Fluid kinematics is a term from
fluid mechanics
Fluid mechanics is the branch of physics concerned with the mechanics of fluids ( liquids, gases, and plasmas) and the forces on them.
It has applications in a wide range of disciplines, including mechanical, aerospace, civil, chemical and bio ...
, usually referring to a mere mathematical ''description'' or specification of a flow field, divorced from any account of the forces and conditions that might actually create such a flow. The term
fluids
In physics, a fluid is a liquid, gas, or other material that continuously deforms (''flows'') under an applied shear stress, or external force. They have zero shear modulus, or, in simpler terms, are substances which cannot resist any shear ...
includes liquids or gases, but also may refer to materials that behave with fluid-like properties, including crowds of people or large numbers of grains
if those are describable approximately under the
continuum assumption
Fluid mechanics is the branch of physics concerned with the mechanics of fluids (liquids, gases, and plasmas) and the forces on them.
It has applications in a wide range of disciplines, including mechanical, aerospace, civil, chemical and biomedi ...
as used in
continuum mechanics
Continuum mechanics is a branch of mechanics that deals with the mechanical behavior of materials modeled as a continuous mass rather than as discrete particles. The French mathematician Augustin-Louis Cauchy was the first to formulate such m ...
.
Unsteady and convective effects
The composition of the material contains two types of terms: those involving the time derivative and those involving spatial derivatives. The time derivative portion is denoted as the local derivative, and represents the effects of unsteady flow. The local derivative occurs during unsteady flow, and becomes zero for steady flow.
The portion of the material derivative represented by the spatial derivatives is called the convective derivative. It accounts for the variation in fluid property, be it velocity or temperature for example, due to the motion of a fluid particle in space where its values are different.
Acceleration field
The acceleration of a particle is the time rate of change of its velocity. Using an Eulerian description for velocity, the velocity field V = V(x,y,z,t) and employing the material derivative, we obtain the acceleration field.
References
{{Reflist
Kinematics
Fluid mechanics