# Linear distortion of a body

## Main Question or Discussion Point

In my thermodynamics class, I'm seeing that when a body gets linearly distorted we use the divergence of the velocity to find how much the body gets distorted and if the divergence is 0 then the body is incompressible.

Div v = (nabla) (v)

Please! Can someone explain to me why this works just shortly? What is divergence???

I had never seen divergence in my life so I'm very confused. Thanks a lot and hope my translation of all the mentioned terms is correct, since my class is in spanish.

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What you are missing is a course in vector calculus, where the nabla operator (also called del) and the divergence are discussed in detail.

In my opinion, the best concise treatment is in the preliminary chapter of an Electromagnetism textbook, Introduction to Electrodynamics by David Grifiths.

Have you learnt what a vector field is ? Divergence is a property of such a field. It tells us about the way the field 'flows'. It is used a lot in fluid dynamics and electromagnetism.

Yeah, I know I need a vector calculus course. However, can any one give me an idea of what a divergence of a velocity mean? How is the idea of the way the field flows relate with a velocity?

vanesch
Staff Emeritus