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1 INTRODUCTION
Despiteofthenumberandtypesofnavyshipseachof
EUkeynaviesshouldhaveasetofunmannedsurface
(USV‐Unmanned Surface Vehicle) and underwater
(UUV‐UnmannedUnderwaterVehicle)vehiclesfor
the different missions to perform. Some of the
vehicles should be partially or fully autonomous
(AUV‐AutonomousUnderwaterVehicle).
Thelastdecadeitwastheti
mewhentheresearch
investigations towards implementing a new
generation of the multi‐task small navy ships and
unmanned USV and UUV vehicles has been
conducted. The small multi‐task navy ships despite
the patrol and typical combat missions may be the
pla
tforms for the unmanned air and maritime
vehicles.
The discussion how many small multi‐task navy
shipsandunmannedmaritimevehicles ofwhichtype
anavyneedsseemstobeover.Theresearchteamsare
ready to implement the chosen solutions concerning
boththesmallmulti‐tasknavyshipsandUSV,UUV
andASVvehicles.
ConcerningtheUSV,UUVandASVvehiclesthey
ma
y perform the typical patrol, reconnaissance or
combat missions. Depending on the mission the
vehicles may be equipped with either the
sophisticated reconnaissance electromagnetic, hydro
acoustic and IT‐based equipment or conventional
arms.Themostadvancedvehiclesma
ybeequipped
with the small fast underwater missiles (Gerigk,
2014).
2 ASTEALTHAUVVEHICLECONCEPT
The primary aim of the research is to work out a
functionalmodelofthestealthAUV vehicle moving
inthedataoperationalconditions.
The novel solutions have been applied regarding
sofarthehull form,arrangementof int
ernalspaces,
materialsandpropulsionsystem.Thefinalhullform
Modeling of Combined Phenomena Affecting an AUV
Stealth Vehicle
M.K.Gerigk
GdańskUniversityofTechnology,Gdańsk,Poland
ABSTRACT:Inthepapersomeresultsofresearchconnectedwithmodelingthebasicstealthcharacteristicsof
an AUV vehicle are presented. First of all a general approach to design of the stealth AUV autonomous
underwater vehicles under consideration is introduced. Then the AUV stealth vehicle concept is briefly
described.Nextamethodofmodelingofthestealthcharact
eristicsisbrieflydescribed.Asanexampleofthe
stealth characteristics investigations some results of modeling the boundary layer and wake are presented.
SomeremarksregardingthebehavioroftheAUVstealthvehicleinthesubmergedconditionsaregiven. The
finalconclusionsarepresented.
http://www.transnav.eu
the International Journal
on Marine Navigation
and Safety of Sea Transportation
Volume 10
Number 4
December 2016
DOI:10.12716/1001.10.04.18
666
isacombinedstealthhullform. Thearrangement of
internal spaces has been designed according to the
functionalrequirements andisverymuchaffectedby
thesub‐systemstobeinstalledonboard.
Themajorsub‐systemsofthestealthAUVvehicle
areasfollows(Gerigk,2015;Gerigk,2016):
ballastsub‐system,
energysupplysub‐system(batteries),
water‐jetpropulsionsub‐system,
T‐foilstabilizingsub‐system,
steeringsub‐system,
communicationandnavigationsub‐system.
dedicatedsub‐system.
The main parameters of the stealth AUV vehicle
areasfollows(Gerigk,2015;Gerigk,2016):
overalllengthL‐isequalto2.2meters(4.4meters
forthelargerstealthAUVvehicle(LS‐AUV)),
operationalbreadthB‐isequalto1.1meters(2.2
meters for LS‐AUV) without the additional
equipmentandappendages,
heightH‐isequalto0.35meters(0.70metersfor
LS‐AUV) without the additional equipment and
appendages,
mass is equal to from 0.38 tons to 0.65 tons,
depending on the mass of equipment installed
onboard,
averagedspeedduringtheunderwatermissionfor
thesubmergedconditions(3meters)v
uw‐isequal
to1.0‐2.0meterspersecond.
The general visualizations of the hull form and
arrangement of internal spaces of the stealth AUV
vehiclearepresentedinFigure1.
Figure1. The general visualizations of the hull form and
arrangement of internal spacesof the stealth AUV vehicle
(Gerigk,2014‐2016).
3 THESTEALTHCHARACTERISTICS
The new Polish solutions concerning the unmanned
maritime vehicles (USV, UUV, ASV) have been
workedoutattheGdańsk Universityof Technology
bytheteamconductedbytheauthor.Theteamwork
is devoted to the interdisciplinary research and
application of advanced technologies. Some
implementations concern
development of innovative
smallmulti‐tasknavyshipsandunmannedmaritime
vehicles (mainly UUV and ASV) (Gerigk, 2015;
Gerigk,2016).
The most innovative concept of the unmanned
maritime vehicle work worked out by the author is
theconceptofthestealthtriple‐stateFIST‐RPvehicle.
According to the opinion
of the experts this vehicle
seems to be between the most advanced and
innovativespecialtaskunmannedmaritimevehicles.
The concept is still under development form the
researchanddesignpointofview.Thevisualization
ofthestealthtriple‐stateFIST‐RPvehicleispresented
inFigure2.
Figure2.Thevisualizationofthestealthtriple‐stateFIST‐RP
vehicle(Gerigk,2012‐2016).
Thelatestresearchanddesignconcernsthestealth
AUV vehicle. The research is sponsored by the
National Centre for Research and Development
(NCBiR)(Gerigk,2015;Gerigk,2016).
IntelligentandautonomousstealthAUV.Despite
of the mission the stealth AUV vehicles should be
applied with the coded communication and
navigation subsystems
to operate the vehicles above
thewatersurface,onthewatersurfaceandunderthe
watersurface.Thevehiclesshouldbeequippedwith
the energy supply subsystem (batteries) to perform
up to several hours missions with the possibility to
upload the batters using the submerged energy
loading stands. According to
the performed tasks
some vehicles should be equipped with the
autonomous intelligent (AI‐Artificial Intelligence)
steeringandvehiclepositioningsubsystemsenabling
to use the data obtained from the vehicle sensor
subsystems.ThemostadvancedstealthAUVvehicles
would be those which could independently
communicate with the other vehicles (USV, UUV,
ASV)
andmakedecisionsontheirown.
667
Silent and invisible stealth AUV. Despite the
abovementionedfeaturesthemostimportantforthe
AUV vehicles is to design and manufactured using
themostadvancedSTEALTtechnologies.Nowadays,
ʺstealthʺdoesnotonly mean toavoid and/or absorb
the radar radiation by the unique hull form and/or
hull skin
cover.ʺStealthʺ concerns the propulsion
system.ThestealthAUVvehiclesshouldbeequipped
with the silent both the electric engines and jet
propellers. The noise and vibrations generated by a
vehicle should on the lowest possible level. The
subsystems and construction of the stealth AUV
vehicle should protect the emission
of heat. Moving
under the water surface the stealth AUV vehicle
should generate a small value boundary layer and
waketolimititsownacousticsignal.Thisiswhythe
innovativehullskincoversareofgreatimportance.
Aresearchisconducedtofindacovertomakethe
hullskin
invisible.
ʺStealthʺ means to limit the probability to detect
theAUVvehicle as muchas possibleusing the well
known and hardly known methods and means of
reconnaissance.
The current investigations on the stealth
technologies towards their application onboard the
AUV vehicles are associated with the following
problems:
sizeandvehiclehullform,
hullskincovers,
minimizing the noise, vibrations and heat factors
andimpacts,
minimizing own electromagnetic and acoustic
signals,
avoiding and absorbing the outside
electromagneticandacousticsignals,
maximizingtheinvisibility.
4 APERFORMANCE‐ORIENTEDRISK‐BASED
METHODOFMODELINGTHESTEALTH
CHARACTERISTICS
The research method for modeling the stealth
characteristics,assessmentofthestealthAUVvehicle
performance and risk assessment is a kind of
performance‐oriented risk‐based method which
enables to assess the abovementioned at the design
stage and
in operation (Gerigk, 2010). The method
takes into account the influence of design and
operationalfactorsonthe performance and safetyof
the stealth AUV vehicle including many factors
following from different sources. The holistic
approach and system approach to safety have been
applied.
For assessment of the stealth AUV
vehicle
performance the investigations using the physical
models and computer simulation techniques have
been applied. The performance assessment of the
stealth AUV vehicle enables to identify the
operationalsequenceofeventsfortheconditionsvery
close to reality (Gerigk, 2015; Gerigk, 2016: Gerigk,
Wójtowicz, Zawistowski, 2015; Gerigk, Wójtowicz,
2015).
Therisk
assessmentisbasedonapplicationofthe
matrix type risk model which is prepared in such a
waythatitenablestoconsideralmostallthescenarios
ofevents.Thecriteriaistoachieveanadequatelevel
ofriskusingtheriskacceptancecriteria,riskmatrix,
(Gerigk, 2010). Providing a
sufficient level of safety
basedontheriskassessmentisthemainobjective.It
is either the design, operational or organizational
objective. Safety is the design objective between the
otherobjectives.Themeasureofsafetyofthestealth
AUVvehicleistherisk(levelofrisk).
UAMV
vehicle
Impact of
environment
Hull form
Arrangement of
internal spaces
Loadin
g
conditions
Start
Design requirements, limitations, criteria
Operational requirements, limitations, criteria
Risk acceptance criteria
Safety criteria
Cost and benefit limitations
Definition of UAMV vehicle
and environment
Hazard identification
Identification of accident scenarios
Estimation of the
probability of a hazard
occurence P
i
Assessment of the UAMV
vehicle performance:
- assessment of the vehicle
mass and position of the
centre of gravity
- assessment of possible
loading conditions including
the ballasting
- estimation of the vehicle
floatability and stability
- prediction of the vehicle
resistance and propulsion
analysis
- analysis of the vehicle
manoeuvrability
- estimation of sea loads on
the vehicle and seakeeping
- vehicle operability
Risk estimation
R
i
= P
i
* C
i
Risk assessment:
Is the risk tolerable ?
Ranking the
hazards, Risk
acceptance
criteria
N
o Yes
Risk
control
options:
-prevention
-reduction
-mitigation
Modification of desig and/or
operational procedure
Choice of optimal design and/or
operational procedure
System of making the decisions on the UAMV
vehicle
p
erformance and safet
y
End
Estimation of
occurence of the data
consequences C
i
Are costs too hi
g
h?
N
o Yes
Analysis of costs and benefits
Risk models
Accident categories
Waves
Water de
p
th
Loss of
stability
Loss of
energy
supply
Hull dama
g
e
,
floodin
g
P
i
, C
i
, R
i
– concerns the
iterations in respect to all
the events and accident
scenarios considered
Hazard assessment
Figure3. A Structure of the method for assessment of the
UAMV vehicle performance and risk assessment (Gerigk,
2014‐2016).
Themethoditselfisbasedonthe following main
steps:
setting the requirements, criteria, limitations,
safetyobjectives;
defining the stealth AUV vehicle and operational
environment;
identifying the hazards and identifying the
sequencesofevents(scenarios);
assessingthestealthAUVvehicleperformance;
estimatingthe risk according to the event tree
analysis ETA and matrix type risk model (risk is
estimated separately for each scenario
development);
assessingtheriskaccordingtotheriskacceptance
criteria(riskmatrix)andsafetyobjectives;
managing the risk according to the risk control
options;
selecting the design (or operational procedure)
that meet the requirements, criteria, limitations,
safetyobjectives;
optimizingthedesign(oroperationalprocedure);
makingthedecisionsonsafety.
668
The structure of the method which combines the
typical design/operational procedures with the risk
assessment techniques is presented in Figure 3
(AUVSI/ONR, 2007; Abramowicz‐Gerigk, Burciu,
2014; Cwojdziński, Gerigk, 2014; Dudziak, 2008;
Faltinsen, 1990; Faltinsen, 2005;Gerigk, 2010;
Gerigk,2015;Lamb,2003;Szulist,Gerigk,2015).
5 ANEXAMPLEOF
INVESTIGATIONSOFTHE
STEALTHCHARACTERISTICS
As an example of investigations concerning
predictingtheinfluenceof a stealthcharacteristicon
the stealth AUV vehicle performance the impact of
different hull skin covers (generated during the
computer simulation) on the flow (boundary layer
andwake)aroundthestealthAUVvehiclehasbeen
modeled.
During the computer simulation the mesh
consisted of 3 275 000 elements. The numerical
domain had the size (Kardaś, Tiutiurski, Gerigk,
2016):
5metersx1.5metersx1.2meters
(1)
anditispresentedinFigure4.
Figure4. A visualization of the numerical domain for
simulating the impact of different hull skin covers on the
flowaroundthestealthAUVvehicle.
Thewaterflowvelocitywasanticipatedtobefrom
0.5meters per secondto 2.5 metersper secondwith
thestep0.5meterspersecond.
During the computer simulation the hull skin
coverwasgeneratedbytheskinroughnessasfollows:
Ra80‐asanormalsteelplatesurface,
Ra1.25‐asaslightlypolishedsteelplatesurface,
Ra0.01‐asapolishedsteelplatesurface,
Ra0.0025‐extremelypolished steelplatesurface
(nano‐surface).
Theflowwasestimatedforexample0.5meters,1.0
meters, 1.5 meters and 2.0 meters behind the stealth
AUVvehicle.Someresultsoftheflowestimationfor
thedataskinroughnessandvelocityarepresentedin
Figure5(Kardaś,Tiutiurski,
Gerigk,2016).
0,80
0,90
1,00
1,10
1,20
1,30
1,40
1,50
1,60
1,70
‐0,75 ‐0,55 ‐0,35 ‐0,15 0,05 0,25 0,45 0,65
Averagedvelocity‐ 1mbehindAUV
Ra0.0025
Ra0.01
Ra1.25
Ra80
Figure5. Some results of the impact of different hull skin
coverson theflowbehind thestealthAUV vehicleforthe
dataskinroughnessandflowvelocity.
6 CONCLUSIONS
In the paper some results connected with
developmentofafunctionalmodelofthestealthAUV
vehiclearepresented.
Some data on the stealth AUV vehicle concept,
major stealth characteristics, performance‐oriented
risk‐based method of modelling the stealth
characteristicsaredescribedinthepaper.
Asanexamplesome
resultsconcerningpredicting
the influence of the different hull skin covers
(generated during the computer simulation) on the
boundarylayerandwakearepresentedinthepaper.
At the current stage of research an influence of
combined stealth characteristics on the stealth AUV
vehicleperformanceisinvestigated.
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