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Homework Help: Polar Coordinates

  1. Feb 13, 2008 #1
    1. The problem statement, all variables and given/known data

    The velocity field for a line source in polar coordinates (r,theta) is given by:

    V=m/(2(pi)r) (in the "e" little r vector direction)

    convert to cartesian and calculate the strain rate tensor.

    2. Relevant equations

    R=Sqrt(x2+y2);
    Theta=ArcTan(Y/X);

    Cartesian form:
    X= R*cos(Theta)
    Y= R*sin(Theta)


    3. The attempt at a solution

    I just need to convert this, i understand how to get the strain rate tensor. I know how to compute between polar and cartesian but need theta. Or am I suppposed to assume theta=0?

    if theta=0 then y=0 andf x=r*sin(theta) but what do i use for r? If i solve for r i th efirst equation I get r=m/(2pi)

    x=rcos(0)
    x=m/(2pi)

    This doesn't seem right becasue I need a velocity field in terms of V(u,v) where u and v are in terms of x and y.

    Any help is greatly appreciated, Thanks
     
  2. jcsd
  3. Feb 13, 2008 #2
    I do not know what exactly you are asking, but if you are just asknig how to get from cartesian coordinates to polar ones than

    theta=arctan(y/x) while R=sqrt(x^2+y^2)
     
  4. Feb 13, 2008 #3
    I understand that as stated in my post under "Relevant Equations", thanks anyways
     
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