variavel0=<b>Ricardo Lopes Ferreira</b> - ricardo@dem.feis.unesp.br Unesp
<b>Edson Del Rio Vieira</b> - delrio@dem.feis.unesp.br Unesp
<b>Abstract.</b> The flow around a circular cylinder has awaken the attention of different researchers since the historic Strouhal`s work of 1878. Ever since, many experimental and numeric works have been carried out in order to determine the relationship between the vortex shedding frequency and the flow regime. Recently, a number of studies have been developed using several small modifications in circular cylinder. In this work a circular cylinder modified with a longitudinal concave notch, has been tested in order to determine the relationship between the non-dimensional vortex shedding frequency (Strouhal number) and the Reynolds number has been determined to Reynolds up to 600. Additionally a modified circular cylinder with a longitudinal slit also has been tested in order to determine the Strouhal-Reynolds relationship in several attack angle configurations. The experiments have been carried out in a vertical low turbulence hydrodynamic tunnel with 146x146x500 mm of test section operating in continuous mode. Flow visualization by direct liquid dye injection has been utilized in order to produce vortex images. These images have been captured in still chemical photography for different Reynolds numbers. A hot-film probe has been adequately positioned in the vortex wake to determine the vortex shedding frequency and consequently the Strouhal number.
<b>Keywords.</b> Strouhal number, vortex shedding, modified cylinder, flow visualization, vortex wake.