Читать книгу Finite Element Analysis - Barna Szabó - Страница 37

Direct computation of in the point x₀ involves the computation of the corresponding standard coordinate using eq. (1.83) and evaluating the following expression:

(1.85)

where . The computation of the higher derivatives is analogous.

Remark 1.8 When plotting quantities of interest such as the functions and , the data for the plotting routine are generated by subdividing the standard element into n intervals of equal length, n being the desired resolution. The QoIs corresponding to the grid‐points are evaluated. This process does not involve inverse mapping. In node points information is provided from the two elements that share that node. If the computed QoI is discontinuous then the discontinuity will be visible at the nodes unless the plotting algorithm automatically averages the QoIs.