Discussion Forum

Can any one help me, please :)

Hi,

you must provide more information. These error messages are not very instructive. You can upload your model so forum members can have a look and try to find errors.

Cheers
Edgar

Hi,

you must provide more information. These error messages are not very instructive. You can upload your model so forum members can have a look and try to find errors.

Cheers
Edgar

Thanks for you, this is the work file
and in the first post the print screen image.

i want any one help me in solving this error, to complete my graduation project.

Thanks.

Hi,

I had a quick look and there are some errors:

All your domains are in the piezoelectric material study node, but probably not all are piezoelectric.

You don't have the piezoelectric material parameters in your materials. See the red buttons in the top 3 lines of the material contents.

So move the non-piezoelectric domains into a linear elastic (?) node and provide the piezoelectric material parameters for the remaining piezoelectric domain(s).

There may be more errors but I suggest to fix those most obvious ones and see what happens.

Cheers
Edgar

Hi,

I had a quick look and there are some errors:

All your domains are in the piezoelectric material study node, but probably not all are piezoelectric.

You don't have the piezoelectric material parameters in your materials. See the red buttons in the top 3 lines of the material contents.

So move the non-piezoelectric domains into a linear elastic (?) node and provide the piezoelectric material parameters for the remaining piezoelectric domain(s).

There may be more errors but I suggest to fix those most obvious ones and see what happens.

Cheers
Edgar

Thank you very much

now only one error

----------------
Variables not coupled to any degrees of freedom.
- Detail: mod1.V
-----------------

the file is attached

i insert all domain to Linear Elastic material, but i don't understand why ?

Thanks

I'll wait your replay.

Hi,

if you moved ALL domains into linear elastic, then the piezoelectric node is empty and that might be the reason for the error.
You must keep the piezoelectric domain in in the piezoelectricity node and provide the required material constants, i.e. the elasticity matrix, the coupling matrix and permittivity.

Cheers
Edgar

Hi,

if you moved ALL domains into linear elastic, then the piezoelectric node is empty and that might be the reason for the error.
You must keep the piezoelectric domain in in the piezoelectricity node and provide the required material constants, i.e. the elasticity matrix, the coupling matrix and permittivity.

Cheers
Edgar

Hi,

i don't understand each physics , so when i want to design >> can't select the right physics to work with

i will try again and tell you, Thanks,
Mohamed Aref.

Can anyone help me with the formulae to calculate the elasticity matrix and tha coupling matrix of a material

Dear all,

I'm facing the following problem:

I would like to calculate the following channel flow in a rectangular channel and given that my inlet condition is: laminar flow with an inlet velocity, I have to calculate the entrance length using the formula provided in the COMSOL documentation. I need to calcultae the Re-Number and therefore I need to use rho an mu from the material defintions using the following commands:
for rho:
comp1.mat1.def.rho

for mu:
comp1.mat1.def.mu

Now I allways get the same error when I compute the simulation:

Failed to evaluate variable.
Failed to evaluate variable.
- Variable: T
- Geometry: 1
- Boundary: 5
Failed to evaluate variable.
- Variable: comp1.mat1.def.rho
- Defined as: ((unit_kg_cf*comp1.mat1.def.rho((T/unit_K_cf)))/(unit_m_cf^3))
Failed to evaluate variable.
- Variable: Reynolds
- Defined as: (((mean_vel*comp1.mat1.def.rho)*dHydr)/comp1.mat1.def.mu)
Failed to evaluate variable.
- Variable: comp1.spf.Lentr
- Defined as: ((0.5*Reynolds)*dHydr)

Can someone tell me, how the problem can be solved.

Best
Sergio

p.s: I can't attach the file because of a size problem