Analysis of a cylinder submitted to acoustic excitation due to turbulent boundary layer
Costa, T. A.1; Brandão, J. G. T.2; Souto, C.A.3
1 DCTA/FEG-UNESP; 2 FEG-UNESP; 3 DCTA/IAE/ITA
doi:10.20906/CPS/COB-2015-0453
Resumo
A launching rocket and its payload are submitted to strong acoustic loads in some moments of its flight like lift off, during transonic flight and in the instant of maximum dynamic pressure. These loads could affect the payload and other rocket internal equipment. It must be taken into account that in the higher stages, where delicate control equipment and the payload are placed, the acoustic excitations are dominant. The knowledge of the acoustic loads is of great importance in order to provide estimated loads for the design phase, define intensity levels to specify qualification and acceptation acoustic tests to which subsystems and elements of the launcher and its payload shall be submitted and to design an acoustic protection system. In the three types of acoustic loads oscillating pressures are applied to all vehicle external surfaces. These pressure oscillations behave randomly and need to be analyzed by evaluating its statistical properties as: power spectrum and correlation coefficients along the principal axes of the structure. In this work the structural vibrations of a module of the IAE Microsatellite Launcher Vehicle (VLM) caused by the Turbulent Boundary Layer (TBL) during flight are evaluated numerically. A reference power spectrum and the correlation coefficients corresponding to a specific Mach number obtained from an IAE internal report were used to define the acoustic random load due to TBL. The structure modal parameters (natural frequencies and mode shapes) were obtained by using the finite element method. A MATLAB routine use the already calculated structure modal basis to evaluated the structure frequency response functions. By combining the system frequency response functions and the load power spectrum the routine calculates the structure response.
Palavras-chave: Microsatellite launching vehicle; Turbulent Boundary Layer; Random vibrations