First-Order Slip Effects on the Laminar Boundary Layer Over a Slender Body of Revolution Wth Zero Pressure Gradient

1962 ◽  
Vol 29 (9) ◽  
pp. 1136-1138 ◽  
Author(s):  
Jay M. Solomon
Keyword(s):  
Boundary Layer ◽  
Pressure Gradient ◽  
Laminar Boundary Layer ◽  
Slender Body ◽  
Body Of Revolution ◽  
First Order ◽  
Slip Effects ◽  
Slender Body Of Revolution

BUOYANCY EFFECTS ON UNSTEADY LAMINAR AND ROTATIONALLY SYMMETRICAL BOUNDARY LAYER

1999 ◽  
Vol 23 (3-4) ◽  
pp. 397-408 ◽  
Author(s):  
A. Öztürk ◽  
M.C. Ece
Keyword(s):  
Boundary Layer ◽  
Velocity Field ◽  
Mixed Convection ◽  
Laminar Boundary Layer ◽  
Boundary Layer Flow ◽  
Buoyancy Force ◽  
Body Of Revolution ◽  
First Order ◽  
In Series ◽  
Layer Flow

Initiai development of the laminar boundary-layer flow over an impulsively started translating and spinning isothermal body of revolution in the case of mixed convection is investigated. Velocity components and temperature are expanded in series in powers of time. Leading and first order functions are obtained analytically and second order functions are determined numerically. The general results are applied to a sphere to investigate the effects of density variations on velocity field and on the onset of separation. The buoyancy force is more effective for small rotational speeds and facilitates the onset of separation for opposing flow and retards it for aiding flow.

Turbine Cascade Flow Control Using a “Wake Filling” Pulsed Plasma Actuator

2005 ◽  
Author(s):  
H. Perez-Blanco ◽  
Robert Van Dyken ◽  
Aaron Byerley ◽  
Tom McLaughlin
Keyword(s):  
Boundary Layer ◽  
Pressure Gradient ◽  
Laminar Boundary Layer ◽  
Separation Bubble ◽  
Adverse Pressure Gradient ◽  
Suction Side ◽  
Plasma Actuator ◽  
Pulsed Plasma ◽  
Power Cost ◽  
Hot Film

Separation bubbles in high-camber blades under part-load conditions have been addressed via continuous and pulsed jets, and also via plasma actuators. Numerous passive techniques have been employed as well. In this type of blades, the laminar boundary layer cannot overcome the adverse pressure gradient arising along the suction side, resulting on a separation bubble. When separation is abated, a common explanation is that kinetic energy added to the laminar boundary layer speeds up its transition to turbulent. In the present study, a plasma actuator installed in the trailing edge (i.e. “wake filling configuration”) of a cascade blade is used to excite the flow in pulsed and continuous ways. The pulsed excitation can be directed to the frequencies of the large coherent structures (LCS) of the flow, as obtained via a hot-film anemometer, or to much higher frequencies present in the suction-side boundary layer, as given in the literature. It is found that pulsed frequencies much higher than that of LCS reduce losses and improve turning angles further than frequencies close to those of LCS. With the plasma actuator 50% on time, good loss abatement is obtained. Larger “on time” values yield improvements, but with decreasing returns. Continuous high-frequency activation results in the largest loss reduction, at increased power cost. The effectiveness of high frequencies may be due to separation abatement via boundary layer excitation into transition, or may simply be due to the creation of a favorable pressure gradient that averts separation as the actuator ejects fluid downstream. Both possibilities are discussed in light of the experimental evidence.

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