Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Issues solving this DE

  1. Jul 14, 2009 #1
    I am trying to solve this differential equation: http://sites.google.com/site/theuntouchableproject/" [Broken]
    I believe i can come up with 2 boundary conditions for p and dp/dx.
    i want to create a mesh such that i can solve this equation at different locations that i perscribe. What methods can i use to solve this equation... this is the first time i have ran into an equation of this form.
    Last edited by a moderator: May 4, 2017
  2. jcsd
  3. Jul 15, 2009 #2
    Hi there Mad MechE,

    Your mention of a mesh makes me inclined to think you are asking about the most suitable numeric algorithm to solve the equation, is it the case?

    In any case the ODE looks to me rather well behaved and depending on the accuracy you are looking for any standard method would do your purposes.

    I attach a copy of the resulst given by the quickest of the alogorithms I know, i.e. just use MathCAD. But any home built algorithm would do the same.



    Attached Files:

  4. Jul 15, 2009 #3


    User Avatar
    Science Advisor

    Why do you have partial derivative signs on the left side when "x" appears to be the only variable? If there is some other variable, say "y" or "t", since it does not appear in the equation, you can just ignore it.

    We can immediately integrate both sides with respect to x to get
    [tex]h^3\frac{dp}{dx}= 6U\mu h[/itex]
    [tex]\frac{dp}{dx}= \frac{6U\mu}{h^2}+ C[/tex]
    and, since [itex]h= x_0+ x^2/2R[/itex], that is
    [tex]\frac{dp}{dx}= \frac{6U\mu}{(x_0+ x^2/2R)^2}[/tex]
    and you just have to integrate, using, I would recommend, "partial fractions".
  5. Jul 15, 2009 #4
    I think i may have over simplified the problem... which is good because now i have a baseline for the data i want... later tonight i will write up the problem i am having and upload them!
    Thank you all for your help!!

  6. Jul 17, 2009 #5
    Alright... i found this paper that has the ability to solve my problem but i don't know any real way about setting it up to do it numerically. I have attached that paper such that it can be referenced to. I read it several times and i don't think i fully comprehend the way the solution was set up. I was hoping that i could produce some matlab code to solve the problem but i need to understand it first. Could you please assist me in figuring out what it all means?



    Attached Files:

Share this great discussion with others via Reddit, Google+, Twitter, or Facebook