______ tends to occur in large diameter pipes in which fluid flows with high velocity.

Explanation:

Turbulent flow:

• Turbulent flow is the flow in which fluid particles flow in a random fashion where intermixing/intermingling is present.
• In Turbulent flow inertial force dominates over viscous force.
• It is unsteady in nature i.e. flow is not constant with time.
• In a pipe flow, flow becomes turbulent at Reynold number greater than 4000 i.e. Re ≥ 4000.
• Fluid layers are not parallel to each other. They can cross each other.

• Reynolds number, \({R_e} = \frac{{Vd}}{\nu }\;\) When Re < Rec Laminar flow occurs at very small velocities or through narrow passage (small d) or for highly viscous fluids, the Re will be small and flow will remain laminar.
• For high velocities, through large diameter pipes, Reynolds number will be sufficient to cause turbulence.