Effect of the separated approximation of input data in the accuracy of the resulting PGD solution

Abstract

The proper generalized decomposition (PGD) requires separability of the input data (e.g. physical properties, source term, boundary conditions, initial state). In many cases the input data is not expressed in a separated form and it has to be replaced by some separable approximation. These approximations constitute a new error source that, in some cases, may dominate the standard ones (discretization, truncation…) and control the final accuracy of the PGD solution. In this work the relation between errors in the separated input data and the errors induced in the PGD solution is discussed. Error estimators proposed for homogenized problems and oscillation terms are adapted to asses the behaviour of the PGD errors resulting from approximated input data. The PGD is stable with respect to error in the separated data, with no critical amplification of the perturbations. Interestingly, we identified a high sensitiveness of the resulting accuracy on the selection of the sampling grid used to compute the separated data. The separation has to be performed on the basis of values sampled at integration points: sampling at the nodes defining the functional interpolation results in an important loss of accuracy. For the case of a Poisson problem separated in the spatial coordinates (a complex diffusivity function requires a separable approximation), the final PGD error is linear with the truncation error of the separated data. This relation is used to estimate the number of terms required in the separated data, that has to be in good agreement with the truncation error accepted in the PGD truncation (tolerance for the stoping criteria in the enrichment procedure). A sensible choice for the prescribed accuracy of the PGD solution has to be kept within the limits set by the errors in the separated input data.

Proper generalized decomposition solutions within a domain decomposition strategy

“…Thus, the error of PGD approximation compared with the analytical solution is always larger than the FE error. () In this example, the influence of the polynomial degree on the interface polynomials, the number of modes used in the PGD approximation, and the mesh discretization in the final error is studied.…”

A nonintrusive proper generalized decomposition scheme with application in biomechanics

“…Nevertheless, the selected loading locations may not necessarily be the subset of the spatial nodes. In this case, we would like to point out that proper selections of the location of DOF is important for avoiding interpolative instabilities …”

Proper generalized decomposition solution of the parameterized Helmholtz problem: application to inverse geophysical problems

“…The next section presents some details on f sep and the error introduced by this separation. A detailed study of how separation of given data affects PGD can be found in [24].…”

“…The choice of the sampling points T h  has an impact on the convergence of the PGD method as shown in [24]. We compare two different choices.…”