Finding streamlines from velocity components

  • Thread starter CMJ96
  • Start date
2 replies · 2K views · last reply
CMJ96
Messages
50
Reaction score
0

Homework Statement


Exam question text: Question 2 (24 marks) asking for the streamline and pathline of the flow velocity (x/(1+t), 1) for x > 0, with parts (a) to (f).


Homework Equations


$$\frac{dy}{dx}=\frac{v_y}{v_x}$$[/B]

The Attempt at a Solution


I have subbed the given values for $$v_y$$ $$v_x$$ into the equation above, and integrated, i got the following expression
$$y=\left(1+t \right) lnx $$
I'm not sure where to go next, do I sub in $$x_0$$ $$y_0$$ ?
 
Attachments
  • Exam question text: Question 2 (24 marks) asking for the streamline and pathline of the flow velocity (x/(1+t), 1) for x > 0, with parts (a) to (f).
    w1CNc3i.png
    22.7 KB · Views: 881
Last edited by a moderator:
You cannot solve it like that. Your differential equation depends on time ##t##, which is not constant. You need to solve the system
$$
\frac{dx}{dt}= v_x, \quad \frac{dy}{dt}= v_y.
$$

Edit: Sorry, missed the title. Those are the pathlines. For the streamlines yes, but you are missing an integration constant that you will need to adapt your solution to the initial condition. Otherwise you would have only one streamline.
 
So I should sub in limits of x=x_0 and y=y_0 up to y=y and x=x and add in a constant of integration?
 
Last edited: