The Influence of Laminar Boundary Layer Transition on Entry Vehicle Design and Its Performance

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.

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The Critical Height of Distributed Roughness to Cause Boundary Layer Transition

Journal of the Royal Aeronautical Society ◽

10.1017/s0001924000093301 ◽

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.

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Physical Mechanisms of Laminar-Boundary-Layer Transition

Annual Review of Fluid Mechanics ◽

10.1146/annurev.fl.26.010194.002211 ◽

1994 ◽

Vol 26 (1) ◽

pp. 411-482 ◽

Cited By ~ 316

Author(s):

Y S Kachanov

Keyword(s):

Boundary Layer ◽

Laminar Boundary Layer ◽

Boundary Layer Transition ◽

Layer Transition ◽

Physical Mechanisms

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Hypersonic Boundary-Layer Transition: Application to High-Speed Vehicle Design

Journal of Spacecraft and Rockets ◽

10.2514/1.31134 ◽

2008 ◽

Vol 45 (2) ◽

pp. 176-183 ◽

Cited By ~ 16

Author(s):

Kei Y. Lau

Keyword(s):

Boundary Layer ◽

High Speed ◽

Boundary Layer Transition ◽

Vehicle Design ◽

Hypersonic Boundary Layer ◽

Layer Transition ◽

High Speed Vehicle

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Keel Design for Low Viscous Drag

Journal of Ship Research ◽

10.5957/jsr.1989.33.2.145 ◽

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.

Download Full-text