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This section reviews the concepts of curl and divergence in vector fields, particularly within fluid dynamics. We explore how a velocity vector field, represented by F, behaves in terms of rotation and divergence. The example provided illustrates a diverging vector field that is irrotational, as well as a rotating field with non-zero curl. Differential identities involving curl and divergence are also discussed, highlighting their importance in computing vector field properties. These concepts are essential for understanding fluid behavior and dynamics.
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MA 242.003 • Day 57 – April 8, 2013 • Section 13.5: • Review Curl of a vector field • Divergence of a vector field
Let F represent the velocity vector field of a fluid. What we find is the following: Example: F = <x,y,z> is diverging but not rotating curl F = 0
All of these velocity vector fields are ROTATING. What we find is the following: F is irrotational at P. Example: F = <x,y,z> is diverging but not rotating curl F = 0
All of these velocity vector fields are ROTATING. What we find is the following:
All of these velocity vector fields are ROTATING. What we find is the following: Example: F = <-y,x,0> has non-zero curl everywhere! curl F = <0,0,2>
Differential Identity involving curl Recall from the section on partial derivatives: We will need this result in computing the “curl of the gradient of f”
The Divergence of a vector field Then div F can be written symbolically as:
The Divergence of a vector field Then div F can be written symbolically as:
So the vector field Is incompressible
So the vector field Is incompressible However the vector field
So the vector field Is incompressible However the vector field Is NOT – it is diverging!