The Method of Harmonic Balance for the Giesekus Model under Oscillatory Shear

TL;DR

This paper adapts the harmonic balance method to efficiently compute the stress response of the Giesekus model under large amplitude oscillatory shear, demonstrating rapid convergence and superior accuracy over traditional numerical integration.

Contribution

The paper introduces a spectral harmonic balance approach for the Giesekus model in LAOS, showing improved efficiency and accuracy compared to conventional methods.

Findings

HB converges exponentially with the number of harmonics.

HB is about three orders of magnitude cheaper than numerical integration.

HB achieves several orders of magnitude higher accuracy.

Abstract

The method of harmonic balance (HB) is a spectrally accurate method used to obtain periodic steady state solutions to dynamical systems subjected to periodic perturbations. We adapt HB to solve for the stress response of the Giesekus model under large amplitude oscillatory shear (LAOS) deformation. HB transforms the system of differential equations to a set of nonlinear algebraic equations in the Fourier coefficients. Convergence studies find that the difference between the HB and true solutions decays exponentially with the number of harmonics ($H$) included in the ansatz as $e^{-m H}$. The decay coefficient $m$ decreases with increasing strain amplitude, and exhibits a "U" shaped dependence on applied frequency. The computational cost of HB increases slightly faster than linearly with $H$. The net result of rapid convergence and modest increase in computational cost with increasing $H$ implies that HB outperforms the conventional method of using numerical integration to solve differential constitutive equations under oscillatory shear. Numerical experiments find that HB is simultaneously about three orders of magnitude cheaper, and several orders of magnitude more accurate than numerical integration. Thus, it offers a compelling value proposition for parameter estimation or model selection.