Based on the current trend of aircraft development, environmental factors such as noise and emission limits will play a more vital role in future transport aircraft design, driving the need for greener more efficient aircraft. Of the primary objectives of the Clean Sky initiative is achieving a total reduction in aircraft drag of 10% by reducing the wing drag by 25%. Another goal is the reduction of fuel burnt by 20%.

Both the reduction in drag and fuel savings are intertwined since through innovative flow control mechanisms. Flow control is the manipulation of flow characteristics to yield desirable effects. The stall condition is an undesirable phenomenon where controlling it will improve the aircraft performance by enabling it to take off and land at higher incidences and lower speeds. Controlling the stall angle can be achieved through delaying the leading edge separation on the aerofoil, which is usually associated with achieving higher lift magnitudes and lower drag. There are several mechanisms in the field of passive and active flow control to prevent leading edge separation.

In this study, a NACA 0015 aerofoil constructed from perspex with a chord length, c, of 0.24 m and span of 0.40 m is considered.

The characteristics of this aerofoil are well documented in the literature and it exhibits well-behaved leading edge separation at high angles of attack. Aerofoil is flying in chord Reynolds number of 0.2x106.

You will need to:

Determine:

the boundary layer analysis on top surface of the aerofoil in zero AoA through calculations and simulation. You may suppose the boundary layer on a flat plate.the stall angle through simulation,

the flow control techniques that can control separation through simulation.

(Theoretical calculations and Computational analysis using Solidworks Flow Simulation)

Compare and contrast the results obtained via both approaches and if any meaningful discrepancies exist, propose reasons why the

## The Negative Impacts of Transportation on the Environment

The transportation system evolves day by day with the evolution of science and technology. The transport is the most vital thing. There are many modes of transportation in this modern world such as air, water, and road. The automotive industries are making a large number of profits by this transportation business. Everyone in this world needs a form of transportation such as private, public transportation system, etc. This Transportation system helped the humans to save time and make more profit in their business, work, medical emergencies, etc. The Air transport system is the quickest form of transportation available to travel from one country to another or state to another state (Vasigh, B. and Fleming, K., 2016)

According to the survey taken by the International Air transport Association (IATA), there are around 4,100,000,000 amount of people travel by air and it is expected that this number will raise twice in the course of 20 years. Even though these Transportation systems provide an enormous number of pros there are certain negativities which really affects our environment. There are a large number of chemicals and gases which reaches the environment as a result of the chemical combustion that takes place inside the combustion chamber of the vehicles

According to a survey taken by WHO (World Health Organization) The road transportation systems accounts for the 30 % of the total Particulate emissions in a European country. The air pollution due to these harmful Greenhouse Gases also greatly influence the weakening of the ozone layer which will result in a large number of health effects. The ozone layer acts as a protective layer from the solar radiation. If the solar radiation directly touches the human skin it will lead to a large number of diseases and health effects. The radiation will also cause cancer.

There are many types of research and studied carrier out and are in process for the lowering of the emission caused by the automobiles and aircraft. Also, the amount of emission can greatly be reduced if the fuel efficiency of the vehicle is increased. The efficiency of the vehicles can be increased in many ways. In automobiles, the efficiencies can be increased by lowering the amount of fuel consumption in the IC engine and the aerodynamics of the vehicle (Janic, M., 2014).

In the case of Aeroplanes the system works on the principle of four forces which helps to control the movement of the aeroplane. The four forces which act on the aeroplanes are Lift, Drag, Thrust, and Weight. These four forces greatly impact the fuel economy of an aeroplane. The fuel efficiency of an aeroplane can be increased in a large number of ways, but in this study, we will focus on reducing the Drag force in the aeroplane to reduce the fuel consumption. The overall drag of the aeroplane will be reduced by 10 percentage by reducing the drag force acting on the wing by 25 percentage (Matsumoto, H, et.al 2016)

There is a phenomenon known as stalling which needed to be controlled in order to achieve good aircraft performance. This effect will enable taking off the plane at higher insides and lower speeds. The stall angle control can be achieved by delaying the leading edge separation in the aerofoil. All the aeroplane wings utilize the aerofoil shape wing,

## Improving Fuel Efficiency in Aircraft Design

The flight of an aeroplane is achieved by the wings. The wings cross-section is made up of an aerofoil shape. The airfoil shape generates the lift that is necessary for the plane to take off and land. The lift force is generated by the Bernoulli's principle as the airfoil shape consists of curved top surface and flat low surface the air travels more in the top surface than the lower surface which results in the Low air pressure at the top surface and High air pressure at the lower surface which generated the lift. The flaps are used in aid with the wings to increase or decrease the lift and to control the aeroplane take off and landings (Srinivasa, V., et.al 2016).

The aerofoil shape greatly influences the amount of lift and drag an aircraft produces which is directly interlinked with the fuel economy of a plane.

The boundary layer concept explains that if a fluid passes through an airfoil shape the fluid molecules get stickled to the boundary of the aerofoil at the boundary point the velocity of the fluid will be equal to the velocity of the aerofoil body which moves across the fluid. From the surface, the velocity of the fluid starts to raise. Which paves a way for velocity gradient. After some distance from the solid body, the free stream velocity is achieved which is not affected by the solid body moving across the fluid (Schlichting, H. and Gersten, K., 2016.)

There are two types of boundary layers according to the behaviour of the fluid which hits the surface of the body, a) Laminar boundary layer and b) Turbulent boundary layer. Which are determined using the Reynolds number?

The boundary layer thickness is mathematically given as:

=

Where,

is the chord length.

is Reynolds number.

Zhou, et.al 2001 studied the fluctuating and mean forces that are acting on the NACA 0012 airfoil. The Analysis is carried out for a large number of Angle of Attacks starting from 0 to 90 degrees. The chord Reynolds number R_{e }is taken from 5.3e3 to 5.1e4. The measurement was carried out with the help of load cells. The final results have shown that the stall of an aerofoil is decided by the drop in the lift force and change in the drag, which is found to occur at the Reynolds number greater than 1.05e4 and it is not experienced when the Reynolds number is equal to 5.3e3.

Aravind Studied the Profile of the NACA4412 Aerofoil, the study is carried out by creating a model in the CATIA CAD modelling package and then the Flow analysis is carried out with the help of Ansys Fluent. The simulation was carried out for a turbulent flow which flows the rate of 340 m/s and the simulation was carried out for a various angle of attacks such as 0, 16, and 12 degrees.

Lanzafame and Mesina at 2007 developed a mathematical model for improving the Blade design of a wind turbine on the basis of element moment theory. They also simulated and obtained results for the various range of velocities of wind. As they faced difficulty to implement the BEM theory to find the required lift and drag forces, they developed a model from the tangential flow factor. The model optimized the performance of the rotor. A simulation was performed in order to find the required drag and lift coefficients. The obtained results are also compared with the experimental results and a conclusion was drawn.

## Controlling the Stall Angle in Aerofoils

The NACA 4412 was also studied by Kevdiya at 2013. The complete profile of the NACA 4412 aerofoil shape is studied and a flow analysis is carried out. The CAD model of the Aerofoil shape is created using Gambit 3D modelling Package and then CFD (Computational fluid dynamics) was carried out with the help of Ansys Fluent Software package. The AOA (Angle of Attack) was taken from 0 to 12 degrees. The simulation was carried out for turbulent flow conditions the final results are laid out and the discussion was done.

Mittal et.al 2002, carried out a CFD (Computational fluid dynamics) study on the NACA 0012 profile for the 2D model. Diminishing & Expanding approach is utilized for the study. A mathematical model was developed by using Navier strokes mathematical equations and then the profile is evaluated with proper boundary conditions. Finally, the reports are laid and discussed.

The NACA 4415 profile was utilized by Kishiname et.al 2005, for the calculation of power coefficient values of a wind turbine. The NACA standard profiles were used for the wind turbine blades and the study was carried out. The final results showed that the values varied between 0.23 to 0.41 at the speed rate of 4.5 meters per seconds.

Vardar, A and Alibas I, 2008 carried out a Research on the Wind turbine rotors which utilized the NACA 2404 profile for the rotor blades. The same aerofoil profile was also studied by Hiraharan et.al 2005, to find the power coefficient of a wind turbine. The study was carried out for the wind velocity of 3.7 m/s to 21.5 m/s and the result shown that the turbine reached a power coefficient of 0.40.

Theoretical Calculation

The Boundary Layer Analysis on the top layer of the Aerofoil (NACA 0015) at Zero Angle of attack will be carried out by categorizing the problem under the flow over a flat plate. The solid object is the NACA 0015 Aerofoil and the fluid is considered to flow over the aerofoil shape.

The concept of Boundary layer was utilized to solve the problem theoretically, A boundary layer is formed whenever a fluid passes over a solid object. The velocity of the fluid will be equal to that of the velocity of the solid object at the point of the boundary surface of the solid object. The velocity gradient keeps I increasing with the perpendicular distance from the Boundary of Solid surface. The concept of the boundary layer was discussed in depth at the introduction.

The first step in solving the problem is to find the flow conditions. Reynolds number is used to find whether the flow is a turbulent flow or a laminar flow. The found values are used to carry out the Drag force Calculation on the aerofoil. The drag force is the product of the shear stress and the cross-section area of the Aerofoil profile (Williams, B.J., et.al 2014)

The geometry of the NACA 0015 Aerofoil is shown below:

Figure. Illustrates the shape of NACA 0015 Aerofoil (Svoboda, A. and Rozehnal, D., 2017)

## The Aerofoil Shape and Its Impact on Lift and Drag

The calculations were carried out with the formulae given below:

Drag Force,

C is the coefficient of drag of shape

A is the Area of a cross-section of an aerofoil

is the density of a fluid

V is fluid Velocity (considering solid body stationary)

The Reynolds number will be found using the formula:

Boundary-Layer thickness can be found using the Formula:

To carry out Flow Simulation using Solid works Flow Simulate:

The Solid works Flow Simulation is a Computational Fluid Dynamics package which is interlinked with the Solidworks CAD modelling package. The package enables the user to run quick and precise flow calculations on the existing CAD model. The solid works CFD package is being utilized in this project to do a flow analysis on the selected NACA 0015 Aerofoil profile (Raval, N.P, et.al 2017)

The process flow diagram is shown below:

The CAD modelling is the initial step to carry out the simulation. A 3D model of the NACA 0015 Aerofoil must be created with the help of Solidworks CAD modelling package. The profile is created as per the dimensional detail requirements.

The Processing is the stage at which the Solidworks flow simulate will be opened and the input data that are required to carry out the simulation will be provided. The data such as the plane along which the flow occurs, the velocity of the flow, type of fluid, fluid density, fluid speed rate, the angle of attack of the geometry, etc. Will be given as input to carry out the simulation.

The simulation will be run in this stage all the input data should be check thoroughly before running the simulation. Running the simulation means solving the problem. The flow problem will be solved by the computer system.

Post processing is the stage at which the various process such as selecting which result to show, what are the desired outputs and creation of a report for the solved simulation, etc. The post-processing is done after the completion of the simulation.

The results which are obtained at step 4 will be interpreted and discussed in this step. The final results are evaluated.

Theoretical:

Calculation of Shear stress:

Drag Force Calculation (Kurtulus, D.F., 2015):

C is the coefficient of drag of shape

A is the Area of a cross-section of the aerofoil

is the density of the fluid

V is fluid Velocity (considering solid body stationary)

WKT,

C: 0.8 (Assume for shape)

A: 0.00591923 m^{2} (Cross section area)

Step1: The CAD model is imported into the Flow simulation environment

Step2: Flow simulation wizard is clicked

Step3: Measuring unit is selected as SI

Step4: Flow parameters are given.

Step5: Air is selected as fluid

Step6: Axis of flow is taken as X

Step7: Goal is selected as follows:

Step8: Model is meshed

Step9: Click Run

Step10: Go to cut plane and select X axis to view simulation.

Step11: Generate Result.

The problem was solved both theoretically and with the aid of Simulation software.

## The Concept of Boundary Layer

The theoretical results which are obtained as a result of detailed calculations are:

The drag force is calculated to be: 0.26 N

The shear stress is found to be 4.25e-3 Pascal.

The boundary layer thickness is found to be 2.68e-3 meters.

Now the obtained simulation results of the Solidworks flow simulate tool are shown below:

The Detailed report of the Solidworks Simulation is given below:

Inputs

The Ambient input conditions:

Velocities |
Velocity - X direction: 80.000 m/s Velocity - Y direction: 0 m/s Velocity - Z direction: 0 m/s |

Fluid |
Air |

Final Results of the Main goal of the project:

Name |
Unit |
Value |
Progress |
Criteria |
Delta |

GG Min Velocity (Y) 1 |
m/s |
-44.815 |
100 |
0.359871892 |
0.000377324786 |

GG Av Velocity (Y) 1 |
m/s |
-2.121e-004 |
100 |
5.31561222e-005 |
5.25367032e-005 |

GG Max Velocity (Y) 1 |
m/s |
44.800 |
100 |
0.359858483 |
0.00044119023 |

Drag Force 1 |
N |
5.847 |
100 |
0.285217894 |
0.000192379623 |

Lift Force 1 |
N |
0.015 |
100 |
0.0114754481 |
0.00125270582 |

GG Min Shear Stress (Y) 1 |
Pa |
-13.73 |
100 |
0.102809267 |
5.04755612e-005 |

GG Av Shear Stress (Y) 1 |
Pa |
-8.59e-004 |
100 |
7.66800932e-005 |
4.72815289e-005 |

GG Max Shear Stress (Y) 1 |
Pa |
13.73 |
100 |
0.102761954 |
3.89780814e-005 |

The need for the greener and more efficient aircraft has been the need for the century as the travelling has become the inevitable part of human life these days. Aircraft account for the considerable amount of air and noise pollutions. Pollution creates many hazardous effects on both the health and the lifestyle of humans and as well as the environment. The efficiency of the aircraft should be increased in order to reduce the emission of harmful gases as a result of burning fuel. The efficiency of an aircraft can be increased by reducing the drag in the aeroplane wings. The aerofoil shape and its working were discussed briefly in the introduction. The various studies carried out by various researchers on the different profiles of the NACA aerofoil shapes were discussed in the Literature survey. Then the calculation of shear force, boundary layer thickness and drag force are carried out theoretically with the help of formulae.

Then a Flow simulation is carried out with the help of solid works simulate. The boundary conditions were given and then the simulation is carried out for getting the goals as shear force, velocity profile along the y-axis, lift force, and drag force. Then finally the solve button is pressed. After completing the results the solution is saved and the report is generated.

Theoretical calculations Vs Simulation Results:

The result section shows the various results of the theoretical and simulated results.

Drag force:

The theoretically calculated value of Drag Force: 0.26 N

Simulation result of Drag Force: 0.28 N

Thus we can see that the Calculated Value of the Drag force and the simulated value of the drag force is having a difference of 0.02N. This deviation in the result can be reduced by:

- More precise calculation
- Making sure no manual error
- Taking high decimal values up to 4digits

The graphical plot of the Velocity along Y axis:

The plot shows the Variation of velocity along the y-axis this helps to find the variation in the velocity profile along the Y-axis. It is visible that the velocity gradient is higher at the point of attack which is the nose of the Aerofoil. Then I gradually reduce. The velocity of the fluid is lower at the bottom side of the aerofoil. The other goals of the simulations are also obtained and the results are shown in the result section.

Conclusion:

Thus in this report, the environmental effects of the air transportation system and the need for more efficient aeroplanes were explained. The concept of the boundary layer and the four forces acting on a plane were discussed. Then the Boundary layer analysis is carried out on the aerofoil shape by considering a flow over a flat plate at zero angles of attack. The drag force was calculated manually. Then a CAD model is developed, which is then imported into the simulation environment and proper boundary conditions were provided. The simulation was carried out and the simulation results were explained properly. Finally, a discussion is drawn between the theoretical calculations and the simulated results, the deviation between them and the method to improve the accuracy were discussed.

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