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bio website tudelft.nl
location Delft, Netherlands
age 27
visits member for 1 year, 11 months
seen Dec 16 at 6:48

May
18
comment Existence and uniqueness of Stokes flow
@Qmechanic Ok! I have corrected the referencing.
May
18
comment Existence and uniqueness of Stokes flow
Don't pin me down on it, but I believe the situation is only unsolvable if the far-field is unbounded
May
18
answered Existence and uniqueness of Stokes flow
May
13
awarded  Caucus
May
4
awarded  Citizen Patrol
May
3
revised Inaccuracy in numerical calculation of arclength of part of an ellipse
deleted 111 characters in body
May
3
accepted Inaccuracy in numerical calculation of arclength of part of an ellipse
May
3
comment Inaccuracy in numerical calculation of arclength of part of an ellipse
ok, this is pretty embarrassing. The mistake was in a function call where I had swapped the parameters of 2 ellipses. So I got the shape-plot for 1 ellipse (with b=2.5) while I got the integral for a different one (with b=0.52). Anyway, it's solved. Thanks for the effort and sorry about the dumb mistake
May
3
comment Inaccuracy in numerical calculation of arclength of part of an ellipse
Ah ok, so I am at least getting the same number. So maybe the error is already somewhere earlier: in the value of $\phi_s$. I will look into it and come back here when I sorted things out. Thanks for the help!! It's much appreciated
May
3
comment Inaccuracy in numerical calculation of arclength of part of an ellipse
You're right, they both are the same (I was missing a bracket), but still I get a much higher value. What I noticed by the way is that you use b=2.5 while I have b=0.52. What do you get with that smaller b?
May
3
comment Inaccuracy in numerical calculation of arclength of part of an ellipse
mmm that's odd. I found this for the integrand: $$a b \sqrt{\frac{b^4 \cos^2\phi+a^4 \sin^2\phi}{(b^2\cos^2\phi+a^2\sin^2\phi)^3}}$$ which is supposed to be the same according to ($\cos^2\phi+\sin^2\phi=1$) but apparently it is not????
May
3
comment Inaccuracy in numerical calculation of arclength of part of an ellipse
By the way: I agree that a different parametrization would be better. The thing is that I also need the polar angle so I will have to do a bit of work connecting the parametrization you suggest with the polar angle
May
3
revised Inaccuracy in numerical calculation of arclength of part of an ellipse
added 111 characters in body
May
3
comment Inaccuracy in numerical calculation of arclength of part of an ellipse
yeah, I see that now. Do you have a symbolic answer to the integrand? Then at least I can start looking for my mistake from there! Anyways, Thanks for the quick help!!
May
3
comment Inaccuracy in numerical calculation of arclength of part of an ellipse
@your first comment: sorry I wrote down the value in degrees instead of radian, I fixed it in the post. The relative distance comes from the fact that I know where the tip of the ellipse and the point $\phi_s$ are ---- your second comment: So you are saying that the problem is most likely caused by the parametrization in combination with round-off errors?
May
3
revised Inaccuracy in numerical calculation of arclength of part of an ellipse
added some clarification
May
3
revised Inaccuracy in numerical calculation of arclength of part of an ellipse
fixed mistake in integral
May
3
asked Inaccuracy in numerical calculation of arclength of part of an ellipse
Apr
29
comment Wisdom of the crowd in estimative calculation
@joriki yes, I think it is safe to assume that the estimates for the individual quantities are normally distributed
Apr
29
asked Wisdom of the crowd in estimative calculation