Predictions of turbulent mixing in axisymmetric compressible shear layers

AIAA Journal ◽  
1992 ◽  
Vol 30 (6) ◽  
pp. 1529-1536 ◽  
Author(s):  
K. Viswanathan ◽  
P. J. Morris
Keyword(s):  
Turbulent Mixing ◽  
Shear Layers

Free Turbulent Shear Layers on Plug Nozzles

1977 ◽  
Vol 99 (2) ◽  
pp. 301-308
Author(s):  
C. J. Scott ◽  
D. R. Rask
Keyword(s):  
Turbulent Mixing ◽  
Schmidt Number ◽  
Error Function ◽  
Mixing Layer ◽  
Shear Layers ◽  
Turbulent Shear ◽  
Gas Chromatograph ◽  
Plug Nozzle ◽  
Turbulent Schmidt Number ◽  
Plug Nozzles

Two-dimensional, free, turbulent mixing between a uniform stream and a cavity flow is investigated experimentally in a plug nozzle, a geometry that generates idealized mixing layer conditions. Upstream viscous layer effects are minimized through the use of a sharp-expansion plug nozzle. Experimental velocity profiles exhibit close agreement with both similarity analyses and with error function predictions. Refrigerant-12 was injected into the cavity and concentration profiles were obtained using a gas chromatograph. Spreading factors for momentum and mass were determined. Two methods are presented to determine the average turbulent Schmidt number. The relation Sct = Sc is suggested by the data for Sc < 2.0.

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.

Effects of Turbulence on the Pressure Distribution Around a Square Cylinder and Possibility of Reduction

1983 ◽  
Vol 105 (2) ◽  
pp. 140-145 ◽  
Author(s):  
K. C. S. Kwok
Keyword(s):  
Pressure Distribution ◽  
Turbulent Mixing ◽  
Peak Pressure ◽  
Shear Layers ◽  
Transverse Force ◽  
Force Characteristic ◽  
Square Cylinder ◽  
Pressure Coefficients ◽  
Prismatic Structure ◽  
Scale Turbulence

When a prismatic structure is subjected to air flow, especially at small angle of wind incidence, the separated shear layers may reattach onto the streamwise surface. The turbulent mixing in the shear layers and the extrainment of fluid results in highly fluctuating and strongly negative pressures under the reattaching shear layers. Wind tunnel tests were carried out to determine the pressure distribution around a square cylinder. It was found that an increase in turbulence, in particular fine scale turbulence, significantly altered the pressure distribution, the transverse force characteristic, and hence the galloping behavior of the square cylinder. When small vanes were fitted to the corners of the cylinder, and by maintaining a vent between the vane and the corner, the magnitude of the negative mean and peak pressure coefficients under the shear layer were substantially reduced.

scholarly journals The mixing transition in turbulent flows

2000 ◽  
Vol 409 ◽  
pp. 69-98 ◽  
Author(s):  
PAUL E. DIMOTAKIS
Keyword(s):  
Reynolds Number ◽  
Turbulent Flow ◽  
Turbulent Flows ◽  
Turbulent Mixing ◽  
Spatial Scales ◽  
Relative Magnitude ◽  
Shear Layers ◽  
Outer Scale ◽  
Flow Phenomena ◽  
Fully Developed Turbulent Flow

Data on turbulent mixing and other turbulent-flow phenomena suggest that a (mixing) transition, originally documented to occur in shear layers, also occurs in jets, as well as in other flows and may be regarded as a universal phenomenon of turbulence. The resulting fully-developed turbulent flow requires an outer-scale Reynolds number of Re = Uδ/v [gsim ] 1–2 × 104, or a Taylor Reynolds number of ReT = u′ λT/v [gsim ] 100–140, to be sustained. A proposal based on the relative magnitude of dimensional spatial scales is offered to explain this behaviour.

Case studies on turbulence in different tropopause folds

2021 ◽  
Author(s):  
Jens Söder ◽  
Christoph Zülicke ◽  
Michael Gerding ◽  
Franz-Josef Lübken
Keyword(s):  
Shear Layer ◽  
Turbulent Mixing ◽  
Weather Prediction ◽  
Shear Zones ◽  
Shear Layers ◽  
Mixing Processes ◽  
Exchange Processes ◽  
Upper Level ◽  
Upper Level Jet ◽  
Ageostrophic Circulation

&lt;p&gt;Tropopause folds are known as areas of enhanced stratosphere-troposphere exchange. These exchange processes are governed by turbulent mixing in the upper-tropospheric and lower-stratospheric shear zones around the tropopause jet. Since the 1970s, turbulence is also predicted to enhance the ageostrophic circulation around the jet, which leads to the formation of the tropopause fold in an upper-level jet-front system. This claim was recently confirmed by a numerical weather prediction study using the ECMWF-IFS.&lt;/p&gt;&lt;p&gt;With our balloon-borne turbulence measuring instrument LITOS, we recently sounded a deep and a medium tropopause fold with astonishing results: in both cases, the strength of turbulence in the lower stratospheric shear layer was three orders of magnitude higher compared to the upper tropospheric shear layer, reaching &lt;em&gt;severe&lt;/em&gt; turbulence strengths in the deep-fold case. This has not been reported before, potentially because hardly any observational turbulence study covering both shear layers exists in the literature. In our study, we also quantitatively compare turbulence induced PV changes with PV profiles from the IFS and assess the meteorological situation using further IFS data. Additionally, we investigate mixing processes from tracer-tracer correlations of ozone and water vapour along the flight track of our instrument.&lt;/p&gt;

Hairpin vortices and highly elongated flow structures in a stably stratified shear layer

2019 ◽  
Vol 878 ◽  
pp. 37-61
Author(s):  
Tomoaki Watanabe ◽  
James J. Riley ◽  
Koji Nagata ◽  
Keigo Matsuda ◽  
Ryo Onishi
Keyword(s):  
Turbulent Mixing ◽  
Reynolds Numbers ◽  
Shear Layers ◽  
Flow Structures ◽  
Late Time ◽  
Large Contribution ◽  
Turbulent Structures ◽  
Hairpin Vortices ◽  
Shear Parameter ◽  
O 10

Turbulent structures in stably stratified shear layers are studied with direct numerical simulation. Flow visualization confirms the existence of hairpin vortices and highly elongated structures with positive and negative velocity fluctuations, whose streamwise lengths divided by the layer thickness are $O(10^{0})$ and $O(10^{1})$, respectively. The flow at the wavelength related to these structures makes a large contribution to turbulent kinetic energy. These structures become prominent in late time, but with small buoyancy Reynolds numbers indicating suppression of turbulent mixing. Active turbulent mixing associated with the hairpin vortices, however, does occur. The structures and the vertical profile of the integral shear parameter show connections between stable stratified shear layers and wall-bounded shear flows.

Turbulent mixing in plane and axisymmetric shear layers

1990 ◽  
Author(s):  
PHILIP MORRIS ◽  
M. GIRIDHARAN ◽  
K. VISWANATHAN
Keyword(s):  
Turbulent Mixing ◽  
Shear Layers ◽  
Axisymmetric Shear

Turbulent mixing in uniform channels of irregular cross-section

1994 ◽  
Vol 32 (1) ◽  
pp. 67-86 ◽  
Author(s):  
R. I. Nokes ◽  
G. O. Hughes
Keyword(s):  
Cross Section ◽  
Turbulent Mixing
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