Text this

Number:

Provider:

CAPTCHA:

  _  _     ______             __   __    _____   
 | \| ||  /_   _//   ____     \ \\/ //  |__  //  
 |  ' ||   -| ||-   |    \\    \ ` //     / //   
 | .  ||   _| ||_   | [] ||     | ||     / //__  
 |_|\_||  /_____//  |  __//     |_||    /_____|| 
 `-` -`   `-----`   |_|`-`      `-`'    `-----`  
                    `-`

Please enter what you see:

Text this: Head-on collisions of vortex rings upon round cylinders