SHEDDING PROCESS OF FINITE CYLINDERS WITH HIGH BLOCKAGE RATIO

Marcos Leandro Woyciekoski¹; Sergio Viçosa Möller¹

¹ Universidade Federal do Rio Grande do Sul - UFRGS

doi:10.20906/CPS/COB-2015-0426

Resumo

An important parameter which can affect the flow, influencing others parameters like Reynolds Numbers, it is called blockage ratio. Increasing blockage ratio causes an increase in velocity around the cylinder outside the boundary layer, influencing the pressure and velocity distribution. In case of finite cylinder, to obtain a high blockage ratio it is necessary to test cylinders with larger diameters. The use of larger diameters leads to an approximation with the near wall region directly affecting the flow. This paper presents an experimental study about the shedding process of a finite cylinder with high blockage ratio (between 12 and 25%) and its effects, where finite cylinders of different diameters are tested. The vortex shedding frequency is obtained through auto spectral density function with the use of hot-wires anemometry. To observe the blockage ratio effects, measurements were performed at different flow velocities to maintain the Reynolds number of 20000 constant. Analysis of the results of time series obtained from the experiment was performed by means of Fourier and Wavelet techniques. Results confirm the high blockage ratio has influence in the shedding process of finite cylinders.

Palavras-chave: turbulent flow; hot-wire anemometry; blockage ratio; finite cylinder