Angle of diverging portion of the venturimeter is limited to 7°, because:

1) Flow decelerates in the diverging portion and pressure increases in the downstream direction. Hence, the fluid experiences an adverse pressure gradient, if the divergence angle is large.

2) Flow separation takes place due to adverse pressure gradient when divergence angle Is large.

3) If the divergence angle is large an negative pressure is created at the throat which obstructs the throat which obstructs the flow of fluid.

Which of the above reasons are correct?