On the Free Shear Layer Downstream of a Backstep in Supersonic Flow

1973 ◽  
Vol 95 (3) ◽  
pp. 361-366 ◽  
Author(s):  
P. M. Gerhart ◽  
H. H. Korst
Keyword(s):  
Experimental Data ◽  
Shear Layer ◽  
Reasonable Agreement ◽  
Mixing Layer ◽  
Outer Region ◽  
Initial Boundary ◽  
Supersonic Stream ◽  
Free Shear Layer ◽  
Rate Of Spread ◽  
Technique Comparison

The free shear layer downstream of a backstep immersed in a supersonic stream is analyzed. The effects of the initial boundary layer and the expansion at the step corner are taken into account. The shear layer is divided into two distinct regions, an outer rotational nondissipative region and an inner dissipative locally similar mixing region which spreads both into the rotational outer region and the wake. The dynamic characteristics of the shear layer including the rate of spread of the inner mixing layer and the location of the jet boundary streamline are determined by an integral technique. Comparison of predicted velocity profiles with experimental data shows reasonable agreement.

Phase decorrelation of coherent structures in a free shear layer

1991 ◽  
Vol 230 ◽  
pp. 319-337 ◽  
Author(s):  
Chih-Ming Ho ◽  
Yitshak Zohar ◽  
Judith K. Foss ◽  
Jeffrey C. Buell
Keyword(s):  
Shear Layer ◽  
Coherent Structures ◽  
Physical Mechanism ◽  
Mixing Layer ◽  
Single Frequency ◽  
Free Shear Layer ◽  
Phase Jitter ◽  
Laminar Mixing

The vortices near the origin of an initially laminar mixing layer have a single frequency with a well-defined phase; i.e. there is little phase jitter. Further downstream, however, the phase jitter increases suddenly. Even when the flow is forced, this same transition is observed. The forcing partially loses its influence because of the decorrelation of the phase between the forcing signal and the passing coherent structures. In the present investigation, this phenomenon is documented and the physical mechanism responsible for the phase decorrelation is identified.

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.

A Transformation for the Numerical Solution of Two-Dimensional Free Mixing Flow Problems

1973 ◽  
Vol 95 (1) ◽  
pp. 103-107
Author(s):  
R. J. Elassar
Keyword(s):  
Experimental Data ◽  
Boundary Layer ◽  
Difference Scheme ◽  
Mixing Layer ◽  
Two Dimensional ◽  
Coordinate Plane ◽  
Free Shear Layer ◽  
Layer Width ◽  
Boundary Layer Equations ◽  
Flow Problems

A coordinate transformation which removes the variation of the mixing layer width is introduced. The boundary layer equations are then solved in the new coordinate plane using a multilevel difference scheme. The calculated results for two-dimensional symmetric mixing and free shear layer flows for turbulent flow are compared with experimental data and with other solutions.

A turbulent mixing layer constrained by a solid surface. Part 2. Measurements in the wall-bounded flow

1984 ◽  
Vol 139 ◽  
pp. 347-361 ◽  
Author(s):  
D. H. Wood ◽  
P. Bradshaw
Keyword(s):  
Shear Stress ◽  
Shear Layer ◽  
Normal Stress ◽  
Mixing Layer ◽  
Turbulent Energy ◽  
Free Shear Layer ◽  
Calculation Methods ◽  
Turbulent Mixing Layer ◽  
High Reynolds ◽  
The Individual

The single- and two-point measurements made in a high-Reynolds-number single-stream mixing layer growing to encounter a wind-tunnel floor on its high-velocity side that were described by Wood & Bradshaw (1982) have been extended to the wall-bounded flow. It is shown that the expected large amplification of the normal-stress components in the plane of the wall does not occur until after the mixing layer reaches the surface. There is some evidence that the double-roller component of the large-eddy structure of the original free shear layer is being re-established in the wall-bounded flow after having been stretched and weakened by the initial effect of the wall. The triple-product terms appearing in the turbulent-energy and shear-stress equations are altered in a way that cannot be reproduced by models used in current calculation methods. It appears that all the pressure-fluctuation terms in the individual normal-stress and shear-stress transport equations respond in a non-monotonic manner to the imposition of the wall. The implications for calculation methods suitable for predicting the change from an initially unaffected free shear layer to a wall-bounded flow are discussed.

A numerical investigation into the effects of compressibility and total enthalpy difference on the development of a laminar free shear layer

1971 ◽  
Vol 50 (4) ◽  
pp. 785-799 ◽  
Author(s):  
Peter W. Carpenter
Keyword(s):  
Boundary Layer ◽  
Shear Layer ◽  
Free Stream ◽  
Equations Of Motion ◽  
Initial Boundary ◽  
Free Shear Layer ◽  
Total Enthalpy ◽  
Enthalpy Difference ◽  
Coefficient Of Viscosity ◽  
Boundary Layer Profile

A method is presented for integrating numerically the equations of motion for a compressible free shear layer developing from a boundary-layer profile of arbitrary shape. Sutherland's law is used to determine the coefficient of viscosity and the Prandtl number is taken as 0·72. Calculated results are reported for free-stream Mach numbers ranging from 0 to 10 and for stagnation-enthalpy ratios ranging from 0 to 5·0. The effects of varying the initial boundary-layer profile and of a discontinuity in temperature at the origin are also studied. The results include graphs showing the development of dividing-streamline velocity, of local Nusselt number, and of dividing-streamline location.

scholarly journals NUMERICAL SIMULATION OF SECONDARY CIRCULATION IN THE LEE OF HEADLANDS

1984 ◽  
Vol 1 (19) ◽  
pp. 162 ◽  
Author(s):  
Roger A. Falconer ◽  
Eric Wolanski ◽  
Lida Mardapitta-Hadjipandeli
Keyword(s):  
Numerical Simulation ◽  
Numerical Model ◽  
Shear Layer ◽  
Eddy Viscosity ◽  
Mixing Layer ◽  
Secondary Circulation ◽  
Shear Stresses ◽  
Free Shear Layer ◽  
Lateral Velocity ◽  
Lateral Mixing

The paper gives details of a study to refine and further develop a two-diirensional depth average numerical model to predict more accurately the eddy shedding features often observed in the lees of headlands. Details are given of the application of the model to Rattray Island, just east of Bowen, North Queensland, Australia, where the strong tidal currents flowing past the island give rise to separation and hydrodynamic circulation in the lee of the island. In the governing differential equations used to predict the secondary circulation, particular emphasis has been placed on the representation of the shear stresses associated with the free shear lateral mixing layer in the downstream wake of the headland. Use of an experimentally determined lateral velocity distribution in the shear layer, together with an eddy viscosity approach, have led to the use of a relatively simple turbulence model, including both free shear layer and bed generated turbulence. A comparison of the numerically predicted velocities with corresponding field measured results around Rattray Island has shown an encouraging agreement, although there were some differences. The main difference between both sets of results was that the vorticity strength of the secondary circulation predicted in the numerical model was noticeably less than that measured in the field.

On the Correlation of Analytical and Experimental Free Shear Layer Similarity Profiles by Spread Rate Parameters

1971 ◽  
Vol 93 (3) ◽  
pp. 377-382 ◽  
Author(s):  
H. H. Korst ◽  
W. L. Chow
Keyword(s):  
Similarity Solutions ◽  
Free Shear Layer ◽  
Spread Rate ◽  
Empirical Parameter ◽  
Jet Mixing ◽  
Free Jet ◽  
Rate Of Spread ◽  
Profile Matching ◽  
Entire Flow ◽  
Definition Of

Analysis of turbulent isobaric free jet mixing normally requires the introduction of suitably formulated viscosity models. Similarity solutions can then be established which contain one empirical parameter. Such a parameter, however, not only describes the rate of spread of the mixing region, but also determines in detail the structure of the entire flow field. It is pointed out that this “spread rate parameter” σ depends on the selected viscosity model, the method of theoretical analysis, and the definition of profile matching. A comparison of different theoretical profiles can only be accomplished after these factors are properly recognized. Any attempts to contribute to the rather incomplete knowledge of the spread parameter must be cognizant of its dependence on the theoretical mixing model employed. This paper also establishes theoretical relations which allow comparison and consolidation of information based on different analytical concepts.

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