Contraction-ratio variation and prediction of large experimental pressure-drops in sharp-corner circular contraction-expansions–Boger fluids
| Autor: | J.E. López-Aguilar, M.F. Webster, H.R. Tamaddon-Jahromi, Octavio Manero, M. Pérez-Camacho |
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| Jazyk: | angličtina |
| Rok vydání: | 2016 |
| Předmět: |
Coalescence (physics)
Materials science 010304 chemical physics Applied Mathematics Mechanical Engineering General Chemical Engineering Rotational symmetry Thermodynamics Condensed Matter Physics 01 natural sciences 010305 fluids & plasmas Vortex Planar Classical mechanics 0103 physical sciences Dissipative system Newtonian fluid General Materials Science Contraction ratio |
| Popis: | This study is concerned with the continuum modelling of sharp-corner contraction-expansion axisymmetric flows, under contraction-ratio variation, and more particularly, in the precise capture of the large-levels of experimental excess pressure-drops ( epd ) for Boger fluids. The particular contraction-ratios ( α ) considered are those studied experimentally by M. Perez-Camacho, J.E. Lopez-Aguilar, F. Calderas, O. Manero, M.F. Webster, J. Non-Newton. Fluid Mech. 222 (2015) 260–271; of α ={2, 4, 6, 8, 10}. Their experimental PAA/corn-syrup Boger fluids have been characterized and modelled with the so-called swanINNFM model through dissipative continuum-scale modelling. This facilitates the precise capture of experimental-levels of epd- data (largest epd = O(6) under α = 10 contraction-ratio and sharp corners). The swanINNFM model has already proven capable of reproducing the large excess pressure-drops reported by J.P. Rothstein, G.H. McKinley, J. Non-Newton. Fluid Mech. 98 (2001) 33–63, in their experiments ( epd = O(3) for α = 4 contraction-ratio and PS/PS Boger fluids); it is also capable of reproducing the Boger-fluid pressure-drop rise, relative to Newtonian-instance, in axisymmetric α = 4 contraction-flow, as opposed to the null rise observed in the planar counterpart reported by S. Nigen, K. Walters, J. Non-Newton. Fluid Mech., 102 (2002) 343–359. In the present study, at each contraction-ratio and under De -rise (flow-rate-increase), one may identify two main phases: i) an epd plateauing-region at low deformation-rates, and ii) a sudden epd -rise above the Newtonian unity reference- line. With elevation in contraction-ratio, the first plateaued- epd phase is elongated and the maximum epd -levels rise significantly. Such epd -elevation is captured theoretically and numerically, with counterpart rise in extensional-viscosity. In addition, this position in epd -response correlates well against trends in vortex-dynamics - correctly capturing lip-vortex appearance, lip-vortex and salient-corner vortex co-existence and coalescence, and ultimate elastic corner-vortex domination. In this respect, their presence and transitions, may themselves be linked to increased elastic effects and normal-stress response. |
| Databáze: | OpenAIRE |
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