The reattachment and relaxation of a turbulent shear layer

1972 ◽  
Vol 52 (1) ◽  
pp. 113-135 ◽  
Author(s):  
P. Bradshaw ◽  
F. Y. F. Wong
Keyword(s):  
Boundary Layer ◽  
Shear Layer ◽  
Flow Region ◽  
Turbulent Shear ◽  
Length Scale ◽  
Low Speed ◽  
Turbulent Shear Layer ◽  
Recirculating Flow ◽  
Speed Flow ◽  
Complicated Nature

Existing experiments on the low-speed flow downstream of steps and fences, and some new measurements downstream of a backward-facing step, are used to demonstrate the complicated nature of the flow in the reattachment region and its effect on the slow non-monotonic return of the shear layer to the ordinary boundary-layer state. A key feature of the flow is found to be the splitting of the shear layer at reattachment, where part of the flow is deflected upstream into the recirculating flow region to supply the entrainment; the part of the flow that continues downstream suffers a pronounced decrease in eddy length scale, evidently because the larger eddies are torn in two. This phenomenon will occur in all cases where a shear layer reattaches after a prolonged region of separation, either at low speed or in supersonic flow. For simplicity, the discussion in the present paper is confined to low-speed flows.

Turbulent Shear Layer Re-Attachment with Special Emphasis on the Base Pressure Problem

1964 ◽  
Vol 15 (3) ◽  
pp. 247-280 ◽  
Author(s):  
H. McDonald
Keyword(s):  
Boundary Layer ◽  
Shear Layer ◽  
Shape Parameter ◽  
Separated Flow ◽  
Initial Boundary ◽  
Base Pressure ◽  
Turbulent Shear ◽  
Turbulent Shear Layer ◽  
Blunt Trailing Edge ◽  
A Value

SummaryAn analysis is presented which enables the boundary-layer thickness parameters of a re-attaching shear layer to be determined when the free-stream flow upstream of the base is supersonic, the base pressure is known, and die initial boundary layer is turbulent. The application of this analysis to some experimental results, on the flow behind blunt-trailing-edge wings and over a back-step where both the base pressure and the initial boundary layer are known, would appear to indicate that the re-attached profile could be specified by one parameter, namely the transformed shape parameter, the transformation used being a turbulent analogue of the well-known Stewartson-Illingworth transformation of the laminar boundary layer and where the shape parameter is defined as the ratio of boundary-layer displacement to momentum thickness. By adopting a value of the shape parameter in advance, it is possible to use the analysis to determine the base pressure by an iterative process and so, on this basis, it is suggested that this analysis is used to replace the existing recompression criterion of the Chapman-Korst model of separated flow which aims to predict base pressures and is known to be capable of improvement.As part of this investigation, an improvement had to be made to the existing compressible turbulent shear layer velocity profiles of Korst and others and this was achieved by means of the compressibility transformation.

Investigation of a Reattaching Turbulent Shear Layer: Flow Over a Backward-Facing Step

1980 ◽  
Vol 102 (3) ◽  
pp. 302-308 ◽  
Author(s):  
J. Kim ◽  
S. J. Kline ◽  
J. P. Johnston
Keyword(s):  
Boundary Layer ◽  
Shear Layer ◽  
Eddy Viscosity ◽  
Flow Characteristics ◽  
Turbulent Shear ◽  
Turbulence Structure ◽  
Backward Facing Step ◽  
Turbulent Shear Layer ◽  
Separated Shear Layer ◽  
Layer Flow

Incompressible flow over a backward-facing step is studied in order to investigate the flow characteristics in the separated shear-layer, the reattachment zone, and the redeveloping boundary layer after reattachment. Two different step-heights are used: h/δs = 2.2 and h/δs = 3.3. The boundary layer at separation is turbulent for both cases. Turbulent intensities and shear stress reach maxima in the reattachment zone, followed by rapid decay near the surface after reattachment. Downstream of reattachnent, the flow returns very slowly to the structure of an ordinary turbulent boundary layer. In the reattached layer the conventional normalization of outerlayer eddy viscosity by U∞ δ* does not collapse the data. However, it was found that normalization by U∞ (δ − δ*) does collapse the data to within ± 10% of a single curve as far downstream as x/xR ≈ 2, the last data station. This result illustrates the strong downstream persistence of the energetic turbulence structure created in the separated shear layer.

Features of a reattaching turbulent shear layer in divergent channelflow

AIAA Journal ◽  
1985 ◽  
Vol 23 (2) ◽  
pp. 163-171 ◽  
Author(s):  
David M. Driver ◽  
H. Lee Seegmiller
Keyword(s):  
Shear Layer ◽  
Turbulent Shear ◽  
Turbulent Shear Layer

Turbulence structure of a reattaching mixing layer

1981 ◽  
Vol 110 ◽  
pp. 171-194 ◽  
Author(s):  
C. Chandrsuda ◽  
P. Bradshaw
Keyword(s):  
Boundary Layer ◽  
Shear Stress ◽  
Reynolds Shear Stress ◽  
Mixing Layer ◽  
Three Dimensional ◽  
Flow Region ◽  
Turbulent Energy ◽  
Turbulence Structure ◽  
Hot Wire ◽  
Recirculating Flow

Hot-wire measurements of second- and third-order mean products of velocity fluctuations have been made in the flow behind a backward-facing step with a thin, laminar boundary layer at the top of the step. Measurements extend to a distance of about 12 step heights downstream of the step, and include parts of the recirculating-flow region: approximate limits of validity of hot-wire results are given. The Reynolds number based on step height is about 105, the mixing layer being fully turbulent (fully three-dimensional eddies) well before reattachment, and fairly close to self-preservation in contrast to the results of some previous workers. Rapid changes in turbulence quantities occur in the reattachment region: Reynolds shear stress and triple products decrease spectacularly, mainly because of the confinement of the large eddies by the solid surface. The terms in the turbulent energy and shear stress balances also change rapidly but are still far from the self-preserving boundary-layer state even at the end of the measurement region.

Simulation of inviscid vortex-stretched turbulent shear-layer flow

AIAA Journal ◽  
1986 ◽  
Vol 24 (4) ◽  
pp. 680-682
Author(s):  
Arthur Rizzi ◽  
Charles J. Purcell
Keyword(s):  
Shear Layer ◽  
Turbulent Shear ◽  
Turbulent Shear Layer ◽  
Layer Flow
Sign in / Sign up

Export Citation Format

Share Document