Models Methods Software

Dan Hughes

Fluid Systems Mechanically Coupled Through a Wall

Method of Exact Solutions Verification Problems for Transient Compressible Flows: Two Fluid Systems Mechanically Coupled Through a Wall

The analysis given in these previous notes:

Implicit Function Theory Introduction

Initial Method of Exact Solutions Calculations

Single Isolated Node Calculations

are expanded to include the case of coupled fluid systems. Numerical solution results are given for an illustrative application.

The mathematical model, an exact continuous analogue of the discrete approximations used in many numerical solution methods, provides analytical and numerical-benchmark problems for verification by the Method of Exact Solutions ( MES ).

I have uploaded a file.

March 15, 2011 Posted by | Calculation Verification, Code Verification, Verification | , , , | 2 Comments

Implicit Function Theory: Single Fluid System Calculations

I have completed some additional verification of the single-node calculations, and other results, given in the previous notes here.

A short introduction to implicit function theory was given in the notes here.

In the present notes I’ve tuned up the original calculations and cleared out a few bugs as follows.

(1) I found some bugs in the summary tables of the EOS derivatives and give new Tables below in these notes. I have also posted the corrected Tables with the notes introducing implicit function theory.

(2) I have made the fluid thermodynamic state and thermophysical properties more consistent by using a single source for these numbers. The source is an old National Research Council ( Canada )/ National Bureau of Standards ( USA ) water property program. For the original calculations I had used whatever convenient values could find and these did not always correspond to the exact same fluid state. The program is based on the equations in this document.

(3) I coded the fluid properties and the primitive elements of the derivatives along with a routine to numerically evaluate the various determinants in order to compare these with my analytically derived derivatives. This process led to discovery of several coding errors that, when cleared, led to agreement with my analytical derivatives. And, yes, coding of the analytical derivatives was also verified by various means. I have abandoned the original spread sheet approach and now rely on the new coded routines.

(4) I have tuned up the wall-material properties and at the same time expanded the discussion of the interaction of the fluid and wall material relative to the base pressure-wave speed.

(5) I dug into the fluid-structure literature a little bit to see if my derivation of the effective sound speed was correct. I discovered that the formulation obtained by use of implicit function theory and the equation of state gives exactly the classical value. That equation was first obtained, as reported by Tijsseling ( 1996 ), by Korteweg in 1878. The center of the hydraulic-transient / fluid-structure-interaction universe seems to have moved from the University of Michigan and Wiggert, Wylie, and Streeter, to Tijsseling and Eindhoven University of Technology.

(6) I have investigated the numerical solution method in some more detail. The second-order explicit Euler method shows growth of the difference between the analytical and numerical solutions. The fourth-order explicit Runga-Kutta method shows much improved performance.

All these changes have been implemented and additional calculations carried out for the single-node case. The better focus on the calculations in contrast to the theory has also led to corrections in the consistency of the reported values for the calculations. The length of the node was incorrectly reported in parts of the previous notes.

The mathematical model seems to be a very good candidate for production of Method of Exact Solutions ( MES ) and Numerical Benchmark results for Verification of numerical solution methods for transient, compressible hydraulic-transient codes.

I have uploaded the file.

I see that the Table 3 did not come out too good in the file. A copy is also here. There was a bug in the first column of the third row.

February 26, 2011 Posted by | MMS, ODEs, Verification | , | 3 Comments

U. S. Environmental Protection Agency: The Science is Settled

EPA Chief Goes Toe-To-Toe With Senate GOP Over Climate Science.

U.S. EPA Administrator Lisa Jackson today defended the science underpinning pending climate regulations despite Senate Republicans’ claims that global warming data has been thrown into doubt.

“The science behind climate change is settled, and human activity is responsible for global warming,” Jackson told the Senate Environment and Public Works Committee.

Administrator Jackson was speaking for the EPA, and the Climate Science communicated to the US EPA by Climate Scientists.

The Science is Settled, it’s on the EPA Web site:

Statement on Litigation on EPA Endangerment Finding

The question of the science is settled.

Here’s the Introduction to The Statement on Litigation on EPA Endangerment Finding:

Statement on Litigation on EPA Endangerment Finding

The evidence of, and threats posed by a changing climate are right before our eyes.

EPA issued its endangerment finding because the U.S. Supreme Court ruled three years ago that greenhouse gas emissions constitute air pollution and that EPA therefore must determine whether that pollution threatens the health and welfare of Americans. EPA proceeded to carry out the instructions of the highest court in the land, and in doing so undertook a comprehensive and transparent review of the soundest available science. That science came from an array of highly respected, peer-reviewed sources from both within the United States and across the globe, and took into consideration hundreds of thousands of comments from members of the public, which were addressed in the finding. The conclusion: the scientific evidence of climate change is overwhelming and greenhouse gases pose a real threat to the American people.

The question of the science is settled. [ my em-bolding ] The debate that should be taking place now is how to address this challenge and take advantage of the opportunity it offers. EPA is proceeding with common sense measures that are helping to protect Americans from this threat while moving America into a leadership position in the 21st Century green economy, creating millions of good-paying jobs along the way. Unfortunately, special interests and other defenders of the status quo are now turning to the courts in an attempt to stall progress, with the added effect, if they are successful, of halting the creation of millions of new jobs.

EPA is confident the finding will withstand legal challenge, allowing the Agency to protect the American people from the significant dangers posed by greenhouse gases and carbon pollution.

The US EPA is committed to science-based policy. In this case, its findings are based The Science as determined by The Climate Science Community and the associated Climate Scientists.

February 6, 2011 Posted by | Uncategorized | Leave a comment

Verification: Can’t Ever Do Too Much of It

Big Fine Over Bug in ‘Quant’ Program

February 4, 2011 Posted by | Calculation Verification, Documentation, Verification | Leave a comment

Implicit Function Theory Applications; Part 1: Method of Exact Solutions

In a previous post I gave some background info about implicit function theory and how it might be useful. In these notes I have used results from applications to the equation of state to develop a few exact solutions for extremely simple transient, compressible flows that include fluid-structure interaction. These notes address the case of mechanical coupling of the fluid to a deformable / flexible wall. I have also included an introduction to the case of coupling of fluid systems through a common deformable / flexible wall. Additional notes will address the case of thermal interactions for both a single fluid system and coupled systems.

I kind of ran out of steam when I got to coupled-systems part of the present notes. There’s a lot of ground to cover for this case and I’m thinking a separate report might be the way to go. With coupled systems you get more that just twice as many things to look at compared to the single-system case.

I think these solutions might be candidates for analytical, and numerical-benchmark-grade, Method of Exact Solutions ( MES ) for verification of limited aspects of coding of transient compressible fluid flow model equation systems and solution methods.

I have uploaded a file.

Consider these notes as a rough draft of a report and let me know what you think about all aspects.

January 19, 2011 Posted by | Calculation Verification, Verification | , , , , | 4 Comments

Implicit Function Theory Applications; Part 0

I developed analytical solutions for a couple of simple transient compressible fluid flow problems that include fluid-structure interactions. I think the problems and solutions might be candidates for standard problems / benchmarks / Method of Exact Solutions.

Implicit function theory is an important aspect of the analytical solutions. Getting the required implicit function theory results was proving to take more pages and space that the analytical solutions. I decided to document those results in these separate notes. The results needed for the analytical solutions are given in the latter part of the notes, beginning with Variable Fluid Control Volume.

I have uploaded a Table that is in landscape and that I don’t now how to get into a portrait layout-document. That Table is here and should open in a separate window.

There are tons and tons of algebra associated with this work; straightforward but tedious algebra. I have checked and re-checked but maybe haven’t cleared out all the errors. If you plan to use any of this material, let me know what is of interest and I’ll work with you to ensure that the equations are correct.

The PDF file is here and should open in a separate window.

Update February 26, 2011

A corrected version of Table 3 is here. There was a bug in the first column of the third row.

Update January 14, 2011

There’s a typo in Eq. (1.8). The X_sub i in the last line ( the bottom part of the bottom ) should be Y_sub i. That’s a strange kind of bug; a typo in a nemonic device.

In the Section, The Bridgman Method, I say:

I have uploaded the table as a PDF file and provided this URL link in my post: . You’ll have to copy-n-paste the link into your browser.

That is the same Table mentioned in the Post, and you don’t have to copy-n-paste the URL; it’ll open from the PDF.

Note that Eq. (1.33) can be written in terms of the square of the sound speed.

And in a few places following Tables of derivatives, I said that the entropy derivatives had not been reduced when in fact they are shown reduced form in the tables.

Let me know if you find any problems.

January 14, 2011 Posted by | Calculation Verification, Uncategorized, Verification | 10 Comments

The Great Roads List ca. 1994 ( oops 1993)

Highway 28 in NC / SC has been discovered. Now known as Moonshiner 28. Road described here.

I’ve uploaded a historial copy of The Great Roads List from ca. 1994 1993. The Denizens of Doom ( DoD ) Internet Motorcycle Club maintained the list in the early days of The Web. Or, was that before the early days and we used text and e-mail? We used a 7-bit word and binary arithmetic to assign Member Numbers; I’ve forgotten mine. Route 28 was well-known among some Biker Trash even back then.

It’s a great ride !!

January 12, 2011 Posted by | moto touring | Leave a comment

An Interesting and Important Discussion

Steve Fitzpatick is summarizing important aspects of radiative energy transport and its interaction with material in the Earth’s atmosphere, at Jeff Id’s tAV. I think many of these phenomena and processes are represented by parameterizations.

Continue reading

January 3, 2011 Posted by | Uncategorized | Leave a comment

Analytical Sensitivity Analysis

Sensitivity Analysis [Hardcover]
A. Saltelli (Editor), K. Chan (Editor), E. M. Scott (Editor)

Sensitivity Analysis in Practice: A Guide to Assessing Scientific Models [Hardcover]
A. Saltelli (Author), Stefano Tarantola (Author), Francesca Campolongo (Author),Marco Ratto (Author)

Uncertainty Modeling and Analysis in Engineering and the Sciences [Hardcover]
Bilal M. Ayyub (Author), George J. Klir (Author)

Sensitivity & Uncertainty Analysis, Volume 1: Theory[Hardcover]
Dan G. Cacuci (Author)

Sensitivity and Uncertainty Analysis, Volume II: Applications to Large-Scale Systems [Hardcover]
Dan G. Cacuci (Author), Mihaela Ionescu-Bujor (Author), Michael Navon (Author)

Sensitivity Analysis in Practice: A Guide to Assessing Scientific Models [Hardcover]
A. Saltelli (Author), Stefano Tarantola (Author), Francesca Campolongo (Author),Marco Ratto (Author)

December 17, 2010 Posted by | Analytical Sensitivity Analysis, Sensitivity Analysis | , | Leave a comment

More on V&V and SQA at LANL for ASC and the NNSA

This previous post mentioned V&V and SQA at Los Alamos National Laboratory ( LANL ) within the framework of the Advanced Simulation & Computing ( ASC ) Program for the National Nuclear Security Administration ( NNSA )

Verification and Validation of scientific and engineering software seems to have become a very important part of scientific and engineering software at Los Alamos National Laboratory.

This section:
Typical Questions That V&V Can Answer…

Has this entry:

• “Models can be validated without data.”
Wrong! There is no validation without data because model validation must assess prediction accuracy relative to a physical reality. While code verification and calculation verification are concerned with the accuracy of the numerical implementation and convergence, respectively, validation activities focus on the adequacy of numerical simulations when applied to the description of reality, which requires experimental observations. We nevertheless recognize that the lack of test data can pose serious problems to model validation. Rigorously controlled expert elicitation techniques can provide information that is substituted to experimental testing in cases of severe lack of data and uncertainty.

Code-to-code comparisons are not Validation. Never have been, never will be.

More LANL info here and and here.

December 14, 2010 Posted by | Verification | , , | Leave a comment