Automatic Control of Laminar Boundary-Layer Transition

AIAA Journal ◽  
10.2514/2.66 ◽  
1997 ◽  
Vol 35 (1) ◽  
pp. 85-90 ◽  
Author(s):  
P. A. Nelson ◽  
M. C. M. Wright ◽  
J.-L. Rioual
Keyword(s):  
Boundary Layer ◽  
Automatic Control ◽  
Laminar Boundary Layer ◽  
Boundary Layer Transition ◽  
Layer Transition

Automatic control of laminar boundary-layer transition

AIAA Journal ◽  
1997 ◽  
Vol 35 ◽  
pp. 85-90
Author(s):  
P. A. Nelson ◽  
M. C. M. Wright ◽  
J.-L. Rioual
Keyword(s):  
Boundary Layer ◽  
Automatic Control ◽  
Laminar Boundary Layer ◽  
Boundary Layer Transition ◽  
Layer Transition

Keel Design for Low Viscous Drag

1987 ◽  
Author(s):  
Clifford J. Obara ◽  
C. P. van Dam
Keyword(s):  
Boundary Layer ◽  
Laminar Flow ◽  
Laminar Boundary Layer ◽  
Leading Edge ◽  
Boundary Layer Transition ◽  
Viscous Drag ◽  
Hydrodynamic Characteristics ◽  
Sweep Angle ◽  
Layer Transition ◽  
Layer Flow

In this paper, foil and planform parameters which govern the level of viscous drag produced by the keel of a sailing yacht are discussed. It is shown that the application of laminar boundary-Layer flow offers great potential for increased boat speed resulting from the reduction in viscous drag. Three foil shapes have been designed and it is shown that their hydro­dynamic characteristics are very much dependent on location and mode of boundary-Layer transition. The planform parameter which strongly affects the capabilities of the keel to achieve laminar flow is lea ding-edge sweep angle. The two significant phenomena related to keel sweep angle which can cause premature transition of the laminar boundary layer are crossflow instability and turbulent contamination of the leading-edge attachment line. These flow phenomena and methods to control them are discussed in detail. The remaining factors that affect the maintainability of laminar flow include surface roughness, surface waviness, and freestream turbulence. Recommended limits for these factors are given to insure achievability of laminar flow on the keel. In addition, the application of a simple trailing-edge flap to improve the hydrodynamic characteristics of a foil at moderate-to-high leeway angles is studied.

The Critical Height of Distributed Roughness to Cause Boundary Layer Transition

1959 ◽  
Vol 63 (588) ◽  
pp. 722-722
Author(s):  
R. L. Dommett
Keyword(s):  
Boundary Layer ◽  
Reynolds Number ◽  
Laminar Boundary Layer ◽  
Boundary Layer Transition ◽  
Critical Height ◽  
Layer Transition ◽  
Local Conditions ◽  
Additional Advantage ◽  
Boundary Layer Equations ◽  
General Method

It has been found that there is a critical height for “sandpaper” type roughness below which no measurable disturbances are introduced into a laminar boundary layer and above which transition is initiated at the roughness. Braslow and Knox have proposed a method of predicting this height, for flow over a flat plate or a cone, using exact solutions of the laminar boundary layer equations combined with a correlation of experimental results in terms of a Reynolds number based on roughness height, k, and local conditions at the top of the elements. A simpler, yet more general, method can be constructed by taking additional advantage of the linearity of the velocity profile near the wall in a laminar boundary layer.

Keel Design for Low Viscous Drag

1989 ◽  
Vol 33 (02) ◽  
pp. 145-155
Author(s):  
Clifford J. Obara ◽  
C. P. van Dam
Keyword(s):  
Boundary Layer ◽  
Laminar Flow ◽  
Laminar Boundary Layer ◽  
Leading Edge ◽  
Boundary Layer Transition ◽  
Viscous Drag ◽  
Hydrodynamic Characteristics ◽  
Sweep Angle ◽  
Layer Transition ◽  
Layer Flow

Foil and planform parameters which govern the level of viscous drag produced by the keel of a sailing yacht are discussed. It is shown that the application of laminar boundary-layer flow offers great potential for increased boat speed resulting from the reduction in viscous drag. Three foil shapes have been designed and it is shown that their hydrodynamic characteristics are very much dependent on location and mode of boundary-layer transition. The planform parameter which strongly affects the capabilities of the keel to achieve laminar flow is leading-edge sweep angle. The two significant phenomena related to keel sweep angle which can cause premature transition of the laminar boundary layer are crossflow instability and turbulent contamination of the leading-edge attachment line. These flow phenomena and methods to control them are discussed in detail. The remaining factors that affect the maintainability of laminar flow include surface roughness, surface waviness, and freestream turbulence. Recommended limits for these factors are given to insure achievability of laminar flow on the keel. In addition, the application of a simple trailing-edge flap to improve the hydrodynamic characteristics of a foil at moderate-to-high leeway angles is studied.

Experiments on the automatic control of boundary-layer transition

1994 ◽  
Vol 31 (6) ◽  
pp. 1416-1418 ◽  
Author(s):  
J.-L. Rioual ◽  
P. A. Nelson ◽  
M. J. Fisher
Keyword(s):  
Boundary Layer ◽  
Automatic Control ◽  
Boundary Layer Transition ◽  
Layer Transition

The automatic control of boundary-layer transition ? Experiments and computation

1995 ◽  
Vol 54 (4) ◽  
pp. 293-311 ◽  
Author(s):  
Petra Hackenberg ◽  
Jean-Luc Rioual ◽  
Owen R. Tutty ◽  
Philip A. Nelson
Keyword(s):  
Boundary Layer ◽  
Automatic Control ◽  
Boundary Layer Transition ◽  
Layer Transition
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