Hydrodynamics is a branch of physics dealing with the motion of fluids and forces on objects within fluids, and this document discusses key hydrodynamic concepts like diffusion, gradients, osmosis, and velocity, as well as techniques like analytical ultracentrifugation and dynamic light scattering. It also examines how biological macromolecules behave as hydrodynamic particles in terms of properties like hydration, friction, and Reynolds number, and how their frictional properties can be predicted based on particle shape.

1. Hydrodynamics
Presented by
Mr.Halavath Ramesh
M.A,M.sc,B.ED,PGDCAQM,PGDCA,M.Phil,(P.HD)(UoH)
E-mail: halavathramesh39@gmail.com
University of Madras
Dept. of Chemistry
Loyola College ,Chennai.

2. INTRODUCTION
 Hydrodynamic: Hydrodynamic is a branch of physics that deals with
the motion of fluids and the forces acting on solid bodies immersed in fluids
and in motion relative to them.
 Diffusion: Diffusion derives from the Latin word, which means” to spread
way out”. Diffusion is the net movement of molecules from a region of higher
concentration to a region of lower concentration. Diffusion is driven by a
gradient in chemical potential of the diffusing species.
 Gradient: The gradient is a multi-variable generalization of the derivative.
Function of several variables.
 Osmosis: Osmosis is a spontaneous net movement of solvent molecules
through a selectively permeable membrane into a region of higher solute
concentration in the direction that tends to equalize the solute concentration on
the two sides.
 Velocity: The speed at which an object is travelling ,velocity is defined as a
vector measurement of the rate and direction of motion.

3. Speed:
Radius: Radius is a line from the centre to the outside of the of a circle or
sphere.
Example. Bike wheel.
Diameter: Diameter is a straight line passing from side to side through the
centre of a body or figure especially a circle or sphere.

4. Hydrodynamic Techniques
1. Analytical ultracentrifugation
2. Electrophoresis
3. Electric birefringence
4. Flow birefringence
5. Dynamic Light Scattering
6. Fluorescence correlation spectroscopy
7. Viscosity
8. Diffusion
9. Hydration
10. Friction

5. Biological macromolecules as hydrodynamic particles
Traditionally, hydrodynamic deals with the behaviour of bodies in fluids and in
particular, with phenomena in which a force acts on a particle in a viscous in particular ,
with phenomena in which a force acts on a particles in a viscous solution. Very eminent
scientists, such as Isaac Newton, James clerk maxwell,Lord Rayleigh and Albert Einstein
,started their careers with major contributions to the science of hydrodynamics. Note that
not only are the discoveries from more than 100 years ago still highly relevant today, but
also that they continues to stimulate important new developments in the field.
Reynolds number
we consider an object moving with some velocity through a fluid of specific density
and viscosity. The Reynolds number is a dimensionless parameter, which determines the
relative importance of inertial and viscous effects
Reynolds number = fluid density * speed*particle size
____________________________ =R= ƥǔƖ / Ƞ
Viscosity
When the Reynolds number is low , viscous forces dominate. If it is high, inertial
forces dominate.

6. Hydration
In hydrodynamic experiments, a biological macromolecules moves with a certain amount
of bound solvent, thus defining the concept of a hydrated particles as a core of particles
material and envelope of bound water.
Protein hydration ,ᵟ (gg-1), express the ratio of the mass of the bound water to that of the
protein.
ᵟ = grams(water)
____________
gram (protein)
Determination of particle friction properties
Stick boundary conditions: In stick condition the solvent layer sticks to the particle
surface and moves with it.
Slip boundary conditions: In slip condition there is no interaction between the
solvent and particle and the solvent slips over the particle surface.

7. Prediction of particle friction properties
Modern hydrodynamics allows the prediction of the frictional properties of
biological macromolecules of any shape. The computing procedure used essentially
depends on the particle shape.
1. Particles of” round “shape
2. Particles with a ‘ broken ‘ shape
3. Particles of arbitrary shape
4. Particles with a known three- dimensional structure