Page 98 - Practical Design Ships and Floating Structures

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Figure 9: Global shape variation in perspective view
The rendered view depicted in Figure 9, shows the same hull variations as displayed in Figure 8. The
automated adoption of the topology of representation is illustrated here clearly. The hull in the
foreground, featuring no parallel midbody, consists of less surface patches than its two variations with
a parallel part.

4.2 Bulbous Bow Variation
After several principle dimensions have been fixed as a result of economic and / or hydrodynamic
optimisations, a subsequent improvement of the hydrodynamic performance is usually carried out to
refine the design. Parameters typically used for the manipulation of wave resistance are related to the
shape of the bulbous bow. Also, to increase the propulsive efficiency a stem gondola could be subject
of changes. Figure 10 presents a variation of a single geometric parameter of the bulbous bow, namely
the buttock angle of the bulb contour at the forward perpendicular. The parameterisation of the bulb is
closely related to the parameters proposed by Kracht (1978). All of them have been implemented and
can be applied in any suitable combination. In addition, the contour of the bulb can be defined by a
number of parameters, defining the slope of the buttock, the location of the top of the bulb as well the
length and height of the fairing into the bare hull. The bulb is regarded as a blister-type appendage and
its volume is specified by means of a separate sectional area curve.

Figure 10: Local shape variation of the buttock angle at the FP
The variation depicted in Figure 10 features a variation of the buttock angle from 5' through 10" to 15"
of buttock slope.