Ship Design and Performance Assessment

AFT’s unique combination of efficiency and accuracy enables RANS to be used just like a towing tank in traditional naval architecture.  RANS can perform resistance tests, powering tests, wave cuts, and nominal wake surveys.  It can also be used to compute effective wake — the propulsor inflow present with a propeller operating.  True effective wake is essential for good propeller design, but is difficult to obtain in the towing tank.  Traditional approaches extrapolate from data obtained without the propulsor, and more accurate results require expensive laser doppler velocimeter surveys. 

RANS has other advantages over the towing tank.  Since RANS can be run with any combination of Reynolds and Froude numbers, it is possible to obtain crucial design information at full scale.  Total turn-around time is shorter for RANS because digital models can be constructed much faster than physical tank models.  More design options can be compared over a wider range of parameters, and a more diverse set of operating conditions considered.  The bottom line is that additional passes can be made around the design spiral resulting in increased overall performance.  These advantages eliminate major sources of uncertainty in the design process, and lead to improved final products. 

It should be noted that AFT’s RANS codes are not intended to replace the towing tank, but rather to supplement it.  The best approaches utilize RANS to streamline the identification of good design ideas, and towing tank tests to verify progress.  Click on a menu item at left to see examples of how AFT has been used to improve our customers’ ship design processes.