Fraunhofer-Forschungsgruppe Hydroakustik FHAK

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  • Publication
    Richtcharakteristik einer einseitig eingespannten ebenen Platte
    ( 1991)
    Homm, A.
    ;
    Ganser, A.
    ;
    Bartels, F.
    Experiments on vibration and sound radition of a cantilever aluminium plate were carried out. For 3 eigenfrequencies the mode shapes were visualized by the Chladni method and the directivity patterns of the radiated sound were determined by the reciprocity method. The directivity patterns could be measured for nearly the whole of all directions in a 2 degree step resolution are represented in a 3-dimensional hidden line technique.
  • Publication
    Directivity pattern of a cantilever plate. Comparison of numerical results with experimental data
    ( 1991)
    Homm, A.
    ;
    Bartels, F.
    ;
    Estorff, O. von
    For a cantilever aluminium plate, the vibration modes were investigated experimentally by means of the Chladni method and numerically with the FE-method (NASTRAN). The sound radiation of three selected eigenfrequencies was determined by the reciprocity method and was calculated with a coupled FEM/BEM-approach. The comparison of the experimental and numerical results shows excellent agreement.
  • Publication
    Numerical and experimental study of noise generated by a vibrating plate
    ( 1991)
    Estorff, O. von
    ;
    Homm, A.
    ;
    Bartels, F.
    Applying an indirect Boundary Element Method the sound radiation of a vibrating cantilever plate is investigated. The numerically obtained results are compared with measured data in order to show the accuracy and applicability of the numerical approach. The study clearly enhances the confidence in the computational solution of noise problems which are of particular importance in connection with the qualification of large spacecraft structures like HERMES.
  • Publication
    Sound radiation of a cantilever plate - comparisons of BEM results with experimental data
    ( 1991)
    Estorff, O. von
    ;
    Homm, A.
    ;
    Bartels, F.
    The sound radiation of a vibrating cantilever plate is investigated by a combined Finite Element / Boundary Element approach. First, in a FE-analysis the mode shapes of the plate are determined. Second, for three selected frequencies the acoustic pressure distribution around the plate is calculated using an indirect boundary element formulation. The results are compared with experimental data in order to show the accuracy and applicability of the numerical approach.
  • Publication
    Finite element calculation of vibration modes of clamped propeller blades
    ( 1991)
    Homm, A.
    ;
    Bartels, F.
    The study presents results of numerical FE- calculations for modern skew propeller blades and their experimental validation. It is restricted to single clamped blades, an assumption easy to implement in the theoretical calculation but difficult to achieve in an experiment. Assumptions for the FE- calculations and the incomplete rigid clamped boundary condition in the experiment yield differences between experiment and theory, mainly in the eigenfrequencies. The fluid coupling to the structure is limited to the inviscid, incompressible case or k 1 << 1. In the limits of these assumptions the results of both, theory and experiments agree fairly.