Comparison of Flow Characteristics of Different Sphere Geometries Under the Free Surface Effect


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Ozgoren M., Dogan S., Okbaz A., Aksoy M. H., SAHIN B., AKILLI H.

7th International Conference on Experimental Fluid Mechanics (EFM), Hradec-Kralove, Czech Republic, 20 - 23 November 2012, vol.45 identifier identifier

  • Publication Type: Conference Paper / Full Text
  • Volume: 45
  • Doi Number: 10.1051/epjconf/20134501022
  • City: Hradec-Kralove
  • Country: Czech Republic
  • Yıldız Technical University Affiliated: No

Abstract

Comparison of the experimental results of turbulent flow structures between a smooth sphere and a sphere with a vent hole, roughened, and o-ring is presented in the presence of a free-surface. Dye visualization and particle image velocimetry (PIV) techniques were performed to examine effects of passive control methods on the sphere wake for Reynolds number Re = 5000 based on the sphere diameter with a 42.5mm in an open water channel. Instantaneous and time-averaged flow patterns in the wake region of the sphere were examined from point of flow physics for the different sphere locations in the range of 0 <= h/D <= 2.0 where h was the space between the top point of the sphere and the free surface. The ratio of ventilation hole to sphere diameter was 0.15, o-ring was located at 55 degrees with a 2 mm from front stagnation point of the sphere and roughened surface was formed by means of totally 410 circular holes with a 3 mm diameter and around 2 mm depth in an equilateral triangle arrangement. The flow characteristics of instantaneous velocity vectors, vorticity contours, time-averaged streamline patterns, Reynolds stress correlations and streamwise and cross-stream velocity fluctuations for both the smooth and passively controlled sphere were interpreted.