Relationship Between Upstream Turbulent Boundary-Layer Velocity Fluctuations and Separation Shock Unsteadiness

AIAA Journal ◽  
2002 ◽  
Vol 40 (12) ◽  
pp. 2412-2422 ◽  
Author(s):  
S. J. Beresh ◽  
N. T. Clemens ◽  
D. S. Dolling
Keyword(s):  
Boundary Layer ◽  
Turbulent Boundary Layer ◽  
Velocity Fluctuations ◽  
Separation Shock ◽  
Shock Unsteadiness ◽  
Layer Velocity

scholarly journals Sonic Eddy Model of the Turbulent Boundary Layer

Fluids ◽  
2022 ◽  
Vol 7 (1) ◽  
pp. 37
Author(s):  
Paul Dintilhac ◽  
Robert Breidenthal
Keyword(s):  
Boundary Layer ◽  
Mach Number ◽  
Turbulent Boundary Layer ◽  
Skin Friction ◽  
Entrainment Rate ◽  
Square Root ◽  
Reynolds Stresses ◽  
Free Shear Layer ◽  
Velocity Fluctuations ◽  
Acoustic Signaling

The effects of Mach number on the skin friction and velocity fluctuations of the turbulent boundary layer are considered through a sonic eddy model. Originally proposed for free shear flows, the model assumes that the eddies responsible for momentum transfer have a rotation Mach number of unity, with the entrainment rate limited by acoustic signaling. Under this assumption, the model predicts that the skin friction coefficient should go as the inverse Mach number in a regime where the Mach number is larger than unity but smaller than the square root of the Reynolds number. The velocity fluctuations normalized by the friction velocity should be the inverse square root of the Mach number in the same regime. Turbulent transport is controlled by acoustic signaling. The density field adjusts itself such that the Reynolds stresses correspond to the momentum transport. In contrast, the conventional van Driest–Morkovin view is that the Mach number effects are due to density variations directly. A new experiment or simulation is proposed to test this model using different gases in an incompressible boundary layer, following the example of Brown and Roshko in the free shear layer.

PIV investigation of role of boundary layer velocity fluctuations in unsteady shock-induced separation

2000 ◽  
Author(s):  
O. Unalmis ◽  
Y. Hou ◽  
P. Bueno ◽  
N. Clemens ◽  
D. Dolling
Keyword(s):  
Boundary Layer ◽  
Velocity Fluctuations ◽  
Layer Velocity

Wall shear stress fluctuations: Mixed scaling and their effects on velocity fluctuations in a turbulent boundary layer

2017 ◽  
Vol 29 (5) ◽  
pp. 055102 ◽  
Author(s):  
Carlos Diaz-Daniel ◽  
Sylvain Laizet ◽  
J. Christos Vassilicos
Keyword(s):  
Boundary Layer ◽  
Shear Stress ◽  
Wall Shear Stress ◽  
Turbulent Boundary Layer ◽  
Velocity Fluctuations ◽  
Wall Shear

Effect of Streamline Curvature on Film Cooling

1977 ◽  
Vol 99 (1) ◽  
pp. 77-82 ◽  
Author(s):  
R. E. Mayle ◽  
F. C. Kopper ◽  
M. F. Blair ◽  
D. A. Bailey
Keyword(s):  
Boundary Layer ◽  
Turbulent Boundary Layer ◽  
Film Cooling ◽  
Flat Surface ◽  
Temperature Measurements ◽  
Adiabatic Wall ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Streamline Curvature ◽  
Layer Velocity

The effects of streamline curvature on film cooling effectiveness are discussed. Experiments for air discharged through a slot and into a turbulent boundary layer along a flat, convex, and concave surface are described. Adiabatic wall effectiveness measurements on each surface for several blowing rates are presented. Boundary-layer velocity and temperature measurements are also presented for one of the blowing rates. Compared to the results for the flat surface, convex curvature is found to increase the adiabatic wall effectiveness whereas concave curvature is found to be detrimental.

Physics of unsteady blunt-fin-induced shock wave/turbulent boundary layer interactions

1994 ◽  
Vol 273 ◽  
pp. 375-409 ◽  
Author(s):  
Leon Brusniak ◽  
David S. Dolling
Keyword(s):  
Boundary Layer ◽  
Turbulent Boundary Layer ◽  
Time History ◽  
Separated Flow ◽  
Flow Region ◽  
Horseshoe Vortex ◽  
Wall Pressure ◽  
Pressure Measurements ◽  
Separation Shock ◽  
Pressure Distributions

Fluctuating wall-pressure measurements have been made on the centreline upstream of a blunt fin in a Mach 5 turbulent boundary layer. By examining the ensemble-averaged wall-pressure distributions for different separation shock foot positions, it has been shown that local fluctuating wall-pressure measurements are due to a distinct pressure distribution, [weierp ]i, which undergoes a stretching and flattening effect as its upstream boundary translates aperiodically between the upstream-influence and separation lines. The locations of the maxima and minima in the wall-pressure standard deviation can be accurately predicted using this distribution, providing quantitative confirmation of the model. This model also explains the observed cross-correlations and ensemble-average measurements within the interaction. Using the [weierp ]i model, wall-pressure signals from under the separated flow region were used to reproduce the position–time history of the separation shock foot. The unsteady behaviour of the primary horseshoe vortex and its relation to the unsteady separation shock is also described. The practical implications are that it may be possible to predict some of the unsteady aspects of the flowfield using mean wall-pressure distributions obtained from either computations or experiments; also, to minimize the fluctuating loads caused by the unsteadiness, flow control methods should focus on reducing the magnitude of the [weierp ]i gradient (∂[weierp ]i/∂x).

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