Easy Question, What does this symbol mean?

[BadWolf]

What does the upside down hat mean in vector notation. I stumbled across this symbol in my fluid mechanics book compressible flow, Munson seems to like use lots of non standard notations to begin with but I figure this symbol is still commonly used somewhere. Hat usually implies a unit vector but upside down hat?

$$c_{v}=\frac{\partial\check{u}}{\partial T}$$

I would guess that Munson uses the check as latex calls it to make sure you notice that he means internal energy rather than velocity as u often represents. I was curious what the history of this symbol is as this is the first time I've seen it used.

 

[lippyka]

The upside down hat in vector notation is typically used to denote the gradient of a vector field. The check symbol, as you correctly pointed out, is commonly used to denote internal energy rather than velocity. The upside down hat is often used to signify that the gradient of the vector field is being taken in the direction of the vector rather than the magnitude of the vector.