13-07-2012, 11:31 AM
Fluid Kinematics
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Fluid kinematics is the study on fluid motion in space and time without considering the force which causes the fluid motion.
According to the continuum hypothesis the local velocity of fluid is the velocity of an infinitesimally small fluid particle/element at a given instant t. It is generally a continuous function in space and time.
Velocity Field
Eulerian Flow Description
Lagrangian Flow Description
Streamline
Pathline
Streakline
Flow Dimensionality
Most of the real flow are
3-dimensional and unsteady :
For many situations simplifications can be made :
2-dimensional unsteady and steady flow
1-dimensional unsteady and steady flow
Streakline
A streakline consists of all fluid particles in a flow that have previously passed through a common point. Such a line can be produced by continuously injecting marked fluid (smoke in air, or dye in water) at a given location.
For steady flow : The streamline, the pathline, and the streakline are the same.
Continuity Equation of a Steady Flow
For a steady flow the stream-tube formed by a closed curved fixed in space is also fixed in space, and no fluid can penetrate through the stream-tube surface, like a duct wall.