This Week in CFD

Why is meshing so hard?

Today’s thought-provoking reading is a two-year old blog post from CFMS that asks “Why is meshing so hard?” I have often asked myself the same question and today decided – as is standard practice nowadays – to ask Google. I didn’t even have to complete the search to see what everyone else is asking.

Google-why-is-meshing-so

Here are the thoughts the article provoked in me.

  • The article quotes a meshing researcher as saying “anyone can write a CFD solver before lunchtime, but to write a good mesh generator takes a lifetime.”
    • I am proving the latter. Still striving for good.
    • While this person is obviously engaging in a bit of hyperbole to make a point, I have actually heard CFD people seriously claim to be able to write a CFD solver over a weekend.
    • A prospective customer once told us that their company’s policy was that any software that cost more than $10,000 per year was cheaper for them to develop themselves.
  • The challenge in meshing, according to the author, is the volume mesh. I disagree a bit because my personal experience has shown that most volume meshing problems are the result of a poor surface mesh.
  • The author wonders why has meshing remained challenging for so long.
    • The Navier-Stokes equations are the Navier-Stokes equations are the Navier-Stokes equations. Meshing has no such equivalent, common, mathematical basis and virtually anything goes to generate points. (Structured grid techniques using elliptic PDEs and the Delaunay technique for unstructured meshes come close.)
    • All CFD solvers (do not take the word “all” literally) solve the N-S equations. But they each solve them in different ways that a mesher must support.
      • There was a structured grid flow solver that required meshes to be left-handed. Really?
      • Cell type support varies from hexes (structured and unstructured) to tets, prisms, pyramids (but really, don’t use pyramids they say), polyhedra. This doesn’t account for codes that allow (or don’t allow) hanging nodes and edges.
      • Of course, the mesh quality levels desired by each solver differ, not only in value but in method of computation.
    • CFD problem size and scope continue to evolve and expand. What took me a year to do in 1986 wouldn’t even qualify as an undergraduate homework assignment now. Today the geometry models to be meshed have more entities in them than there were grid points in the meshes I used to generate decades ago.
    • In the beginning, everyone doing CFD had to be an expert. Now, with more and more people using CFD, there are a lot more non-experts. (This is a good thing.) But this makes designing software user experience (what we used to call graphical user interface back in the day) more challenging when you have to serve a broader range of users. Keep in mind that UX is important for meshing because we lack N-S equations that can simply be converged.
    • Bottom line: all the unglamorous, dirty work flows downhill from the solver to the mesher.
  • The author was quite prescient when wondering whether there should be mesh generation workshop. In fact, the 1st AIAA Geometry and Mesh Generation Workshop was held this past June and plans are underway for a second.
  • Finally, the author (who has many more degrees than I) opines that the future of meshing may be massively parallel and involve machine learning. Smarter people than I will have to figure that out.

And y’all would be disappointed if I didn’t end with a comment I’ve repeated more than a couple of times, “Mesh generation exists in order to make turbulence modeling seem respectable.”

Upcoming Pointwise Events

IFCPT_BaselineDuct

CFD simulation results for an S-duct. Meshing for this simulation will be discussed in the webcast linked to below.

Software

  • MSC released Adams 2017.2 for multibody dynamics simulation including a new aerodynamics module.
  • Beta CAE released v17.1.2 of their software suite.
  • Mentor released a new version of FloTherm for electronics cooling with a new feature called the command center with which users can define variations of base models.
  • ANSYS Fluent has demonstrated scalability to 200,000 cores. [Wow.]

Applications, Events, and Jobs

  • CFD helps with the design of vertical turbine pumps that lead to less cavitation and wear in boilers.
  • Inside HPC delves into how the Exaflow project is working toward exascale simulations.
  • DCS Computing’s Open Source CFD Workshop will be held 14 September 2017 in Linz, Austria. Keynote speakers will include Drs. Darrin Stephens and Chris Sideroff from Applied CCM and Applied CCM Canada, respectively. (Full disclosure, Applied CCM is a Pointwise partner.)
  • Areva in Washington state seeks a thermal-hydraulics CFD engineer.
  • Registration for TFAWS (Thermal & Fluids Analysis Workshop) is now open.

More Than an Array of Quads

Sometimes it’s just nice to see something that has a surface simplicity that hides an underlying complexity. The painting below is the work of Cheyney Thompson.

Cheyney-Thompson-StochasticProcessSet-Detail-2017

Cheyney Thompson, StochasticProcessSet (DETAIL), 2017. See link above.

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This Week in CFD

On Validation

This week’s must-read article comes from Bill Rider on the The Regularized Singularity blog: Good Validation Practices are our Greatest Opportunity to Advance Modeling and Simulation. In it he makes the case that chasing FLOPS at this stage in simulation’s maturity is foolhardy while validation is the proverbial low-hanging fruit.

News & Events

  • Everyone has heard this news by now so while it might appear to be anti-climactic, ANSYS has acquired CEI, makers of the EnSight CFD visualization and post-processing software. You can read the details from many sources.
  • Speaking of EnSight, their EnSight European User Meeting will be in Munich on 30 Nov – 01 Dec and their EnSight Japan User Meeting will be in Tokyo on 27 October.
  • The Numeca International User Meeting 2017 will be 13-15 November in Brussels.
  • Tech-Clarity invites you to answer their survey question “What Skills Do You Wish Engineering Graduates Had?” Respondents are eligible for a drawing for an Amazon gift card. [I recommend you take the survey. This is an important topic.]
    • [My first reaction to this question was “strong communication skills, both written and verbal.” Engineers spend more time writing and talking (presenting) than students think.]
    • [My second reaction was to the word “skills” and my reaction was justified somewhat by questions in the survey. A college of engineering is not a trade school. Colleges should teach students the fundamentals of various engineering sub-disciplines in addition to teaching them how to learn. Employers can train them on skills.]
  • Final presentations from the 1st AIAA Geometry and Mesh Generation Workshop are now available for download from the workshop website.
STC-VWT-bike

How about some rider-specific CFD for cycling? CFD by STAC Performance. Image from SlowTwitch.com.

From Pointwise

Software

  • HOPR is an open-source project for high-order mesh generation.
  • Gismo is an open-source Grasshopper plugin for “GIS environmental analysis.” It looks like it could be used to prepare geometry for CFD simulations of an urban environment.
    • An example of such – albeit not using Gismo – can be seen here.
  • SCORG is a mesh generator for screw compressors, expanders, pumps, and motors.
  • OpenCFD released OpenFOAM v1706 with new overset mesh functionality and more.
  • Introducing the Tdyn CFD+HT CFD solver from Compass.
  • Introducing Trampo, “next-gen cloud computing for STAR-CCM+ users.”
gridpro-nesting

An example of GridPro’s new nesting technique. Image from PDC.

Applications, Jobs, and More

Facets in Motion

An alert reader pointed me to Kouhei Nakama’s video Makin’ Moves in which the dancers get the mesh treatment at about the 2-minute mark.

makin-moves-video

Kouhei Nakama, screen capture from Makin’ Moves. See link above.

Lest you think this is a new concept, consider the photo below from 1883 that was created as part of a study of human walking motion by putting a slotted, rotating disk in front of a camera lens as someone walked past.

Marey-human-gait-1883

Etienne-Jules Marey, Chronophotograph, 1883. Image from Futility Closet. See link above.

Marey’s Chronophotograph supposedly inspired Marcel Duchamp’s fantastic Nude Descending a Staircase about which he said “My aim was a static representation of movement.” It’s important [to me] to share this Duchamp painting to offset his notoriety for Fountain, a porcelain urinal.

Duchamp-Nude-Descending-1912

Marcel Duchamp, Nude Descending a Staircase, 1912. Image from Futility Closet. See link above.

Bonus: Mathematicians have derived the governing fluid mechanics for optimizing your daily cup of coffee accounting for 20 parameters including density, porosity, and height of the ground coffee bed. Read a brief summary from Discover or the full paper from SIAM.

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Introducing Pointwise’s Summer Interns

Our full complement of summer interns has reported for the summer and we’d like to introduce them to you.

PWI-Interns-Summer-2017

Pointwise’s Summer Interns 2017 (left to right): Brian Ta, Sydney Wood, Christian Atwood, Brian Zdeb

Brian Ta is majoring in computer science with a minor in math at Texas A&M University where he’ll be a senior when he returns in the fall. He’s working in our Product Development team and writing code for our new grid import plugin SDK that will give you the ability to write your own mesh importer. You can read all about Brian in his This is How I Mesh profile.

Sydney Wood will be a senior at Texas Christian University this fall where she’s a dual major in entrepreneurial management and sociology. She’s working in our Business and Administrative Services team, helping with upcoming events and maintaining our customer relationship management system. Sydney is considering law school after graduation.

Christian Atwood is a recent high school graduate who plans to attend Embry-Riddle Aeronautical University in the fall where he’ll begin his pursuit of a degree in aerospace engineering with a minor in computer science. Christian is working in our Technical Support team and contributing to our quality assurance testing.

Brian Zdeb comes to us from Caltech where he’s majoring in mechanical engineering with an expected graduation in June of 2018. Working in our Technical Support team, Brian is generating a mesh for an upcoming wind energy conference and is assisting the other engineers on the team by researching customers’ issues.

Not pictured above is Andrew Jefferies, a music dance theater major from Brigham Young University (planned graduation 2020) , who is working in our Business and Administrative Services team. Andrew also interned with us last summer so his This Is How I Mesh profile is already online. So far, Andrew is the only Pointwise intern who has sung their end-of-summer presentation.

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I’m Brian Ta and This Is How I Mesh

Brian Ta, Product Development Intern.

Howdy everybody! I am a Vietnamese born American originally from Fountain Valley, California.  The only memories I have from there are of the beach in addition to being robbed…the reason why my family moved to Texas.  I have been living in southwest Fort Worth for almost 16 years (I’m 21 now) so I can say that Fort Worth is where I’ve been truly raised.  My life story includes some twists and turns and I have been able to find solidarity through a couple of key moments:

  • Using my first computer (a Compaq Presario 5000 series). When I was around 9, I developed a strong fascination with computers and the internet.  My first memories were of Limewire, early YouTube, making friends from the UK through internet games, and infecting the family computer with viruses and malware.
  • Becoming a Texas A&M Aggie. I was graciously offered full tuition to Texas A&M through different programs. One of them was the Regents’ Scholar Program, given to low-income, first-generation university students.  WHOOP!  Before that, I was considering trials for D3 tennis at Sul Ross University, and believe it or not, passed on a full-ride offer to attend TCU with hopes to study engineering at A&M.  At A&M I had initially enrolled as a physics student after being inspired by some books and videos by Richard Feynman (in addition to applying late to the Engineering school).  I moved on in my second year to pursue computer science, something that I’ve always been fascinated with growing up.  My favorite course so far has been in Computer Graphics taught by Dr. Shinjiro Sueda.
  • Location: Fort Worth, TX
  • Current position: Intern, Product Development
  • Current computer: They call him Dooku. Specs:
    • Windows 10
    • Intel i7 860 @ 2.8 GHz
    • 8 GB DDR3 RAM @ 1333 MHz
    • NVIDIA GT 220
  • One word that best describes how you work: Curiously

What software or tools do you use every day?

  • The main tool I use nowadays is Microsoft’s Visual Studio 2015 for debugging and compilation. It’s great tool and the feature set enables me to complete my tasks efficiently.
  • For scripting, I’ve been trying to familiarize myself with vi. I was one of the 1 million views of the Stack Overflow post, “How to exit the Vim editor?
  • Outlook for email.
  • Spark for chat.
  • Microsoft Teams looks promising for collaboration. Even though I haven’t used it much, I like to keep it open just in case.
  • And of course, Pointwise for grid generation.

What does your workspace look like?

It’s fairly simple and unorganized.

What are you currently working on?

This summer I am working on grid import plugins for the different CAE solver types that are currently unsupported.  We are adding grid import support for the following solvers: FUN3D, CFD++, SU2, CFX, OpenFOAM, Fluent, and Star-CCM+.

In addition, I am also working on a Glyph script that generates automatic nearfield and farfield blocks around a user defined group of domains to be used for automotive and aerospace applications.  Admittedly as a first time user, learning a lot of these meshing techniques for scripting have been over my head, but I find it really cool that there is so much control built into Pointwise. And a huge thanks to David Garlisch for helping me through the process.

What would you say is your meshing specialty?

As a computer science major, I don’t have much meshing experience.  However, I like to think that I can help others by working behind the scenes on the meshing software.  That said, being able to understand how to generate high quality meshes goes hand in hand with understanding the use cases of the software itself, so I am trying to keep a holistic mindset and learn as I go.

Any tips for our users?

Learning how to use new software can be quite intimidating. However, when it comes to learning Pointwise, there are a number of great resources out there you can use.  For example, Pointwise’s YouTube channel has a number of tutorial videos you can watch to help you quickly come up to speed with the features and meshing best practices.

I like the basic nature of the organization Pointwise provides for meshing.  For example, you can work on different parts of a complicated mesh using the layer manager in addition to using selection masks to select the different entity types you desire.

Mesh automation with Glyph is very useful and powerful.  Pointwise’s GitHub repository includes several example scripts you can run to get started.

Also, the support team is great a group and are always willing help and to take your feedback. User input is always welcomed and greatly appreciated.

What project are you most proud of and why?

I have completed the import plugin for the FUN3D solver, which will enable users to import their exported FUN3D grid files back into Pointwise.  This project involved efficiently reading in data represented in binary and ASCII formats and stuffing the data into importer API calls.  David had set up the API quite well making it relatively straightforward.

Apart from the other Pointwise projects I’m assigned (that are in progress), I do want to share some of the projects I’ve completed in school.  The first is a Software as a Service full stack web-application developed with the Ruby on Rails platform. This project was a Course Assignment Submission System (email me if you want to login info) to be used locally by the Computer Science & Engineering department which gives instructors, students, and teaching assistants a multitude of functionalities on courses and assignments.

The second, which I particularly enjoyed, is a project where we implemented a heartrate monitor using a microcontroller.  We used a TI-MSP430 and a Bluetooth chip to capture an electrocardiogram signal and then perform the necessary calculations on the data to output the user’s heartrate in real-time.  In retrospect, I realize that it is quite basic, but this gives me a stronger appreciation of the commonality and the impact of embedded systems in day to day machinery like automobiles, aircraft, medicine, and so much more.

A fun personal project I worked on was a Python script (repo is very outdated) which grabbed data from the Fantasy Premier League website.  I am a big follower of English football (soccer) and I compete in a fantasy league with my friends where we pick our team and get virtual points depending on how well our teams do.  The script gets a JSON response on different links of the website, parses through all of the competitive league data (team info, players picked, captains, previous points) that I’m in, and outputs it nicely in .csv files to give me a useless edge on my fellow competitors.

What CFD solver and postprocessor do you use most often?

I don’t directly use any CFD solvers or postprocessors, but I do change solver types in Pointwise to export test grids to be reimported.

Are you reading any interesting technical papers we should know about?

I read an interesting ACM paper earlier this year, First Steps Towards a Conceptual Framework for the Analysis of Wiki Discourses, which details the collaborative nature of Wikipedia.

This isn’t really technical, but I like the story of the ENIAC, (Electronic Numerical Integrator and Computer) which is a computer developed by six brilliant women for the U.S. Army during the WWII era who recently received credit for their work.

Do you plan on attending any conferences or workshops this year?

Probably not.  I’d love to attend Apple’s WWDC one day though.

What do you do when you’re not generating meshes?   

Video games (old console emulators), watching Netflix, hurting myself skateboarding, tennis, listening to 80s rock, and questioning the meaning of life.

Recently I’ve been planning and looking up things I can do to help out low-income communities bring computer science into their schools.  This is a long term goal, but I hope I can help out someday.

What is some of the best advice you’ve received in your field?

“Developing software is like building a doghouse, sometimes you just do it, if you fail you do it again, in the worst case you annoy your dog, but you can always get a new dog.” – Grady Booch (check out the talk he did at ICSE 2015).

If you had to pick a place to have dinner, where would you go?

Cousins Barbeque, Pho 95, or Whataburger.

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Looking Ahead Three Versions: New Meshing Capabilities

From the 2017 Q2 issue of The Connector:

badge-new-180x180A new update for Pointwise, Version 18.0 R3, has just been released, and it includes a variety of new capabilities to help you generate better meshes faster. Later during 2017, a multi-year development effort will come to fruition, resulting in a suite of new tools in V18.1 for all types of meshing, including overset. Finally, the longer-term future of our meshing capabilities is coming into focus as our high-order meshing research transitions into production code. (more)

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Top 5 Reasons to Mesh with Pointwise in Maryland

Pointwise will be hosting Efficient Meshing with Pointwise, a 1-day workshop in our Let’s Talk Meshing series of events, on 22 August in College Park, Maryland.

Here are the top 5 reasons why it’s worth your time to join us.

Geometry model preparation for meshing is perhaps the biggest bottleneck in meshing. You’ll learn about the two suites of tools in Pointwise for geometry model prep – Fault Tolerant Meshing and Solid Meshing – and all the related tools available in the software for making this process as painless as possible.

Pointwise isn’t just for airplanes and meshes aren’t an end unto themselves. You’ll see how the software can not only mesh marine propellers in a variety of ways, but how those different meshes influence solution efficiency and accuracy.

skew-block

Volume mesh skewness for a hybrid mesh around the Potsdam Propeller Test Case.

The software is constantly evolving. For those new to Pointwise, you’ll see an overview of everything the software can do. For those more familiar with the software, you’ll be introduced to the latest features that have been added. For everyone, you’ll get a preview of where the software is headed.

Tour an aviation museum. The workshop will be held at the College Park Airport where they also have an aviation museum with aircraft on display from the first half of the 20th century and much more.

The workshop is free – there’s no registration fee.

Don’t delay: learn more and register today.

action-register-today-200x50

 

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This Week in CFD

Software

bac-mono-artcar-1

Briggs Automotive Co. painted their BAC Mono car with colorful streamlines that are intended to mimic the CFD results they obtained from Autodesk’s CFD tools. Image from carscoops.com.

News from Pointwise

  • At AIAA Propulsion and Energy, you’ll find Pointwise in the exhibit hall and in several technical presentations on mesh adaption, nozzle aerodynamics, and the recently completed Propulsion Aerodynamics Workshop. All the details are on our website at www.pointwise.com/aiaa-propulsion.
  • Pointwise will be in College Park, Maryland in August for a 1-day workshop on Efficient Meshing. Register today before this free event fills up.

Reading, Reading, and More Reading

JordanGriska__05

Jordan Griska, Wreck, 2016. Image from Colossal. Read more here. [You didn’t think I’d post an artistic rendering of CFD on a car without also showing a mesh on a car, did you?]

Events and…

nose-airflow

CFD simulation of airflow in the nose. From Image-based CFD in the lung: virtual reality or new clinical practice? Image from Wiley Online Library.

My Mesh is Slipping Away

Alert Twitter follower @Vincent_Lab saw a sculpture in South Kensington outside the office of the Royal British Society of Sculptors and was kind enough to think of us. After a bit of research (and emails from the RBS – thank you) I learned that the work is by a fellow of the society, Joseph Hillier. This piece, Breathe, is part of his Digitalrendition exhibition.

According to the exhibit’s website, “The works in this exhibition are a poignant analysis of humanity’s relationship to our new world of ephemeral data structures and their reconfiguration of time and space. It is Hillier’s way of holding onto and making physical some of the visual information around us which is continually slipping away.”

RBS_Sculptors

Joseph Hillier, Breathe. Photo credit: @Vincent_Lab. See link above.

P.S. Here’s wishing my fellow citizens a happy Independence Day weekend.

P.S. P.S. After a final-read through of this post I see the headings don’t really relate to each section’s content reminding me of the common clause in legal agreements “The section headings contained in this agreement are for reference purposes only and shall not affect the meaning or interpretation of this agreement.”

P.S. P.S. P.S. This proves I read too many legal agreements.

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