Talk:Potential flow around a circular cylinder

Regarding the Janzen-Rayleigh expansion, the formula given in the section was incorrect. I checked physically and I ran simulations, it makes no sense to have a plus sign as it was :$$\phi(r,\theta) = Ur\left(1+ \frac{a^2}{r^2}\right)\cos\theta - \mathrm{M}^2 \frac{Ur}{12} \left[\left( \frac{13 a^2}{r^2} - \frac{6 a^4}{r^4} + \frac{a^6}{r^6}\right) \cos\theta + \left(\frac{a^4}{r^4} - \frac{3a^2}{r^2} \right) \cos 3\theta\right]+ \mathrm{O}\left(\mathrm{M}^4\right) \,$$ I believe it is :$$\phi(r,\theta) = Ur\left(1- \frac{a^2}{r^2}\right)\cos\theta - \mathrm{M}^2 \frac{Ur}{12} \left[\left( \frac{13 a^2}{r^2} - \frac{6 a^4}{r^4} + \frac{a^6}{r^6}\right) \cos\theta + \left(\frac{a^4}{r^4} - \frac{3a^2}{r^2} \right) \cos 3\theta\right]+ \mathrm{O}\left(\mathrm{M}^4\right) \,$$. Therefore I changed it that way. — Preceding unsigned comment added by 2A01:CB08:189:DA00:AD69:8CA3:7B17:3888 (talk) 16:54, 4 April 2024 (UTC)