A modified deformation field method for integral constitutive models

This paper presents a modification to the numerical treatment of integral constitutive equations initiated by Peters et al. [E.A.J.F. Peters, M.A. Hulsen, B.H.A.A. van den Brule, Instationary Eulerian viscoelastic flow simulations using time separable Rivlin–Sawyers constitutive equations. J. Non-Newtonian Fluid Mech., 89 (2000) 209–228] that enables computational stability to be achieved for higher Weissenberg number for steady flows. Increased efficiency is also achieved so that computational times are of the same order (2 or 3 times) as equivalent differential models and of similar accuracy. The memory cost for storage of the deformation fields is approximately 300 times that of the stress tensor for each grid point to yield approximations that lie within 0.01% of predictions of equivalent differential models. The good agreement between equivalent integral and differential models found here suggests that more general integral models with no differential equivalent may be used reliably for steady flow simulations. A modification of the deformation fields method that avoids the introduction of a cut-off time and which is applicable to transient flows is also presented.