Discussion Closed This discussion was created more than 6 months ago and has been closed. To start a new discussion with a link back to this one, click here.
Poroelastic model_undefined variable kd
Posted 26 oct. 2022, 02:51 UTC−4 Structural & Acoustics, Acoustics & Vibrations Version 6.0 2 Replies
Please login with a confirmed email address before reporting spam
Hello,
I am using three Physics for the acoustic simulation, including Pressure Acoustics (acpr), Solid mechanics (solid), and poroelastic waves (pelw).
The poroelastic waves model I used is Biot-Allard (thermal and viscous losses). Also, the Biot-Willis coefficient is set to "Rigid assumption".
After setting all the parameters in the materials and in the Physics, which means no warning sign (STOP) in all of my setting. I still receive the following error message after starting the study:
- Feature: Stationary Solver 1 (sol1/s1) Undefined variable.
- Variable: Kd
- Geometry: geom1
- Domain: 1 Failed to evaluate Jacobian of expression.
- Expression: dvol*((1/comp1.pelw.rho_c)*(comp1.pelw.delta*(-(comp1.pelw.p_t*(comp1.pelw.ik^2))))) Failed to evaluate Jacobian of expression.
- Expression: ((-comp1.pelw.gradpX*comp1.pelw.gradtestpX-comp1.pelw.gradpY*comp1.pelw.gradtestpY-comp1.pelw.gradpZ*comp1.pelw.gradtestpZ-comp1.pelw.p_t*test(comp1.p2)*comp1.pelw.ik^2)*comp1.pelw.delta/comp1.pelw.rho_c)*(dvol)
Apparently, I need to define the "kd (drained bulk modulus" as it is used in the Biot-Wills coefficient (as in the brochure of COMSOL's Acoustic module.), but there's no such parameters in the variables nor in the materials (I checked this part with Ctrl+F and looked into every setting in comp1.).
Furthermore even it is not necessary to define the Biot-Willis coefficient, I still set a number(1 or 0.8 or 0.3, just making trial and error), however the error message (above) didn't change.
I assume that this Kd is the key to solve the Jacobian of expression error also...?
Could someone give me a hint what could be the error message came from? Also, is the kd error message a bug or my wrong setting?
Please login with a confirmed email address before reporting spam
Dear Albert,
It is possible that that the domain assignments for materials and the physics are not consistent. Based on the error message I would double check Domain 1. It would be easier to comment if you attach your .mph model file.
Best,
Mark
Please login with a confirmed email address before reporting spam
Dear Albert,
It is possible that that the domain assignments for materials and the physics are not consistent. Based on the error message I would double check Domain 1. It would be easier to comment if you attach your .mph model file.
Best,
Mark
Hello Mark,
Thanks for your reply.
I've checked it several times for the identity between the domain material and the options in Physics. I found a possible issue, could you check with it?
My poroelastic material is drained matrix Orthotropic material. I forgot to mention it at the beginning.
In the equation view, when opening the equation from "Global Definitions" > "Show More Options" >...so on.):
While it is an isotropic poroelastic material (Drained matrix, Isotropic), there is pelw.K defined as pelw.Kd. Then, the pelw.Kd is defined as 2pelw.Gd(1+pelw.nud)/(3(1-2pelw.nud)).
If I choose the Orthotropic option (Drained matrix, Orthotropic), the Kd is never defined, however the Kd is used in the other equations, e.g., pelw.Ks is defined as Kd/(1-pelw.epsilon_p).
Could it be the problem, Mark?
Thanks in advance for checking this and your reply. Wish to hear back from you soon.
Albert Hu