scholarly journals Effects of moderate Reynolds numbers on subsonic round jets with highly disturbed nozzle-exit boundary layers

2012 ◽  
Vol 24 (10) ◽  
pp. 105107 ◽  
Author(s):  
Christophe Bogey ◽  
Olivier Marsden ◽  
Christophe Bailly
Keyword(s):  
Boundary Layers ◽  
Nozzle Exit ◽  
Reynolds Numbers ◽  
Round Jets ◽  
Exit Boundary

Effects of Disturbed Nozzle-exit Boundary Layers on Acoustic Waves from Ideally-expanded Supersonic Jet

2016 ◽  
Author(s):  
Taku Nonomura ◽  
Akira Oyama ◽  
Kozo Fujii ◽  
Koichi Morihira ◽  
Gabriel Pichon ◽  
...  
Keyword(s):  
Boundary Layers ◽  
Nozzle Exit ◽  
Acoustic Waves ◽  
Supersonic Jet ◽  
Exit Boundary

Influence of Initial Conditions at Nozzle Section on Flow Structure and Instability of Plane Jet

2008 ◽  
Vol 3 (3) ◽  
pp. 14-33
Author(s):  
Grigory V. Kozlov ◽  
Genrich R. Grek ◽  
Aleksandr M. Sorokin ◽  
Yuriy A. Litvinenko
Keyword(s):  
Nozzle Exit ◽  
Initial Conditions ◽  
Plane Channel ◽  
Reynolds Numbers ◽  
Sine Wave ◽  
Smoke Visualization ◽  
Round Jets ◽  
Streaky Structures ◽  
The Right ◽  
Plane Jet

Experimental data concerning the influence of initial conditions at the nozzle exit on the structure and development characteristics of plane jet are reported. Features in the development of laminar and turbu-lent round jets emanating from variously elongated nozzles at identical Reynolds numbers are revealed. Smoke visualization pictures obtained for jets formed under different initial conditions (with different distributions of mean and pulsating flow velocities at the nozzle exit), influence of acoustic and interac-tion of streaky structures with vortex trail of laminar plane jet are discussed. It is established that, the laminar and turbulent jet on an output of the plane channel of Hagen-Poiseuille undergoes sine wave os-cillations, as a single whole. It is established that, the symmetric mode of instability of a laminar plane jet are suppressed asymmetrical. It is shown that, interaction of the streaky structures generated on one side of plane nozzle, with vortices of a laminar plane jet with a parabolic velocity profile leads to appearance of Λ- or Ω-vortices on vortices of a vortex trail, on the right as well as on the left side of the nozzle.

scholarly journals An Experimental Investigation of Nozzle-Exit Boundary Layers of Highly Heated Free Jets

1992 ◽  
Vol 114 (2) ◽  
pp. 469-475
Author(s):  
J. Lepicovsky
Keyword(s):  
Boundary Layer ◽  
Experimental Investigation ◽  
Reynolds Number ◽  
Boundary Layers ◽  
Laminar Boundary Layer ◽  
Nozzle Exit ◽  
Total Pressure ◽  
Free Jets ◽  
Exit Boundary ◽  
Mach Numbers

An experimental investigation of the effects of nozzle operating conditions on the development of nozzle-exit boundary layers of highly heated air free jets is reported in this paper. The total pressure measurements in the nozzle-exit boundary layer were obtained at a range of jet Mach numbers from 0.1 to 0.97 and jet total temperatures up to 900 K. The analysis of results shows that the nozzle-exit laminar boundary-layer development depends only on the nozzle-exit Reynolds number. For the nozzle-exit turbulent boundary layer, however, it appears that the effects of the jet total temperature on the boundary-layer integral characteristics are independent from the effect of the nozzle-exit Reynolds number. This surprising finding has not yet been reported. Further, laminar boundary-layer profiles were compared with the Pohlhausen solution for a flat-wall converging channel and an acceptable agreement was found only for low Reynolds numbers. For turbulent boundary layers, the dependence of the shape factor on relative Mach numbers at a distance of one momentum thickness from the nozzle wall resembles Spence’s prediction. Finally, the calculated total pressure loss coefficient was found to depend on the nozzle-exit Reynolds number for the laminar nozzle-exit boundary layer, while for the turbulent exit boundary layer this coefficient appears to be constant.

scholarly journals An Experimental Investigation of Nozzle-Exit Boundary Layers of Highly Heated Free Jets

1990 ◽  
Author(s):  
J. Lepicovsky
Keyword(s):  
Boundary Layer ◽  
Experimental Investigation ◽  
Reynolds Number ◽  
Boundary Layers ◽  
Laminar Boundary Layer ◽  
Nozzle Exit ◽  
Total Pressure ◽  
Free Jets ◽  
Exit Boundary ◽  
Mach Numbers

An experimental investigation of the effects of nozzle operating conditions on the development of nozzle-exit boundary layers of highly heated air free jets is reported in this paper. The total pressure measurements in the nozzle-exit boundary layer were obtained at a range of jet Mach numbers from 0.1 to 0.97 and jet total temperatures up to 900 K. The analysis of results shows that the nozzle-exit laminar boundary-layer development depends only on the nozzle-exit Reynolds number. For the nozzle-exit turbulent boundary layer, however, it appears that the effects of the jet total temperature on the boundary-layer integral characteristics are independent from the effect of the nozzle-exit Reynolds number. This surprizing finding has not yet been reported. Further, laminar boundary-layer profiles were compared with the Pohlhausen solution for a flat-wall converging channel and an acceptable agreement was found only for low Reynolds numbers. For turbulent boundary layers, the dependence of the shape factor on relative Mach numbers at a distance of one momentum thickness from the nozzle wall resembles Spence’s prediction. Finally, the calculated total pressure loss coefficient was found to depend on the nozzle-exit Reynolds number for the laminar nozzle-exit boundary layer, while for the turbulent exit boundary layer this coefficient appears to be constant.

Essential Ingredients for the Computation of Steady and Unsteady Blade Boundary Layers

1991 ◽  
Vol 113 (4) ◽  
pp. 608-616 ◽  
Author(s):  
H. M. Jang ◽  
J. A. Ekaterinaris ◽  
M. F. Platzer ◽  
T. Cebeci
Keyword(s):  
Boundary Layer ◽  
Boundary Layers ◽  
Stokes Equations ◽  
Inviscid Flow ◽  
Reynolds Numbers ◽  
Navier Stokes ◽  
Transitional Region ◽  
Low Reynolds Numbers ◽  
Flow Equations ◽  
Low Reynolds

Two methods are described for calculating pressure distributions and boundary layers on blades subjected to low Reynolds numbers and ramp-type motion. The first is based on an interactive scheme in which the inviscid flow is computed by a panel method and the boundary layer flow by an inverse method that makes use of the Hilbert integral to couple the solutions of the inviscid and viscous flow equations. The second method is based on the solution of the compressible Navier–Stokes equations with an embedded grid technique that permits accurate calculation of boundary layer flows. Studies for the Eppler-387 and NACA-0012 airfoils indicate that both methods can be used to calculate the behavior of unsteady blade boundary layers at low Reynolds numbers provided that the location of transition is computed with the en method and the transitional region is modeled properly.

Two-point statistics for turbulent boundary layers and channels at Reynolds numbers up to δ+ ≈ 2000

2014 ◽  
Vol 26 (10) ◽  
pp. 105109 ◽  
Author(s):  
Juan A. Sillero ◽  
Javier Jiménez ◽  
Robert D. Moser
Keyword(s):  
Boundary Layers ◽  
Reynolds Numbers ◽  
Turbulent Boundary Layers

Turbulent Transport in Pin Fin Arrays: Experimental Data and Predictions

2005 ◽  
Author(s):  
F. E. Ames ◽  
L. A. Dvorak
Keyword(s):  
Heat Transfer ◽  
Fluid Dynamics ◽  
Boundary Layers ◽  
Fluid Dynamic ◽  
Turbulent Transport ◽  
Turbulence Models ◽  
Reynolds Numbers ◽  
Velocity Profiles ◽  
Pin Fin ◽  
Pin Fin Arrays

The objective of this research has been to experimentally investigate the fluid dynamics of pin fin arrays in order to clarify the physics of heat transfer enhancement and uncover problems in conventional turbulence models. The fluid dynamics of a staggered pin fin array have been studied using hot wire anemometry with both single and x-wire probes at array Reynolds numbers of 3000; 10,000; and 30,000. Velocity distributions off the endwall and pin surface have been acquired and analyzed to investigate turbulent transport in pin fin arrays. Well resolved 3-D calculations have been performed using a commercial code with conventional two-equation turbulence models. Predictive comparisons have been made with fluid dynamic data. In early rows where turbulence is low, the strength of shedding increases dramatically with increasing in Reynolds numbers. The laminar velocity profiles off the surface of pins show evidence of unsteady separation in early rows. In row three and beyond laminar boundary layers off pins are quite similar. Velocity profiles off endwalls are strongly affected by the proximity of pins and turbulent transport. At the low Reynolds numbers, the turbulent transport and acceleration keep boundary layers thin. Endwall boundary layers at higher Reynolds numbers exhibit very high levels of skin friction enhancement. Well resolved 3-D steady calculations were made with several two-equation turbulence models and compared with experimental fluid mechanic and heat transfer data. The quality of the predictive comparison was substantially affected by the turbulence model and near wall methodology.

Low-Reynolds-Number Turbulent Boundary Layers in Zero and Favorable Pressure Gradients

1983 ◽  
Vol 27 (03) ◽  
pp. 147-157 ◽  
Author(s):  
A. J. Smits ◽  
N. Matheson ◽  
P. N. Joubert
Keyword(s):  
Friction Coefficient ◽  
Skin Friction ◽  
Boundary Layers ◽  
Leading Edge ◽  
Reynolds Numbers ◽  
Skin Friction Coefficient ◽  
Turbulent Boundary Layers ◽  
Pressure Gradients ◽  
Mean Flow ◽  
Low Reynolds

This paper reports the results of an extensive experimental investigation into the mean flow properties of turbulent boundary layers with momentum-thickness Reynolds numbers less than 3000. Zero pressure gradient and favorable pressure gradients were studied. The velocity profiles displayed a logarithmic region even at very low Reynolds numbers (as low as Rθ = 261). The results were independent of the leading-edge shape, and the pin-type turbulent stimulators performed well. It was found that the shape and Clauser parameters were a little higher than the correlation proposed by Coles [10], and the skin friction coefficient was a little lower. The skin friction coefficient behavior could be fitted well by a simple power-law relationship in both zero and favorable pressure gradients.

scholarly journals Predictions of Separated and Transitional Boundary Layers Under Low-Pressure Turbine Airfoil Conditions Using an Intermittency Transport Equation

2003 ◽  
Vol 125 (3) ◽  
pp. 455-464 ◽  
Author(s):  
Y. B. Suzen ◽  
P. G. Huang ◽  
Lennart S. Hultgren ◽  
David E. Ashpis
Keyword(s):  
Transport Equation ◽  
Boundary Layers ◽  
Eddy Viscosity ◽  
Reynolds Numbers ◽  
Low Pressure ◽  
Equation Model ◽  
Intermittent Behavior ◽  
Low Pressure Turbine ◽  
Transitional Boundary Layer ◽  
Intermittency Factor

A new transport equation for the intermittency factor was proposed to predict separated and transitional boundary layers under low-pressure turbine airfoil conditions. The intermittent behavior of the transitional flows is taken into account and incorporated into computations by modifying the eddy viscosity, μt, with the intermittency factor, γ. Turbulent quantities are predicted by using Menter’s two-equation turbulence model (SST). The intermittency factor is obtained from a transport equation model, which not only can reproduce the experimentally observed streamwise variation of the intermittency in the transition zone, but also can provide a realistic cross-stream variation of the intermittency profile. In this paper, the intermittency model is used to predict a recent separated and transitional boundary layer experiment under low pressure turbine airfoil conditions. The experiment provides detailed measurements of velocity, turbulent kinetic energy and intermittency profiles for a number of Reynolds numbers and freestream turbulent intensity conditions and is suitable for validation purposes. Detailed comparisons of computational results with experimental data are presented and good agreements between the experiments and predictions are obtained.

scholarly journals A Note on Interior Pathways in the Meridional Overturning Circulation

2018 ◽  
Vol 48 (3) ◽  
pp. 643-646 ◽  
Author(s):  
Joseph Pedlosky
Keyword(s):  
Boundary Layers ◽  
Turbulent Flows ◽  
Intrinsic Property ◽  
Reynolds Numbers ◽  
Meridional Overturning Circulation ◽  
Western Boundary ◽  
Source To Sink ◽  
Basin Geometry ◽  
Meridional Overturning ◽  
Source Sink

AbstractA simple oceanic model is presented for source–sink flow on the β plane to discuss the pathways from source to sink when transport boundary layers have large enough Reynolds numbers to be inertial in their dynamics. A representation of the flow as a Fofonoff gyre, suggested by prior work on inertial boundary layers and eddy-driven circulations in two-dimensional turbulent flows, indicates that even when the source and sink are aligned along the same western boundary the flow must intrude deep into the interior before exiting at the sink. The existence of interior pathways for the flow is thus an intrinsic property of an inertial circulation and is not dependent on particular geographical basin geometry.

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