A pair of infinitely long, counter-rotating line vortices of the same circulation strength $\Gamma$ are situated a distance $h$ apart in a fluid, as shown in the figure. The vortices will

(A) rotate counter-clockwise about the midpoint with the tangential velocity at the line vortex equal to $\frac{\Gamma}{2 \pi h}$

(B) rotate counter-clockwise about the midpoint with the tangential velocity at the line vortex equal to $\frac{\Gamma}{4 \pi h}$

(C) $\quad$ translate along $+y$ direction with velocity at the line vortex equal to $\frac{\Gamma}{2 \pi h}$

(D) $\quad$ translate along $+y$ direction with velocity at the line vortex equal to $\frac{\Gamma}{4 \pi h}$

A pair of infinitely long, counter-rotating line vortices of the same circulation strength $\Gamma$ are situated a distance $h$ apart in a fluid, as shown in the figure. The vortices will

(A) rotate counter-clockwise about the midpoint with the tangential velocity at the line vortex equal to $\frac{\Gamma}{2 \pi h}$

(B) rotate counter-clockwise about the midpoint with the tangential velocity at the line vortex equal to $\frac{\Gamma}{4 \pi h}$

(C) $\quad$ translate along $+y$ direction with velocity at the line vortex equal to $\frac{\Gamma}{2 \pi h}$

(D) $\quad$ translate along $+y$ direction with velocity at the line vortex equal to $\frac{\Gamma}{4 \pi h}$

1 Answer

127 votes

(C) $\quad$ translate along $+y$ direction with velocity at the line vortex equal to $\frac{\Gamma}{2 \pi h}$

127 votes

127