Numerical viscosity as a function of the wave number measured for all schemes and resolutions. The numerical viscosity is estimated using the procedure outlined in Section
and it is defined by equation (
). The different panels are, from left to right and from top to bottom, the results obtained with PPM_HLLC, PPM_HLLC_CFL0.8, PPM_HLLE, TVD_HLLE and WENOZ_HLLC. The bottom right panel show a comparison of all of the methods at 5123. The numerical viscosity shows large variations across the wave number space. The choice of the Riemann solver plays a role that is at least as important as the choice of the reconstruction method in affecting the numerical viscosity throughout the entire the spectrum.