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  _____    __   __  __    __   __   __   _    _   
 |__  //   \ \\/ // \ \\ / //  \ \\/ // | || | || 
   / //     \ ` //   \ \/ //    \ ` //  | || | || 
  / //__     | ||     \  //      | ||   | \\_/ || 
 /_____||    |_||      \//       |_||    \____//  
 `-----`     `-`'       `        `-`'     `---`

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