Blade bulbous-bow concept application research using commercial CFD - PowerPoint PPT Presentation

Master thesis presentation Blade bulbous-bow concept application research using commercial CFD software Author: Mukhitdin Kakenov Supervisor: Prof.Dario Boote, University of Genova SAB Meeting – LA SPEZIA February 2018

Mukhitdin KAKENOV Kazakhstan Marine Engineer • Previous education : Saint-Petersburg State Marine Technical University (SMTU) • Field of interest : Seakeeping; Hull Optimization; Ship Theory; Safe Operation of a ship, marine technologies in maritime area • Seeking Career & objectives : Naval Designer, Project Engineer, Research Engineer in hull form and ship structure optimization study branches. SAB Meeting – LA SPEZIA February 2018

Example 1. Benetti’s F-125 http://www.charterworld.com/news/f125-yacht-hull-arrives-benetti-yard-italys-viareggio

F-125

F-125 Length on waterline – 31.0 meters Maximum beam – 8.23 meters Half load draught – 2.01 meters High-speed range – 17.5-22 knots https://www.pressreader.com/italy/superyacht/20170109/282428463876372

F-125. Now how it looks on a serial ship: https://sandpeoplecommunication.wordpress.com/2013/12/16/benetti-news-from-the-yard-november- december-2013

Next example: ILUMEN 28M http://robbreport.com/motors/marine/dominators-ilumen-now-more-spacious-and- preparing-launch-231479/

ILUMEN 28M Length on waterline – 28 meters Maximum beam – 8.23 meters Half load draught – 1.85 meters High-speed range – 17-29 knots https://www.superyachttimes.com/yacht-news/dominator-ilumen-28m-taking- shape-in-italy

ILUMEN 28M in towing tank https://www.pressreader.com/italy/superyacht/20170109/282428463876372

ILUMEN 28M in towing tank

ILUMEN 28M in towing tank TOTAL RESISTANCE – pay attention on this! Which force component had been mostly reduced?

The Object of Interest Rhinoceros software was used to build the model of the yacht

The Object of Interest

General arrangements and The Object of Interest some technical information: LengthPP 54.2 m Breadth 12.6 m Designed draught 3.3 m Velocity range up to 22 kn

CFD [Star-CCM+ CFD software was chosen] • Set rules of physics • Change a flow as ever you want • Change a ship and an experimental domain models so many times as you need

What mesh size is better? Calculation quality vs. Time spent The lower the cell size the more accurate the results of simulation *Image has been taken from the Star-CCM+ 11 ver. manual HOWEVER: the lower the cell size, the longer the time spent to compute a problem. Where is the golden middle???

Mesh convergence study • Let’s define some geometrical parameter to use it as a relative value: In Star-CCM+ it is a “Base size” argument • What is it? It’s a value, percentage of which may characterize an elemental size (length) of a computing cell • How long should be this length? => any easy to operate with setting different cells sizes

Mesh convergence study • Let’s define some geometrical parameter to use it as a relative value: In Star-CCM+ it is a “Base size” argument • What is it? It’s a value, percentage of which may characterize an elemental size (length) of a computing cell • How long should be this length? => any easy to operate with setting different cells sizes

Mesh convergence study

Mesh convergence study Shear drag, mesh convergence 31 29 27 Force, kN 25 23 21 19 13.5 14 14.5 15 15.5 16 16.5 17 17.5 Velocity, knots Base 10 meters Base 7.5 meters Base 6 meters

Mesh convergence study Pressure drag, mesh convergence 60 55 50 Base 10 meters Pressure, kPa 45 Base 7.5 meters 40 Base 6 meters 35 30 25 20 13.5 14 14.5 15 15.5 16 16.5 17 17.5 Velocity, knots

Mesh convergence study Sinkage, mesh convergence -0.15 13.5 14 14.5 15 15.5 16 16.5 17 17.5 -0.17 -0.19 -0.21 Meters Base 10 meters -0.23 Base 7.5 meters Base 6 meters -0.25 -0.27 -0.29 -0.31 Velocity, knots

Mesh convergence study Trim, mesh convergence 0.65 0.63 0.61 0.59 0.57 Degrees 0.55 Base 10 meters Base 7.5 meters 0.53 Base 6 meters 0.51 0.49 0.47 0.45 13.5 14 14.5 15 15.5 16 16.5 17 17.5 Velocity, knots

Mesh convergence study

Mesh convergence study

Yacht with the bulbous bow

Yacht with the bulbous bow

Yacht with the bulbous bow

Yacht with the bulbous bow Kelvin waves

Gathered reference DATA: Resistance components (17 knots)

Gathered reference DATA: ship motions (17 knots)

REFERENCE DATA COLLECTED Shear drag Pressure drag 55 29 50 Pressure, kPa 27 Force, kN 45 25 40 23 35 21 30 19 25 13.5 14.5 15.5 16.5 17.5 13.5 14.5 15.5 16.5 17.5 Velocity, knots Velocity, knots Sinkage Trim -0.15 0.65 Pressure, kPa 13.5 14.5 15.5 16.5 17.5 0.6 -0.2 Meters 0.55 -0.25 0.5 -0.3 0.45 13.5 14.5 15.5 16.5 17.5 -0.35 Velocity, knots Velocity, knots

Changing the bulbous bow to a blade one • Features of the blade bow concept should be noticed: Front view Side view Bottom view Top view

Blade bow. First design

Blade bow. First design

Blade bow. First design

Blade bow. First design Bottom view

Blade bow, 1 st design. Produced wave profile on 17 knots forwarding

17 knots

17 knots

17 knots. Blade bow

Changing the bulbous bow to a blade one • Features of the blade bow concept should be noticed: Front view Side view Bottom view Top view

Blade bow, 2 nd variant

Blade bow, 2 nd variant

17 knots. Blade bow, 2 nd variant

17 knots. Blade bow, 2 nd variant

17 knots. Blade bow, 2 nd variant

17 knots. Blade bow, 2 nd variant

Friction comparison Frictional resistance 31 29 27 Resistance, kN 25 23 21 19 13.5 14 14.5 15 15.5 16 16.5 17 17.5 Velocity, knots Bulbous bow Blade bow 1 Blade bow 2, more inclined top …

Pressure drag comparison Pressure drag 69 64 59 54 Pressure, kPa 49 44 39 34 29 24 19 13.5 14 14.5 15 15.5 16 16.5 17 17.5 Velocity, knots Bulbous bow Blade bow 1 Blade bow 2, more inclined top

Sinkage comparison Sinkage -0.15 13.5 14 14.5 15 15.5 16 16.5 17 17.5 -0.2 Sinkage, meters -0.25 -0.3 -0.35 -0.4 Velocity, knots Bulbous bow Blade bow 1 Blade bow 2, more inclined top

Trim comparison Trim 1.1 1 0.9 Trim, degrees 0.8 0.7 0.6 0.5 0.4 13.5 14 14.5 15 15.5 16 16.5 17 17.5 Velocity, knots Bulbous bow Blade bow 1 Blade bow 2, more inclined top

So, what do we have now… • Trim had been changed (involving or separately from the sinkage - ?) • Pressure drag increased – in what areas of the bow? • Frictional drag is almost the same

CONCLUSION • The bow shape gives direct influence on ship motions behavior. Changing the bow we will change the trim and sinkage, in particular; • The pressure drag of the yacht’s new shape had been increased – how to reduce it, modifying the bow? The new problem to future additional research; • The blade bow does not function as the initial one – does not help against wave producing effect. How to optimize the bow in connection to this aspect? This is a new problem appeared – to be studied in optimization study subject.