## Name

field_transfer (B2000++ Pro) — Couple adjacent incompatible surface meshes

## Synopsis

field_transfer id
interface i faceset faceset-id
interface i facelist facelist-id
interface i epatch epatch-id f1-f7
...
[interface i num_subdivisions n]
transfer displacement|temperature minimise_on interface i
end

## Description

The field_transfer command is available in B2000++ Pro; it specifies a coupling condition between two adjacent but in general incompatible surface meshes. In stress analysis, it represents a kinematic coupling condition. A typical application is global-local analysis with shell-to-solid, shell-to-shell, or solid-to-solid coupling. Another application is skin-stiffened structures with independent meshes for skin, stringers, frames, etc. In heat analysis, it couples the temperature fields of the two adjacent surfaces. The coupling is a weighted-residual method based on the L2-norm of the difference of the interpolated fields at the surfaces.

A field_transfer condition must be activated in the case command. If the specified id is 0, it will be automatically added to all analysis cases. It is required to specify a constraint method other than the default reduction method for which the accuracy of the calculated solution cannot be guaranteed when field_transfer conditions are active. See also Imposing Constraints.

The surfaces to be coupled with are defined by interface i where i is either 1 or 2. An arbitrary number of facesets or facelists may be added to each interface.

When the analysis is started, a common-refined mesh consisting of surface triangles is created from the intersection of the two coupling interfaces, according to the element face shapes. In the case of flat geometries, this common-refined mesh coincides exactly with both surface meshes. In the case of curved geometries, the common-refined mesh approximates both surface meshes. The approximation error can be reduced by setting num_subdivision to a positive value. In this case, the surface mesh of the respective interface will be n-times recursively subdivided.

The calculation of the interpolated field at the interfaces is conducted using the shape functions of the involved elements. Integration over the triangles of the common-refined mesh is carried out according to the element interpolation order(s). This way, the coupling is accurate for low-order as well as for high-order elements.

The transfer directive specifies the type of field to be transferred and on which interface i the residuum shall be minimized.