AA311.Lecture9.Slides

AA311.Lecture9.Slides - Flow separation. Is laminar or...

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AA311: Atmospheric Flight Mechanics Aerodynamics of Cylinders and Spheres Dr. Laszlo Techy University of Washington October 19, 2011 Dr. Laszlo Techy AA311: Atmospheric Flight Mechanics
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Viscosity is internal friction between the fluid elements. When a fluid is in motion, tangential stresses appear between the fluid elements themselves, and between the fluid elements and other objects that are exposed to the fluid flow. Due to viscosity, there can be no relative velocity between fluid in motion and a solid body at their surface of contact. τ = μ U h , Coefficient of viscosity μ . If the viscous forces are negligibly small in comparison to other forces (pressure, gravity, inertial), viscosity can be neglected, and the fluid is considered inviscid . Dr. Laszlo Techy AA311: Atmospheric Flight Mechanics
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Skin friction: Larger or smaller for a laminar boundary layer?
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Unformatted text preview: Flow separation. Is laminar or turbulent boundary layer better? Dr. Laszlo Techy AA311: Atmospheric Flight Mechanics Skin friction: small for laminar boundary layer. Large for turbulent boundary layer. Flow separation. Laminar turbulent layer promotes, turbulent boundary layer inhibits. Dr. Laszlo Techy AA311: Atmospheric Flight Mechanics Ideal Flow vs. Real Flow Dr. Laszlo Techy AA311: Atmospheric Flight Mechanics Ideal Flow vs. Real Flow Dr. Laszlo Techy AA311: Atmospheric Flight Mechanics Drag variation as a function of Reynolds number Transition from laminar to turbulent boundary layer is critical. Dr. Laszlo Techy AA311: Atmospheric Flight Mechanics Transition Transition from laminar to turbulent boundary layer is critical. Dr. Laszlo Techy AA311: Atmospheric Flight Mechanics Transition Dr. Laszlo Techy AA311: Atmospheric Flight Mechanics...
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AA311.Lecture9.Slides - Flow separation. Is laminar or...

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