Three-dimensional flow structures and evolution of the leading-edge vortices on a flapping wing

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.

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Three-dimensional flow and heat transfer calculations of film cooling at the leading edge of a symmetrical turbine blade model

International Journal of Heat and Fluid Flow ◽

10.1016/s0142-727x(00)00084-9 ◽

2001 ◽

Vol 22 (2) ◽

pp. 113-122 ◽

Cited By ~ 48

Author(s):

D. Lakehal ◽

G.S. Theodoridis ◽

W. Rodi

Keyword(s):

Heat Transfer ◽

Turbine Blade ◽

Film Cooling ◽

Three Dimensional ◽

Leading Edge ◽

Three Dimensional Flow ◽

Dimensional Flow ◽

Flow And Heat Transfer ◽

Blade Model

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Modelling three-dimensional flow structures and patterns of boundary shear stress in a natural pool-riffle sequence

Earth Surface Processes and Landforms ◽

10.1002/esp.210 ◽

2001 ◽

Vol 26 (5) ◽

pp. 553-576 ◽

Cited By ~ 121

Author(s):

D. J. Booker ◽

D. A. Sear ◽

A. J. Payne

Keyword(s):

Shear Stress ◽

Three Dimensional ◽

Flow Structures ◽

Three Dimensional Flow ◽

Dimensional Flow ◽

Boundary Shear ◽

Boundary Shear Stress

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Experimental Study on the Three-Dimensional Flow Within a Compressor Cascade With Tip Clearance: Part I—Velocity and Pressure Fields

Journal of Turbomachinery ◽

10.1115/1.2929270 ◽

1993 ◽

Vol 115 (3) ◽

pp. 435-443 ◽

Cited By ~ 40

Author(s):

S. Kang ◽

C. Hirsch

Keyword(s):

Three Dimensional ◽

Leading Edge ◽

Surface Flow ◽

Tip Clearance ◽

Tip Vortex ◽

Compressor Cascade ◽

Three Dimensional Flow ◽

Tip Leakage Vortex ◽

Tip Leakage ◽

Dimensional Flow

Experimental results from a study of the three-dimensional flow in a linear compressor cascade with stationary endwall at design conditions are presented for tip clearance levels of 1.0, 2.0, and 3.3 percent of chord, compared with the no-clearance case. In addition to five-hole probe measurements, extensive surface flow visualizations are conducted. It is observed that for the smaller clearance cases a weak horseshoe vortex forms in the front of the blade leading edge. At all the tip gap cases, a multiple tip vortex structure with three discrete vortices around the midchord is found. The tip leakage vortex core is well defined after the midchord but does not cover a significant area in traverse planes. The presence of the tip leakage vortex results in the passage vortex moving close to the endwall and the suction side.

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