196,266 research outputs found
Integrated Aeroacoustoelastic Modeling for the Analysis of the Propeller--Driven Cabin Noise
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Aeroacoustoelasticity in State-Space Format Using CHIEF Regularization
No full textThis paper deals with aeroacoustoelastic modeling for analysis of the acoustic field inside an aircraft cabin. The aim is the identification of a state-space format for aeroacoustoelasticity equations applicable, for instance, for synthesis of an
active control law devoted to cabin noise abatement. Specifically, attention is focused on the development of the aeroelastic operator, starting from a boundary integral equation method for the exterior compressible-aerodynamics solution. As is well known, in such a type of application of the boundary integral equation method, singularities occur in the algebraic equations resulting from discretization of the integral operator. Here, the discretized aerodynamic operator is regularized by using the CHIEF technique, that consists of augmenting the algebraic problem with
homogeneous conditions at points in the interior domain (the cabin space, in our problem). Then, in order to obtain the state-space format model of the aeroacoustoelastic operator, the resulting trascendental aerodynamic transfer functions between structural Lagrangean variables and generalized aerodynamic forces are approximated through rational
polynomials, and the additional aerodynamic states induced by their poles are included in the set of state-space variables
A Boundary-Field Integral Equation for Analysis of Cavity Acoustic Spectrum
No full textThe acoustic spectrum of cavities can be identified using integral equation formulations. Because of the
transcendental dependence on frequency of the Green function, difficulties arise in calculating acoustic frequencies and modes of vibration when the Kirchhoff–Helmholtz boundary-integral operator is applied. This trouble is
circumvented by the present, nonstandard, integral formulation that, by using the fundamental solution of the Laplace operator, allows the identification of acoustic spectra of cavities through solution of a standard eigenvalue problem. This formulation is compared both with that based on the Kirchhoff–Helmholtz operator and with an alternative
integral approach introduced in the past that, akin to the one used here, analyzes cavity acoustics in terms of an eigenvalue problem. The numerical investigation deals both with a simple box-shaped cavity and with cavities related to applications of aeronautical interest
Reduced-order modeling for linearized aeroelasticity of fixed wings in transonic flight
No full textThis paper presents a methodology for the identification of a reduced-order model (ROM) for the perturbation aeroelastic analysis of fixed wings in transonic flight. It is based on a linearized, frequency-domain, boundary-field
integral equation for the solution of the unsteady perturbation potential flow about steady-state reference wing configurations. The resulting transfer functions between structural Lagrangean variables and generalized aerodynamic forces are approximated by means of rational expressions, and the aeroelastic ROM is identified by coupling them with the structural operator. With the aeroelastic operator recast in a reduced-order form, transonic flutter boundaries are detected through a classical eigenvalue analysis and the time-domain statespace aeroelastic model is also obtained. Applications of the methodology presented to a widely known aeroelastic test case reveal a remarkable agreement with the measured speed and frequency of flutter
A Novel Potential-Flow Boundary Integral Formulation for Helicopter Rotors in BVI Conditions
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