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Preliminary power prediction during early design stages of a ship
Author(s)
Moody, Robert D.
Date Issued
1996
Type
Thesis
Publisher
Cape Technikon
Abstract
A need exists whereby the preliminary power requirement of a ship can be rapidly
estimated. Because the majority of methods available for this purpose are manual and
consist of a number of independent components, they are tedious and time consuming to
use. With the advent of the personal computer and its widespread acceptance, it was
logical to examine the various components involved to determine their suitability for
computerisation and general accuracy. In total eleven hull resistance prediction methods
were examined, eight of which were computerised. Model test data of four vessels were
used to evaluate these eight programs. The methodproviding the best results was selected
to form the core of an integrated Power Prediction program.
Factors such as appendage resistance, fouling and hull roughness were examined and
appropriate methods selected for inclusion into the integrated program.
Various propeller series were examined and evaluated against a variety of examples and
model data. Two propeller optimisation programs were written and a general method for
determining the optimum characteristics from Kr-KQ polynomials is described.
Methods for determining propulsion coefficients were examined and their results compared
with those obtained from model tests. The method providing the best overall results was
incorporated into the Power Prediction program
Added resistance due to sea state was broken down into two components, namely wind
and wave resistance. Only the head sea and wind conditions were considered. Various
methods for estimating wind resistance were examined and a program developed capable
of providing resistance estimates regardless of wind direction. The problem of added
resistance due to waves was examined and two programs written around the methods
examined. To facilitate prediction estimates, sea state was chosen as the prime function.
Wave height is estimated for the appropriate sea state and wind speed in turn from the
wave height
Actual sea trial data ofa twin screw channel ship is used to determine the overall accuracy
ofthe Power Prediction Program
estimated. Because the majority of methods available for this purpose are manual and
consist of a number of independent components, they are tedious and time consuming to
use. With the advent of the personal computer and its widespread acceptance, it was
logical to examine the various components involved to determine their suitability for
computerisation and general accuracy. In total eleven hull resistance prediction methods
were examined, eight of which were computerised. Model test data of four vessels were
used to evaluate these eight programs. The methodproviding the best results was selected
to form the core of an integrated Power Prediction program.
Factors such as appendage resistance, fouling and hull roughness were examined and
appropriate methods selected for inclusion into the integrated program.
Various propeller series were examined and evaluated against a variety of examples and
model data. Two propeller optimisation programs were written and a general method for
determining the optimum characteristics from Kr-KQ polynomials is described.
Methods for determining propulsion coefficients were examined and their results compared
with those obtained from model tests. The method providing the best overall results was
incorporated into the Power Prediction program
Added resistance due to sea state was broken down into two components, namely wind
and wave resistance. Only the head sea and wind conditions were considered. Various
methods for estimating wind resistance were examined and a program developed capable
of providing resistance estimates regardless of wind direction. The problem of added
resistance due to waves was examined and two programs written around the methods
examined. To facilitate prediction estimates, sea state was chosen as the prime function.
Wave height is estimated for the appropriate sea state and wind speed in turn from the
wave height
Actual sea trial data ofa twin screw channel ship is used to determine the overall accuracy
ofthe Power Prediction Program
Additional information
Thesis (Masters Diploma (Mechanical Engineering)) -- Cape Technikon, Cape Town,1996
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