Turbulent Wall Jets With Cylindrical Streamwise Surface Curvature

1976 ◽  
Vol 98 (3) ◽  
pp. 550-557 ◽  
Author(s):  
D. J. Wilson ◽  
R. J. Goldstein
Keyword(s):  
Convex Surface ◽  
Reynolds Shear Stress ◽  
Surface Curvature ◽  
Wall Jet ◽  
Mean Velocity ◽  
Plane Flow ◽  
Development Models ◽  
Curvature Effects ◽  
Turbulence Velocity ◽  
Turbulent Wall

The effect of surface curvature on the development of a two-dimensional wall jet is investigated experimentally by direct comparison between a wall jet flowing around the convex surface of a circular cylinder, and its plane flow equivalent. Centrifugal force instabilities introduce rapid mixing of the curved wall jet with its surroundings, and cause significant increases in turbulence intensity and Reynolds shear stress in the jet. Large departures from self-preservation of the turbulence velocity field in the curved jet are observed, while the streamwise mean velocity profiles retain similar shapes for downstream development. Models for curvature effects on eddy viscosity are compared with experimentally measured values, and indicate that a simple correction for the effects of curvature is possible.

Surface Curvature Effects on Film Cooling Performance for Shaped Holes on a Model Turbine Blade

2020 ◽  
Vol 142 (11) ◽  
Author(s):  
Jacob D. Moore ◽  
Christopher Yoon ◽  
David G. Bogard
Keyword(s):  
Flat Plate ◽  
Turbine Blade ◽  
Film Cooling ◽  
Gas Turbines ◽  
Convex Surface ◽  
Adverse Pressure Gradient ◽  
Suction Side ◽  
Surface Curvature ◽  
Cooling Performance ◽  
Curvature Effects

Abstract Surface curvature has been shown to have significant effects on the film cooling performance of round holes, but the literature include few studies of its effects on shaped holes despite their prevalence in gas turbines. Experiments were performed using two rows of holes placed on the suction side of a scaled-up turbine blade in a low Mach number linear cascade wind tunnel with low freestream turbulence. The rows were placed in regions of high and low convex surface curvature. Geometries and flow conditions for the rows were matched to those from previous flat plate studies. Comparison of the adiabatic effectiveness results from the high curvature and flat plate rows revealed the same trends as those in the literature using round holes, with increased performance for the high curvature row at lower blowing ratios and the opposite at higher ones. The low curvature row had similar performance to the flat plate row at lower blowing ratios, suggesting the mild convex curvature had little beneficial effect. At higher blowing ratios, the low curvature row had inferior performance, which was attributed to the local freestream adverse pressure gradient that generated additional turbulence, promoting jet-to-mainstream mixing and decreasing performance.

Turbulent Vorticity Diffusion in the Stronger Wall Jet Managed by a Flat Plate Wing in the Outer Layer

2015 ◽  
Author(s):  
Takuma Katayama ◽  
Shinsuke Mochizuki
Keyword(s):  
Shear Stress ◽  
Flat Plate ◽  
Outer Layer ◽  
Large Scale ◽  
Reynolds Shear Stress ◽  
Three Dimensional ◽  
Quantitative Relationship ◽  
Wall Jet ◽  
Mean Velocity ◽  
The Mean

The present experiment focuses on the vorticity diffusion in a stronger wall jet managed by a three-dimensional flat plate wing in the outer layer. Measurement of the fluctuating velocities and vorticity correlation has been carried out with 4-wire vorticity probe. The turbulent vorticity diffusion due to the large scale eddies in the outer layer is quantitatively examined by using the 4-wire vorticity probe. Quantitative relationship between vortex structure and Reynolds shear stress is revealed by means of directly measured experimental evidence which explains vorticity diffusion process and influence of the manipulating wing. It is expected that the three-dimensional outer layer manipulator contributes to keep convex profile of the mean velocity, namely, suppression of the turbulent diffusion and entrainment.

An Experimental Study of a Turbulent Wall Jet on Smooth and Transitionally Rough Surfaces

2011 ◽  
Vol 133 (11) ◽  
Author(s):  
N. Rostamy ◽  
D. J. Bergstrom ◽  
D. Sumner ◽  
J. D. Bugg
Keyword(s):  
Friction Coefficient ◽  
Skin Friction ◽  
Laser Doppler Anemometry ◽  
Skin Friction Coefficient ◽  
Wall Jet ◽  
Roughness Effects ◽  
Mean Velocity ◽  
Turbulent Wall ◽  
Inner Region ◽  
Effect Of Surface

The effect of surface roughness on the mean velocity and skin friction characteristics of a plane turbulent wall jet was experimentally investigated using laser Doppler anemometry. The Reynolds number based on the slot height and exit velocity of the jet was approximately Re = 7500. A 36-grit sheet was used to create a transitionally rough flow (44 < ks+ < 70). Measurements were carried out at downstream distances from the jet exit ranging from 20 to 80 slot heights. Both conventional and momentum-viscosity scaling were used to analyze the streamwise evolution of the flow on smooth and rough walls. Three different methods were employed to estimate the friction velocity in the fully developed region of the wall jet, which was then used to calculate the skin friction coefficient. This paper provides new experimental data for the case of a plane wall jet on a transitionally rough surface and uses it to quantify the effects of roughness on the momentum field. The present results indicate that the skin friction coefficient for the rough-wall case compared to a smooth wall increases by as much as 140%. Overall, the study suggests that for the transitionally rough regime considered in the present study, roughness effects are significant but mostly confined to the inner region of the wall jet.

The forced turbulent wall jet

1992 ◽  
Vol 242 ◽  
pp. 577-609 ◽  
Author(s):  
Y. Katz ◽  
E. Horev ◽  
I. Wygnanski
Keyword(s):  
Maximum Velocity ◽  
Wall Stress ◽  
Coherent Motion ◽  
Settling Chamber ◽  
Wall Jet ◽  
Appreciable Effect ◽  
External Excitation ◽  
Mean Velocity ◽  
The Mean ◽  
Turbulent Wall

The effects of external two-dimensional excitation on the plane turbulent wall jet were investigated experimentally and theoretically. Measurements of the streamwise component of velocity were made throughout the flow field for a variety of imposed frequencies and amplitudes. The present data were always compared to the results generated in the absence of external excitation. Two methods of forcing were used: one global, imposed on the entire jet by pressure fluctuations in the settling chamber and one local, imposed on the shear layer by a small flap attached to the outer nozzle lip. The fully developed wall jet was shown to be insensitive to the method of excitation. Furthermore, external excitation has no appreciable effect on the rate of spread of the jet nor on the decay of its maximum velocity. In fact the mean velocity distribution did not appear to be altered by the external excitation in any obvious manner. The flow near the surface, however, (i.e. for 0 < Y+ < 100) was profoundly different from the unforced flow, indicating a reduction in wall stress exceeding at times 30%. The production of turbulent energy near the surface was also reduced, lowering the intensities of the velocity fluctuations. External excitation enhanced the two-dimensionality and the periodicity of the coherent motion. Spectral analysis and flow visualization suggested that the large coherent structures in this flow might be identified with the most-amplified primary instability modes of the mean velocity profile. Detailed stability analysis confirmed this proposition though not at the same level of accuracy as it did in many free shear flows.

On streamwise vortices in a turbulent wall jet that flows over a convex surface

2001 ◽  
Vol 13 (6) ◽  
pp. 1822-1825 ◽  
Author(s):  
O. Likhachev ◽  
R. Neuendorf ◽  
I. Wygnanski
Keyword(s):  
Convex Surface ◽  
Wall Jet ◽  
Streamwise Vortices ◽  
Turbulent Wall

scholarly journals The Development of the Mean Flow and Turbulence Structure in an Annular S-Shaped Duct

1994 ◽  
Author(s):  
K. M. Britchford ◽  
J. F. Carrotte ◽  
S. J. Stevens ◽  
J. J. McGuirk
Keyword(s):  
Reynolds Stress ◽  
Laser Doppler Anemometry ◽  
Reynolds Shear Stress ◽  
Turbulence Models ◽  
Test Facility ◽  
Turbulence Structure ◽  
Mean Flow ◽  
Mean Velocity ◽  
Curvature Effects ◽  
The Mean

This paper describes an investigation of the mean and fluctuating flow field within an annular S-shaped duct which is representative of that used to connect the compressor spools of aircraft gas turbine engines. Data was obtained from a fully annular test facility using a 3-component Laser Doppler Anemometry (LDA) system. The measurements indicate that development of the flow within the duct is complex and significantly influenced by the combined effects of streamwise pressure gradients and flow curvature. In addition CFD predictions of the flow, using both the k-ε and Reynolds stress transport equation turbulence models, are compared with the experimental data. Whereas curvature effects are not described properly by the k-ε model, such effects are captured more accurately by the Reynolds stress model leading to a better prediction of the Reynolds shear stress distribution. This, in turn, leads to a more accurate prediction of the mean velocity profiles, as reflected by the boundary layer shape parameters, particularly in the critical regions of the duct where flow separation is most likely to occur.

Plane-Jet Flow over a Backward-Facing Step

1973 ◽  
Vol 187 (1) ◽  
pp. 447-454
Author(s):  
L. Matthews ◽  
J. H. Whitelaw
Keyword(s):  
Shear Stress ◽  
Reynolds Shear Stress ◽  
Surface Flow ◽  
Wall Jet ◽  
Asymmetric Flow ◽  
Backward Facing Step ◽  
Mean Velocity ◽  
Visualization Experiments ◽  
Plane Jet ◽  
Jet Blowing

Measurements of mean velocity, the three components of fluctuating velocity and Reynolds shear stress are reported for the turbulent flow downstream of a wall jet blowing over a backward-facing step. The results quantify the complexity of this asymmetric flow and demonstrate the extent to which the slot-lip and backward-facing step destroy the jet-like nature of the flow in the near-slot region. Surface flow visualization experiments demonstrate the influence of the slot flow on the reattachment distance.

The Turbulent Wall Jet in an Arbitrary Pressure Gradient

1969 ◽  
Vol 20 (1) ◽  
pp. 25-56 ◽  
Author(s):  
I. S. Gartshore ◽  
B. G. Newman
Keyword(s):  
Boundary Layer ◽  
Pressure Gradient ◽  
Practical Interest ◽  
Adverse Pressure Gradient ◽  
Wall Jet ◽  
Mean Velocity ◽  
Momentum Coefficient ◽  
Large Eddy ◽  
Trailing Edge Flap ◽  
Turbulent Wall

SummaryA method for calculating the growth of a turbulent wall jet in streaming flow has been developed. The flow is assumed to be two-dimensional, incompressible and over a plane, smooth wall. Downstream variations of pressure are permitted and separation in an adverse pressure gradient may be predicted. The method incorporates procedures for matching the flow to that at the blowing slot, although it is postulated that the upstream boundary layer there is thin enough that the wall jet develops without an unmixed wake (i.e. there is not a minimum in the mean-velocity profile).The method incorporates four integral momentum equations taken from the wall to various points in the flow. The calculation of the outer shearing stress, although empirical, is based on the large-eddy equilibrium hypothesis and therefore has some foundation. The remaining empiricism in the method is based on measurements in self-preserving wall jets.The method has been used to predict the jet-momentum coefficient required to suppress separation over a trailing-edge flap attached to a thin aerofoil. Plausible curves have been obtained Using assumed values of upstream boundary layer at the slot. Of some practical interest is the indication that large savings in power are possible if the upstream boundary layer is removed. This indicates that blowing combined with upstream suction, or multiple-slot blowing, may give useful savings in the application of blowing to prevent separation.

Calculation of Turbulent Wall Jets With an Algebraic Reynolds Stress Model

1980 ◽  
Vol 102 (3) ◽  
pp. 350-356 ◽  
Author(s):  
M. Ljuboja ◽  
W. Rodi
Keyword(s):  
Reynolds Stress ◽  
Reynolds Stress Model ◽  
Transport Equations ◽  
Turbulent Shear ◽  
Wall Jet ◽  
Wall Jets ◽  
Mean Velocity ◽  
Empirical Constant ◽  
Turbulent Wall Jets ◽  
Turbulent Wall

A modified version of the k-ε turbulence model is developed which predicts well the main features of turbulent wall jets. The model relates the turbulent shear stress to the mean velocity gradient, the turbulent kinetic energy k, and the dissipation rate ε by way of the Kolmogorov-Prandtl eddy viscosity relation and determines k and ε from transport equations. The empirical constant in the Kolmogorov-Prandtl relation is replaced by a function which is derived by reducing a model form of the Reynolds stress transport equations to algebraic expressions, retaining the wall damping correction to the pressure-strain model used in these equations. The modified k-ε model is applied to a wall jet in stagnant surroundings as well as to a wall jet in a moving stream, and the predictions are compared with experimental data. The agreement is good with respect to most features of these flows.

Three-Dimensional Wall Jet Originating from a Circular Orifice

1972 ◽  
Vol 23 (3) ◽  
pp. 188-200 ◽  
Author(s):  
B G Newman ◽  
R P Patel ◽  
S B Savage ◽  
H K Tjio
Keyword(s):  
Three Dimensional ◽  
Plane Wall ◽  
Similarity Analysis ◽  
Length Scale ◽  
Wall Jet ◽  
Mean Velocity ◽  
Lateral Direction ◽  
Rate Of Growth ◽  
Circular Orifice ◽  
Turbulent Wall

SummaryAn incompressible three-dimensional turbulent wall jet originating from a circular orifice located adjacent to a plane wall is studied both theoretically and experimentally. An approximate similarity analysis predicts that the two transverse length scales,l0and L0, and the inverse of the mean velocity scale grow linearly with distance downstream x from the orifice. Experimental measurements of mean velocity and longitudinal turbulence intensity profiles were made both in air and water with hot-wire and hot-film anemometers respectively. The behaviour predicted by the similarity analysis was verified. It was found that the rate of growth of the length scale normal to the plane wall, dl0/dx, was somewhat less than that found for a two-dimensional wall jet, whereas the rate of growth of the length scale in the lateral direction, dL0/dx, was about seven times greater than dl0/dx.

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