| Author | Message | ||
     Jack Zhang (lovekk) Member Username: lovekk Post Number: 4 Registered: 01-2007 |
Suppose i have built a groundwater flow model in flexpde, and i also have some measurement data from the real world. My objective is to find a set of model parameters, such as permeability, that can produce prediction that is closest to the measurement data. I wonder whether i can realize this in flexpde? Besides, can i perform matrix inversion in flexpde? Thank you! | ||
| Robert G. Nelson (rgnelson) Moderator Username: rgnelson Post Number: 760 Registered: 06-2003 |
FlexPDE was used by Lawrence Livermore Laboratory in an extensive inverse modeling program in 1999. See the report at http://www-afim.llnl.gov/UCRL-ID-126377_Fin.pdf. See especially Appendix B for a theoretical description and Appendix D, which lists FlexPDE scripts. A major problem with this kind of modeling is that the sparse sampling data do not uniquely define a solution. There may be many permeability patterns that will reproduce a scattered data set. The approach taken in the LLNL study was to impose a strong diffusion term in the K equation and to similarly filter representations of the head gradient, to filter out high frequency modes and select the lowest order spatial distribution that fits the scattered data. As to the matrix inversion question, No, you cannot use FlexPDE as a generalized matrix inversion package. The solution methods are of course based on finding solutions to matrix equations. But the matrices are built dynamically from finite element models, and there an inverse matrix is never computed. | ||
| Jack Zhang (lovekk) Member Username: lovekk Post Number: 6 Registered: 01-2007 |
Nelson: you information is very helpful. Thank you! | ||
| Julia Derx (juliamelie) Junior Member Username: juliamelie Post Number: 3 Registered: 09-2008 |
I am also interested how one could implement inverse modeling with FlexPDE for groundwater problems. Unfortunately, the website link to the report cited above does not work. Is this report still available or is there any other documentary for inverse modeling? | ||
| Robert G. Nelson (rgnelson) Moderator Username: rgnelson Post Number: 1225 Registered: 06-2003 |
The report has apparently been moved. A Google search for "Gelinas Doss Ziagos" finds it at: https://e-reports-ext.llnl.gov/pdf/236651.pdf | ||
| Robert G. Nelson (rgnelson) Moderator Username: rgnelson Post Number: 1227 Registered: 06-2003 |
We have added this report to our "Reprints" page, www.pdesolutions.com/reprints.html |