This work originated from a search for a simple test method to determine the control derivatives of a ship to replace existing more expensive and time consuming methods such as the Horizontal Planar Motion Mechanism. Some years ago, observations of the behaviour of a ship model on a tow line showed there were some combinations of towing point and tow line length which resulted in persistent lateral oscillations of the model. At the time the objective was to avoid these combinations and find a solution which gave a docile tow. However the persistent self generated oscillations suggested that this might be a way of testing a model for its control characteristics. A linear analysis of the equations of motion for a towed vessel generated a fourth order linear differential equation in which the coefficients consisted of the same terms that occur in a free model (stick fixed) plus terms arising from the tow line geometry. It was therefore argued that measurements of the oscillatory motion of the model would allow analysis of the hydrodynamic control coefficients of the hull form. A time stepping computer simulation of a towed vessel with known derivatives was developed and this provided evidence that for certain locations of tow point the vessel performed regular oscillations. Reverse analysis of these results yielded very accurate values of the original derivatives even when some random noise was simulated on the motion measurements. Small scale model tests confirmed the simulated results in qualitative terms and analysis of tests on a MARINER hull form yielded hydrodynamic derivatives for yaw and sway which are in good agreement with published data.

  • Supplemental Notes:
    • RINA, Spring Meeting; 26 April 1995; London, UK. Ppr 4 [14 p, 11 ref, 1 tab, 11 fig]
  • Authors:
    • Burcher, R K
  • Publication Date: 1995


  • English

Subject/Index Terms

Filing Info

  • Accession Number: 00710695
  • Record Type: Publication
  • Source Agency: British Maritime Technology
  • Files: TRIS
  • Created Date: Aug 14 1995 12:00AM