Prediction of Turbulent Boundary Layers With a Second-Moment Closure: Part I—Effects of Periodic Pressure Gradient, Wall Transpiration, and Free-Stream Turbulence

1993 ◽  
Vol 115 (1) ◽  
pp. 56-63 ◽  
Author(s):  
N. Shima
Keyword(s):  
Pressure Gradient ◽  
Boundary Layers ◽  
Free Stream ◽  
Moment Closure ◽  
Second Moment ◽  
Free Stream Turbulence ◽  
Periodic Pressure ◽  
Second Moment Closure ◽  
Oscillating Boundary ◽  
Present Part

The purpose of this two-part paper is to assess the performance of a second-moment closure applicable up to a wall. In the present part, the turbulence model is applied to the boundary layers with periodic pressure gradient, with wall transpiration and with free-stream turbulence. The predictions are shown to be in good agreement with experiments and a direct simulation. In particular, a tendency towards relaminarization and a subsequent retransition in the oscillating boundary layer are faithfully reproduced, and the effect of the length scale of free-stream turbulence is correctly captured.

Prediction of Turbulent Boundary Layers With a Second-Moment Closure: Part II—Effects of Streamline Curvature and Spanwise Rotation

1993 ◽  
Vol 115 (1) ◽  
pp. 64-69 ◽  
Author(s):  
N. Shima
Keyword(s):  
Present Model ◽  
Recovery Process ◽  
Turbulent Boundary Layers ◽  
Moment Closure ◽  
Second Moment ◽  
Streamline Curvature ◽  
Second Moment Closure ◽  
Present Part ◽  
Rotating Boundary ◽  
Spanwise Rotation

Further testing of the second-moment closure employed in Part I is made. The present part considers the effects of streamline curvature and spanwise system rotation. As expected, the exact stress production terms broadly account for these effects. In addition, the present model, which is applied right up to a wall, successfully captures the laminarization in the rotating boundary layer. Attention is also given to the capability to reproduce the recovery process from curvature.

Natural Transition of Boundary Layers—The Effects of Turbulence, Pressure Gradient, and Flow History

1980 ◽  
Vol 22 (5) ◽  
pp. 213-228 ◽  
Author(s):  
B. J. Abu-Ghannam ◽  
R. Shaw
Keyword(s):  
Boundary Layer ◽  
Pressure Gradient ◽  
Boundary Layers ◽  
Free Stream ◽  
Stream Velocity ◽  
Hot Wire ◽  
Empirical Relationships ◽  
Free Stream Turbulence ◽  
Turbomachinery Blades ◽  
Low Speed Wind Tunnel

Natural transition of boundary layers is investigated for a flat plate in a low-speed wind tunnel with free-stream turbulence intensities ranging from 0.3 to 5 per cent, and with pressure-gradient histories typical of turbomachinery blades without separation. Empirical relationships are proposed for the prediction of the start and end of transition, as well as the development of the boundary layer during transition. These relations are based on the recent measurements made with a hot-wire anemometer, and augmented, mainly for the start of transition, by results of previously reported research. Finally, these experimental relationships are used in conjunction with well established methods to predict the entire unseparated boundary layer. To utilize the prediction, all that is required is a knowledge of the free-stream turbulence level and the free-stream velocity distribution, which itself can be derived from potential flow theory.

scholarly journals Measurements in Separated and Transitional Boundary Layers Under Low-Pressure Turbine Airfoil Conditions

2000 ◽  
Vol 123 (2) ◽  
pp. 189-197 ◽  
Author(s):  
Ralph J. Volino ◽  
Lennart S. Hultgren
Keyword(s):  
Boundary Layer ◽  
Reynolds Number ◽  
Pressure Gradient ◽  
Boundary Layers ◽  
Free Stream ◽  
Separation Bubble ◽  
Low Pressure ◽  
Mean Velocity ◽  
Free Stream Turbulence ◽  
Low Pressure Turbine

Detailed velocity measurements were made along a flat plate subject to the same dimensionless pressure gradient as the suction side of a modern low-pressure turbine airfoil. Reynolds numbers based on wetted plate length and nominal exit velocity were varied from 50,000 to 300,000, covering cruise to takeoff conditions. Low and high inlet free-stream turbulence intensities (0.2 and 7 percent) were set using passive grids. The location of boundary-layer separation does not depend strongly on the free-stream turbulence level or Reynolds number, as long as the boundary layer remains nonturbulent prior to separation. Strong acceleration prevents transition on the upstream part of the plate in all cases. Both free-stream turbulence and Reynolds number have strong effects on transition in the adverse pressure gradient region. Under low free-stream turbulence conditions, transition is induced by instability waves in the shear layer of the separation bubble. Reattachment generally occurs at the transition start. At Re=50,000 the separation bubble does not close before the trailing edge of the modeled airfoil. At higher Re, transition moves upstream, and the boundary layer reattaches. With high free-stream turbulence levels, transition appears to occur in a bypass mode, similar to that in attached boundary layers. Transition moves upstream, resulting in shorter separation regions. At Re above 200,000, transition begins before separation. Mean velocity, turbulence, and intermittency profiles are presented.

scholarly journals Measurements in Separated and Transitional Boundary Layers Under Low-Pressure Turbine Airfoil Conditions

2000 ◽  
Author(s):  
Ralph J. Volino ◽  
Lennart S. Hultgren
Keyword(s):  
Boundary Layer ◽  
Reynolds Number ◽  
Pressure Gradient ◽  
Boundary Layers ◽  
Free Stream ◽  
Separation Bubble ◽  
Low Pressure ◽  
Mean Velocity ◽  
Free Stream Turbulence ◽  
Low Pressure Turbine

Detailed velocity measurements were made along a flat plate subject to the same dimensionless pressure gradient as the suction side of a modern low-pressure turbine airfoil. Reynolds numbers based on wetted plate length and nominal exit velocity were varied from 50, 000 to 300, 000, covering cruise to takeoff conditions. Low and high inlet free-stream turbulence intensities (0.2% and 7%) were set using passive grids. The location of boundary-layer separation does not depend strongly on the free-stream turbulence level or Reynolds number, as long as the boundary layer remains non-turbulent prior to separation. Strong acceleration prevents transition on the upstream part of the plate in all cases. Both free-stream turbulence and Reynolds number have strong effects on transition in the adverse pressure gradient region. Under low free-stream turbulence conditions transition is induced by instability waves in the shear layer of the separation bubble. Reattachment generally occurs at the transition start. At Re = 50, 000 the separation bubble does not close before the trailing edge of the modeled airfoil. At higher Re, transition moves upstream, and the boundary layer reattaches. With high free-stream turbulence levels, transition appears to occur in a bypass mode, similar to that in attached boundary layers. Transition moves upstream, resulting in shorter separation regions. At Re above 200,000, transition begins before separation. Mean velocity, turbulence and intermittency profiles are presented.

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