A simple model for boundary layer induced noise in aircraft has been presented, consisting of a simply supported elastic plate forced by a pressure spectrum described by the Efimtsov model (Soviet Physics Acoustics 28(4) (1982) 289-292). The cabin noise level will be determined by the total acoustic power radiated by all the fuselage panels, and on this basis we have investigated the dependence of our models sound radiation on four physical parameters: structural damping, hydrodynamic coincidence, critical frequency and structural inhomogeneity. Our conclusions are as follows: (i) structural damping reduces the radiated sound; (ii) hydrodynamic coincidence, whereby resonant modes with longitudinal trace speed equal to the boundary layer convection velocity are highly excited, is inevitable with current airframe designs, but is not sensitive to small variations in structural properties or cruising speed; (iii) the critical frequency should be kept as high as possible, i.e., structures should be floppier rather than stiffer; (iv) the degree of structural inhomogeneity should be as low as possible, i.e., the fewer reinforcements the better. These conclusions are tentative, as it is known that the cabin interior treatment has a significant modifying effect on the bare plate behavior. Indeed, Part II of this work will show that conclusion (i) must be altered for a 'trimmed' plate. However, one can already see that conclusions (iii) and (iv) imply that design practices which are desirable for other reasons will have adverse effects on cabin noise levels, and therfore that care must be paid to acoustic considerations from the very beginning of the design process.


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    Title :

    Boundary layer induced noise in aircraft, Part I: the flat plate model


    Additional title:

    Randschichtinduzierter Lärm bei Flugzeugen, Teil 1: Das flache Platten-Modell


    Contributors:

    Published in:

    Publication date :

    1996


    Size :

    20 Seiten, 10 Bilder, 1 Tabelle, 37 Quellen




    Type of media :

    Article (Journal)


    Type of material :

    Print


    Language :

    English







    Boundary-Layer Induced Noise in Aircraft

    Graham, W. R. / Deutsche Gesellschaft fur Luft- und Raumfahrt e.V. / AIAA | British Library Conference Proceedings | 1992


    Boundary layer induced noise in aircraft

    Graham, W. R. | TIBKAT | 1992