Discussion Forum

Hi

When I got such meshing it happens sometimes when I do manual meshing and have selected boundaries instead of domains so (some or all off) my boundaries where meshed, but not all domains where filled with a mesh.
Also if you are in 3D "tri" meshes only mesh boundaries, you need at least one "teth" node to mesh the domains

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Good luck
Ivar

Hi Ivar:

I meshed using the "Teth" but when I try to solve I get the following error message:



Failed to evaluate variable.
- Variable: mat.epsilonr21
- Geometry: 1
- Domain: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218
Failed to evaluate variable.
- Variable: mod1.es.epsilonryx
- Defined as: mat.epsilonr21
Failed to evaluate variable.
- Variable: mod1.es.Dy
- Defined as: (epsilon0_const*(((mod1.es.epsilonryx*mod1.es.Ex)+(mod1.es.epsilonryy*mod1.es.Ey))+(mod1.es.epsilonryz*mod1.es.Ez)))
Failed to evaluate expression.
- Expression: d((-mod1.es.Dx*test(mod1.Vx)-mod1.es.Dy*test(mod1.Vy)-mod1.es.Dz*test(mod1.Vz))*(dvol),{test@1})



I do not receive this error when meshing with "tri" instead I get the previous error as in my first post.

Hi

but if you read well this is because your material data epsilonr is not defined for these domains. if you do not mesh for domains you do not need epsilonr. So the true issue is your material data, in my opinion

Check the material and see if you are not missing something ;)

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Good luck
Ivar

Hi Ivar:


I did not have any material data in my model. So
I added some material and get the following error:

Unknown property.
- Property: opname


What does this error mean and how do I go about fixing it?

Best Regards,
Pekir

Hi Ivar:

I got the model to solve. Thanks for you help.
So to further gain understanding, 3D models must be
meshed with teth to allow for domains to be meshed?
Also, materials must be applied to the domain that is
being meshed by teth?

Best Regards,
Pekir

Hi

yes

"tri" triangles (3 node elements) are for 2D elements hence surfaces or domains in 2D or for boundaries in 3D.
"quad" are surface (4 nodes elements) hence also for 2D as above

"thet" tetrahedral are (4 node elements) but are for 3D hence domains in 3D (you cannot find them in 2D physics

you obtain 3D "prism" or "brick" elements by using a "sweep" mesh into the 3rd dimension of a 2D "Tri" or a "quad"

You obtain structured meshing if you use regular sweeping methods

the relation 1D=>2D meshing can be generated as just mentioned for 2D =>3D

Note in COMSOL we use only these "primary" elements. in other FEM tools one can select higher N node elements, while in COMSOL this is governed by the "shape" functions that are defined on the DOMAINS and not on the mesh (we say the mesh inherit its properties from the geometrical entities: domain and boundaries

Note: meshing is a bit of an "art" so you learn by doing (and doing a lot !). Often its useful to "cut" your geometry with interior boundaries to ease the meshing or to make it more symmetric, all depends on your model and your need of precision


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Good luck
Ivar

Hi Pekir,

How did you solve your "unknown property" problem?


Thanks,

Alberto

Hi Pekir,
How did you get you problem solve? I m having the same issue.

Thanks in advance,
David

Hi Ivar:

I got the model to solve. Thanks for you help.
So to further gain understanding, 3D models must be
meshed with teth to allow for domains to be meshed?
Also, materials must be applied to the domain that is
being meshed by teth?

Best Regards,
Pekir