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:

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.[2, 3].

References

[1]   López-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.

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.

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.”

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:

• Dr. Scott Pace
• Elon Musk
• GAO PowerPoint See also this recent GAO report: The Air Force's Evolved Expendable Launch Vehicle Competitive Procurement
• Michael Gass
• Webcast

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.

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!

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.

SU2 v3 Released

The folks at Stanford Aerospace Design Lab have released a new major version of Stanford University Unstructured (SU2). Here's the announcement:

Dear Colleague,

Since its introduction in January 2012, SU2, The Open-Source CFD Code, has been downloaded thousands of times by users and developers in academia, government, and industry, including many leading companies and universities. As an open-source project, the growth of active user and developer communities is a crucial goal for SU2. Given the incredibly positive response, we are pleased to announce a new version of the code with major improvements and a entirely new package for educational purposes.

This release marks the third major version of the SU2 open-source code (su2.stanford.edu). SU2 is a collection of C++ software tools for performing Partial Differential Equation (PDE) analysis and for solving PDE-constrained optimization problems, with special emphasis on Computational Fluid Dynamics (CFD) and aerodynamic shape design.

We'd like to ask you to please distribute this announcement with the attached flyer to any colleagues and students in your department that might be interested.

Version 3.0 has a number of major additional capabilities:

• Adjoint-based RANS shape optimization.
• New unsteady analysis and design optimization capability.
• Upgrades to the underlying parallelization and file I/O.
• Significant improvements to the accuracy, performance, and robustness of the software suite.

Alongside Version 3.0 of SU2, we are introducing SU2 Educational (SU2_EDU): a new, educational version of the Euler/Navier-Stokes/RANS solver from the SU2 suite. The simplified structure of SU2_EDU makes it suitable for students and beginners in CFD. By focusing on a handful of key numerical methods and capabilities, SU2_EDU is ideal for use in CFD courses, for independent studies, or just to learn about a new field!

SU2_EDU is also geared toward anyone interested in high-fidelity airfoil analysis. The initial version of SU2_EDU is an intuitive, easy to use tool for computing the performance of airfoils in inviscid, laminar, or turbulent flow including non-linear effects in the transonic regime, that only requires the airfoil coordinates.

Finally, we would like to thank the open-source community for their interest, help, and support.

The SU2 team

One of the most interesting parts to me is the new SU2_EDU version. I've downloaded the code, but haven't had a chance to browse it or run any examples yet. I think this is a neat idea that will hopefully lower the barriers to entry that George pointed out previously.

CFD Vision 2030: Discretizations, Solvers, and Numerics

There are lots of interesting parts to the study that Phil Roe mentioned in his Colorful Fluid Dynamics lecture. Continuing the theme that algorithm improvements are just as important as hardware improvements here are some of the areas concerning discretizations, solvers and numerics (pp 24) that the report claims will lower the need for high levels of human expertise and intervention in running and understanding CFD analysis:

1. Incomplete or inconsistent convergence behavior: "There are many possible reasons for failure, ranging from poor grid quality to the inability of a single algorithm to handle singularities such as strong shocks, under-resolved features, or stiff chemically reacting terms. What is required is an automated capability that delivers hands-off solid convergence under all reasonable anticipated flow conditions with a high tolerance to mesh irregularities and small scale unsteadiness."
   
2. Algorithm efficiency and suitability for emerging HPC: "In order to improve simulation capability and to effectively leverage new HPC hardware, foundational mathematical research will be required in highly scalable linear and non-linear solvers not only for commonly used discretizations but also for alternative discretizations, such as higher-order techniques89. Beyond potential advantages in improved accuracy per degree of freedom, higher-order methods may more effectively utilize new HPC hardware through increased levels of computation per degree of freedom."