Saturday, December 7, 2013

A Tribute to Nelson Mandela

One of the most visible icons in human history, Nelson Rolihlahla Mandela, passed away on December 5, 2013. 

The world was instantly plunged into a black hole of sorrow and sadness, for it lost one of its most courageous, kind, forgiving and charismatic citizens and leaders. Mandela is such a unifying figure that he commands revere from the entire political, racial, religious spectrum. Many countries (including the U.S.) ordered their flags to half-staff to honor Mandela.

The enduring image of Mandela which is still fresh in my mind was him walking to freedom with his wife from the prison that jailed him for over two decades. One can only imagine his joy, triumph and hope at that historic moment. His incredible journey took him from a layer, to an African National Congress (ANC) leader, a prisoner, and finally the first black president elected in a fully representative democratic election. He dedicated his life to the fight for freedom and justice for all South Africans.

Why is Mandela so adored by so many people? I believe he touches many at a personal level. Millions admire his many great qualities: dedicated, courageous, persistent, optimistic, kind, and forgiving. My favorite story about Mandela was something like the following.

Because of severe turbulence (CFD?) during a routine flight, the airplane he flew in was so bumpy that everybody went panic thinking the plane would crash. The passengers looked up to Mandela, and found him totally unaffected and still working on his speech at the destination. They instantly drew strength from Mandela and calmed down themselves. When the plane safely landed, Mandela was asked why he was so calm. He replied that he was scared to death too.

When I read the story, I could almost hear the hero from a movie saying "I just have no fear".

Mandela is perhaps the greatest leader in history. Can you think of another great leader giving up his power willingly at his pinnacle?

Finally as a tribute to Nelson Mandela for his fight for democracy,  I give you two papers with different views on high-order CFD methods, which are published by the same journal:
  • Z.J. Wang, K. Fidkowski, R. Abgrall, et al, High-order CFD methods: current status and perspective, Int. J. Numer. Meth. Fluids, 2013; 72:811–845.
  • R. Löhner,  Improved error and work estimates for high-order elements, Int. J. Numer. Meth. Fluids 2013; 72:1207–1218.
Democracy is live and well in CFD. Now are you for or against us? Let me know using comments below.

Sunday, July 28, 2013

What a Historic and Inspiring JRV Symposium

The highly anticipated Symposium, Four Decades of CFD: Looking Back and Moving Forward, took place in Westin San Diego on June 22-23, 2013, just before the AIAA summer conference. What a wonderful celebration of the careers of three CFD giants, Antony Jameson, Phil Roe and Bram van Leer (or JRV). The weather could not have been better; the place was breathtaking, and the people were terrific. Everything was "aligned" (天时,地利,人和) for a once-in-a-life-time CFD festival.

We had 20 of the world's top CFD researchers as invited speakers, in addition to the three honorees. The speakers came from  all over the world representing academia, industry and government institutions. A total of nearly 80 attendees came to the celebration. There were a total of four sessions, with three dedicated to each of the three honorees, and a panel discussion session, in which all three spoke. A reception concluded the first day, and a banquet was served on the second day.

True to the theme of the Symposium, the invited talks told stories of how some of the best-known CFD algorithms came into existence, and ventured bold predictions on where CFD might be heading. Simply put, the quality of the invited talks was amazing. At the banquet, former students and colleagues of JRV shared fond memories and stories, many told for the very first time, and the audience could not help bursting into laughs for extended periods of time. It was so much fun, as illustrated by some of the photos posted here.

In order to record history, all the talks will be posted here. I am also attaching several photos. In 30 years, we will all exclaim how young we looked in 2013 and how we managed to gather many of the rock-stars of CFD in one place!

Attendees of the JRV Symposium
A Joyous Moment with the NASA Caps, L-R: H.T. Huynh, Bram van Leer, Phil Roe, Antony Jameson and Z.J. Wang
The KU Gang and the Honorees

Thursday, June 13, 2013

2nd International Workshop on High-Order CFD Methods a Huge Success

The 2nd International Workshop took place in the beautiful German city of Cologne on May 27-28, 2013. Coincidently, we had nearly the same number of attendees as the 1st one. Not surprisingly, most came from Europe (Germany, France, Italy, Belgium, U.K, Netherlands, Spain, ...). Because of the U.S. government sequestration, only a handful came from the U.S. Other countries represented included Canada and China.

We had two full days of presentations and discussions with some very interesting results. All the major methods were represented, e.g., finite difference, finite volume, residual distribution, discontinuous Galerkin, spectral difference and correction procedure via reconstruction methods. The abstracts and summaries will be hosted on the workshop web site:

The final hour of the Workshop was spent on discussing future actions. It was obvious that much research is still needed to impact aircraft design. Two decisions were made in the discussion:

  1. The next workshop will be held in January 2015, coinciding with the winter AIAA conference. After that, future workshops will take place every two years;
  2. Future workshops will focus more on challenging problems faced by industry, including multi-scale, unsteady and turbulent flow problems. It is expected that 4-6 problems will be employed in the next workshop. The problems will be finalized in the coming months.

The identified pacing items are similar to those in the 1st Workshop. The summary paper of that workshop has appeared in International J. of Numerical Methods for Fluids. It was felt generating coarse high-order meshes for real world configurations is now the biggest bottleneck in high-order CFD simulations. Recently, CGNS was extended to handle cubic elements, and work is already in progress to add quartic elements in the near future. We do hope that the grid generation community (Pointwise?) take up this challenge.

Finally, I attach several photos. Note the difference in two of the photos. The co-chair was kicked out of the photo in an uproar, and replaced by the photographer...

The attendees

The attendees + the photographer - the co-chair

The Church

Wednesday, April 3, 2013

A Once in a Generation Opportunity to Honor 3 CFD Giants

If you are reading this blog, you most likely know what CFD is. You also probably have a favorite CFD solver or method, and know a few names associated with various algorithms, techniques, schemes, Riemann solvers...With the proliferation of CFD in many industries, the number of worldwide CFD users and developers is at least in the order of tens of thousands (one of the CFD groups on has more than 17,000 members).

The CFD community is a very diverse one. If a CFD History is written by people from different disciplines, you will likely get dramatically different versions. I googled "CFD History", and the top hit was Cincinnati Fire Department History, perhaps indicating no CFDer has seriously attempted to write a CFD History. This is not at all surprising since "CFD History" is so tightly related to how one learned CFD, which text book one read, and what literature one followed. My version of "CFD History" is presented next, from an aerospace engineer's perspective.

I discovered CFD during my last year in college, and was immediately fascinated. My favorite courses were Mathematics, Physics, Aerodynamics and Programming, but my undergraduate major was solid rockets, which did not use my skills that much. I started looking for a different field to pursue my graduate degree. A professor recommended CFD, and I knew right away that's what I wanted to do. During my senior design, I switched to CFD and was advised by Academician Zhang Hanxin. The first ever CFD paper I read was an AIAA conference paper authored by Professor Bob MacCormack, who solved the shock boundary layer interaction problem using his own famous method. The first CFD book I studied was Computational Fluid Mechanics and Heat Transfer, by Anderson, Tannehill and Pletcher. The first scheme I published a journal paper on is the total variation diminishing (TVD) scheme, introduced to me by Professor Zhang. The TVD and high-resolution method related literature opened my eyes to many wonderful works (of art) by pioneers of compressible flow CFD including Boris, Chakravarthy, Godunov, Harten, Jameson, Lax, Osher, Roe, van Leer, Yee, ... who laid the foundation of modern shock-capturing methods.

For a graduate student studying CFD, the people mentioned in the last paragraph were like rock-stars.   They are all giants in CFD. I consider myself very fortunate to have met nearly all of them (except Harten and Lax), and become colleagues and friends with them over the years.

As mentioned in my previous blog, three of the CFD giants, Jameson, Roe and van Leer, will be honored in a symposium (JRV symposium), Four Decades of CFD: Looking Back and Moving Forward, to be held in San Diego on June 22-23, 2013. The objectives of the symposium are:

  • To provide an open and impartial forum for evaluating the current status of CFD
  • To learn from the past and chart the future of CFD in the coming decades

The three giants (or JRV) have not only made path-breaking contributions themselves, but also educated generations of CFDers, who are shaping CFD today. The symposium is open to participants from all over the world. A special invitation is extended to all former students of JRV by the organizing committee. Please come and share your fond memory. This is a once in a generation opportunity to honor all three giants together.

JRV Symposium web site:

I recommend a very funny Wine-Snob's Guide to Flux Functions from UM: