reynolds number

1. Prepared by :
Mrs. Ankita N Gadge
(Assistant Professor)
SSBT’s Institute of Pharmacy Bambhori , Jalgoan

2. Fluid Dynamics:
Fluid dynamics deals with the study of fluid in
motion.
This knowledge is important of liquid, gels,
ointments which will change their floe behaviour
when expose to different stress conditions.

3. Types of Flow
The flow of fluid through a closed channel can be viscous or
turbulent.
It can be observed by Reynolds experiment
Identification of types of flow is important in,
 Manufacturing of dosage form
 Handling of drugs for administration
MIXING FLOW THROUGH PIPES FILLED IN CONTAINER

6. Laminar flow:
Flow in which fluid particles move in layer sliding with other
and there is no exchange of fluid particles from one layer to other is
called as laminar flow.
Turbulent flow:
When the velocity of water is increased thread of the colored
water disappears and mass of the water gets uniformly colored,
indicates complete mixing of the solution and the flow of the fluid is
called as turbulent flow.
Critical Velocity
The velocity at which the fluid changes from laminar flow to
turbulent flow that velocity is called as Critical Velocity

7. Reynolds Number
In Reynolds experiment the flow conditions are affected by
 Diameter of pipe, m (D)
 Average velocity, m/s (μ)
 Density of liquid, kg/ m3 (p)
 Viscosity of the fluid, (η)
This four factors are combined in one way as Reynolds number,
D μ p
η

8. Reynolds number is obtained by the following equation
Inertial forces Mass × Acceleration of liquid flowing
Viscous forces Shear stress × Area
Inertial forces are due to mass and the velocity of the fluid
particles trying to diffuse the fluid particles.
Viscous force if the frictional force is due to the velocity of the
fluid which make the motion of the fluid in parallel.

9.  At low velocities the inertial force are less when compared to
the frictional forces.
 Resulting flow will be viscous in nature.
 Other hand when the inertial forces are predominant the fluid
layer break up due to the increase in velocity hence turbulent
flow takes place.

10. If Re < 2000 the flow is said to be Laminar
If Re > 4000 the flow is said to be turbulent
If Re lies between 2000 to 4000 the flow change between laminar
to turbulent
Application:
1. Reynolds is used to predict the nature of the flow
2. Stocks law equation is modified to include Reynolds number
to study the rate of sedimentation of suspension.