title: Validity of the essential assumption in a projection operator method.
abstract: The projection operator method developed by Mori involves the essential assumption that chaotic motion is successfully divided into a coherent motion and a fluctuating one. We investigate the validity of the assumption using the Kuramoto-Sivashinsky equation as a model equation of chaotic systems. It has been found that the assumption is reasonable for both long wave modes and short wave modes. We have also evaluated a value of the eddy viscosity as 9.0 by extracting the nonlinear term from the coherent part. This value is consistent with the former estimates with other methods.
authors.affiliation: Research Institute for Applied Mechanics, Kyushu University, Kasuga 816-8580, Japan. okamura@rian.kyushu-u.ac.jp
authors.forename: Makoto
authors.initials: M
authors.lastname: Okamura