(Refer Slide Time: 38:13)
Now, what is the physical meaning of phi, if I look at the physical meaning of phi, because if I look at this like if I considered the integral c my q dot d bar d r bar. What does gives me? This gives me integral over c u d x plus v d y plus w d z and this gives me integral over c. If I say the flow irritational for a rotational flow, this will del phi by del x plus del phi by del y plus sorry d x plus del phi by del y d y plus del phi by del z d z. And this is nothing but d phi integral our c that is nothing but d phi.