5.4.3.3 Three-dimensional flow structures and helicals

2005 ◽  
pp. 373-376
Author(s):  
G. Gust
Keyword(s):  
Three Dimensional ◽  
Flow Structures ◽  
Three Dimensional Flow ◽  
Dimensional Flow

Large‐Eddy Simulation of Three‐Dimensional Flow Structures Over Wave‐generated Ripples

2021 ◽  
Author(s):  
Chuang Jin ◽  
Giovanni Coco ◽  
Rafael O. Tinoco ◽  
Pallav Ranjan ◽  
Jorge San Juan ◽  
...  
Keyword(s):  
Large Eddy Simulation ◽  
Three Dimensional ◽  
Flow Structures ◽  
Three Dimensional Flow ◽  
Dimensional Flow ◽  
Eddy Simulation ◽  
Large Eddy

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.

3-D Flow Structures Around and Fluid-Dynamic Forces Acting on a Rectangular Cylinder in Oscillatory Flow

2003 ◽  
Author(s):  
Takahiro Yasuda ◽  
Atsushi Okajima ◽  
Minoru Moriyoshi
Keyword(s):  
Oscillatory Flow ◽  
Three Dimensional ◽  
Flow Patterns ◽  
Flow Structures ◽  
Inertia Force ◽  
Water Tank ◽  
Height Ratio ◽  
Three Dimensional Flow ◽  
Dimensional Flow ◽  
Rectangular Cylinder

Three-dimensional flow structures around and fluiddynamic forces acting on a rectangular cylinder in oscillatory flow were investigated by numerical simulation using finite volume method. The computations were carried out for three kinds of cross-sections with width/height ratio (d/H) d/H = 0.6, 1.0 and 2.0 and for the amplitude of oscillating flow in the range of 2.5 ≤ the Keulegan-Carpenter number (KC) ≤ 25, the Stokes number (β) = 95. The calculated flow patterns and the drag and inertia force coefficients of Morison equation acting on the cylinder were compared with the experimental ones using a U-tube water tank. In this paper, we note how the KC number and the width/height ratio of the cylinders affect the unsteady and three-dimensional flow structures such as the “longitudinal vortices” and “transverse street” which formed in the case of a circular cylinder fixed in oscillatory flow, and how the CD and the CM values of Morison coefficients change corresponding to the change of the behavior of the flow patterns. Furthermore the relationship between spanwise correlation coefficient of the transverse force R(x3), where x3 is the spanwise position from the bottom of the cylinder, and three-dimensional vortex structures were investigated.

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