Print Email Facebook Twitter Three-dimensional vorticity patterns of cylinder wakes Title Three-dimensional vorticity patterns of cylinder wakes Author Scarano, F. Poelma, C. Faculty Aerospace Engineering Department Aerospace Design, Integration and Operations Date 2009-03-08 Abstract 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 ?/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. To reference this document use: http://resolver.tudelft.nl/uuid:c4467281-8f10-4f42-8e07-7eec363f6469 Publisher Springer ISSN 1432-1114 Source Experiments in Fluids, 47 (1) Part of collection Institutional Repository Document type journal article Rights (c) 2009 Scarano, F.; Poelma, C. Files PDF scarano-2009.pdf 982.5 KB Close viewer /islandora/object/uuid:c4467281-8f10-4f42-8e07-7eec363f6469/datastream/OBJ/view