简介:The wake of a circular cylinder at Re = 2700 is investigated by means of Tomographic PIV
(Tomo-PIV), a recently developed three-dimensional velocimetry technique. The paper presents the
principles of Tomo-PIV and discu简介:The wake of a circular cylinder at Re = 2700 is investigated by means of Tomographic PIV
(Tomo-PIV), a recently developed three-dimensional velocimetry technique. The paper presents the
principles of Tomo-PIV and discusses in details the implementation of the technique to the experimental
conditions. With a measurement volume of approximately 40x40x10 mm2 two configurations are chosen in
order to describe both the 2D wake features and the span wise organization of secondary rollers dominating
the 3D flow organization. The present data allow to directly evaluate the measurement error imposing mass
conservation inside the volume (viz. solenoidal velocity field). The visualization of the wake instantaneous
structure is obtained by means of vorticity vector magnitude iso-surfaces, or decomposing the vorticity in the
span wise and stream-wise(normal)/bi-normal component, which return the separate contribution of the
Kármán rollers and the interconnecting structures between them respectively. The properties of the
secondary rollers are given in terms of span wise wavelength, peak vorticity, vorticity stretching and their
size and shape. A value of the span wise wavelength λ
z/D = 1.2 is recurring and the rollers organization into
pairs is found to be similar to the instability Mode B occurring in lower Reynolds number wakes investigated
with previous studies.详细>