Fourier spectral and wavelet solvers for the incompressible Navier-Stokes equations with volume-penalization: Convergence of a dipole-wall collision. - Geert H. Keetels; Umberto D'Ortona; Werner Kramer; H. J. H. Clercx; Kai Schneider; G. J. F. van Heijst (J. Comput. Phys., 2007)