Yazar "Akkoca, Azize" seçeneğine göre listele

Listeleniyor 1 - 2 / 2
  • Küçük Resim
    Öğe
    Flow details of a circular cylinder mounted on a flat plate
    (Int Assoc Hydraulic Research, 2008) Ozturk, Nurhan Adil; Akkoca, Azize; Sahin, Besir
    The main purpose of this study is to investigate the flow structure up- and downstream of a circular cylinder mounted on a flat surface in the boundary layer region using a Particle Image Velocimetry (PIV) technique for Reynolds numbers ranging from 750 to 9600. The interaction between the primary, incoming, and counter-clock-wise rotating vortices and the trail of the horseshoe vortices formed at the upstream base of the cylinder are quantitatively identified in terms of the instantaneous and time-averaged flow data. The entrainment is shown to be activated between the main and separated flow regions across the shear layer by interactions of opposite signed rotating vortices which are responsible for scour in the upstream region of the cylinder. The surface fluid bursts to create counter-clock-wise rotating vortices upstream of the cylinder to split the incoming clock-wise rotating vortex into an independent vortex. Since the counter-clock-wise rotating vortices are not fed continuously by the surface fluid, they gradually expand in size but lose the strength and later are swept away by the developing vortices.
  • Küçük Resim
    Öğe
    PIV measurements of flow past a confined cylinder
    (2008) Ozturk, N. Adil; Akkoca, Azize; Sahin, Besir
    This study investigates the flow past a confined circular cylinder built into a narrow rectangular duct with a Reynolds number range of 1,500 ? Re d ? 6,150, by employing the particle image velocimetry technique. In order to better explain the 3-D flow behaviour in the juncture regions of the lower and upper plates and the cylinder, respectively, as well as the dynamics of the horseshoe vortex system, both time-averaged and instantaneous flow data are presented for regions upstream and downstream of the cylinder. The size, intensity and interaction of the vortex systems vary substantially with the Reynolds number. Although the narrow rectangular duct with a single built-in cylinder is a geometrically symmetrical arrrangement, instantaneous flow data have revealed that the flow structures in both the lower and upper plate-cylinder junction regions are not symmetrical with respect to the centreline of the flow passage. The vortical flow structures obtained in side-view planes become dominant sometimes in the lower juncture region and sometimes in the upper juncture region in unsteady mode. © 2008 Springer-Verlag.