A lagrangian view of turbulent dispersion and mixing

摘要: Introduction For good practical reasons, most experimental observations of turbulent flow are made at fixed points x in space time t and numerical calculations performed on a spatial grid times. On the other hand, it is possible to describe terms velocity concentration (and quantities interest) point moving with flow. This known as Lagrangian description ((Monin Yaglom, 1971)). The position this + ( t; 0 , ) function some initial x0 t0 which was identified or “labelled”. Its fluid where happens be t, u (t; = (t), t) . We will use superscript (+) denote quantities, after semi-colon independent parameters. refer way particle. Flow statistics obtained times Eulerian statistics. specific by sampling over trajectories, reference passed through points, example, mean displacement those particles that just 〈 − 〉 In both cases, measurement can earlier later than time.