We study the Hawking radiation for the acoustic black hole. In the beginning we follow the outline of T.Jacobson but then we use a different $2+1$ vacuum state similar to the vacuum state constructed by W.Unruh. We also use a special form of the wave packets. The focus of the paper is to treat the 2 dimensional case, in particular, the case when the radial and angular velocity are variable.
Categories: gr-qc math-ph math.AP math.MP