hydrodynamic design and optimization

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A. Mosavi, Hydrodynamic Design and Optimization: Application to Design a General Case for Extra Equipments on the Submarines Hull,

Proceeding on IEEE International Conference on Computer Technology and Development, ICCTD09, Vol. 2, Kota Kinabalu, Malaysia, 13-15

November 2009, pp. 139-143.

Hydrodynamic Design and Multiobjective Optimization: Applicationto Design a General Case on the submarines hull

A.Mosavi

University of Debrecen, Faculty of Informatics

AbstractThere are extra equipments such as sonararrays, electronic devises, antennas and

video cameras which are mounted of the surface of the submarines hull. These equipments

create drag and interfering turbulent noises. Created noises and also vibrations cause failure

for operating and monitoring these devices.

The process of design and optimization the Case for such these devises is presented in order

to reduce the drag and noise. Automatic multi-objective optimization based design method isapplied in two different setups and techniques in order to find the best approach for

hydrodynamic design.

Keywords- CAD, CAE, Multi-objective optimization, hydrodynamic design, submarine

I. INTRODUCTION

In order to improve the performance of the submarine in electronic wars and also better monitoring the

around environment, electronic devises are designed and positioned on the surface of the submarine. These

devices are usually sensors with different applications which present a new ability.

Sonar arrays are well known as a device on the surface of the submarine. Those are electronic

equipments of submarine and ships for detecting and targeting other submarines, ships and other obstaclessuch as mines. Surface warships and submarines are fitted with sonar arrays [2]. Figures number one and

two show the position of side sonar arrays which are the subjects for this project.

Since now there hasnt been a Case for general application in order to cover these devi ses. Usually these

Cases are designed and manufactured temporarily for a special application. Their hydrodynamic designed

shapes leave a lot of space for improvement [1]. Availability of a general Case with the perfect

hydrodynamic design characteristics in all movement scenarios with minimum created drag and noise is a

gift for old brand of submarines. Which means old brand submarines could be armed with new electronic

devices, housing in this Case with generating minimum drag and noise.

Figure number three shows a special purpose Case which is designed to cover a series of ice detector

sensors. Its design hasnt got hydrodynamic shape.

Figure1. Shows sonar arrays on the surface of a submarine [3]


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Figure2. Shows the different arrays on submarine surface [3] Figure3. A side Case which has not hydrodynamic shape [5]

II. REVIEW

Hydrodynamic design -based on the results of the Computational Fluid Dynamic (CFD) simulation- is

one of the complex design procedures. Still there is not any idea for reaction of fluid in new geometry of

shape even after running a couple on simulations. Recently many methods have been developed which have

common applications in hydrodynamic design of Marine industry. These methods are known as Simulation

Based Design (SBD).

The easiest method of SBD is to suggest many possible different designs of a concept and choosing one

of them after running and analyzing the results of simulations. In this method engineer beside designer

analyzes the results of each simulation and together make decision about choosing one of them as the best

design. In this method every things including creating geometry, running the simulations, analyzing theresult of simulations and control the process of design and optimization are depend on experience of

engineer and designer. An example of hydrodynamic shape design applying above SBD method is presented

in the figure number four. In this project finding optimal shape of Ballast bulb of a special yacht in order to

have minimum viscous drag, deep centre of gravity and large effective span is subjected [16].

Methodology of this project was to create finite number of designs, running simulation and pick the best

one.

Figure4. Shows the shape of seven bulb designs which have been developed by designer [16]. Figure5. Shows the pressure contours

on a bulb after a simulation [16].

Twenty different shapes in a Computer Aided Design (CAD) package are modeled. Then the engineer

respectively picks up one model out of all presented ones then initializes the CFD package and runs the

simulation. Engineer studies the effects of fluid around the shape. When all simulations for all design

objectives for each single CAD models are done, results of simulations are compared by engineer in order to

find the best design. Figure five shows the graphical results of a simulation.

Other common method of hydrodynamic design is what Claudio et al. has presented in the second

conference of high performance yacht as a method of SBD to design a sailboat hull [27]. Their Presented

method is more developed as it is consisted of an advanced parametric CAD modeler meanwhile

performance of concepts design regularly is calculated. SBD is not a new method of design but an effectivemethod of SBD is achieved when the CFD applied from the first step of modeling which means creating the

CAD model step by step based on responses of shape's geometry in virtual environment of CFD package.

III. METHODOLOGY

Suggested method is selected according identified targets, design difficulties/conditions and available

academic/in house facilities. The method is managed in the way to be accurate, cheap and speedy. In order

to reach the maximum accuracy and minimize the human faults, the role of CFD engineer is removed


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therefore the results of each interaction of the CFD simulation is analyzed by computer instead of engineer.

Design method is fully automatic and user friendly. Beside initializing the parameters of design-in CAD

package -and simulation-in CFD package- and also running the whole optimization process including all

involved engineering packages is not complicated. Therefore the operator of this method doesnt need to

have high knowledge of mathematics or even fluid dynamics.

This method is not a new way of engineering design but in its presented new style of being automatic, user

friendly and utilizing professional optimization tool, it could be named as a revolutionary method which in

just few years it has got popularity in industrial design of aerodynamics and hydrodynamics. As this design

method is newly presented, it needs enough time to be tested for all design conditions and still much work

should be done in order to improve it.

Presented method is based on utilizing all necessary packages including CFD, CAD, Meshing and reporting

tools under control and commands of optimization package of modeFRONTIER.

IV. DESIGN TERGET

Target is to design an optimal shape for a general purpose Case which is going to position on the curvature

surface of submarine. Shape of the Case must satisfy all design expectations. These expectations of design

are as follow.

Designed shape must deliver minimum drag at the submarine's direct movement minimum drag at the submarine's diving minimum drag at the submarine's rising minimum turbulent noise at the submarine's direct movement minimum turbulent noise at the submarine's diving minimum turbulent noise at the submarine's rising minimum produced pressure on the Case at all movement scenarios

There are not any priorities between these expectations. So all defined design expectations have same

priority.

V. DESIGN DIFFICULTIES

In this project at least there are seven different objectives available to deal with them. Each single of themneeds running a special simulation with different conditions. Simulations to run are as follow.

three of them for drag simulations in different directions of Case into virtual water duct, three of them for turbulent noise simulation in different directions of Case into virtual water duct Three of them for pressure simulation in different directions of Case into virtual water duct in order

to simulate all movements directions.

According to design expectations, obviously the First problem to deal with is the numerous running

simulations, which handling all simulations in the way of studying the results is totally confusing situation

for human mind to even think about it.

Second problem is to create the initial geometry to start the process of shape optimization which is the first

step of project. Third problem is the way of analyzing the results of simulation and applying changes on the

geometry of the initial shape in order to improve it.

The applied method for the explained design conditions, problems and final design expectations, is an

automatic multi-objective optimization based shape design. First requirement for optimizing the shape is a

parametric CAD model. In this case the parametric model is designed by SOLIDWORKS.Optimization is powered by modeFRONTIER which in this case firstly couples CAD with CFD package of

ANSYS CFX and secondly with COSMOS SOLIDWORKS in order to find best packages for optimization.

The idea is to run optimization process with two different tools of meshing and CFD. After the optimisation

is done

the results of both processes are compared to find the better method for hydrodynamic design.

The first tools which are involved in the first method of optimization and design are listed as follow.


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ModeFRONTIER as automatic optimizer SOLIDWORKS as the CAD tool ANSA for meshing applications ANSYS CFX as CFD simulator Microsoft Office Excel as reporting host

The idea of applying second arrangement is to present a new arrangement of tools which is much simpler. In

other words it is tried to utilize minimum tools as possible and ask for than one application from a package.

In this case was tried to do the modeling, meshing, CFD simulation and reporting with SOLIDWORKS. The

tools which are involved in second optimization and design are listed as follow.

ModeFRONTIER as automatic optimizer SOLIDWORKS as the CAD, CFD, Meshing and reporting tools

The method is based on advanced technologies which are coupled each other with the presented ability of

optimizer package. The applied method specifications are listed as below.

Modeling the hydrodynamic surface of Case applying Loft techniques State of the art technology of Parametric Modeling (PM) Running simulations in parallel mode Integrating CAD and CFD packages, applying Multi objective optimization packages of mode

FRONTIER

Generating new geometries utilizing power of PM in changing the shape and distance of curves ineach layer of surface

Running optimization in the modeFRONTIER choosing Design Of Experience (DOE) and GeneticAlgorithm (GA) optimization techniques

Reporting hosts for the presenting of the results of simulation and optimization first of all is the created

graphic figures and charts of modeFRONTIER and secondly is Microsoft office Excel for text results. First

step is to create the initial geometry of Case.

The initial design is modeled in SOLIDWORKS applying Loft techniques based on practical sizes of Sonar

sensors on the curvature surface of submarines hull. It is modelled with thirteen NURBS based curves

positioned in profiles with constant distances. Model is a parametric based design which means distance

between the curves and also shapes of curves have relation with each other and are changeable according todefined equations. It gives the ability to create new models in short time with just changing a dimension of

model. Figure number six shows the initial shape design which is positioned on the hull surface of

submarine. This model is the first step of the process of developing the Case.

A

B

C

Figure6. Shows the initial designed shape of Case; A is pointed at the curvature surface of the hull of

submarine, B is pointed at the Case and C is pointed at a curve profile.

VI. RUNNING THE OPTIMIZATION/DESIGN PROCEDURES

It is managed to run the process for eighty shapes in different geometries which are created and selected

automaticity by system. The methods of optimization are DOE and GA .The process is totally automated.

The process of optimization and design of the first and second combination of tools are presented

respectively in the figure number seven and eight. The CAD parameters are at the left side of figure


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November 2009, pp. 139-143.

connected into the CAD package and the objectives are presented at the right side of the figure. The process

continues till getting the expected results.

Figure7. Shows the combination of SOLIDWORKS, ANSA and ANSYS CFX in the graphical window command of

modeFRONTIER

Figur8. Shows the combination of SOLIDWORKS in the graphical window command of modeFRONTIER

VII. RESULTS AND OPTIMAL SHAPEResults of process are able to be presented graphically in different shapes. Figure number eight shows

two graphical result charts. According to the results, many optimal design configurations there have

been introduced. Finding the best design is completely up to designer.

Based on the selected optimal design the characteristics information of that design could be loaded in to

CAD parametric model in order to model the optimal final design. Information of design contains the

equation of each curve and distance between them. Figure number ten shows the optimal design from

two different views.

Figure. 9 shows the graphical results of optimization


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November 2009, pp. 139-143.

Figure. 10 shows the optimal design of the case

VIII. CONCLUSION

By using the presented method of design and optimization in conjunction with the CFD code ofANSYS CFX and SOLIDWORKS-in the first tools combination- the traditional design

approach of trial and error was substituted by an automatic and logical design procedure.

Running the first tools combination in order to reach the final design geometry was achieved inninedays which is reasonable for applied hardware facilities. But the point is that two thousands CFD

evaluations have been done without operator intervention.

The second tools combination took twelve days to be done. Which means reducing the numberof involved tool packages and do more than one duty with a single package in order to reduce

the optimization time, couldnt be useful.

Applying each package for doing a single job could be a useful way of reducing the time ofoptimization

Combination of SOLIDWORKS, ANSYS CFX and ANSA with modeFRONTIER is a greatcompany for hydrodynamic design

Lofting tools for creating parametric models is a fast and effective method of modeling Shape of the Case or basically the extra equipments affixed on the submarines hull need to be

smoothly joinable into the curvature surface of submarines in order to minimize the drag.

Two different techniques of optimization-DOE and GA- were tested. Each method gavedifferent result and presented a different shape, which means the optimization method of designhas not a unique result.

Besides two different groups of tools combination for a common problem were tested but theresults were totally different. In other words the applied CAD and CFD tools have alsoeffect on the optimal result.

In order to find the most trustable design, all the resulted hydrodynamic shapes must be testedin a real water duct. This is going to be a future project which its result could actually identify

the best hydrodynamic optimization and designs techniques and tools.

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