trajectory

(Or path.) A curve in space tracing the points successively occupied by a particle in motion.

At any given instant the velocity vector of the particle is tangent to the trajectory. In steady- state flow, the trajectories and streamlines of the fluid parcels are identical. Otherwise, the curvature of the trajectory K_T is related to the curvature of the streamline K_S by

where V is the parcel speed and ∂ψ/∂t is the local change of the wind direction. The curvatures and wind change are positive for the cyclonic sense of flow.

An aggregation of sufficiently many atoms or molecules that it can be assigned macroscopic properties such as volume, density, pressure, and temperature.