發送短信 : A visual study of vortex rings fired transversely into a cross-flow

  ______     ___     _    _      ___      ______  
 /_____//   / _ \\  | |  | ||   / _ \\   /_   _// 
 `____ `   | / \ || | |/\| ||  | / \ ||    | ||   
 /___//    | \_/ || |  /\  ||  | \_/ ||   _| ||   
 `__ `      \___//  |_// \_||   \___//   /__//    
 /_//       `---`   `-`   `-`   `---`    `--`     
 `-`