Flutter Analysis – Flutter Prediction
Flutter prediction in recent years has been the subject of considerable and increasing effort in industry. Considerable use is now made of in aerodynamic models in wind tunnels and free flight, techniques of ground resonance testing end. Flight flutter testing are continuously being improved. Perhaps the greatest development, however, has been in the field of high speed computing equipment which has enabled lengthy calculations to be carried out as a matter of routine, where they could not have been attempted a few years ego. With these advances the accuracy of flutter prediction is greatly improved.
Traditional dynamic and flutter analysis demands a detailed finite element model of the aircraft in terms of its mass and stiffness distribution. However, in absence of these details, modal parameters obtained from experimental tests can be used to predict the flutter characteristics of an aircraft. BHSPL has experts with several years of experience in the domain and time tested methods to predict the flutter characteristics of an aircraft structure of unknown configuration under an anticipated aerodynamic loading using software such as MSC Nastran and experimental modal parameters (such as mode shapes, natural frequencies and damping) from ground vibration tests.
The design / methodology adopted for Flutter Analysis is to develop a finite element model with nodes representing the test points on the aircraft is created with appropriate boundary constraints. A direct matrix abstraction program for NASTRAN software is created to carry out a normal modes analysis and replaces the mass normalized eigenvalues and vectors with the experimentally obtained modal parameters. The flutter analysis proceeds with the solution of the flutter equation in the flutter module of NASTRAN. The methodology helps in the realistic prediction of flutter characteristics of a structure with known geometric configuration and does not need material properties, mass or stiffness distributions.
It may be noted that The prediction of flutter is not a precise science and requires flight verification.