caa a22 4500 606197893 CHVBK 20210128100931.0 cr unu---uuuuu 210128e20150301xx s 000 0 eng 10.1007/s00348-015-1926-6 doi (NATIONALLICENCE)springer-10.1007/s00348-015-1926-6 POD analysis of the turbulent flow downstream a mild and sharp bend [Elektronische Daten] [Athanasia Kalpakli Vester, Ramis Örlü, P. Alfredsson] Time-resolved stereoscopic particle image velocimetry measurements have been taken of the turbulent flow at the exit plane of a mild and a sharp pipe bend. Cross-sectional flow fields were obtained 1, 2 and 3 pipe diameters downstream the bend in order to capture the flow evolution. Proper orthogonal decomposition (POD) was applied in order to identify the underlying vortical patterns and revealed the existence of a single cell spanning the whole cross section as the most dominant structure, while the Dean cells appeared in the next most energetic modes. The results from these investigations, which indicate the origin of the oscillatory motion of the Dean vortices, the so-called swirl switching, were found to agree with those presented by Hellström et al. (J Fluid Mech 735:R7, 2013). Furthermore, the effect of a honeycomb, mounted at the bend inlet, on the flow field has been studied by means of statistical and POD analysis in order to test the hypothesis by Sakakibara and Machida (Phys Fluids 24:041702, 2012), viz. whether the unsteady behaviour of the Dean cells is related to large-scale structures existing upstream the bend. As a consequence of the honeycomb, the Dean vortices do not appear in the mean field, nor in the most energetic modes, which opens possibilities to overcome or at least delay the problem of fatigue in piping systems which can be caused by the swirl switching. Springer-Verlag Berlin Heidelberg, 2015 Kalpakli Vester Athanasia CCGEx and Linné FLOW Centre, KTH Mechanics, 100 44, Stockholm, Sweden aut Örlü Ramis CCGEx and Linné FLOW Centre, KTH Mechanics, 100 44, Stockholm, Sweden aut Alfredsson P. CCGEx and Linné FLOW Centre, KTH Mechanics, 100 44, Stockholm, Sweden aut Experiments in Fluids Springer Berlin Heidelberg 56/3(2015-03-01), 1-15 0723-4864 56:3<1 2015 56 348 https://doi.org/10.1007/s00348-015-1926-6 text/html Onlinezugriff via DOI BK010053 XK010053 XK010000 Metadata rights reserved Springer special CC-BY-NC licence nationallicence 1 research-article jats NATIONALLICENCE NATIONALLICENCE NL-springer NATIONALLICENCE 856 40 https://doi.org/10.1007/s00348-015-1926-6 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Kalpakli Vester Athanasia CCGEx and Linné FLOW Centre, KTH Mechanics, 100 44, Stockholm, Sweden aut NATIONALLICENCE 700 1- Örlü Ramis CCGEx and Linné FLOW Centre, KTH Mechanics, 100 44, Stockholm, Sweden aut NATIONALLICENCE 700 1- Alfredsson P. CCGEx and Linné FLOW Centre, KTH Mechanics, 100 44, Stockholm, Sweden aut NATIONALLICENCE 773 0- Experiments in Fluids Springer Berlin Heidelberg 56/3(2015-03-01), 1-15 0723-4864 56:3<1 2015 56 348