Computational optimization of stability, propulsion and maneuverability of a riverine vessel

Computational optimization of stability, propulsion

and maneuverability of a riverine vesseland maneuverability of a riverine vessel

Lieutenant Commander Luis Javier Serrano Tamayo

Colombian Navy

University of the Andes - Naval Academy “Admiral Padilla”

COLOMBIA

Contents

1. Introduction

2. Hull and Stability

3. Resistance and Propulsion System

4. Maneuverability

5. Conclusions

Computational optimization of stability, propulsion and maneuverability of a riverine vessel. Lt Cdr Javier Serrano Tamayo

Riverine importance of Colombia1. Introduction

Coasts and Andean Region:

55% Territory95% Population

Amazon Jungle:

2nd country in biodiversity Caribbean Sea

Pacific Ocean


Amazon Jungle:

45% Territory05% Population

Highways

Rivers

Pacific Ocean

ProblemThe 1rst generation of RPV’s (Riverine Patrol Vessels) are very useful

ships, but the armor is very heavy, the motors were racing just 1500

of the 1800 RPM, the propellers were present cavitation and the

ships should improve their maneuverability due to the narrow rivers.

1. Introduction


20 mm

20 mm

¼”

¼”

¼”

Arena

Arena

20 mm

20 mm

¼”

¼”

¼”

Arena

Arena

Polyurethane

Polyurethane

General goal

The study of the integration between the hull

and the propulsion system of the RPVs in

order recommend improvements to optimize

1. Introduction

order recommend improvements to optimize

its propulsion system and reduce the tactical

diameter in their operational area.


Hull geometry construction in field


Station 4; x=1,75 mhalf width

(axis "y")

height

(axis "z")

Point 1 0 1.7

Point 2 1.7 1.65

Point 3 2.7 1.58

Point 4 2.7 1.295

Is only necessary to write a half width, the software GHS

(General Hydrostatics) completes the shape


Point 4 2.7 1.295

Point 5 1.62 1.115

Point 6 1.18 0.575

Point 7 0.89 0.37

Point 8 0.78 0.31

Point 9 0 0

1st edition results

Reference point 0,0,0

The bow has to be refined


Astern reached soft

curves and it was ready


Refining process (fairing)

The control points were used to

accomodate the geometry

properly, as well as other

Rhinoceros software commands.


It was possible to obtain a faired

surface of the hull and to model

3D the hull of the RPVs.


Tanks construction



The tanks were constructed utilizing different GHS commands which permit fill in or fill out the tnaks in order to evaluate different loading conditions.

Coefficients of form2. Hull and Stability


The curves show the full forms of the ship (above 0.8), as well as the variation of the form coeffcients below 0.5 m of depth, due to the semi-tunnels in the astern (propellers).

Hyidrostatics curves2. Hull and Stability


H. Curves indicate different values to evaluate the intact stability of the ship (no trim) for different loading conditions.

metacentric radius

long. moment I

Weight previous studies (Methods by main characteristics)

Method Result

Method of Benford Used for bigger ships displacements

Method of Danckwardt L/D is too little

Method of Lamb Lenght is too little

Method of Mandel Non logical value


Method of Mandel Non logical value

Method of Murray Non logical value

Method of Osorio Could be useful as a reference

Method of J.L. García G. Too little value

The main characteristics methods evaluate the weight of any ship according

formulas related to other ships of the same type, but as conclusion, none

method satisfied the weight of the RPV precisely.


Weights study. Ship Work Breakdown Structure (SWBS)

GRUPO CONCEPTO

100 Hull Strcuture

200 Propulsion plant

300 Electrical plant

400 Communications and Command

500 Auxiliary services


600 Equipment and Furniture

700 Weapons

M Margins

F Deadweight


The SWBS has subgroups and elements which describe precisely all the shipcomponents. Every one has a weight and a position in the 3D model and allthe weights were inserted to model the ship with its components.

Summary of calculated loads according SWBS



When every weight is calculated and its 3D position is related to the reference point, the final result is the CG of the ship.

Example of weight distribution in the different stations



The example shows the longitudinaldistribution of some elements of the 100SWBS group in the stations used to dividethe lenght of the ship.

Curves of Loads

Light ship. The weight of the ship without

any deadweight. Equitative distribution of

loads. Main weights are astern.

Minimal operational condition. The ship

has the minimum deadweight to


There are three main loading conditions:

has the minimum deadweight to

navigate. Water tanks 2/3 of load and

fuel 1/3 of load.

Full load. The ship has the 100% of

deadweight. Liquid cargo create punctual

weights in some stations.


Stability criterion DDS-079 USN

Protection of vital spaces and main wall spacing

1. Spacing between transversal bulkheads = 10’ + 0.03 LBP

2. Collision bulkhead must be maximum at 5% de LBP

3. Crossed connections must be prevented



The ship passed the spacing criterion

DDS-079 USN. Stability Threats

1. Beam wind combined with rolling

2. Heavy lifting over one side

3. Towing forces

4. People crowding over one side


4. People crowding over one side

5. High speed turning

6. Top icing


The first and the last two pose no threat to the vesselconsidering its characteristics and surroundings.

Stability Criterion. 46CFR Part 170. USCG

Minimal metacentric permitted height

2)1309(028.0 LP +=


)tan(TW

PAHGM ≥

Factor for shallow waters maneuvering


Results for the minimal operational condition

The ship shows good intact stability, because passed the criteria


The ship shows good intact stability, because passed the criteria

established and is confirmed the prediction that if a ship have high

Width/Depth ratio will have a good intact stability. 7.2 m / 1.2 m = 6


• General cargo ship, 40 m/ 20 m = 2

• Container ship, 60 m/ 30 m = 2

• Oiler ship, 80 m/ 35 m = 2.3

• USN Aircrat carrier, 112 m/ 45 m = 2.5

Critical points

The critical points are those that permit a progressive flooding

in the ship, for example, the ventilation of machinery room.

Critical point intersection at 24° of heeling


at 24° of heeling


Analysis of NAVCAD sistematic series

Method Result

Basic Formula Value spectrum too widht

Holtrop Method BWL/T ratio too short

Oortmerssen Method BWL/T ratio too short

Denmark Univ. Method OK, LWL/BWL quite short


USNA YP Series Characteristics matched

60 Series Only for round bilge keel ships

Nordstrom y YP 81-1 Series High dead keel

64, SSPA, NPL y Dutch Series Planning hulls


The ship characteristics must match properply to use the sistematic series of NAVCAD, otherwise is not possible to use.

Hull characteristics



In the hull data, the main influence factor is the wetted surface for resistance prediction

Environmental characteristics



In the environment data, the main influence factor is the depth of the channel (river) for resistance prediction.

The “Squat” effect

Is the change in the draft and trim of a ship, as result of

variations in the hydrodinamic pressure over the hull.


In this critical zone, if the

ship in navigating in shallow


ship in navigating in shallow

waters, eventually can touch

the bottom.

Squat variation at

different depths

0.3

0.4

0.5

0.6

0.7

0.8

Squ

at m

PREDICCIÓN MANACACÍAS-1m.nc4




The squat curve for 1 m depth

shows the three cirtical regions.

The other are always in the

subcritical region.


0 2 4 6 8 10 12 140

0.1

0.2

0.3

Vel ktsregión

subcríticaregión crítica región

supercrítica

subcritical region.

What is the minimum depth for

secure navigation, without

squat effect?

The ship is in full load condition.


Subcritical region

Critical region

Supercritical region

Squat effect in resistance



4000 N difference between 3-6 m

Minimal secure depth = 3 meters


There are other problems associated:

Vibrations


Cavitation of propellers due to reverse trim

Resistance and motor performance

• 02 DD671L motors, 180 BHP

@ 1800 rpm

• 02 Twin Disc gearings, 2.45:1

• 02 FP propellers, 3B, 36”X32”


1800

Detalles of eroded blade

due to cavitation


Previous performance area of the motors

Optimal pitch selection

0.48

0.50

Pro

pEff

BS-3: 0.914x0.813x0.450

BS-3: 0.914x0.555x0.450

BS-4: 0.914x0.530x0.610


2 3 4 5 6 7 8 9 100.44

0.46

Vel kts


The 3 blade propellers show better performance in efficiency evaluation

Optimal expanded area of the blade

0.46

0.48

0.50

Pro

pEff

BS-3: 0.914x0.555x0.450

BS-3: 0.914x0.546x0.800

GA-3: 0.914x0.503x0.800


1 2 3 4 5 6 7 8 90.40

0.42

0.44

Vel kts

Pro

pEff

The comparison between B-Series and Gawn propellers was more favourable toB-Series. In the other hand, not always more blade area means more efficiency.

Optimal performance

• Optimal P/D ratio

• More speed

• More power


Optimal P/D

Previous P/D

• Less carbon in cylinders

• Less manteinance

• Less emissions


Fuel consumption and range

Fuel consumption

Half gallon per hour

less since 12 kph


4,0

5,0

6,0

7,0

8,0

Fu

el c

on

su

mp

tio

n (

gp

h)

less since 12 kph

Range

3 more days of range


0,0

1,0

2,0

3,0

4,0

8,00 9,00 10,00 11,00 12,00 13,00 14,00 15,00 16,00 17,00

Fu

el c

on

su

mp

tio

n (

gp

h)

Ship speed (kph)

Previous propeller Optimal propeller

Field visit and rudder geoemtry

4. Maneuverability

• Before to be a mother vessel for the soldiers, the ship was a river

tug, used for push 3 barges with cargo.

• The rudder area oversized, considering the barges lenght.


Shape ratios. Aspect and balance

• Very low aspect ratio:

= 0.43cb /

4. Maneuverability

Lift coefficient

A1 A2

21 /AA = 0.12 < 0.265

Mínimum for CB = 0.81

• Low balance ratio


Rudder angle, degrees

Sizing the rudderThe calculated rudder shouldn’t touch the semmi tunnel of the hull in

its maximum angle of steering (35˚), procuring the maximum height.

1. Minimum distance propeller – rudder. (0.30 m, facilitation of remove the propeller)

2. Size the rest of the distance till the mirror (last nulkhead, 0.75 m)

3. The distance of the balance ratio should be discounted (0.2 m)

4. Maneuverability


Rudder shape innovation. Schilling rudder

4. Maneuverability


Characteristics and improvements of Schilling rudder

1. One-piece construcition. No additional maintenance

2. Important control improvement at low speed

3. CL is 1.3 times higher, which reduces tactical diameter

4. Maneuverability

3. CL is 1.3 times higher, which reduces tactical diameter

4. Maximum force at bigger stall angle (40 - 45˚)

5. High lift coeffcient going astern

6. Excellent course control (fuel save), even without dead keel


Lift coefficient comparative curves

4. Maneuverability

Source: Schilling Rudder Monovec


Conclusions

1. Instead of the heavy armor, the intact stability of the

RPVs is excellent. However, the heavy armor reduces

cargo capacity.

2. The optimal propeller increased efficiency and range as

well as reduced fuel consumption and cavitation.

3. The Schilling rudder increased significantly the lift and

reduced the tactical diameter since 4 to 2 lenghts.

Additionally the improvement in course control reduced

fuel consumption of the RPV.


Gracias!

Thank you!

Computational optimization of stability, propulsion Computational optimization of stability, propulsion

and maneuverability of a riverine vessel

Lieutenant Commander Luis Javier Serrano Tamayo

Colombian Navy

University of the Andes - Naval Academy “Admiral Padilla”

COLOMBIA

Education

Computational optimization of stability, propulsion and maneuverability of a riverine vessel