Abstract

This work illustrates the application of the fourth-order comprehensive sensitivity analysis methodology for nonlinear systems (abbreviated as “4th-CASAM-N”), which enables the efficient computation of exactly determined 1st-, 2nd-, 3rd-, and 4th-order functional derivatives of results produced by computational models with respect to the model’s parameters. Results produced by computational models are called model “responses” and the respective functional derivatives are called “sensitivities” (with respect) to model parameters. The qualifier “comprehensive” indicates that the 4th-CASAM-N methodology enables the exact and efficient computation not only of response sensitivities with respect to customary model parameters (including computational input data, correlations, initial and/or boundary conditions) but also with respect to imprecisely known material boundaries, as would be caused by manufacturing tolerances. The 4th-CASAM-N enables the hitherto very difficult, if not intractable, exact computation of all of the 1st-, 2nd-, 3rd-, and 4th-order response sensitivities for large-scale systems involving many parameters, as usually encountered in practice. A paradigm model that describes nonlinear heat conduction through a material has been chosen to illustrate the application of the 4th-CASAM-N methodology, as this model enables the derivation of tractable closed-form analytical expressions of representative 1st-, 2nd-, 3rd-, and 4th-order response sensitivities while largely avoiding side-tracking algebraic manipulations. The responses chosen for this paradigm model include not only physically measurable quantities but also a synthetic response designed to illustrate the enormous possible reduction in the number of computation when using the 4th-CASAM-N (rather than other methods) for computing response sensitivities.

Highlights

  • The accompanying Part I [1] has presented the mathematical framework of the “fourthorder comprehensive sensitivity analysis methodology for nonlinear systems” methodology, which enables the most efficient computation of exactly determined expressions for the 1st, 2nd, 3rd, and 4th-order response sensitivities

  • This work has illustrated the application of the “fourth-order comprehensive sensitivity analysis methodology for nonlinear systems to a paradigm model of nonlinear heat conduction

  • The responses chosen for this paradigm model include physically measurable quantities and a synthetic response designed to illustrate the enormous possible reduction in the number of computations when using the 4th-CASAM-N—rather than other methods—for computing response sensitivities

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Summary

Introduction

The accompanying Part I [1] has presented the mathematical framework of the “fourthorder comprehensive sensitivity analysis methodology for nonlinear systems” (abbreviated as “4th-CASAM-N”) methodology, which enables the most efficient computation of exactly determined expressions for (all of) the 1st-, 2nd-, 3rd-, and 4th-order response sensitivities. This work illustrates the enormous computational advantages that could be gained by taking advantage of particularities of the system/model under consideration, by considering a synthetically constructed model response, namely the square of the thermal conductivity, which is related to responses of interest (temperature, thermal conductivity) but which is not directly measurable. This synthetic response will be demonstrated to have only a finite number of non-zero sensitivities, as opposed to the temperature and thermal conductivity responses, which have infinitely many sensitivities.

Illustrative Model
Illustrative Application of the 4th-CASAM-N to the Nonlinear Conduction Model
First-Order Response Sensitivities
First-Order Sensitivities of a Nonlinear Response
Second-Order Response Sensitivities
Third-Order Response Sensitivities
Fourth-Order Response Sensitivities
Discussion

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