy Simulation (LES) software package. HiFiLES is an open-source, high-order, compressible flow solver for unstructured grids built from the ground up to take full advantage of parallel computing architectures. It is specially well-suited for Graphical Processing Unit (GPU) architectures. HiFiLES is written in C++. The code uses the MPI protocol to run on multiple processors, and CUDA to harness GPU performance.

The main reference for the code right now is this V&V paper.[1] The code uses an Energy Stable Flux Reconstruction (ESFR) scheme. Here are a couple papers on that approach.[23].


[1]   L√≥pez-Morales, M. R., Bull, J., Crabill, J., Economon, T. D., Manosalvas, D., Romero, J., Sheshadri, A., Watkins II, J. E., Williams, D., Palacios, F., et al., “Verification and Validation of HiFiLES: a High-Order LES unstructured solver on multi-GPU platforms,” .
[2]   Vincent, P. E., Castonguay, P., and Jameson, A., “A new class of high-order energy stable flux reconstruction schemes,” Journal of Scientific Computing, Vol. 47, No. 1, 2011, pp. 50–72.
[3]   Castonguay, P., Vincent, P. E., and Jameson, A., “A new class of high-order energy stable flux reconstruction schemes for triangular elements,” Journal of Scientific Computing, Vol. 51, No. 1, 2012, pp. 224–256.

Thursday, June 5, 2014

Emerging and Readily Available Technologies and National Security

Here's the description of this report from the NAP site:
Emerging and Readily Available Technologies and National Security is a study on the ethical, legal, and societal issues relating to the research on, development of, and use of rapidly changing technologies with low barriers of entry that have potential military application, such as information technologies, synthetic biology, and nanotechnology. The report also considers the ethical issues associated with robotics and autonomous systems, prosthetics and human enhancement, and cyber weapons. These technologies are characterized by readily available knowledge access, technological advancements that can take place in months instead of years, the blurring of lines between basic research and applied research, and a high uncertainty about how the future trajectories of these technologies will evolve and what applications will be possible.

Wednesday, May 28, 2014

SpaceX SuperDraco Made with DMLS

SpaceX completes Super Draco Qual
From the press release:
The SuperDraco engine chamber is manufactured using state-of-the-art direct metal laser sintering (DMLS), otherwise known as 3D printing. The chamber is regeneratively cooled and printed in Inconel, a high-performance superalloy that offers both high strength and toughness for increased reliability.

“Through 3D printing, robust and high-performing engine parts can be created at a fraction of the cost and time of traditional manufacturing methods,” said Elon Musk, Chief Designer and CEO. “SpaceX is pushing the boundaries of what additive manufacturing can do in the 21st century, ultimately making our vehicles more efficient, reliable and robust than ever before.”

Wednesday, March 5, 2014

SAC-D Hearing on National Security Space Launch Programs

The Senate Appropriations Committee, Defense Subcommittee (SAC-D) held a hearing on 5 March concerning National Security Space Launch Programs. The written testimony and webcast is available from the Senate website:
Chairman Durbin's opening statement emphasized that this hearing had some features that were a bit unusual,
It's been the general practice of the appropriations committee to direct questions about acquisitions programs to the government officials responsible for the use of tax-payer money. Today, we're taking a different approach by going into the details of the EELV program with the two companies most involved in the upcoming competition, as well as two distinguished experts in space acquisitions.

Friday, February 21, 2014

SU2 Community Verification Studies

I think there is quite a bit of excitement and community involvement building around the SU2 code. Other than all of the updates and improvements in the recently released version 3 and SU2_EDU release, I am excited to see the wider community start to do some serious verification studies. The advecting vortex case linked in that discussion thread would be a good one to add to the Test Case collection.

The core SU2 devs have a recent AIAA paper on verification/validation cases that they have successfully run with SU2 and compared favorably to other codes. One thing that is conspicuously absent is grid convergence studies to verify order of accuracy. This is an ideal place for the community to contribute because you don't have to have hugely in-depth knowledge of the source code base to run a grid convergence study or contribute a tutorial or test case (though you do have to be a fairly competent user). Much to their credit, the SU2 team is soliciting just this kind of contribution (my emphasis):
Expanded tutorials: we would like additional tutorials that complement the existing set found in the web-based documentation. The tutorials can either detail and explain the functionality of SU2 (shape optimization, parallel computing, mesh deformation, etc.) or demonstrate general CFD knowledge (highlighting good meshes vs. bad meshes, the importance of CFL number, etc.). Tutorials are intended to be tools for teaching and learning, and they should follow the same style as the existing tutorials. They must provide any mesh or config files that are necessary for their completion. New or unique verification and validation cases would be of particular interest here.

Exciting times in open source CFD!

Thursday, February 6, 2014

TPS Sizing with Complex Step Method

TPS Sizing Optimization Using Complex Variable Differentiation Sensitivity
I stumbled upon an interesting old presentation that shows a neat application of the complex step method of calculating numerical derivatives for use in optimizing thermal protection system (TPS) thickness. The great thing about the method is that it is minimally intrusive.