Hello,
I built geometries in Salome and tried to use coordinate scaling factor for FEM analysis in Elmer. I got effective resistance for a box. But I do not know how shall I calculate the resistivity. I know the surface area of the cross section in Salome. Should I multiply the surface area by the coordinate scaling factor once or twice? Please check the following equation. Thank you.
1) Resistivity=[Resistance*S(Electrode cross-section Surface area)*coordinate scaling factor ]/(Length*coordinate scaling factor)=Resistance*S/L
2) Resistivity=[Resistance*S(Electrode cross-section Surface area)*coordinate scaling factor* coordinate scaling factor]/(Length*coordinate scaling factor)=Resistance*S*coordinate scaling factor/L
About Coordinate Scaling in Elmer Plugin in Salome
About Coordinate Scaling in Elmer Plugin in Salome
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Re: About Coordinate Scaling in Elmer Plugin in Salome
Hi,
The dimensions of the geometry /mesh exported from Salome do not have any unit, and so the same mesh can be designed in many ways in the FEM simulation.
The distance 603.268 is a unitless number, and so you can imagine it to be of any unit.
Now , if the above unitless length of 603.268 is assumed as mm, then the coordinate scaling = 1.0E-03 sets it to be 0.603268 m.
If it is assumed as 603.268 cm, then the coordinate scaling = 1.0e-02 sets it to be 6.03268 m.
If it is assumed as 603.268 m, then the coordinate scaling = 1.0 sets it to be 603.268 m.
If it is assumed as 603.268 inches, then the coordinate scaling = 2.54e-02 sets it to be 15.323 m in the solver input file.
The concept of coordinate scaling is advantageous, as it is easier to plan for constructing a box of l*b*h = 5.5 *7.3*11.25 (initially designing in mm^3 and later using a coordinate scaling of 1.0e-3) than constructing the same box with l*b*h = 0.0055 *0.0073*0.01125 (initial length construction in m and using coordinate scaling = 1 ).
The general convention is to set the FEM simulation in SI units (through the input of numerical values of materials properties and constants) . The time can be set numerically to be in s (timestep size). A timestep size of 1.0e-3 can be thought to be in any units, and for convention we can choose it to be in SI unit (s) and so it can be understood as 1 ms. It is possible to set time and other units in any other unit values .
The unit of resistivity is ohm m . If the resistivity of Cu is to be set in SI units in Material block, then the numerical value of 1.68*10^(-8). This value corresponds to the unit of ohm m.
Summary: If a geometry of a material at nanoscale is to be contructed in Salome (e.g. sphere of radius 20 nm), then it is good to draw a sphere of r = 20 (unitless), and define it as nm in solver input file by using coordinate scaling of 1.0e-9 . It is a better practice than constructing a sphere of radius r=0.00000002 and using coordinate scaling of 1.0 in solver input file.
The dimensions of the geometry /mesh exported from Salome do not have any unit, and so the same mesh can be designed in many ways in the FEM simulation.
The distance 603.268 is a unitless number, and so you can imagine it to be of any unit.
Now , if the above unitless length of 603.268 is assumed as mm, then the coordinate scaling = 1.0E-03 sets it to be 0.603268 m.
If it is assumed as 603.268 cm, then the coordinate scaling = 1.0e-02 sets it to be 6.03268 m.
If it is assumed as 603.268 m, then the coordinate scaling = 1.0 sets it to be 603.268 m.
If it is assumed as 603.268 inches, then the coordinate scaling = 2.54e-02 sets it to be 15.323 m in the solver input file.
The concept of coordinate scaling is advantageous, as it is easier to plan for constructing a box of l*b*h = 5.5 *7.3*11.25 (initially designing in mm^3 and later using a coordinate scaling of 1.0e-3) than constructing the same box with l*b*h = 0.0055 *0.0073*0.01125 (initial length construction in m and using coordinate scaling = 1 ).
The general convention is to set the FEM simulation in SI units (through the input of numerical values of materials properties and constants) . The time can be set numerically to be in s (timestep size). A timestep size of 1.0e-3 can be thought to be in any units, and for convention we can choose it to be in SI unit (s) and so it can be understood as 1 ms. It is possible to set time and other units in any other unit values .
The unit of resistivity is ohm m . If the resistivity of Cu is to be set in SI units in Material block, then the numerical value of 1.68*10^(-8). This value corresponds to the unit of ohm m.
Summary: If a geometry of a material at nanoscale is to be contructed in Salome (e.g. sphere of radius 20 nm), then it is good to draw a sphere of r = 20 (unitless), and define it as nm in solver input file by using coordinate scaling of 1.0e-9 . It is a better practice than constructing a sphere of radius r=0.00000002 and using coordinate scaling of 1.0 in solver input file.
Anil Kunwar
Faculty of Mechanical Engineering, Silesian University of Technology, Gliwice
Faculty of Mechanical Engineering, Silesian University of Technology, Gliwice