Text this: Interactions between circular vortex-rings and free-surfaces

           _    _                ___              
    ___   | || | ||     ___     / _ \\    ____    
   /   || | || | ||    /   ||  | / \ ||  |    \\  
  | [] || | \\_/ ||   | [] ||  | \_/ ||  | [] ||  
   \__ ||  \____//     \__ ||   \___//   |  __//  
    -|_||   `---`       -|_||   `---`    |_|`-`   
     `-`                 `-`             `-`