# In the context of laminar flow, which of the following statements is the most appropriate?

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In the context of laminar flow, which of the following statements is the most appropriate?
1. Flow is always through small tanks.
2. Particles move in a turbulent order.
3. Laminar flow is observed in high viscous fluids at low velocity.
4. There will be an exchange of momentum from fluid particles of one layer to another layer.

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Correct Answer - Option 3 : Laminar flow is observed in high viscous fluids at low velocity.

Explanation:

Laminar flow:

• In fluid dynamics, laminar flow is defined by fluid particles following smooth paths in layers, with each layer moving smoothly past the adjacent layers with little or no mixing.
• The fluid tends to flow without lateral mixing at low velocities, and adjacent layers slide past each other like playing cards.
• There are no cross-currents perpendicular to the direction of flow, nor eddies or swirls of fluids.
• The motion of the fluid particles is very orderly in laminar flow, with particles near a solid surface moving in straight lines parallel to that surface.
• Laminar flow is characterised by low momentum convection and high momentum diffusion.
• Laminar flow is observed in high viscous fluids at low velocity.
• The Reynolds number, a dimensionless flow parameter that also depends on the viscosity and density of the fluid as well as the channel dimensions, determines the velocity.

The Reynolds number is defined as, Re = $\frac{ρ VD}{μ}=\frac{VD}{ν}$

where, ρ = density of the fluid, V = velocity of the fluid, D = diameter of the change, μ = dynamic viscosity of the fluid, and ν = kinematic viscosity of the fluid = $\frac{\mu}{\rho}$

For flow through a pipe, the flow is

• Laminar if Re < 2300
• Transition if 2300 < Re > 4000
• Turbulent if Re > 4000

 Sr. No. Laminar flow Turbulent flow 1 It is a fluid flow in which the fluid layers move parallel to each other and do not cross each other. It is a fluid flow in which the fluid layers cross each other and do not move parallel to each other. 2 The laminar flow generally occurs in the fluid flowing with low velocity. The turbulent flow occurs when the fluid flows with high velocity. 3 Laminar flow occurs in the small diameter pipes in which fluid flows with low velocity. Turbulent flow occurs in large diameter pipes in which fluid flows with high velocity. 4 The fluid flow is laminar when the value of Reynolds number (Re) is less than 2000. The fluid flow is turbulent when the value of Reynolds number is greater than 4000. 5 Shear stress in laminar flow depends only on the viscosity of the fluid and independent of the density. Shear stress in the turbulent flow depends upon the density of the fluid. 6 The fluid flow is very orderly i.e. there is no mixing of adjacent layers of the fluid and they move parallel to each other and also with the walls of the pipe. The fluid flow is not orderly i.e. there is mixing of adjacent layers of fluid with each other and they do not move parallel to each other and also with the walls of the pipe.