Closure to “Discussion of ‘Free Shear Layer Behavior in Rotating Systems’” (1979, ASME J. Fluids Eng., 101, p. 120)

1979 ◽  
Vol 101 (1) ◽  
pp. 120-120
Author(s):  
P. H. Rothe ◽  
J. P. Johnston
Keyword(s):  
Shear Layer ◽  
Free Shear Layer ◽  
Rotating Systems ◽  
Layer Behavior

Free Shear Layer Behavior in Rotating Systems

1979 ◽  
Vol 101 (1) ◽  
pp. 117-120 ◽  
Author(s):  
P. H. Rothe ◽  
J. P. Johnston
Keyword(s):  
Shear Layer ◽  
Separated Flow ◽  
Reynolds Numbers ◽  
Two Dimensional ◽  
Free Shear Layer ◽  
Rotation Direction ◽  
Rotating Systems ◽  
System Rotation ◽  
Steady Rate ◽  
Extensive Flow

Experiments are reported concerning turbulent separated flow downstream of a backward-facing step in a two-dimensional channel that was rotated at a steady rate about a spanwise axis. Reattachment distance is reported as a function of Reynolds number, rotation direction and number and passage aspect ratio. Extensive flow visualization films have been produced. It is demonstrated that turbulent motions in a free shear layer may be suppressed or enhanced by system rotation according to the sense of the rotation. Two-dimensional, spanwise vortices which have been observed in the free shear layer are found to be relatively insensitive to system rotation in the stabilizing direction. These vortices are believed to be important contributors to the high rates of free shear layer entrainment, even in stationary systems at moderate Reynolds numbers.

Deformable bubbles in a free shear layer

1997 ◽  
Vol 23 (5) ◽  
pp. 977-1001 ◽  
Author(s):  
E. Loth ◽  
M. Taeibi-Rahni ◽  
G. Tryggvason
Keyword(s):  
Shear Layer ◽  
Free Shear Layer

Assessment of turbulence models using DNS data of compressible plane free shear layer flow

2021 ◽  
Vol 931 ◽  
Author(s):  
D. Li ◽  
J. Komperda ◽  
A. Peyvan ◽  
Z. Ghiasi ◽  
F. Mashayek
Keyword(s):  
Shear Layer ◽  
Compressible Flows ◽  
Eddy Viscosity ◽  
Turbulence Models ◽  
Correlation Coefficients ◽  
Free Shear Layer ◽  
Smagorinsky Model ◽  
Reynolds Analogy ◽  
Velocity Fluctuations ◽  
Scale Similarity

The present paper uses the detailed flow data produced by direct numerical simulation (DNS) of a three-dimensional, spatially developing plane free shear layer to assess several commonly used turbulence models in compressible flows. The free shear layer is generated by two parallel streams separated by a splitter plate, with a naturally developing inflow condition. The DNS is conducted using a high-order discontinuous spectral element method (DSEM) for various convective Mach numbers. The DNS results are employed to provide insights into turbulence modelling. The analyses show that with the knowledge of the Reynolds velocity fluctuations and averages, the considered strong Reynolds analogy models can accurately predict temperature fluctuations and Favre velocity averages, while the extended strong Reynolds analogy models can correctly estimate the Favre velocity fluctuations and the Favre shear stress. The pressure–dilatation correlation and dilatational dissipation models overestimate the corresponding DNS results, especially with high compressibility. The pressure–strain correlation models perform excellently for most pressure–strain correlation components, while the compressibility modification model gives poor predictions. The results of an a priori test for subgrid-scale (SGS) models are also reported. The scale similarity and gradient models, which are non-eddy viscosity models, can accurately reproduce SGS stresses in terms of structure and magnitude. The dynamic Smagorinsky model, an eddy viscosity model but based on the scale similarity concept, shows acceptable correlation coefficients between the DNS and modelled SGS stresses. Finally, the Smagorinsky model, a purely dissipative model, yields low correlation coefficients and unacceptable accumulated errors.

CFD analysis of free shear layer approximations for a pulsed air jet

2014 ◽  
Vol 43 ◽  
pp. 49-58
Author(s):  
Nawel Khaldi ◽  
Salwa Marzouk ◽  
Hatem Mhiri ◽  
Philippe Bournot
Keyword(s):  
Shear Layer ◽  
Cfd Analysis ◽  
Free Shear Layer ◽  
Air Jet

Shear-layers in magnetohydrodynamic spherical Couette flow with conducting walls

2010 ◽  
Vol 645 ◽  
pp. 145-185 ◽  
Author(s):  
A. M. SOWARD ◽  
E. DORMY
Keyword(s):  
Magnetic Field ◽  
Shear Layer ◽  
Electric Current ◽  
Current Flow ◽  
Outer Boundary ◽  
Free Shear Layer ◽  
Viscous Effects ◽  
Current Leakage ◽  
Axisymmetric Motion ◽  
Relative Conductance

We consider the steady axisymmetric motion of an electrically conducting fluid contained within a spherical shell and permeated by a centred axial dipole magnetic field, which is strong as measured by the Hartmann number M. Slow axisymmetric motion is driven by rotating the inner boundary relative to the stationary outer boundary. For M ≫ 1, viscous effects are only important in Hartmann boundary layers adjacent to the inner and outer boundaries and a free shear-layer on the magnetic field line that is tangent to the outer boundary on the equatorial plane of symmetry. We measure the ability to leak electric current into the solid boundaries by the size of their relative conductance ɛ. Since the Hartmann layers are sustained by the electric current flow along them, the current inflow from the fluid mainstream needed to feed them increases in concert with the relative conductance, because of the increasing fraction ℒ of the current inflow leaked directly into the solids. Therefore the nature of the flow is sensitive to the relative sizes of ɛ−1 and M.The current work extends an earlier study of the case of a conducting inner boundary and an insulating outer boundary with conductance ɛo = 0 (Dormy, Jault & Soward, J. Fluid Mech., vol. 452, 2002, pp. 263–291) to other values of the outer boundary conductance. Firstly, analytic results are presented for the case of perfectly conducting inner and outer boundaries, which predict super-rotation rates Ωmax of order M1/2 in the free shear-layer. Successful comparisons are made with numerical results for both perfectly and finitely conducting boundaries. Secondly, in the case of a finitely conducting outer boundary our analytic results show that Ωmax is O(M1/2) for ɛo−1 ≪ 1 ≪ M3/4, O(ɛo2/3M1/2) for 1 ≪ ɛo−1 ≪ M3/4 and O(1) for 1 ≪ M3/4 ≪ ɛo−1. On increasing ɛo−1 from zero, substantial electric current leakage into the outer boundary, ℒo ≈ 1, occurs for ɛo−1 ≪ M3/4 with the shear-layer possessing the character appropriate to a perfectly conducting outer boundary. When ɛo−1 = O(M3/4) the current leakage is blocked near the equator, and the nature of the shear-layer changes. So, when M3/4 ≪ ɛo−1, the shear-layer has the character appropriate to an insulating outer boundary. More precisely, over the range M3/4 ≪ ɛo−1 ≪ M the blockage spreads outwards, reaching the pole when ɛo−1 = O(M). For M ≪ ɛo−1 current flow into the outer boundary is completely blocked, ℒo ≪ 1.

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