Laminar and Turbulent flow DIFFERENCES.pptx

LAMINAR FLOW

1. BIOMECHANICS UNIT 2 TOPIC: Laminar and Turbulent flow

2. Laminar Flow The fluid flow in which the adjacent layers of the fluid do not mix with each other and moves parallel to each other is called laminar flow . In the laminar flow, the fluid layer moves in straight line. The laminar flow always occurs when the fluid flow with low velocity and in small diameter pipes. The fluid flow having Reynolds number less than 2000 is called laminar flow. 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.

3. Shear stress in laminar flow depends only on the viscosity of the fluid and independent of the density. Example: Consider running water through a hose. You may observe the water flowing in a straight line while the amount and rate of flow remain low. This smooth and streamlined nature of fluid motion is considered a laminar flow.

4. Turbulent Flow The fluid flow in which the adjacent layers of the fluid cross each other and do not move parallel to each other is called turbulent flow. In turbulent flow the fluid layers do not move in a straight line. They move randomly in a zigzag manner. The turbulent flow occurs when the velocity of the fluid is high and it flows through larger diameter pipes . The fluid flow having Reynolds number greater than 4000 is called turbulent flow.

5. The fluid does not flow in a definite order. There is a mixing of different layers and they do not move parallel to each other but cross each other. The shear stress in turbulent flow depends upon its density. Example: Turbulent flow is a common occurrence and can be observed in the flow of rivers, smoke coming out of exhaust pipes, or even experienced during turbulence in aircraft

6. Laminar and turbulent flow

7. Laminar and Turbulent Flow Laminar flow Streamlined Outermost layer moving slowest and center moving fastest Turbulent flow Interrupted Rate of flow exceeds critical velocity Fluid passes a constriction, sharp turn, rough surface

8. Reynolds number is an important dimensionless parameter that identifies the behavior of fluid based on attributes like viscosity or velocity of the fluid. Accordingly, the value of Reynolds number (R e ) can be expressed as : Note that: ρ is the density of the fluid V is the fluid velocity D is the hydraulic diameter (of pipe, tube, or duct). μ is the fluid viscosity Reynolds Number

9. I mportant takeaways from the Reynolds number calculation include: A flow is considered laminar if the Reynolds number is up to 2300. Viscous force is more prominent due to the slower flow rate. A flow is considered turbulent if the Reynolds number is greater than 3500. A faster and irregular flow path maximizes the inertial force in the system.  Flow regime for the Reynolds number between 2300 to 3500 is considered transitional flow.