ESS227
Prof. Jin-Yi Yu
Linking Lagrangian and Eulerian Views
•The conservation laws to be derived contain expressions for the
rates of change of density,
momentum, and thermodynamic energy following the motion of particular fluid parcels.
è The Lagrangian frame is particularly useful for deriving conservation laws.
•However, observations are usually taken at fixed
locations.
è The conservation laws are often applied in the
Eulerian frame.
Therefore, it is necessary to derive a
relationship between the rate of change of a field variable following the
motion (i.e., total derivative; Lagrangian view) and its rate of change at
a fixed point (i.e., local derivative; Eulerian view).