An integrated nonlinear approach for turbomachinery forced response prediction. Part I: Formulation

This paper describes the formulation of an advanced numerical model for the simulation of high- and low-engine-order forced response for turbomachinery applications. The various forced response mechanisms are explained in some detail and a specification for an accurate prediction system is discussed with emphasis on both fluid and structural modelling aspects. The Favre-averaged Navier-Stokes equations are used to represent the unsteady flow in a nonlinear time-accurate fashion. Features such as turbulence modelling, boundary conditions, meshing strategies and numerical treatments are discussed in detail. The structural model is based on a linear modal model, though local nonlinearities due friction dampers can be accommodated using an iterative scheme. The fluid mesh is moved at each-time step according to the structural motion, so that changes in blade aerodynamic damping and flow unsteadiness can be accommodated. It is concluded that the model can be used for large simulations involving multi-bladerow whole-annulus calculations. (C) 2000 Academic Press.