Three-dimensional full potential method for the aeroelastic modeling of propfans
Abstract
Three dimensional, unsteady, subsonic, and transonic flow through a single rotation propeller is studied. The unsteady loads on the blades are obtained by solving the full potential equations using an implicit time-marching scheme. The purpose of the code is to provide a capability of doing propfan aeroelastic analysis in the nonlinear transonic regime. Results will be shown for steady state aerodynamic loading, unsteady aerodynamic response to forced aeroelastic deformations, and free aeroelastic response. The aerodynamic analysis is based on a finite volume discretization of the potential equations. The scheme is fully implicit, with the resulting nonlinear algebraic equations being solved in conservation form by an approximately factored quasi-Newton iteration at each time step. The algorithm is based on the work of Shankar et al. who applied it to fixed wing vehicles. The modifications that have been made to adapt the method to rotors will be described. These modifications include the implementation of periodic boundary conditions and a new artificial density formulation for shock capturing. The blade dynamics are based on the in vacuum modes and frequencies. The scheme uses a moving grid that conforms instantaneously to the deforming blade shape. Grids are generated, a priori, for the undeformed blade and for unit deformations in each of the in vacuum modes. Dynamic grids are then set by linear superposition based on the current state vector of the blade. The state vector may either be prescribed or computed for the equations of motion of the blades. The aeroelastic analysis of propfans has been addressed in two ways: frequency domain analysis and time domain simulation. The frequency domain solution uses the generalized forces that are obtained from transfer function analysis. The results will be compared directly to a linear panel method in terms of damping coefficients. The time domain solution, which solves the structural equations of motion along with the full potential aerodynamic problem, has been applied to propfan blade for aeroelastic analysis. The results of blade displacement histories are monitored and are verified by the frequency domain solution.
Degree
Ph.D.
Advisors
Williams, Purdue University.
Subject Area
Aerospace materials
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