Streak line

Streaklines from smoke show the flow to various objects in a wind tunnel .

A coating line (engl. Streakline ) draws in the fluid mechanics the path of several particles according to the same position of a successively flow field are released. An illustrative example is a chain of buoys that are placed one after the other from a jetty into a river, or the flow of exhaust gas from a chimney.

Stroke lines , along with streamlines , railway lines and timelines, are part of the visualization concept “Characteristic Lines” for flow fields. In the case of steady currents , there is no difference between streamline, streakline and railway line .

calculation

If the time-dependent velocity field is known, streak lines can be calculated by numerically integrating the following initial value problems : ${\displaystyle {\vec {u}}({\vec {x}},t)}$

${\displaystyle {\begin{cases}\displaystyle {\frac {d{\vec {x}}_{\tau }}{dt}}={\vec {u}}({\vec {x}}_{\tau },t)\\[1.2ex]{\vec {x}}_{\tau }(t=\tau )={\vec {x}}_{0}\end{cases}}}$

where the streak line starting from is parameterized . ${\displaystyle \tau }$ ${\displaystyle {\vec {x}}_{0}}$