Turbulent Spots and Wall Roughness Effects in Shock Tube Boundary Layer Transition

1967 ◽  
Vol 10 (1) ◽  
pp. 17 ◽  
Author(s):  
W. Paul Thompson
Keyword(s):  
Boundary Layer ◽  
Shock Tube ◽  
Boundary Layer Transition ◽  
Wall Roughness ◽  
Roughness Effects ◽  
Layer Transition ◽  
Turbulent Spots

Large Eddy Simulation of Boundary Layer Transition Mechanisms in a Gas-Turbine Compressor Cascade

2018 ◽  
Author(s):  
Ashley D. Scillitoe ◽  
Paul G. Tucker ◽  
Paolo Adami
Keyword(s):  
Boundary Layer ◽  
Large Eddy Simulation ◽  
Boundary Layer Transition ◽  
Bypass Transition ◽  
Suction Surface ◽  
Layer Transition ◽  
Turbulent Spots ◽  
Pressure Surface ◽  
Eddy Simulation ◽  
Large Eddy

Large Eddy Simulation (LES) is used to explore the boundary layer transition mechanisms in two rectilinear compressor cascades. To reduce numerical dissipation, a novel locally adaptive smoothing scheme is added to an unstructured finite-volume solver. The performance of a number of Sub-Grid Scale (SGS) models is explored. With the first cascade, numerical results at two different freestream turbulence intensities (Ti’s), 3.25% and 10%, are compared. At both Ti’s, time-averaged skin-friction and pressure coefficient distributions agree well with previous Direct Numerical Simulations (DNS). At Ti = 3.25%, separation induced transition occurs on the suction surface, whilst it is bypassed on the pressure surface. The pressure surface transition is dominated by modes originating from the convection of Tollmien-Schlichting waves by Klebanoff streaks. However, they do not resembled a classical bypass transition. Instead, they display characteristics of the “overlap” and “inner” transition modes observed in the previous DNS. At Ti = 10%, classical bypass transition occurs, with Klebanoff streaks incepting turbulent spots. With the second cascade, the influence of unsteady wakes on transition is examined. Wake-amplified Klebanoff streaks were found to instigate turbulent spots, which periodically shorten the suction surface separation bubble. The celerity line corresponding to 70% of the free-stream velocity, which is associated with the convection speed of the amplified Klebanoff streaks, was found to be important.

scholarly journals Effects of Shock-Tube Cleanliness on Hypersonic Boundary Layer Transition at High Enthalpy

AIAA Journal ◽  
2017 ◽  
Vol 55 (1) ◽  
pp. 332-338 ◽  
Author(s):  
Joseph S. Jewell ◽  
Nicholaus J. Parziale ◽  
Ivett A. Leyva ◽  
Joseph E. Shepherd
Keyword(s):  
Boundary Layer ◽  
Shock Tube ◽  
Boundary Layer Transition ◽  
Hypersonic Boundary Layer ◽  
Layer Transition ◽  
High Enthalpy

Investigation of the Laminar-Turbulent Transition of Boundary Layers Disturbed by Wakes

1982 ◽  
Author(s):  
H. Pfeil ◽  
R. Herbst ◽  
T. Schröder
Keyword(s):  
Boundary Layer ◽  
Pressure Gradient ◽  
Boundary Layers ◽  
Transition Process ◽  
Boundary Layer Transition ◽  
Layer Transition ◽  
Turbulent Spots ◽  
Turbulent Transition ◽  
Time Space ◽  
Favorable Pressure Gradient

The boundary layer transition under instationary afflux conditions as present in the stages of turbomachines is investigated. A model for the transition process is introduced by means of time-space distributions of the turbulent spots during transition and schematic drawings of the instantaneous boundary layer thicknesses. To confirm this model, measurements of the transition with zero and favorable pressure gradient are performed.

Further Experiments on Shock Tube Wall Boundary-Layer Transition

AIAA Journal ◽  
1983 ◽  
Vol 21 (7) ◽  
pp. 1046-1048 ◽  
Author(s):  
Michael J. Chaney ◽  
William J. Cook
Keyword(s):  
Boundary Layer ◽  
Shock Tube ◽  
Tube Wall ◽  
Boundary Layer Transition ◽  
Layer Transition ◽  
Wall Boundary Layer ◽  
Wall Boundary

A Review of Surface Roughness Effects in Gas Turbines

2010 ◽  
Vol 132 (2) ◽  
Author(s):  
J. P. Bons
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Surface Roughness ◽  
Gas Turbines ◽  
Engine Performance ◽  
Boundary Layer Transition ◽  
Roughness Effects ◽  
Layer Transition ◽  
Laminar Separation

The effects of surface roughness on gas turbine performance are reviewed based on publications in the open literature over the past 60 years. Empirical roughness correlations routinely employed for drag and heat transfer estimates are summarized and found wanting. No single correlation appears to capture all of the relevant physics for both engineered and service-related (e.g., wear or environmentally induced) roughness. Roughness influences engine performance by causing earlier boundary layer transition, increased boundary layer momentum loss (i.e., thickness), and/or flow separation. Roughness effects in the compressor and turbine are dependent on Reynolds number, roughness size, and to a lesser extent Mach number. At low Re, roughness can eliminate laminar separation bubbles (thus reducing loss) while at high Re (when the boundary layer is already turbulent), roughness can thicken the boundary layer to the point of separation (thus increasing loss). In the turbine, roughness has the added effect of augmenting convective heat transfer. While this is desirable in an internal turbine coolant channel, it is clearly undesirable on the external turbine surface. Recent advances in roughness modeling for computational fluid dynamics are also reviewed. The conclusion remains that considerable research is yet necessary to fully understand the role of roughness in gas turbines.

Further experiments on shock tube wall boundary-layer transition

AIAA Journal ◽  
1985 ◽  
Vol 23 (8) ◽  
pp. 1298-1299
Author(s):  
William J. Cook ◽  
Michael J. Chancy
Keyword(s):  
Boundary Layer ◽  
Shock Tube ◽  
Tube Wall ◽  
Boundary Layer Transition ◽  
Layer Transition ◽  
Wall Boundary Layer ◽  
Wall Boundary
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