Higher-order approximation for free shear layers in almost rigid rotations

1975 ◽  
Vol 69 (1) ◽  
pp. 191-195 ◽  
Author(s):  
L. Pamela Cook ◽  
G. S. S. Ludford
Keyword(s):  
Angular Velocity ◽  
Order Approximation ◽  
Shear Layers ◽  
Higher Order ◽  
Rigid Rotation ◽  
Free Shear Layer ◽  
Curvature Effects ◽  
Parallel Disks ◽  
Free Shear Layers ◽  
Theory And Experiment

The free shear layer stemming from a discontinuity in angular velocity at either of two parallel disks in almost rigid rotation with fluid between is re-examined. The sole discrepancy between theory and experiment is unaffected by higher-order approximation unless curvature effects are included, when it is reduced.

The effect of initial conditions on the development of a free shear layer

1966 ◽  
Vol 26 (2) ◽  
pp. 225-236 ◽  
Author(s):  
P. Bradshaw
Keyword(s):  
Turbulent Mixing ◽  
Initial Conditions ◽  
Mixing Layer ◽  
Initial Boundary ◽  
Shear Layers ◽  
Free Shear Layer ◽  
Turbulent Mixing Layer ◽  
Free Shear Layers ◽  
Final Approach ◽  
Reynolds Number Effects

The distance between the separation point and the final approach to a fully developed turbulent mixing layer is found to be of the order of a thousand times the momentum-deficit thickness of the initial boundary layer, whether the latter be laminar or turbulent. There are correspondingly large shifts in the virtual origin of the mixing layer, resulting in spurious Reynolds-number effects which cause considerable difficulties in tests of model jets or blunt-based bodies, and which are probably responsible for the disagreements over the influence of Mach number on the development of free shear layers. These effects are explained.

Spectral broadening and flow randomization in free shear layers

2012 ◽  
Vol 706 ◽  
pp. 431-469 ◽  
Author(s):  
Xuesong Wu ◽  
Feng Tian
Keyword(s):  
Phase Modulation ◽  
Numerical Solutions ◽  
Nonlinear Evolution ◽  
Present Theory ◽  
Shear Layers ◽  
Evolution System ◽  
Free Shear Layer ◽  
Spectral Broadening ◽  
Free Shear Layers ◽  
Combination Frequencies

AbstractIt has been observed experimentally that when a free shear layer is perturbed by a disturbance consisting of two waves with frequencies ${\omega }_{0} $ and ${\omega }_{1} $, components with the combination frequencies $(m{\omega }_{0} \pm n{\omega }_{1} )$ ($m$ and $n$ being integers) develop to a significant level thereby causing flow randomization. This spectral broadening process is investigated theoretically for the case where the frequency difference $({\omega }_{0} \ensuremath{-} {\omega }_{1} )$ is small, so that the perturbation can be treated as a modulated wavetrain. A nonlinear evolution system governing the spectral dynamics is derived by using the non-equilibrium nonlinear critical layer approach. The formulation provides an appropriate mathematical description of the physical concepts of sideband instability and amplitude–phase modulation, which were suggested by experimentalists. Numerical solutions of the nonlinear evolution system indicate that the present theory captures measurements and observations rather well.

Separation and the Taylor-column problem for a hemisphere

1974 ◽  
Vol 66 (4) ◽  
pp. 767-789 ◽  
Author(s):  
J. D. A. Walker ◽  
K. Stewartson
Keyword(s):  
Angular Velocity ◽  
Incompressible Fluid ◽  
Viscous Incompressible Fluid ◽  
Shear Layers ◽  
Constant Angular Velocity ◽  
Vertical Shear ◽  
Rossby Number ◽  
Ekman Number ◽  
Free Shear Layers ◽  
Taylor Column

A layer of viscous incompressible fluid is confined between two horizontal plates which rotate rapidly in their own plane with a constant angular velocity. A hemisphere has its plane face joined to the lower plate and when a uniform flow is forced past such an obstacle, a Taylor column bounded by thin detached vertical shear layers forms. The linear theory for this problem, wherein the Rossby number ε is set equal to zero on the assumption that the flow is slow, is examined in detail. The nonlinear modifications of the shear layers are then investigated for the case when ε ∼ E½, where E is the Ekman number. In particular, it is shown that provided that the Rossby number is large enough separation occurs in the free shear layers. The extension of the theory to flow past arbitrary spheroids is indicated.

An Enhanced Flow Visualization Technique for Planar Free Shear Layers

AIAA Journal ◽  
1984 ◽  
Vol 22 (3) ◽  
pp. 439-441 ◽  
Author(s):  
Y. Hsia ◽  
D. Baganoff ◽  
A. Krothapalli ◽  
K. Karamcheti
Keyword(s):  
Flow Visualization ◽  
Shear Layers ◽  
Visualization Technique ◽  
Free Shear Layers
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