The emphasis of the present investigation is on the unsteady flow structure and the crossflow topology on delta wings involving two basic planforms designated as diamond and lambda. The sweep angle of the leading edge of both planforms is 38.7 deg in the fore region of the wing; at a chord length of C' = 101.6 mm, however, the sweep angle changes abruptly to zero. The cords C of the diamond and lambda wings have values, respectively, of 195 and 167 mm. The trailing edge of the diamond planform planforms is broken symmetrically by one corner pointing backwards, whereas the trailing edge of the lambda planform has a symmetric zigzag structure, i.e. one corner pointing backwards surrounded by two forward-pointing corners. Each wing has a thickness of 3 mm, and the leading edge is beveled at an angle of 30 deg. Experiments were performed in a large-scale water channel using a high-image-density particle image velocimetry, which allows whole-field representations of both the time-averaged and instantaneous structure. A cinema mode of image acquisition allows time records of the flow at a large number of locations with a framing rate of 15 s-1, and thereby determination of the corresponding spectra of the fluctuating velocity field. Illumination was provided by a dual-pulsed YAg laser system using cylindrical and spherical lenses to generate a vertical laser sheet. The laser sheet was located at a cord length x/C' = 1.4, i.e. between the abrupt change in sweep angle and the trailing edge. The streamline topology of both the diamond and lambda planforms shows, at low angle of attack (alpha = 7 deg), a focus of a spiral pattern of streamlines at the leading edge, rather than inboard of the leading edge. At moderate angles of attack (alpha = 13 deg), this focus shifts inboard of the leading edge, and at higher angle of attack (alpha = 17 deg and 25 deg), where a large scale separated zone occurs adjacent to the wing surface, the pattern of streamline topology loses its ordered structure. For the lambda planform, a saddle point is located outboard of the leading edge, which does not appear for the diamond planform. At low angles of attack, the vorticity concentration is nearly centered at the leading edge, whereas at larger angles of attack, this concentration is placed significantly away from the edge. Furthermore, well-defined vortical substructures are observed in the elongated layers of time-averaged vorticity adjacent to the surface of the wing. Corresponding images of instantaneous vorticity fields show that this time-averaged pattern is actually made up for well-defined vorticity concentrations, whose spatial distributions are approximately commensurate with those of time-averaged patterns. Contours of constant rms velocity fluctuation adjacent to the wing have extrema that are generally coincident with the outer regions of the elongated, time-averaged vorticity layers. The spectral content of these fluctuations, evaluated from space-time imaging, shows well-defined peaks, which are associated with the aforementioned modulation of instantaneous vorticity patterns. The spectral content of these fluctuations shows well-defined peaks (at dimensionless frequencies of 2.13 <= fC/U <= 3.97), which are associated with the modulations of the instantaneous vorticity patterns.


    Zugriff

    Zugriff über TIB

    Verfügbarkeit in meiner Bibliothek prüfen

    Bestellung bei Subito €


    Exportieren, teilen und zitieren



    Titel :

    Flow structure on diamond and Lambda planforms: trailing-edge region


    Weitere Titelangaben:

    Strömungsstruktur an der Hinterkante von Diamant- und Lambda-Deltaflügeln


    Beteiligte:
    Yaniktepe, B. (Autor:in) / Rockwell, D. (Autor:in)

    Erschienen in:

    AIAA Journal ; 43 , 7 ; 1490-1500


    Erscheinungsdatum :

    2005


    Format / Umfang :

    11 Seiten, 9 Bilder, 29 Quellen




    Medientyp :

    Aufsatz (Zeitschrift)


    Format :

    Print


    Sprache :

    Englisch