Bernoulli principle or due to Viscosity?

[abrowaqas]

Why the speed of water in the middle of the smooth flowing stream is high than its speed on the sides?

Is it due to Adhesion or cohesion forces or viscosity or Bernoulli principle holds here?
Kindly tell me exact reason .

 

[arildno]

What is your precise reasoning for thinking Bernoulli might be relevant here?
In particular:
What is a streamline?

 

[RandomGuy88]

It is due to viscosity. You should look read about a boundary layer.

 

[abrowaqas]

But if we apply bernoulli's principle here: I-e
" where the pressure is high in a fluid there is low velocity and where the pressure is low in a fluid motion , velocity will be higher..
We know that at sides there is more pressure due to Adhesion and Cohesion forces hence speed is low.
However at middle only cohesion forces are available that low pressure hence more velocity ..

 

[boneh3ad]

Like RandomGuy88 said, all you have to think about is viscosity. Viscosity enforces the no-slip condition, i.e. the velocity at the wall relative to the wall is zero, hence you have zero velocity at the wall. In the middle it is obviously faster than zero.