THE PASSIVE CONTROL OF UNSTEADY FLOW STRUCTURE DOWNSTREAM OF A CIRCULAR CYLINDER IN SHALLOW WATER


DURHASAN T. , PINAR E. , AKSOY M. , ÖZKAN G. M. , AKILLI H. , ŞAHİN B.

ASME International Mechanical Engineering Congress and Exposition (IMECE2013), California, Amerika Birleşik Devletleri, 15 - 21 Kasım 2013 identifier

  • Cilt numarası:
  • Basıldığı Şehir: California
  • Basıldığı Ülke: Amerika Birleşik Devletleri

Özet

In the present study, it was aimed to suppress the vortex shedding occurred in the near wake of a circular cylinder (inner cylinder) by perforated cylinder (outer cylinder) in shallow water flow. The inner cylinder (D-i) and outer cylinder (D-o) have fixed diameters, such as D-i=50 mm and D-o=100 mm, respectively. The effect of porosity, beta, was examined using four different porosity ratios, 0.3, 0.5, 0.6 and 0.8. In order to investigate the effect of arc angle of outer cylinder, alpha, four different arc angles, alpha=360 degrees, 180 degrees, 150 degrees and 120 degrees were used. The experiments were implemented in a recirculating water channel using the particle image velocimetry, PIV technique. The depth-averaged free-stream velocity was kept constant as U-infinity=100 mm/s which corresponded to a Reynolds number of Re=5000 based on the inner cylinder diameter. The results demonstrated that the suppression of vortex shedding is substantially achieved by perforated outer cylinder for arc angle of alpha=360 degrees at beta=0.6. Turbulence Kinetic Energy statistics show that porosity, beta, is highly effective on the flow structure. In comparison with the values obtained from the case of the bare cylinder, at porosity beta=0.6, turbulence characteristics are reduced by %80. Also, the point, which the values of maximum TKE, shift to a farther downstream compared to the case of bare cylinder.