Linear viscoelastic fluid
= Linear viscoelastic fluid
A linear viscoelastic fluid has causal stress response linear in the deformation history, often expressed as $\sigma^d(t)=2\int_0^\infty G(s)E(t-s)\,ds$. The approximation requires small deformation and rotation over the relevant memory times. High frequency is allowed at sufficiently small amplitude. An integrable decaying <relaxation modulus> gives a finite <zero-shear viscosity>; an instantaneous solvent term may be written separately.