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Least-squares fitting of a diffusive flux

Posted 03.11.2011, 08:41 GMT-4 Optimization Version 4.2 4 Replies

Johannes Schikora
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Hi all,

I have experimental data from a diffusion experiment, where we have measured the diffusive flux out of a clay sample. I want to fit my model to this measured values via least-squares fitting using the optimization module. It's a time-dependent problem and every time I try to compute the solution COMSOL crashes.

I have attached my model. Has anyone an idea where I made a mistake.

Thanks in advance.

--
Johannes
4 Replies Last Post 24.11.2011, 07:04 GMT-5
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago 08.11.2011, 03:30 GMT-5
Hi

what exactly is wrong no I do not see, but definitively it crashes

You should send it to support, so they can find out, COMSOL should crash like that, even if you have missed something important, in my opinion

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Good luck
Ivar
Hi what exactly is wrong no I do not see, but definitively it crashes You should send it to support, so they can find out, COMSOL should crash like that, even if you have missed something important, in my opinion -- Good luck Ivar
Certified Consultant
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Posted: 1 decade ago 08.11.2011, 05:09 GMT-5
It seems to work on 4.2a update 1, which was released today. See Help->Check for updates for instructions.

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Niklas
It seems to work on 4.2a update 1, which was released today. See Help->Check for updates for instructions. -- Niklas
baraka
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Posted: 1 decade ago 24.11.2011, 06:42 GMT-5
hello

I have experimental data from a biaxial experiment, where we have measured the strains on the surface of the martial out of our sample. I want to fit my model to this measured values via least-squares fitting . and using the optimization module to determine the optimum martial property for Orthotropic plane stress martial such as elastic modulus and shear modulus . It's not a time-dependent problem. i could not found in the documentation how to do this in COMSOL 4.2 optimization module. Can you tell how to define this problem in comsol or can you give some similar example problems which helps me to solve my optimization problems. thank you !

Regards
hello I have experimental data from a biaxial experiment, where we have measured the strains on the surface of the martial out of our sample. I want to fit my model to this measured values via least-squares fitting . and using the optimization module to determine the optimum martial property for Orthotropic plane stress martial such as elastic modulus and shear modulus . It's not a time-dependent problem. i could not found in the documentation how to do this in COMSOL 4.2 optimization module. Can you tell how to define this problem in comsol or can you give some similar example problems which helps me to solve my optimization problems. thank you ! Regards
Johannes Schikora
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Posted: 1 decade ago 24.11.2011, 07:04 GMT-5
Hello,

I know that there is an introduction available in the documentation for the Optimization Module (at least in COMSOL 4.2a). It's about fitting two parameters that define a nonlinear material model (Mooney-Rivlin). In the tutorial the SNOPT-Algorithm is used to minimize the least-squares error and it's a stationary problem. So maybe this introduction is helpful for you.

Regards,
Johannes
Hello, I know that there is an introduction available in the documentation for the Optimization Module (at least in COMSOL 4.2a). It's about fitting two parameters that define a nonlinear material model (Mooney-Rivlin). In the tutorial the SNOPT-Algorithm is used to minimize the least-squares error and it's a stationary problem. So maybe this introduction is helpful for you. Regards, Johannes

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