On 06/10/2021 04:39, firstname.lastname@example.org wrote:
My question is about order of approximation in field as well as integral. My understanding is that the order of field is the order of the polynomial shape functions in element and order of integral is for the integration in qp. For a 3 point triangular element as well as 4 point quadrilateral element, I think order of field should be 1 and using any other value is "wrong". Is this correct ? Also, I noticed from user manual that the order of integral = 2* order of field. I was curious what is the basis for this assumption ?
You can use field orders higher than 1, because internally, sfepy enriches the elements with the required additional nodes. So although you have a mesh with 3 point triangles, the calculation occurs on an augmented mesh with appropriate higher order elements.
The integral = 2* order works well for bilinear forms with constant (on each element) material parameters. For example, a dot product involves integrating u
Of course, there are terms that could use a lower quadrature order, or higher, depending on the data.