NUMERICAL VISCOSITIES OF DIFFERENCE-SCHEMES

Numerical visocisities of finite-difference schemes are usually obtain ed from truncation-error analyses based on Taylor series expansions. H ere we observe that numerical viscosities can also be obtained very si mply and directly from the growth factor xi in a conventional Fourier stability analysis. A general formula is derived for the numerical vis cosity in terms of the first and second derivatives of xi with respect to the wavenumber k, evaluate at k = 0. A single Fourier analysis the refore suffices to determine both stability limits and numerical visco sities.