Design and fabrication of Unmanned Underwater vehicle

Chapter 1

Introduction and Project background

Introduction

Unmanned underwater vehicles (UUV), sometimes known as underwater drones, are any vehicles that are able to operate underwater without a human. Unmanned underwater vehicles (UUV), which are controlled by a remote human operator

 Unmanned Underwater vehicle is a robot which is operated automatically. It is a watercraft capable of independent operation underwater. It differs from a submersible, which has more limited underwater capability. The term most commonly refers to a large, crewed, autonomous vessel.

Most large submarines consist of a cylindrical body with hemispherical (or conical) ends and a vertical structure.

An underwater vehicle is a mobile robot designed for aquatic work environments. It is operated via a remote. A human operator sits in a shore-based station, boat or submarine bubble while watching a display that shows what the robot "sees."

An (UUV) is an underwater vehicle which is linked to a battery that carry electrical power, video and data signals back and forth between the operator and the vehicle through transceiver. Additional equipment is commonly added to expand the vehicle’s capabilities. These may include sonar's, magnetometers, a still camera, a manipulator or cutting arm, water samplers, and instruments that measure water clarity, light penetration and temperature.

History

The first AUV was developed at the Applied Physics Laboratory at the University of Washington as early as 1957 by Stan Murphy, Bob Francois and later on, Terry Ewart. The "Special Purpose Underwater Research Vehicle", or SPURV, was used to study diffusion, acoustic transmission, and submarine wakes.

                                                Figure 1: Special Purpose Underwater Research Vehicle

Other early AUVs were developed at the Massachusetts Institute of Technology in the 1970s. One of these is on display in the Hart Nautical Gallery in MIT. At the same time, AUVs were also developed in the Soviet Union (although this was not commonly known until much later). [1]

In 1980s UUVs became essential when new offshore development exceeded the reach of human divers. A serious stagnation in technological development has faced by UUVs industry in mid 1850s due to global economic recession. Since then there is was increase in research and development of underwater remotely operated vehicle and now a day’s modern UUVs can perform variety of tasks and projects. Modern UUVs can perform inspection of subsea structures, pipelines and platforms to connecting pipelines and placing underwater manifolds. It is used in initial construction of subsea development repair and maintenance. UUVs is also used to locate historic wreck and to recover material from sea floor as well as in oil and gas industry for exploration purposes.

Types of underwater vehicles:

There are different types of UUV classified on the basis of size, weight and power. Some of them are as following.

There are 3 main types of submarines. They are:

Pleasure Submarine:

Pleasure submarines are generally very small and expensive, used by the rich people to admire marine life.

Scientific submarines:

 Scientific submarines are used to investigate the bottom of oceans or lakes and bring back biological samples or relic. One of the most popular scientific submarines is “DSV Alvin”, a 16-ton deep ocean research submersible that was the first and foremost

Figure 2:scientific submarine

maneuverable deep sea research vessel. The DSV Alvin is one of the few craft in subsistence that can travel

more than about half a mile under the surface of the ocean. Most other craft, including military submarines, would be entirely crushed at a depth of no more

than half a mile. The vessel was made possible by the development of syntactic foam, a composite material that consists of minute hollow micro-spheres implanted in a larger structure. The microspheres decrease its density while maintaining strength, facilitating for deeper dives. [2]

   

Military submarines:

Military submarines are used for naval wars, recon, and to hold nuclear weaponry, making up an essential node of the nuclear chord along with ballistic missiles and heavy bombers. The largest and top most expensive submarines are all used by the militaries of the world, especially the US, UK, and Russian military. One example would be the “American Seawolf” class submarine, which has a displacement of 8,000 tons, length of 353 ft (107 m), width of 40 ft (12 m), and, due to its nuclear power plant, a range limited only by the food supplies and sanity of the crew.

Figure 3: Military submarine

These submarines can go anywhere on Earth where the World Ocean stretches, including the water underneath the floating ice of the North Pole.

Different types of submarine:

Diesel-electric: In 1928 the United States Navy's Bureau of Engineering proposed a diesel-electric transmission; instead of driving the propeller directly while running on the surface, the submarine's diesel would drive a generator which could either charge the submarine's batteries or drive the electric motor. Either way, the submarine would have to surface daily to get oxygen for fuel combustion underwater or to charge the batteries before diving back

Nuclear Power: Nuclear-powered submarines have a relatively small battery and diesel engine/generator power plant for emergency use if the reactors must be shut down. Nuclear power is now used in all large submarines. The single biggest advantage with nuclear-powered submarines is that they continue to function submerged for months without ever having to surface 

Alternative propulsion: Oil-fired steam turbines powered the British submarines, built during the First World War and later, to give them the surface speed to keep up with the battle fleet. By the end of the 20th century, some submarines, such as the British Vanguard class, began to be fitted with pump-jet propulsions instead of propellers. Pump-jet is a marine system that creates a jet of water for propulsion. [3]

The Navy has three types of submarine, each with a different purpose

The guided-missile submarines: These carry up to 154 cruise missiles for land attacks and they also support other naval operations.

Ballistic missile submarines: These carry nuclear missiles for intercontinental attacks.

The attack submarine class: These targets enemy ships and submarine, lay mines and collect intelligence data. [4]

Types of submarine according to size:

Micro underwater vehicle:

This class of underwater remotely operated vehicle is in smaller size and weight. It weight is up to 3 kg and it is used in those places where the diver is not able to approach that place physically example sewer, pipeline or small cavity. It is shown in following fig.

Figure 4: micro underwater vehicle

Mini underwater vehicle

This vehicle is used as an alternative and it weight is around 15 kg. One person is able to control and guide it from the small ship via a joy stick. Both Micro and Mini classes are referred to as "eyeball" class to differentiate them from ROVs that may be able to perform intervention tasks. A typical mini UROV is shown in fig 5. [5]

Figure 5: mini water vehicle

Summery:

At this stage, different types of UUVs classed on the operational characteristic, basis of size, weight and power discussed in this section. Micro and mini UUVs models advantages and disadvantages also discussed. At this stage, considered to design an unmanned underwater vehicle because it is unmanned vehicle to save the human life (diver). The characteristic of this vehicle is less weight and design for 5m depth. To choose a best design performance, functionality, neutral buoyancy, stability, 3d mobility and Camera system are much important factors. A detail review of Components of UUVs also added in this section. Its application in Sonar technology, Military purpose, underwater construction with the help of Robotic Arm and many more. The effecting parameter in underwater discussed in next Chapter 2.

Chapter 2

Theory and LITERATURE REVIEW

Viscosity:

Viscosity is a measure of the resistance of a fluid to deformation under shear stress. It is commonly perceived as "thickness", or resistance to pouring. Viscosity describes a fluid's internal resistance to flow and may be thought of as a measure of fluid friction. Thus, water is "thin" having a low viscosity, while vegetable oil is "thick" having a high viscosity.

Types of Viscosity

Viscosity (Dynamic)

The SI physical unit of dynamic viscosity is the Pascal-second (Pa·s), which is identical to 1N·s/m2 or 1 kg/ (m·s). In France there have been some attempts to establish the Poiseuille (Pl) as a name for the Pa·s but without international success. Care must be taken in not confusing the poiseuille with the poise named after the same person. The cgs physical unit for dynamic viscosity is the poise (P) named after Jean Louis Marie Poiseuille. It is more commonly expressed, particularly in ASTM standards, as centipoise (cP). The centipoise is commonly used because water has a viscosity of 1.0 cP (at 20 °C). 1 poise = 100 centipoise = 1 g/ (cm·s) = 0.1 Pa·s (Pascal second). [6]

Viscosity (Static)

The SI physical unit of kinematic viscosity is the (m2/s). The cgs physical unit for kinematic viscosity is stokes (abbreviated S or St), named after George Gabriel Stokes. It is sometimes expressed in terms of centistokes (cS or cSt). In U.S. usage, stoke is sometimes used as the singular form.1 stokes = 100 centistoke = 1 cm2/s = 0.0001 m2/s. Viscosity of some common materials given in table 1 below. Table 1. Viscosity of Gases Some dynamic viscosities of Newtonian fluids are listed below in table 2.

Liquids (at 20 °C)	Viscosity (Pa·s)
Water	1.025 × 10-3

Table 1

Gases (at 0 °C)	Viscosity (Pa·s)
Hydrogen	8.4 × 10-6
Air	17.4 × 10-6
Xenon	21.2 x 10 – 6

Table 2

Ethyl alcohol	0.248 × 10-3
Acetone	0.326 × 10-3

Table 3
Viscosity of Dynamic Newtonian Fluids.

Newton Theory

when a shear stress is applied to a solid body, the body deforms until the deformation results in an opposing force to balance that applied, equilibrium. However, when a shear stress is applied to a fluid, such as a wind blowing over the surface of the ocean, the fluid flows, and continues to flow while the stress is applied. When the stress is removed, in general, the flow decays due to internal dissipation of energy. The "thicker" the fluid, the greater is resistance to shear stress and the more rapid the decay of its flow.
In general, in any flow, layers move at different velocities and the fluid's "thickness" arises from the shear stress between the layers that ultimately oppose any applied force. Velocity

and shear stress relation shown in fig. 6 below.

 

Figure 6: newton theory

                                    Relationship between velocity and shear stress

Isaac Newton postulated that, for straight, parallel and uniform flow, the shear stress, τ, between layers is proportional to the velocity gradient, ∂u/∂y, in the direction perpendicular to the layers, in other words, the relative motion of the layers. Here, the constant μ is known as the coefficient of viscosity, viscosity, or dynamic viscosity. Many fluids, such as water and most gases satisfy Newton's criterion and are known as Newtonian fluids. Non-Newtonian fluids exhibit a more complicated relationship between shear stress and velocity gradient than simple linearity. [7]

Reynold Number

In fluid mechanics, the Reynolds number (Re) is a dimensionless number that gives a measure of the ratio of inertial forces to viscous forces and consequently quantifies the relative importance of these two types of forces for given flow conditions

.

Reynolds numbers frequently arise when performing dimensional analysis of fluid dynamics problems, and as such can be used to determine dynamic similitude between different experimental cases.

 They are also used to characterize different flow regimes, such as laminar or turbulent flow: laminar flow occurs at low Reynolds numbers, where viscous forces are dominant, and is characterized by smooth, constant fluid motion turbulent flow occurs at high Reynolds numbers and is dominated by inertial forces, which tend to produce chaotic eddies, vortices and other flow instabilities.

 Reynolds number can be defined for a number of different situations where a fluid is in relative motion to a surface. These definitions generally include the fluid properties of density and viscosity, plus a velocity and a characteristic length or characteristic dimension. This dimension is a matter of convention – for example a radius or diameter is equally valid for spheres or circles, but one is chosen by convention. For aircraft or ships, the length or width can be used. For flow in a pipe or a sphere moving in a fluid the internal diameter is generally used today. Other shapes such as rectangular pipes or non-spherical objects have an equivalent diameter defined. For fluids of variable density such as compressible gases or fluids of variable viscosity such non-Newtonian fluids, special rules apply. The velocity may also be a matter of convention in some circumstances, notably stirred vessels. The inertial forces, which characterize how much a particular fluid resists any change in motion, are not to be confused with inertial forces defined in the classical way.

                                         

 Where:   V is the mean velocity of the object relative to the fluid (SI units: m/s)

 L is a characteristic linear dimension, (travelled length of the fluid; hydraulic diameter when dealing with river systems) (m)

 μ is the dynamic viscosity of the fluid (Pa·s or N·s/m² or kg/(m·s))

 ν is the kinematic viscosity (m²/s) ρ is the density of the fluid (kg/m³).

Pressure

Pressure is defined as force per unit area. It is usually more convenient to use pressure rather than force to describe the influences upon fluid behavior. The standard unit for pressure is the Pascal, which is a Newton per square meter. For an object sitting on a surface, the force pressing on the surface is the weight of the object, but in different orientations it might have a different area in contact with the surface and therefore exert a different pressure. Pressure distribution shown in fig. 2.0 below.

Figure 7: pressure on body

Fluid Pressure
Fluid pressure is the pressure at some point within a fluid such as water or air.
Fluid pressure occurs in one of two situations:

1.      An open condition, called "open channel flow"

2.      · The ocean

3.      · Swimming pool

4.      · The atmosphere

2.     A closed condition, called closed conduits

· Water line 24
· Gas line

Pressure in open conditions usually can be approximated as the pressure in "static" or nonmoving conditions, because the motions create only negligible changes in the pressure. Such conditions conform to principle of fluid static. The pressure at any given point of a non-moving (static) fluid is called the hydrostatic pressure.

 Closed bodies of fluid are either "static" when the fluid is not moving, or "dynamic" when the fluid can move as in either a pipe or by compressing an air gap in a closed container. The pressure in closed conditions conforms to the principles of fluid dynamics.

The concepts of fluid pressure are predominantly attributed to the discoveries of Blaisi Pascal and Daniel Bernoulli. Bernoulli Equation can be used in almost any situation to determine the pressure at any point in a fluid. The equation makes some assumptions about the fluid, such as the fluid being ideal and incompressible. An ideal fluid is a fluid in which there is no friction, it is in viscid, zero viscosity. The equation is written between any two points in a system that contain the same fluid. [8]

Hydrostatic Pressure

Hydrostatic pressure is the pressure exerted by a fluid at equilibrium due to the force of gravity. A fluid in this condition is known as hydrostatic fluid. The hydrostatic pressure can be determined from a control volume analysis of an infinitesimally small cube of fluid. Since pressure is defined as the force exerted on a test area (p = F/A, with
p: pressure, F: force normal to area A, a: area), and the only force acting on any such small cube of fluid is the weight of the fluid column above it, hydrostatic pressure can be calculated according to the following formula:    

     

Where:
· p is the hydrostatic pressure (Pa),

· ρ is the fluid density (kg/m3),

· g is gravitational acceleration (m/s2),

· A is the test area (m2),

· z is the height (parallel to the direction of gravity) of the test area (m),

 · z0 is the height of the zero reference point of the pressure(m).

 For water and other liquids, this integral can be simplified significantly for many practical
applications, based on the following two assumptions: Since many liquids can be considered incompressible, a reasonably good estimation can be made from assuming a constant density throughout the liquid. (The same assumption cannot be made within a gaseous environment.) Also, since the height h of the fluid column between z and z0 is often reasonably small compared to the radius of the Earth, one can neglect the variation of g.      Under these circumstances, the integral boils down to the simple formula.                                                                                              

        

Where H is the total height of the liquid column above the test area the surface, and patm is the atmospheric pressure, i.e., the pressure calculated from the remaining integral over the air column from the liquid surface to infinity. Hydrostatic pressure has been used in the preservation of foods in a process called Pascalization. Hydrostatic pressure in water tank is shown in fig. below. [8]

Archimedes Principle:

The magnitude of the upward force (buoyant force) of an object immersed in a fluid is equal to the magnitude of the weight of fluid displaced by the object. Archimedes principle shown in fig

Figure 8: Archimedes Principle

Stability of Unconstrained Submerged Bodies in Fluid

§ The equilibrium of a body submerged in a liquid requires that the weight of the body
acting through its center of gravity should be collinear with equal hydrostatic lift acting
through the center of buoyancy.

§ In general, if the body is not homogeneous in its distribution of mass over the entire
volume, the location of center of gravity G does not coincide with the center of volume,
i.e., the center of buoyancy B.

§ Depending upon the relative locations of G and B, a floating or submerged body attains
three different states of equilibrium Let us suppose that a body is given a small angular displacement and then released. Then it will be said to be in

§ Stable Equilibrium: If the body returns to its original position by retaining the originally vertical axis as vertical.

§ Unstable Equilibrium: If the body does not return to its original position but moves further from it.

§ Neutral Equilibrium: If the body neither returns to its original position nor increases its displacement further, it will simply adopt its new position. [9]

Specific Gravity:

Specific gravity is defined as the ratio of the density of a substance to the density of water. Water has a specific gravity of 1.0: any object with a specific gravity less than 1.0 will float in water and anything with a density greater than 1.0 will sink. The human body has a density slightly less than that of water and averages a specific gravity of 0.974, therefore we float. Also, known as relative density, the ratio of the density of a substance to that of a reference material at a specified temperature, usually water at 4°C. If the specific gravity (sg) of an inert substance is less than unity, it will float in water at 4°C. The sg of liquids is measurement with a hydrometer. [10]

Drag:

Resistance to motion through a fluid as applied to aircraft and spacecraft passing through the atmosphere, it is the component of the resultant force due to relative airflow measured parallel to 29 the direction of motion. It is directly opposed to thrust. Lift is one of the four forces of flight acting on an airplane, the others being weight, thrust, and lift.

Drag is generated by nine conditions associated with the motion of air particles over an aircraft. There are several types of drag – form, pressure, skin friction, parasite, induced, and wave which are described below.

 The term "separation" refers to change from the smooth flow of air as it closely hugs the surface of a wing to where it suddenly breaks free of the surface, creating a chaotic flow. The picture to the right shows examples of air flowing past a variety of objects. The bottom shows well behaved, laminar flow (flow in layers) where the flow stays attached (close to the surface) of the object. The object just above has a laminar flow for the first half of the object and then the flow begins to separate from the surface and form many chaotic tiny vortex flows called vortices. The two objects just above them have a large region of separated flow. The greater the region of separated flow, the greater is the drag. This is why airplane designers go to such effort to streamline wings and tails and fuselages – to minimize drag. Form and pressure drag shown. [11]

Figure 9: drag  forces

2.7. Types of Drag

2.7.1. Form and Pressure Drag

Form drag and pressure drag are virtually the same type of drag. Form or pressure drag is caused by the air that is flowing over the aircraft or airfoil. The separation of air creates turbulence and results in pockets of low and high pressure that leave a wake behind the airplane or airfoil (thus the name pressure drag). This opposes forward motion and is a component of the total drag. Since this drag is due to the shape, or form of the aircraft, it is also called form drag. Streamlining the aircraft will reduce form drag, and parts of an aircraft that do not lend 30 themselves to streamlining are enclosed in covers called fairings, or a cowling for an engine, that have a streamlined shape. Airplane components that produce form drag include  

(1) The wing and wing flaps

(2) The fuselage

(3) Tail surfaces (4) Nacelles (5) Landing gear

(6) Wing tanks and external stores (7) Engines

Skin Friction Drag

Skin friction drag is caused by the actual contact of the air particles against the surface of the aircraft. This is the same as the friction between any two objects or substances. Because skin friction drag is an interaction between a solid (the airplane surface) and a gas (the air), the magnitude of skin friction drag depends on the properties of both the solid and the gas. For the solid airplane, skin fiction drag can be reduced, and airspeed can be increased somewhat, by keeping an aircraft's surface highly polished and clean. For the gas, the magnitude of the drag depends on the viscosity of the air. Along the solid surface of the airplane, a boundary layer of low energy flow is generated. The magnitude of the skin friction depends on the state of this flow. Friction on leading edge of wing is shown in fig. 2.4 below. Fig. 2.4 Friction on leading edge of wing [13]

Figure 10:skin friction drag

 Parasitic Drag

Parasite drag is simply the mathematical sum of form drag and skin friction drag.

            Parasite drag = form drag + skin friction drag

  Induced Drag

Induced drag is the drag created by the vortices at the tip of an aircraft's wing. Induced drag is the drag due to lift. The high pressure underneath the wing causes the airflow at the tips of the wings to curl around from bottom to top in a circular motion. This results in a trailing vortex. Induced drag increases in direct proportion to increases in the angle of attack. The circular motion creates a change in the angle of attack near the wing tip which causes an increase in drag. The greater the angle of attack up to the critical angle (where a stall takes place), the greater the induced drag. Induced drag shown

Figure 11: Induced drag

Thrust:

Thrust is a reaction force described quantitatively by Newton's second and third laws. When a system expels or accelerates mass in one direction, the accelerated mass will cause a force of equal magnitude but opposite direction on that system. UUVs generates thrust (or reverse thrust) when the propellers are turned to accelerate water backwards (or forwards). The resulting thrust pushes the boat in the opposite direction to the sum of the momentum change in the water flowing through the propeller.

Where,

  · T is the thrust generated (force)

· dm/dt is the rate of change of mass with respect to time (mass flow rate of exhaust);

· v is the speed of the exhaust gases measured relative to the rocket. [12]

   Stability of Unconstrained Submerged Bodies in Fluid

• The equilibrium of a body submerged in a liquid requires that the weight of the body acting through its center of gravity should be collinear with equal hydrostatic lift acting through the center of buoyancy.
• In general, if the body is not homogeneous in its distribution of mass over the entire volume, the location of center of gravity G does not coincide with the center of volume, i.e., the center of buoyancy B.
• Depending upon the relative locations of G and B, a floating or submerged body attains three different states of equilibrium-

Let us suppose that a body is given a small angular displacement and then released.                      Then it will be said to be in

• Stable Equilibrium: If the body returns to its original position by retaining the originally vertical axis as vertical.
• Unstable Equilibrium: If the body does not return to its original position but moves further from it.
• Neutral Equilibrium: If the body neither returns to its original position nor increases its displacement further, it will simply adopt its new position.

Chapter 3

Design and calculations

Design under Consideration:

Figure 12: UUV design under consideration

This is also an aesthetic and eye catching design model, the main difference in this design than the previous two designs is the placement of only one depth controlling thruster instead of two depth controlling thrusters. There is only one thruster in the upper cylinder to control UUVs submersion and bring it upward in the water. Motion in one direction of depth controlling thruster causes increase in UUV depth while motion in other direction cause decrease in UUVs depth. Driving control concept is same as previous designs. Thrusters on both left and right are used for drive control i.e. forward, backward, left and right i.e. their motion in clockwise direction work for moving backward and anti-clockwise motion causes motion in forward direction, while one of them working at a time and other one switched off or change in speed of these drive control thrusters cause change in ROV’s direction. In this design also the circuitry was to be put inside cylinder and we had to use waterproof camera or to make it waterproof and then we had to mount our camera on the upper cylinder.

            But the main issue was using thrusters for submersion and decrease in depth, because faculty members forbade us to use thrusters for depth controlling, they suggested us to implement the concept like a naval submarine as it changes its depth by allowing water to fulfill inside its water storage tank hence its density and weight increases which causes a submarine to submerge and go into the depth; And when submarine comes at the surface of the water it outlets the stored water from its storage tank into the ocean hence its volume increases while its density and weight decreases which causes it to decrease its depth and to come at the surface of the water [9]

Proposed Design:

As we discussed the above devices we can see that this is a commercial design and this design cannot be made in student level.

This is the actual design made by the students. 3 thruster are used to move the UUV forward and backward. One wing is used for upward and downward and another wing is used for left and right.

We have used PVC pipe for low weight and for fast speed. PVC is low cost material and can be easily available in the market. The pipe is used as a turbine. The water easily flow inside the pipe while not resisting on the speed of prototype.

The head shape is made like cone on which the drag force of water is very less so that the prototype can easily move in the water and have good speed underwater.

MATHEMATICAL CALCULATIONS:

Basic Forces on a Submarine:

Figure 13: forces on submarine

The forces shown in the above figure are the four basic forces on a submarine, where Buoyancy force is an upward force exerted by a fluid that opposes the weight of an immersed object. And it is equal to the weight of the fluid displaced by the object.

Where;

= Buoyancy force

=    Volume of immersed part

= water and immersed object density difference

g = Gravitational acceleration

A = Area of immersed part

            And Water Resistance or Drag force is force acting opposite to the relative motion of any object moving in water.

                                                                                                                                             (1)

Where;

=   Drag force

=   water density

v   =   speed of moving object

=   Drag force co efficient (0.82 for cylindrical shapes)

A   =   Cross sectional Area

7.2 Thrust

            (Nomenclature used in thrust calculation)

F = Thrust (N)

    = mass flow rate (kg/sec)

    = exit velocity of water through propeller (m/sec)

    = inlet velocity of water through propeller (m/sec)

    = propeller pitch speed (m/sec)

    = water density (                 )

A  = area through propeller , normal to water flow (        )

P   = Pressure (Pa   ,                 ,                        )

Newton’s 2^nd law when mass held constant

(2)

Source: Research Article ‘Propellers Static and dynamic thrust calculation’ written by Gabriel Staples [April 12, 2014]

Newton’s 2^nd law when velocity held constant

(3)

Theoretical static thrust

(4)

Theoretical dynamic thrust

 (5)

 

(6)

Where ‘A’ is cross sectional area covered by spinning propeller

(7)

Where;

r = radius of propeller

r =diameter of propeller

Putting eq (7) in eq(6);

(8)

Inlet speed of water is zero in static fluid. So above equation becomes;

V_e is assumed to be approximately equal to the pitch speed of the propeller, as

RPM of propeller is in (rev/min) and its pitch is in inches

                                                                                                                                           (10)

Putting this in eq (8);

 

(11)

Theoretical to Empirical: Making the Equations Work For Real Life

Gabriel Staples graphical analyzed and concluded that higher diameter and lower pitch propellers must be more efficient,

(12)

Pretty soon Gabriel Staples realized that relationship of (d/pitch) to static thrust was non-linear, so he added in a second constant to raise the diameter-to-pitch ratio to some power.

(13)

Where ‘k1’ is ‘co-efficient constant’ and ‘k2’ is the ‘power constant’. Putting values of ‘k1’ and ‘k2’ after calibration, it was the final static thrust equation with Correction factor

.

(14)

It is calculated for a propeller having 2 blades, Birger Jacobsan gave the below calculation of RPM  of propellers having more than 2 blades.

(15)

Where;

Source: Research Article ‘Propellers Static and dynamic thrust calculation’ written by Gabriel Staples [April 12, 2014]

CHAPTER 4

FABRICATION OF UNMANNED UNDERWATER VEHICLE

Fabrication:

 Fabrication is the building of structures by cutting, bending, drilling, coupling and assembling processes. It is a value added process that involves the construction of machines and structures from various raw materials.

Different machine used in manufacturing of our design.

1.      Cutting blade

2.      Acrylic sheet

3.      Plastic tube

4.      Heat gun

5.      Glue gun

6.      Silicon

7.      Vernier caliper

8.      Measuring tape

Cutting blade:

Cutting blade is the steel material having sharp teeth which is used for cutting the PVC material in the manufacturing of wind turbine blades

Used for cutting of turbine blades.

Figure 14: Cutting blade

 Acrylic sheet:

Acrylic which has been used for commercial and personal purposes for years is still the one plastic that is most widely used. It is a manmade material that versatile and one that is commonly used almost all over the world. There are other reasons why acrylic sheets are the most widely and popularly used materials.

Figure 15: Acrylic sheet

 Plastic tube:

PVC known as polyvinyl chloride, or PVC, is a thermoplastic material, which means that it can be reprocessed using heat. Because vinyl can be processed using heat

Figure 16: plastic tube

       

Glue gun

A usually gun-shaped electric tool used for melting and applying sticks of adhesive.

Figure 17: glue gun

 Silicon:

The chemical element of atomic number 14, a non-metal with semiconducting properties. It is used in electronic circuits and also used as adhesive elements which assemble parts.

Figure 18: silicon pipe

 Vernier caliper

A vernier caliper outputs measurement readings in centimeters (cm) and it is precise up to 2 decimal places

Figure 19: Vernier calliper

 Measuring tape

A tape measure or measuring tape is a flexible ruler. It consists of a ribbon of cloth, plastic, fiber glass, or metal strip with linear-measurement markings.

Figure 20: measuring tape

: Components:

Ø  Propeller ( 3 blade propeller)

Ø  12 v Battery

Ø  12 v DC motors ( 3 motors )

Ø  Wings ( 4 wings)

Ø  Wireless camera

Ø  Stand

Ø  H- bridge L298

Ø  Nuts and bots

  Propeller (3 blade propeller)

A propeller is a type of fan that transmits power by converting rotational motion into thrust. A pressure difference is produced between the forward and rear surfaces of the airfoil-shaped blade,

Figure 21: Propeller (3 blade propeller)

     12 v Battery

The DC motor is an electrical device which converts from dc electrical energy into mechanical energy 

Figure 22:12 V DC Battery

      12 v DC motors (3 motors)

12 V DC motor

2400 RPM

12 V DC motors are used to convert electrical energy to mechanical energy.

Figure 23:12 V DC motor

   Underwater glider

An underwater glider is a type of wings which control left and right motion and up and down motion of vehicle, which is also control the balance of the vehicle.

                                                                       Figure 24: Underwater glider

  Wireless camera

Camera that transmit a video and audio signal to a wireless receiver through a radio band

Figure 25:camera

     H- bridge L298

The L298N H-bridge can be used with motors that have a voltage of between 5 and 35V DC. With the module used in this tutorial, there is also an onboard 5V regulator, so if your supply voltage is up to 12V you can also source 5V from the board.

Figure 26: H- bridge L298

  Nuts and bots

A nut is a type of fastener with a threaded hole. Nuts are almost always used in conjunction with a mating bolt to fasten two or more parts together.

 Dimensions:

Full vehicle length: 18.5 inch

Full vehicle dia:      4 inch

Wings:

Length: 3.5 inch

Width: 2 inch

Propeller blade:

Length: 1.7 inch

Thrust: 0.7

Stand:

Length: 4 inch

Weight:

Total weight: 1 KG

 Assembly:

We joined all the parts to assemble the prototype.

 

                                                                                                  Figure 27: UUVs model

Chapter 5

Experimentations and results

                                                                              Figure 28: experimentation

Experimental procedures:

The experiment was conducted in two stages floating on water and underwater. We have conducted these two types of results. experiment was conducted on Sunday March 16, 2017. The vehicle was run many times on the surface of water and underwater. The weight of the body was also calculated.

We have conducted these results both when vehicle was both underwater and floating on the surface of the water.

Formulas used in calculations:

For drag force we have use this formula      

C = drag coefficient

  = density

A = area 

V = velocity

For bouncy force, we use formula              

 = density  

V = displaced body volume of liquid 

G = gravity

Floating on water:

experiment was conducted on Sunday March 16, 2017. The vehicle was run many times on the surface of water. The weight of the body was also calculated.

We have conducted these results both when vehicle was both underwater and floating on the surface of the water.

Stability Calculations:

Extra mass for balancing	0.5
Motors mass	0.3
Circuit	0.2
Battery	0.4
Side cylinders	0.2
Main cylinder	0.5
Total mass	2.1 Kg

Table 4

Drag calculations:

Run no	Recorded speed (m/s)	Drag force (N)
1	0.25 m/s	0.0577 N
2	0.5 m/s	1.01 N

Table 5

Testing results:

Run No.	Velocity (m/s)	bouncy Force (N)
1	0.25	0.02878
2	0.506	0.11793

Table 6

Material used:

Components	Final design
Hollow main cylinder	PVC sheet
Side cylinders	PVC sheet
Left right wing	Acrylic sheet
Up down wing	Acrylic sheet
Turbines	PVC sheet
Water proofing	Silicon
Balancing	Iron plates
Supporting materials	Aluminum plate

Table 7

Depth measurement:

Under water (f)	On surface (f)
2 feet	Half drown

chapter 6

Circuit diagram

Circuit diagram of proposed project  

The above fig is the diagram of circuit of proposed project. It is a simple diagram in which microcontroller gets information from transceiver and send it to another transceiver which is attached to microcontroller.  Microcontroller gives commands to the different parts of the project and project works on those commands.

Two H bridges are also used which are attached to the microcontroller which gives 12 v of power to the motors.

Two transceivers DRF 7020 are used which receive commands from laptop and give it to the microcontroller.  Microcontroller send commands to the project different parts which start to work.

One H bridge is attached with Arduino microcontroller D6, D7, D8 and D9 pins and another is attached with D10, D11, D12 and D13 pins. H bridge basically convert  5 v to 12 v.

DRF transceiver is connected to Arduino Do and D1 pins. Which receive signal from another transceiver and give to Arduino.

Conclusions:

This investigation has involved the design, construction and testing of a submersible vessel and has allowed a more thorough understanding of key fluid mechanic principles be developed through application. For the purpose of this project, a relationship between buoyancy, materials, propulsion, and size was determined. Water propeller’s thrust calculation was derived. It is the fact that neutrally buoyant UUV can be moved in all directions by the proper placement of thrusters. The shape of UROV will also resist its performance because drag force and buoyancy force can vary with change in shape. Most of the previous projects used thrusters to change UUV’s depth but we implemented the concept of a naval submarine by controlling its depth by using buoyancy force by varying its weight by fulfilling and draining water from its water storage tanks. And we concluded that thrust produced by propellers and UUV’s speed in water are very much dependent upon diameter, pitch and blades of propellers. Thrust produced by propellers can be varied by changing propeller’s pitch, diameter of propeller’s blades and by changing the angle of propeller’s blade. Thrust can also be varied by changing the speed of the motor. The UUV proved to be capable of completing all objectives and measure its depth in water.