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I am very confused with this thing can someone clarify these problems given below-- 1 //Do or can the streamlines of a fluid particle show the position of the particle at a time( using the streamlines)?? 2// I know that streamlines cannot intersect because at a specific instant the particle reaching the intersection will have two different directions of motion (in the steady flow of particles), but can I say the same thing in turbulent flow for the LINE OF FLOW of the particles // why or why not?? 3//is it necessary that a streamLINE will be a perfect straight line(to a good approximation)?? If know why is it called a line then??

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  • $\begingroup$ @Fabrice I don't know how or why this happened ?? Never happened before ??,as I only run this site from smartphone?? $\endgroup$ – Freelancer Oct 28 '15 at 12:42
  • $\begingroup$ Maybe because of the hash will remove them $\endgroup$ – Freelancer Oct 28 '15 at 12:43
  • $\begingroup$ yep ! NB: you get item bullets just using '- blah ' + return. $\endgroup$ – Fabrice NEYRET Oct 28 '15 at 12:46
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  • On a steady flow, streamlines correspond to the trajectory of "fluids particles" or parcels. (Not to be confused with the one of the real "particles" that are the molecules.)
  • But if it's not a steady flow, it's wrong. You might even see appearant source and sink in the lines that do not exist as a flow.
  • Steady flow streamlines cannot cross because of basic continuity and conservation laws: otherwise a particle should teleport itself on the other side of the obstacle that is the crossing flow ;-)
  • A streamline is a curve, not especially a straight line.
  • More on wikipedia.
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  • $\begingroup$ For your first point -- are fluid particles not molecules ?? Then want are they!! Just some imaginary particles!! $\endgroup$ – Freelancer Oct 28 '15 at 12:49
  • $\begingroup$ Also can you please clarify the answer of my first question?? Couldn't get it, $\endgroup$ – Freelancer Oct 28 '15 at 12:50
  • $\begingroup$ "are fluid particles not molecules ?" : No they aren't. For instance what you think is still air is indeed made of molecules swarming around at very high speed ( ranging up to more than 1000 km/h. And their mutual shock is what makes pressure). Same for what you think is calm water flowing in a precise direction. Fluid "parcels" are the averaging of more complex microscopic motion. $\endgroup$ – Fabrice NEYRET Oct 28 '15 at 12:52
  • $\begingroup$ Also you didn't answer or I couldn't understand!! The answer to the question that can the LINE OF FLOW (not streamlines) intersect in turbulent flow?? $\endgroup$ – Freelancer Oct 28 '15 at 12:52
  • $\begingroup$ NB: did you had a look on the definitions and schemes in the wikipedia link I gave ? $\endgroup$ – Fabrice NEYRET Oct 28 '15 at 12:56
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Two particle cannot overcome each other because if it crosses then the direction of particles will be two different tangents at 1point which is not possible

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