Flow Simulation over NACA 2412 Airfoil using Solidworks Flow Simulation
OBJECTIVE:
To perform flow simulation over a NACA 2412 airfoil for various angle of attack using Solidworks Flow Simulation and also compare the lift & drag forces.
ABSTRACT:
The project purpose was to perform flow motion analysis over a NACA 2412 airfoil having air as a fluid using SolidWorks Flow Simulaion. The flow simulation was performed in total 6 cases for different angle of attack i.e. 0, 2, 4, 6, 8, 10. Velocity & Pressure contours were obtained using cut plots for each case. The lift & drag forces were calculated through the established goals for each case. Further, for all the angle of attack, lift & drag forces were compared and a conclusion was made from the analysis results.
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CONTENTS:
1. Introduction
- Computational Fluid Dynamics (CFD)
- NACA 2412 Airfoil
- Angle of attack
- Lift Force
- Drag Force
Case 1: Angle of Attack is ‘0’
- Geometry Model
- Setup
- Computational Domain
- Global Mesh
- Goals
- Result
3. Case 2: Angle of Attack is ‘2’
- Geometry Model
- Setup
- Computational Domain
- Mesh Parameter
- Goals
- Result
4. Case 3: Angle of Attack is ‘4’
- Geometry Model
- Setup
- Computational Domain
- Mesh Parameter
- Goals
- Result
Case 4: Angle of Attack is ‘6’
- Geometry Model
- Setup
- Computational Domain
- Mesh Parameter
- Goals
- Result
6. Case 5: Angle of Attack is ‘8’
- Geometry Model
- Setup
- Computational Domain
- Mesh Parameter
- Goals
- Result
7. Case 6: Angle of Attack is ‘10’
- Geometry Model
- Setup
- Computational Domain
- Mesh Parameter
- Goals
- Result
8. Observation
Conclusion
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1. INTRODUCTION:
Computational Fluid Dynamics (CFD)
Computational fluid dynamics (CFD) is a branch of fluid mechanics that uses numerical analysis and data structures to analyse and solve problems that involve fluid flows. Computers are used to perform the calculations required to simulate the free-stream flow of the fluid, and the interaction of the fluid (liquids and gases) with surfaces defined by boundary conditions. With high-speed supercomputers, better solutions can be achieved, and are often required to solve the largest and most complex problems.
CFD is applied to a wide range of research and engineering problems in many fields of study and industries, including aerodynamics and aerospace analysis, weather simulation, natural science and environmental engineering, industrial system design and analysis, biological engineering, fluid flows and heat transfer, and engine and combustion analysis.
NACA 2412 Airfoil
An airfoil (American English) or aerofoil (British English) is the cross-sectional shape of a wing, blade (of a propeller, rotor, or turbine), or sail (as seen in cross-section).
An airfoil-shaped body moving through a fluid produces an aerodynamic force. The component of this force perpendicular to the direction of motion is called lift. The component parallel to the direction of motion is called drag.
NACA 4-digit airfoil specification
Fig: NACA 2412 Airfoil Cross-Section
This NACA airfoil series is controlled by 4 digits e.g. NACA 2412, which designate the camber, position of the maximum camber and thickness. If an airfoil number is NACA MPXX
e.g. NACA 2412 then:
M is the maximum camber divided by 100. In the example M=2 so the camber is 0.02 or 2% of the chord
P is the position of the maximum camber divided by 10. In the example P=4 so the maximum camber is at 0.4 or 40% of the chord.
XX is the thickness divided by 100. In the example XX=12 so the thiickness is 0.12 or 12% of the chord.
Angle of Attack
In aerodynamics, angle of attack specifies the angle between the chord line of the wing of a fixed-wing aircraft and the vector representing the relative motion between the aircraft and the atmosphere. Angle of attack is the angle between the body's reference line and the oncoming flow.
Lift Force
A fluid flowing around the surface of an object exerts a force on it. Lift is the component of this force that is perpendicular to the oncoming flow direction.[1] It contrasts with the drag force, which is the component of the force parallel to the flow direction. Lift conventionally acts in an upward direction in order to counter the force of gravity, but it can act in any direction at right angles to the flow.
The lift force FL is given by-
FL = CL 1/2 ρ v2 A
where
FL = lifting force (N)
CL = lifting coefficient
ρ = density of fluid (kg/m3)
v = flow velocity (m/s)
A = body area (m2)
Drag Force
A drag force is the resistance force caused by the motion of a body through a fluid, such as water or air. A drag force acts opposite to the direction of the oncoming flow velocity. This is the relative velocity between the body and the fluid.
The drag force FD exerted on a body traveling through a fluid is given by-
FD = CD 1/2 ρ v2 A
where:
FD = drag force (N)
CD is the drag coefficient, which can vary along with the speed of the body. But typical values range from 0.4 to 1.0 for different fluids (such as air and water)
ρ is the density of the fluid through which the body is moving
v is the speed of the body relative to the fluid
A is the projected cross-sectional area of the body perpendicular to the flow direction.
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2. Case 1: Angle of Attack is ‘0⁰’
- Geometry Model
The XYZ Coordinates of NACA 2412 airfoil were downloaded from http://airfoiltools.com/search/airfoils.
In this case, 0⁰ angle of attack was provided.
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- Setup
- Project name: angle_of_attack_0
- Analysis type: External; Time-Dependent; Simulation Time (5s); Time Step (1s)
- Type of fluid: Air
- Type of flow: Laminar & Turbulent
- Wall Condition: Adiabatic Wall with 0 micro-meter roughness
- Initial Condition: Pressure (101325 Pa), Temperature (293.2K), Velocity x-direction (600 m/s)
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- Computational Domain
Computational Domain Type – 2D Simulation
*The length & height of the domain should be such that the distance at inflow should be 5 times the chord length and distance at outflow should be 10-15 times the chord length.
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- Global Mesh
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- Goals
Global Goals
Force(x), Force(y), Frictional Force(x) & Frictional Force(y)
Surface Goals
Force(x) refers to the drag force & Force(y) refers to the lift force.
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- Result
Drag Force – Surface Goal Force (X)
Lift Force – Surface Goal Force (Y)
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Velocity Contour
In order to generate a contour, a cut plot was provided parallel to the cross-section of the airfoil and at the mid length.
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Pressure Contour
In order to generate a contour, a cut plot was provided parallel to the cross-section of the airfoil and at the mid length.
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3. Case 2: Angle of Attack is ‘2⁰’
- Geometry Model
The XYZ Coordinates of NACA 2412 airfoil were downloaded from http://airfoiltools.com/search/airfoils.
In this case, 2⁰ angle of attack was provided.
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- Setup, Computational Domain, Global Mesh & Goals all are same as case 1
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- Result
Drag Force – Surface Goal Force (X)
Lift Force – Surface Goal Force (Y)
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Velocity Contour
In order to generate a contour, a cut plot was provided parallel to the cross-section of the airfoil and at the mid length.
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Pressure Contour
In order to generate a contour, a cut plot was provided parallel to the cross-section of the airfoil and at the mid length.
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4. Case 3: Angle of Attack is ‘4⁰’
- Geometry Model
The XYZ Coordinates of NACA 2412 airfoil were downloaded from http://airfoiltools.com/search/airfoils.
In this case, 4⁰ angle of attack was provided.
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- Setup, Computational Domain, Global Mesh & Goals all are same as case 1
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- Result
Drag Force – Surface Goal Force (X)
Lift Force – Surface Goal Force (Y)
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Velocity Contour
In order to generate a contour, a cut plot was provided parallel to the cross-section of the airfoil and at the mid length.
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Pressure Contour
In order to generate a contour, a cut plot was provided parallel to the cross-section of the airfoil and at the mid length.
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5. Case 4: Angle of Attack is ‘6⁰’
- Geometry Model
The XYZ Coordinates of NACA 2412 airfoil were downloaded from http://airfoiltools.com/search/airfoils.
In this case, 6⁰ angle of attack was provided.
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- Setup, Computational Domain, Global Mesh & Goals all are same as case 1
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- Result
Drag Force – Surface Goal Force (X)
Lift Force – Surface Goal Force (Y)
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Velocity Contour
In order to generate a contour, a cut plot was provided parallel to the cross-section of the airfoil and at the mid length.
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Pressure Contour
In order to generate a contour, a cut plot was provided parallel to the cross-section of the airfoil and at the mid length.
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6. Case 5: Angle of Attack is ‘8⁰’
- Geometry Model
The XYZ Coordinates of NACA 2412 airfoil were downloaded from http://airfoiltools.com/search/airfoils.
In this case, 8⁰ angle of attack was provided.
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- Setup, Computational Domain, Global Mesh & Goals all are same as case 1
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- Result
Drag Force – Surface Goal Force (X)
Lift Force – Surface Goal Force (Y)
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Velocity Contour
In order to generate a contour, a cut plot was provided parallel to the cross-section of the airfoil and at the mid length.
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Pressure Contour
In order to generate a contour, a cut plot was provided parallel to the cross-section of the airfoil and at the mid length.
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7. Case 6: Angle of Attack is ‘10⁰’
- Geometry Model
The XYZ Coordinates of NACA 2412 airfoil were downloaded from http://airfoiltools.com/search/airfoils.
In this case, 10⁰ angle of attack was provided.
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- Setup, Computational Domain, Global Mesh & Goals all are same as case 1
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- Result
Drag Force – Surface Goal Force (X)
Lift Force – Surface Goal Force (Y)
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Velocity Contour
In order to generate a contour, a cut plot was provided parallel to the cross-section of the airfoil and at the mid length.
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Pressure Contour
In order to generate a contour, a cut plot was provided parallel to the cross-section of the airfoil and at the mid length.
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8. Observation
The following table shows a collection of results of all the above cases-
From the above table the following observations can be made-
- On increasing the angle of attack (AOA) from 0⁰ to 10⁰, the drag & lift force increases.
- Since, up to 10⁰ of AOA, the lift force is increasing. Therefore, the stall angle has not achieved yet.
- In first case, the lift forces are negative as the camber profile is curved above the horizontal axis of the airfoil.
- As the AOA increases up to 8⁰, the maximum velocity of air over the airfoil increases with increase in AOA but at 10⁰ AOA, it reduces due to sudden high increase in the drag force.
- The maximum pressure experienced by the airfoil is at 0⁰ AOA and the pressure exerted over the airfoil reduces as the AOA increases.
- From figure 1, it can be observed that at 0⁰ AOA, the velocity distribution of air over the upper & lower surface of the airfoil is almost symmetrical but as the AOA increases, the velocity of the air over the upper surface increases and the velocity of air decreases over the lower surface of the airfoil.
- From figure 2, it can be observed that at 0⁰ AOA, the pressure distribution over the upper & lower surface of the airfoil is almost symmetrical but as the AOA increases, a lower pressure region is formed on the upper surface while a higher pressure region is formed on the lower surface. This pressure difference created on the upper & lower surface of the airfoil causes the airfoil to generate lift.
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9. Conclusion
As the angle of attack increases, the lift & drag forces also increases but as the AOA reaches the critical AOA or stall angle, then the lift force starts to reduce.
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