scholarly journals Three-dimensional flow simulations for polymer extrudate swell out of slit dies from low to high aspect ratios

2019 ◽  
Vol 31 (9) ◽  
pp. 093103 ◽  
Author(s):  
Dahang Tang ◽  
Flavio H. Marchesini ◽  
Ludwig Cardon ◽  
Dagmar R. D’hooge
Keyword(s):  
Three Dimensional ◽  
Extrudate Swell ◽  
Three Dimensional Flow ◽  
Flow Simulations ◽  
Dimensional Flow ◽  
Aspect Ratios

Three-dimensional instabilities in oscillatory flow past elliptic cylinders

2016 ◽  
Vol 798 ◽  
pp. 371-397 ◽  
Author(s):  
José P. Gallardo ◽  
Helge I. Andersson ◽  
Bjørnar Pettersen
Keyword(s):  
Circular Cylinder ◽  
Flow Direction ◽  
Three Dimensional ◽  
Circular Cylinders ◽  
Flow Structures ◽  
Three Dimensional Flow ◽  
Elliptical Cross ◽  
Dimensional Flow ◽  
Aspect Ratios ◽  
Flow Past

We investigate the early development of instabilities in the oscillatory viscous flow past cylinders with elliptic cross-sections using three-dimensional direct numerical simulations. This is a classical hydrodynamic problem for circular cylinders, but other configurations have received only marginal attention. Computed results for some different aspect ratios ${\it\Lambda}$ from 1 : 1 to 1 : 3, all with the major axis of the ellipse aligned in the main flow direction, show good qualitative agreement with Hall’s stability theory (J. Fluid Mech., vol. 146, 1984, pp. 347–367), which predicts a cusp-shaped curve for the onset of the primary instability. The three-dimensional flow structures for aspect ratios larger than 2 : 3 resemble those of a circular cylinder, whereas the elliptical cross-section with the lowest aspect ratio of 1 : 3 exhibits oblate rather than tubular three-dimensional flow structures as well as a pair of counter-rotating spanwise vortices which emerges near the tips of the ellipse. Contrary to a circular cylinder, instabilities for an elliptic cylinder with sufficiently high eccentricity emerge from four rather than two different locations in accordance with the Hall theory.

Unsteady and Three-Dimensional Flow Simulations in the Human Aorta

2001 ◽  
pp. 233-238
Author(s):  
Nader Shahcheraghi ◽  
Harry A. Dwyer ◽  
Angela Y. Cheer ◽  
Thomas Rutaganira ◽  
Abdul Barakat
Keyword(s):  
Three Dimensional ◽  
Human Aorta ◽  
Three Dimensional Flow ◽  
Flow Simulations ◽  
Dimensional Flow
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