FLUID MECHANICS ASSIGNMENT
Name: Dhiraj Mohan Pathori
Roll no. :20045039
Fluid Mechanics involves the movement, forces related to fluid. Fluid is a substance
which cannot resist any shear force. It deforms easily under application of any shear
force as its molecules are loosely bound. Fluids are studied as continuous medium as
there is no change in density & viscosity, etc. The Knudsen Number (Kn) is a
dimensionless number defined as the ratio of the molecular mean free path length to
a representative physical length scale. It is used to determine the type of flow a fluid
may show such as continuum flow, slip flow, etc. Further there are two types of
observation- Eulerian (Observer is static) and Lagrangian (Observer is moving). Fluid
Element that we take for study should be big enough for no molecular fluctuation and
also all properties should remain same throughout. Also, Viscosity is the fluid’s
resistance to flow. Newton’s Law of Viscosity helps us in defining the relation between
shear stress, viscosity and the deformation rate of fluid particles. Fluids which follows
this law are called Newtonian fluids (Benzene, Water) and rest are called Non
Newtonian fluids (Pastes, Gels). Non Newtonian fluids have two behavior under the
increased influence of shear stress over time such as Rheopetic (thicken or solidify)
and Thixotropic (becomes less viscous). Kinematic Viscosity of a fluid is the ratio of
the viscosity of fluid to fluid’s density used to measure the fluid’s internal resistance
to flow under gravitational forces. In gases as temperature increases viscosity
increases but in liquids as temperature increases viscosity decreases. Compressibility
is a measure of the relative volume change of a fluid or solid as a response to a
pressure change. Surface tension is the surface film of a fluid caused by the attraction
of the particles in the surface layer by the bulk of the liquid, which tends to minimize
surface area. Fluid Statics used to identify forces acting on submerged body, etc
doesn’t mean fluid at rest only but that means that deformable nature of fluid
element is absent. Its restrictions are that fluid must be static, gravity is the only body
force, and shear stress must be vertically upward. In fluid mechanics we always use
control volume system as individual particles of fluid are not identified. Torricelli did
an experiment to prove that the source of vacuum comes from atmospheric pressure.
Reynolds Transport Theorem is a three dimensional generalization of the Leibniz
integral rule used for formulating basic equations of continuum mechanics.