2.4.1 Concept of Continuum
Typically matter is made up of atomic and sub-atomic particles. Thus, when
analyzing those at micron level, matter becomes discontinuous in space with
inter-atomic separation. However, when considering fluids as a continuum material,
assumptions have to be made where we have to neglect that atoms are the smallest
unit. And, the matter/fluid must be defined in terms of continuous fields, such as
density and force density (defined as per unit volume), rather than discrete physical
quantities, such as mass and force. The continuum can be confirmed for fluids by
first reducing the sample volume to a very small magnitude and then measuring
intrinsic properties, like density, at several points in liquid space. The density
should be equal to approve the consideration of fluid continuum.
2.4.2 Important Intrinsic Properties
- Mass density (ρ; Kg/m^3 ): It is the mass distribution over a unit volume,
- Specific volume (V; m^3 /Kg): It is the volume occupied by a unit mass,
- Weight density or Specific weight (γ; N/m^3 ): It is the force due to gravity on the
mass in a unit volume and is expressed as
γ¼gρ ð 1 : 10 Þ- Specific gravity or Relative density (δ): it is the ratio of density of the fluid to the
density of water, - Viscosity: It is the resistance offered by the fluid to gradual deformation by
neighboring fluid layers under an external force, namely shear stress or tensile
stress. It is also known as thickness of the fluids. This parameter also represents
Fig. 1.3 Buoyancy-driven mixing in liquids with various types of bubble flows. Each type of
bubble flow introduces mixing which could be diffusive or turbulent
10 C.K. Dixit