Three-dimensional vorticity patterns of cylinder wakes

By Fulvio Scarano, Christian Poelma. 2009

243 citations recorded by the source corpus.

The vortex organization of cylinder wakes is experimentally studied by time-resolved tomographic Particle Image Velocimetry at Reynolds numbers ranging from 180 to 5,540. Time resolved measurements are performed at Re = 180, 360 and 540, whereas the transitional (Re = 1,080) and turbulent regimes (Re = 5,540) are investigated by snapshots separated in phase by more than π/4. The vortex structure evolution is visualized by the 3D vorticity field, revealing a regular shedding at the lowest Reynolds, whereas at Re > 500 the Bénard-Kármán vortex street exhibits counter-rotating stream-wise vortex pairs (characteristic of Mode B) dominating the 3D motion. The regime at Re = 360 produces a transitional pattern where the counter-rotating vortex pairs (Mode B), coexist with profoundly distorted shedding of oblique elements forming a chain of rhombus-like vortex cells. In the turbulent flow regime (Re = 5,540) a large increase in the range of flow scales is directly observed with the appearance of Kelvin-Helmholtz type vortices in the separated shear layer consistently with what is abundantly reported in literature. The statistical description of the secondary structures is inferred from a 3D autocorrelation analysis yielding two span-wise wavelengths for the counter-rotating pairs, an inner length given by (twice) the distance between counter-rotating elements and an outer one given by the distance between pairs. The uncertainty analysis of the present tomographic PIV experiments reveals that this approach is suited for the investigation of vortex wakes with a typical error of 2 and 10% on the velocity and vorticity vectors, respectively.

Subfields: Computational Mechanics, Environmental Engineering

View Paper: https://www.semanticscholar.org/paper/69c696f6c81539fe4c48dae81503eda2a5338830

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In Computational Mechanics

In Environmental Engineering

Citations in the corpus

Three-dimensional synthetic aperture particle image velocimetry (2010, methodology): “02 Tomo-PIV [16] 100 × 100 × 20 4 100 000 0.”
Motion tracking-enhanced MART for tomographic PIV (2010, methodology): “The deformation of one object (e.g. from the exposure at time t + t) to obtain the intensity field that would be expected at time t is made by the deformation technique used for the 3D iterative interrogation (discussed for instance in Scarano and Poelma (2009)).”
PIV uncertainty quantification by image matching (2013, background): “In 3D data from incompressible flows, the fluctuating velocity divergence (Liu and Katz 2006, Scarano and Poelma 2009) indicates the error level of the velocity and its derivatives.”
Volumetric particle image velocimetry with a single plenoptic camera (2015, methodology): “A more advanced version of this basic concept uses a multi-pass, multi-grid window deformation technique known as VODIM (Scarano and Poelma [15]).”
Lagrangian and Eulerian pressure field evaluation of rod-airfoil flow from time-resolved tomographic PIV (2011, methodology): “order polynomial least-square fit over a kernel of 5 spatiotemporal samples (Scarano and Poelma 2009).”
Shake-The-Box: Lagrangian particle tracking at high particle image densities (2016, background): “Applications range from (often spatially highly resolved) two-pulse measurements in water (e.g. Hain et al. 2008; Scarano and Poelma 2009) and air (e.g. Elsinga et al. 2006a; Schanz et al. 2012; Hennings-son et al. 2015) to time-resolved measurements in water (e.g. Schröder et al. 2011; Violato et…”
On the use of helium-filled soap bubbles for large-scale tomographic PIV in wind tunnel experiments (2015, background): “as the turbulent sub-structures such as the ribs or fingers reported in previous tomographic experiments on the same geometry (Elsinga et al. 2006; Scarano and Poelma 2009).”
Dense velocity reconstruction from tomographic PTV with material derivatives (2016, background): “For tomographic PIV, the amount of grid nodes typically also exceeds the amount of tracer particles, as the window overlap factor is often set to 75 % to avoid unnecessary truncation when evaluating spatial derivatives (Scarano and Poelma 2009; Togkoz et al. 2012).”
Tomographic PIV: principles and practice (2012, methodology): “A further work included the temporal analysis of the 3D vorticity pattern as illustrated in figure 21 (top left) (Michaelis et al 2006, Scarano et al 2007, Scarano and Poelma 2009), highlighting the role of spanwise instabilities at different values of the Reynolds number.”