ON THE APPLICATION OF THE MULTIPLE INPUT ANALYSIS TO THE STUDY OF SHIP'S BEHAVIOUR AND AN APPROACH TO THE NON-LINEARITY OF RESPONSES

Previously, this author intended to judge the extent of linearity of the response of a system working under the stochastic environments, by the level of coherency, that is an important function in the spectrum analysis of time series. However, finding the fact that the simple coherency could stay at low level because of the secondary effect of the spectrum window on the estimation of the cross-spectrum, he proposed a practical method to remove this difficulty. This was made clear also theoretically later. It is natural that the coherency stays at low level (or sometimes high, anyway at erroneous value), also when some other co-existing inputs which are affecting that output, are not taken into account. The theory of multiple input analysis that has been publsihed by a few authors gives us a function called multiple coherency, that takes account of all inputs affecting one output simultaneously, and also the partial coherency that is the coherency of one definite input to the output, under the condition that other inputs co-exist simultaneously, although very few results of application are published. Here this fact will be checked for the analysis of ship's responses in waves, and the necessity and the usefulness of the multiple input analysis will be demonstrated. The identification of non-linear response was the initial motive for this study. Every stage of the trials to find out the simple non-linearity was checked, and the multiple analysis was found to be helpful even for this kind of purpose. The multiple input analysis technique can be expected to be used effectively in future for the analysis of ship's behaviour, for example thrust or torque increase of propeller shaft in irregular waves, together with the identification technique of their non-linearity.

• Corporate Authors:

  Society of Naval Architects of Japan

  23 Shiba-kotohiracho, Minato-ku
  Tokyo 135,   Japan 
• Authors:
  • Yamanouchi, Y
• Publication Date: 1971

Media Info

• Pagination: p. 92-11
• Serial:
  • Selected Papers, J of Soc of Naval Arch of Japan
  • Volume: 7
  • Publisher: Society of Naval Architects of Japan

Subject/Index Terms

• TRT Terms: Deflection; Force; Hulls; Hydrodynamics; Ship motion
• Old TRIS Terms: Hull deflection; Hull forces; Wave force analysis
• Subject Areas: Design; Hydraulics and Hydrology; Marine Transportation;

Filing Info

• Accession Number: 00035106
• Record Type: Publication
• Source Agency: Society of Naval Architects of Japan
• Files: TRIS
• Created Date: Oct 27 1972 12:00AM