Direct minimization of the discontinuous least-squares spectral element method for viscoelastic fluids

In this paper direct minimization of the discontinuous least-squares spectral element formulation is described. The method will beapplied to the Upper Convected Maxwell (UCM) model which describes a viscoelastic fluid. The new ideas presented in this paper consist of the weak coupling of the fluxes in the least-squares formulations instead of imposing weak continuity of the dependent variables. Furthermore, direct minimization is employed instead of the conventional variational least-squares formulation. The resulting system is solved iteratively using LSQR.