Types Of Fluid Flow

Card # 24 Types of fluid flow: Due to pressure (level difference) fluid flows towards the low pressure region from high pressure region. Fluid flow is mainly of two types: 1. Steady flow or streamline flow 2. Turbulent flow Streamline or Steady flow In streamline flow each particle follows the path of its preceding particle passing through the given point. In this flow the velocity of all particles passing through a point is the same. The path is straight line or curved. Turbulent flow In this turbulent flow each particle follows a path independent of any preceding particle and the velocity of particles passing through a point may be different. The path of the particles in this flow will be irregular and zigzag. Critical velocity of flow: In a fluid the flow remains streamline only when the velocity of flow is lesser than a definite value. The maximum value of the velocity of flow of a liquid below which flow remains streamlined is called its critical velocity of flow. Note: In case of steady flow of liquid velocity of flow < critical velocity In case of turbulent flow of liquid velocity of flow > critical velocity Reynold’s number Experiments indicate that a combination of four factors determines whether the flow of a fluid through a pipe is laminar or turbulent. This combination is known as Reynold’s number R. For the flow of a viscous liquids the average speed of flow η = coefficients of viscosity V αη

Vα

1

ρ = Density of the liquid

ρ 1 Vα D V αη V= R=

D =Diameter of the tube

Rη ρD V ρD

η

For low value of V ρ D and large η & R <200 flow will be streamlined For high value of V ρ D and low η &R= 2000 to 3000 flow will be unsteady R > 3000 flow will be turbulent.