VARIATIONAL-PRINCIPLES FOR CONSTRUCTING FEW-MODE MODELS OF THE LAMINAR-TO-TURBULENT TRANSITION

A method based on variational principles is proposed for constructing few-mode models of distributed nonlinear systems to a higher accuracy of approximation than the Galerkin method for a prespecified basis of trial functions. This method may be useful for studying the initial st ages of the laminar-to-turbulent transition, when the increase in the number of trial functions sharply increases the stiffness of the reduc ed system, so that it is advisable to use optimal few-mode models. The proposed method is used to construct and analyze a modification of th e Lorenz model for a Saltzman system. (C) 1997 American Institute of P hysics.