A multi blade-row linearised analysis method for flutter and forced response predictions in turbomachinery

A three-dimensional time-linearised unsteady Navier-Stokes solver is presented for the computation of multistage unsteady flow in turbomachinery. The objective is to address multistage aeroelastic effects for both flutter and forced response. Since the method is currently being developed, only forced response applications are studied in this paper With this approach, travelling waves, known as spinning modes, are propagated across the multistage domain in order to take into account the interaction between the blade-rows. The method is first validated over two simple test cases for which analytical solutions were available. It is then tested on a turbine stage test case and multistage effects are evaluated from the contribution of one spinning mode included in the model. The results are compared with both time-linearised single-row and nonlinear multirow methods. Multirow effects are shown not to be important in this case. However, the test case serves as a validation for the implementation of the methodology and further work will focus on the implementation of several spinning modes and the computations of forced response and flutter cases with several blade-rows.