Cascadic multigrid method for P 1-nonconforming quadrilateral element

Abstract In this paper, a cascadic multigrid method for P 1-nonconforming quadrilateral finite element approximation of second order elliptic problem is studied. A new intergrid transfer operator is constructed to connect the nonnested coarse and fine grid spaces. We show that the cascadic multigrid method is accurate with optimal complexity for conjugate gradient smoother, and suboptimal complexity for some other traditional multigrid smoothers. Finally, some numerical experiments are reported to support the theory.