DESIGN AND CONSTRUCTION OF A SUBMARINE HULL
ABSTRACT
This project entails the systematic approach used by the authors to design and construct a submarine hull that is watertight to at least a depth of one meter. A NACA 6- series airfoil shape was used because of its emphasis on maximizing laminar flow, owing to the fact that resistance can be reduced by maintaining a laminar boundary layer. Included is detailed literature research acting as a basis of the design, results from resistance test and other relevant information. Results obtained from the final calculation showed an L: D ratio of 5.0 and the drag at 2.57m/s to be 354.022N. The results were conclusive as they confirmed the hull to have a good hydrodynamic performance with respect to the propulsive power. This project has allowed the team to gain a better understanding of the application of fluid mechanic principles in a real-world environment.
TABLE OF CONTENTS
CERTIFICATION…………………………………………………………………………….…II
DECLARATION………………………………..………………………………………….…...III
DEDICATION……………………….………………………………………………………….IV
ACKNOWLEDGMENTS……………………………………………………………………..…V
ABSTRACT………………………………………………………………………………….….VI
LIST OF FIGURES……………………………………………………………………………....X
LIST OF TABLES…………………………………………………………………………….....XI
NOMENCLATURE………………………………………………………………………..…...XII
CHAPTER ONE 2
1.0 INTRODUCTION 2
1.1 Background Study 2
1.2 Definition of Problem 3
1.3 Aim/Objectives 4
1.4 Significances 4
1.5 Scope/Limitation 4
CHAPTER TWO 6
2.0 LITERATURE REVIEW 6
2.1 The Role of the Submarine 6
2.2 Principles 7
2.2.1 Archimedes’ principle 7
2.2.2 Boyles’ law 7
2.2.3 Bernoulli’s equation 8
2.2.4 Newton’s third law of motion 8
2.3 Hull Design 8
2.3.1 Hull hydrodynamic design 8
2.4 Submarine Length to Diameter (Beam) Ratio: Ideal versus Practical 15
2.5 Characteristics of Submerged Body Resistance 16
2.5.1 Skin friction resistance 16
2.5.2 Form resistance 17
2.6 Effect of Hull Geometry and Appendages on Submerged Submarine Resistance 19
2.7 Background of Airfoils 22
2.7.1 Airfoils nomenclature 24
2.7.2 Interaction of hull and airfoils 24
CHAPTER THREE 26
3.0 PROJECT DESIGN METHODOLOGY 26
3.1 Introduction 26
3.3 Design Considerations 26
3.4 Design Assumptions 26
3.5 Design Constraints Considerations 26
3.6 Elements of the Hull (Exostructure) 27
3.7 Selecting a Suitable Airfoil Shape (NACA AIRFOIL SERIES) 28
3.8 2D and 3D Drawing of the Airfoil Shape 29
3.9 Resistance Calculation 29
3.10 Resistance analysis (CFD Analysis) 30
3.11 Comparison between Calculated Resistance and Resistance from the CFD. 30
3.12 Resistance Relationship with Speed 31
3.13 Material Selection 31
3.14 Data Presentation and Calculations of the Submarine Hull 32
3.14.1 Calculating the wetted surface area 32
3.14.2 Calculating the total bare hull resistance of the submarine 32
3.14.3 Calculating for the coefficient of friction 32
3.14.4 Calculating for Reynold number 33
3.14.5 Calculating for Appendage Resistance 33
3.13.6 Calculating effective power 34
CHAPTER 4 35
4.0 RESULTS AND DISCUSSION 35
4.1 Hullform Characteristics and Parameters 35
4.2 Results 36
Table 4.3 Effective Power for the various Speeds 38
4.2 Data interpretation and Analysis 39
4.2.1 Fineness ratio (L: D) 39
4.2.2 Resistance 39
4.2.3 Wetted surface area 39
CHAPTER 5 40
5.0 CONCLUSION AND RECOMMENDATION 40
5.1 Conclusion 40
5.2 Recommendations 40
APPENDICES 45
CHAPTER ONE
1.0 INTRODUCTION
1.1 Background Study
Submarine is an autonomous underwater craft capable of working under the water. Unlike the submersibles, it is independent. It consists of a cylindrical body with hemispherical (and/or conical) ends and a vertical structure, usually located amidship which houses communication and sensing devices as well as periscopes though in modern submarines, these structures are the fin or the sail. There is a propeller or a jet pump at the rear and various hydrodynamic control fins. For reasons of naval tradition, submarines are usually referred to as “boats” rather than as ships regardless of their size, hence the name “underwater boats”.
The strategic capabilities and importance of the submarine were not fully realized untilafter the Second World War (WWII). Arguably, it was the United States’ use of the submarine during the American Civil War that established the platform as a coastal and inland waterway aggressor. But despite some degree of success during the national conflict, the submarine was still regarded as having limited application in naval combat. Although each of the world’s major navies possessed sizable submarine fleets at the beginning of WWI, their effective deployment was hampered by a lack of operational and strategic thinking, limited technology-based capability and an overwhelming prejudice against the evolving submarine doctrine (Polmar N. , 1963). As the conflict grew and evolved, so did the submarine and its operational capabilities. The size, shape and speed of submarines began to change in response to their operational shortcomings and emerging requirements. The ocean-going submarine established itself as a threat to all shipping and expanded the range of operation to beyond the confines of coastal waters. This era also saw the development of the submarine as an anti-submarine warfare asset. However, it is important to understand that the smaller conventional submarine was, and is today, an effective littoral patrol and attack platform.Submarines can be used in the military as an underwater war craft or can be used in marine sciences, salvage, exploration, facility inspection and maintenance. It can also be modified to perform more specialized function such as search and rescue missions or undersea cable repair, tourism and for undersea archaeology; though its use in commercial fleets is very limited. This is as a result of their significant operating and construction cost. However, with the increasing use of the seas, the submarine will have an ever growing role.
Since the 19th century, some major developments have taken place that impact on the ability to conduct feasibility studies of submarines. One is the increase on the use of nuclear power which has almost unlimited power source resulting in the ability to maintain high speeds for long periods with essentially constant weight. The second is the nature of the hull form. As aforementioned, the volume and the shape of the submarine hull are the most important in all phases of the concept design. Any shape to be considered is a subject to very rigorous examinations by the use of calculations to any degree of sophistication required. There are many decisions to make while designing the hull of a submarine including shape, dimension, and construction materials. Modern submarines have a tear-drop hull. The shape of this hull should be able to create the volume in which the submariners work, maximize the strength of submarine so that it does not collapse under the huge water pressure, minimizes costs and minimizes hydrodynamic drag and noise thus, maximum speed. Submarine hull structure consists of water tight envelop which could withstand the external hydrostatic pressure to which it is subjected during the operations.
There are two hulls in submarine, the inner hull or pressure hull and the outer hull. The former holds all the pressure sensitive systems of the submarine including the submariners. It must withstand the hydrostatic pressure to the submarine’s maximum or test depth therefore; it is made of high strength material. Any ingress of water into the pressure hull can have a considerable effect on the submariner’s morale. Consequently, the inner hull has to be very strong. The outer hull is the smooth fairing that covers the non-pressure sensitive equipment of the underwater boat such as Main Ballast Tanks and Anchors, so as to improve its hydrodynamic characteristics. It does not need to withstand the diving depth therefore; high strength materials are not required.
1.2 Definition of Problem
Hydrodynamic drag (frictional drag and form drag)has been a problem in the design of submarine hulls. Frictional drag which is caused as a result of water running along the hull and the form drag which is caused when the water is pushed aside as the hull moves through it. Therefore, the problem to be tackled is the drag
1.3 Aim/Objectives
The aim of the project is to design and produce a submarine hull with as minimum practical resistance as possible.
The objectives of the project are:
⦁ To construct a hull form to its specifications whilst only utilizing the available materials and equipment.
⦁ To design and construct a hull which is water tight to a depth of at least 1 meter and to produce a hull form with reduced resistance
⦁ To produce a hull shape which is stable on surface, submerged and during transit
1.4 Significances
⦁ To help understand the drag and resistance principles and tackle the drag problems involved with the design and construction of a submarine hull.
⦁ The Nigerian Navy can conduct a feasibility study on the design of the submarine hull, and make some major modifications and developments to suit their specifications.
1.5 Scope/Limitation
The final project plan is delimited to do the detailed design of a submarine hull, detailed calculations, computerized drawings and construction of the submarine hull with the affordable materials available due to the cost and unavailability of the materials
1.6 Project Structure
The project is structured so as to present it in a coherent and logical manner. The following provides a description of each of the chapters within this document:
Chapter 1 presents the introduction to the project which encompasses the background study, the problem definition, and the aims/objectives of the project. It also includes the significance of the project and its scope.
Chapter 2 provides a literature review of the project. Focus on existing submarine in the world history, principles used and usage. Also includes all the research that has been done to provide ideas and specification as a guideline to produce the design.
Chapter 3 describes the experimental setup and methods used to design and construct the submarine hull, Focus on Proposed Design Process, Product Design Specification ConceptDevelopment and then the Final concept in selecting the concepts and the detail design analysis of the selected concept.
Chapter 4 shows the construction, tests, result and discussion of the project with the Bill of Engineering Measurement and Evaluation.
Chapter 5 provides the conclusion drawn on the project, the problem encountered, the areas that are considered to need further investigation to address the breadth of the project problem.
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