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Old   April 27, 2009, 02:24
Default Negative Vorticity
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Hi,
I want to learn that what negative vorticity means.İf vorticity is negative, what is hapening?...or what makes vorticity negative?
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Old   April 27, 2009, 04:11
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I believe its a relative term to indicate the direction of fluid rotation. You can use the right hand thumb rule to conclude that positive vorticity is related to counter-clockwise rotation of the fluid and negative vorticity is related to clockwise rotation of the fluid. As an example, consider the unseparated, laminar flow past a flat plate in the XY plane (from left->right): on top of the plate, you will find negative vorticity. You can imagine this negative vorticity as infinite number of cylinders rotating in the clockwise direction due to fluid moving towards the positive x-direction ( towards the right)...
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Old   April 27, 2009, 07:14
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Vorticity is a vector and can therefore have an indefinite number orientations. In 2D the vector only has a component in the direction perpendicular to the plane. A positive value of this component indicates counter-clockwise and a negative value a clock-wise rotation (right hand rule). In 3D positive or negative only relates to one of the components of the vector (eg. spanwise component for a cylinder vortex shedding flow).
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