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Hi

Think of the mesh elements as a discretisation: if you listen to music which sampling rate do you choose for best response ? and would you use the same for rock, classical, bass, treble ... type music ?

It's the same with FEM, the mesh is a discretisation (this is well identified in COMSOL as you define the physics on the geometry and then you decide how to mesh, while in classical "old 50 years or more) type FEM you define the mesh and get the physics already "squeezed" in the mesh, (this is numerically OK, but conceptually from the physics and FEM methodology not the correct way of using "physics - PDE's - mesh" concept)

To answer your question short, the accuracy depends on the optimum mesh density w.r.t. the dependent variable variations, not directly on the geometry size.

So be modern catch "the Concept", now finally possible also in FEM with COMSOL :)

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Have fun COMSOLing
Ivar

Dear Ivar,

Thanks very much for your kind answer.

So the relevant parameter here is the mesh density. For example, for a transport problem in the radial direction, the relevant parameter to be optimised is the number of mesh elements in the radial direction rather the total number of elements in the geometry.

Kind regards!

Mesh elements assume a simplified situation, for example a linear distribution of temperature within the element. The complexity of the real heat distribution in the geometry is achieved by dividing it into a sufficiënt amount of mesh elements. The mesh elements should be small enough for the approximation to hold. If everything scales appropriately with the size of the geometry (for example if all dimensions of a geometry are multiplied by 10, and the temperature difference imposed is also multiplied by 10), then a meshing that is appropriate for the smaller geometry should also be appropriate for the bigger one (so the dimensions of the mesh elements can also be multiplied by 10 and the amount of mesh elements stays the same). However if not everything scales the same, you should re-check the appropriateness of your mesh size.
The 'easiest' check to see if your mesh is fine enough is repeating the calculation with a finer mesh. If the results are the same then your mesh was probably fine enough, otherwise you might need to make it even finer.

Thanks for your answer.

The approach I have taken is to optimise the number of mesh elements in the transport direction. I am using a mapped geometry...

Thanks