The Naval Architect March 2008

Contents | maRch 2008
20-83 Features bow thruster tunnels, see Fig. 4. Further the flow in the neighbourhood of the propeller shafts and the
propeller brackets was computed to investigate the flow interaction between these components.
Feature 1 Tankers of the 21st century
20-23 Tanker designs for whitefield
64
Surface grid for
CFD analysis.
developments
24 To MARS via Korea?
26-28 Stena adds to P-MAX class
31 Shell tankers will be ready to trade
32 Lindenau breaks green ground
32 PSM stays level headed
33 Odfjell subtracts 12, adds seven
34 First Aframaxes for GEM
34 Latest Eagle has landed
37 MAN’s first S50ME-B
37 Skaugen opts for Solasafe
37 VLCC roped into strong fibre
Fig. 4 Surface grid for CFD analysis
Feature 2 Diesel and gas technology
39-45 Ships’ emissions reach crucial stage
47 MAN breaks through with dual fuel option
49 Cat has IMO II in its sights Numerical
72
Simulation
51-52 Wärtsilä invests for the future
53 8000 series comes into its own
A Reynolds-averaged
Civil work being done at
Pipavav Shipyard, the
Navier-Stokes equation (RANSE) solver was used. The conservation equations
55 The future is turbocharged
for
site of what could well
56-57 Optimising air management
become India’s largest mass and momentum in their integral form serve as the starting point. The solution domain is
58 Composite shafts press their case
subdiv
shipyard in times to come.
The first ship delivery is due ided into a finite number of control volumes that may be of arbitrary shape. The integrals are
59 Sealed pumps offer safety first numerically
in March 2009.
approximated using the midpoint rule. The mass flux through the cell face is taken from the
59 Largest transmission from ZF
previous iteration, following a simple Picard iteration approach. The unknown variables at the center of
60-63 The Chinese connection
the cell face are determined by combining a central differencing scheme (CDS) with an upwind
Feature 3 Noise and vibration
differencing scheme (UDS). A two-equation turbulence model was used.
64-69 Advanced thinking on tricky excitations
70-71 The case of the singing propeller The ship was treated as a double body, consisting of the ship hull below the calm-water surface and its
mirror image above the calm-water surface. The free surface was not considered. Velocities that
Feature 4 Indian shipbuilding
initialize the flow field arose from the inverse of ship speed imposed at the inlet boundary. The three-
72-77 New players in shipbuilding boom
dimensional flow field surrounding the ship was computed as a transient process. The fluid domain was
Feature 5 Singapore report
ide
78 From niche to nub
7
alize
9
Keppel vessels line the
d by a
waterfront of its seven
volume grid comprising about 6 million hexahedral control volumes (cells). To avoid flow
yards in Singapore.
disturbances at grid boundaries, they were located at sufficiently large distances ahead of the bow, aft
79 Keppel on the up and up
of the stern, and beneath the keel.
81 Sembcorp sets the pace
82 Ro-pax first for Singapore
Results of CFD-Analysis
83 SmartMarine saves Six Tee time
83 MacGregor Offshore moves forward
The simulations revealed vortex shedding at the bow thruster tunnels and at the exhaust gas outlets. A
stationary vortex was observed port side at the trailing edge of the skeg near the keel. However, no
vortex shedding was observed there. Pronounced bow thruster vortex shedding was revealed, but the
corresponding fluctuating force amplitudes occurred at a quite lower frequency. The frequency of the
vortex shedding at the exhaust pipes was computed to be about 1.4 Hz.
As these results did not allow to pin point the possible source of excitation the numerical simulation was
The Naval Architect March 2008
deviated to the flow surrounding the ship’s ster

n in the vicinity of the propeller shafts.
The computations showed that the flow at the propeller tunnel and surrounding the propeller shafts was
NA Mar 08 - p1+3.indd 3 10/03/2008 14:58:35
characterized by the formation of vortices. To help visualize this vortex shedding, Figs. 5, 6 and 7 show
samples of computed flow velocities in the neighborhood of the propeller tunnels. The vortex shedding
frequency was computed to be 3.8 Hz for the outer tunnels, for the V-brackets and the I-brackets, and
for the outer shafts. So, at least one of these components was to be considered as a possible exciting
source for the 1-node torsional hull vibration at 3.6 Hz.
Page 1 | Page 2 | Page 3 | Page 4 | Page 5 | Page 6 | Page 7 | Page 8 | Page 9 | Page 10 | Page 11 | Page 12 | Page 13 | Page 14 | Page 15 | Page 16 | Page 17 | Page 18 | Page 19 | Page 20 | Page 21 | Page 22 | Page 23 | Page 24 | Page 25 | Page 26 | Page 27 | Page 28 | Page 29 | Page 30 | Page 31 | Page 32 | Page 33 | Page 34 | Page 35 | Page 36 | Page 37 | Page 38 | Page 39 | Page 40 | Page 41 | Page 42 | Page 43 | Page 44 | Page 45 | Page 46 | Page 47 | Page 48 | Page 49 | Page 50 | Page 51 | Page 52 | Page 53 | Page 54 | Page 55 | Page 56 | Page 57 | Page 58 | Page 59 | Page 60 | Page 61 | Page 62 | Page 63 | Page 64 | Page 65 | Page 66 | Page 67 | Page 68 | Page 69 | Page 70 | Page 71 | Page 72 | Page 73 | Page 74 | Page 75 | Page 76 | Page 77 | Page 78 | Page 79 | Page 80 | Page 81 | Page 82 | Page 83 | Page 84 | Page 85 | Page 86 | Page 87 | Page 88 | Page 89 | Page 90 | Page 91 | Page 92 | Page 93 | Page 94 | Page 95 | Page 96 | Page 97 | Page 98 | Page 99 | Page 100