Flow over an airfoil
Aim : Model the flow over a NACA0017 airfoil for the angle of attacks 0,2,4,6,8,10 . compare the lift and drag forces
Introduction :
Flow simulation is a form of computational fluid dynamics which digitally replicates flows in surface water or collection systems. Performing flow simulation allows for the prediction and analysis of how a flow might be impacted by complex geometry in an operational environment.
Basic theory on the simulation:
Airfoil : An airfoil or aerofoil is the cross-sectional shape of a wing, blade, or sail. 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.
Angle of Attack : The Angle of Attack is the angle at which relative wind meets an Aerofoil. It is the angle formed by the Chord of the aerofoil and the direction of the relative wind or the vector representing the relative motion between the aircraft and the atmosphere.
Entire Study Setup :
An airfoil is created by using convert entities then line command.
For the different angle of attacks rotate entities is used.
The airfoil is extruded to 0.2 m.
Now save the file.
The flow simulation is created using the wizard menu.
The analysis type is selected as external. Time-dependent is selected.
Total analysis time is selected as 5 sec and output time is 1sec.
The fluid is selected as air and velocity parameter over X-direction is selected as 600m/s and then click finish.
Now a computational domain is created by using the 2D option.
The computational domain is expanded along both y-directions and x-direction .in flow length should be 5 times of chord length and outflow length should be 10-15 times of chord length.
The Global mesh is defined and the local mesh is defined by selecting the surface. It is refined up to a level of 3.
The goals option is selected then force x and force y selected after selecting the surfac
Run the simulation.
Now a cut plot is made along x-direction and velocity over the airfoil is selected.
Color refining is given 200.
A goal plot is plotted between drag force along the x-direction and lift along the y-axis.
The above procedure is followed for different attack angles and the following results are used to plot the necessary graphs.
Results :
Case 1). Angle of Attack = 0 Degree
Results Calculation :
Velocity Cut plot :
Drag force and Lift Force:
Plots:
Case 2). Angle of Attack = 2 Degree
Results Calculation :
Velocity Cut plot :
Drag force and Lift Force:
Plots:
Case 3). Angle of Attack = 4 Degree
Results Calculation :
Velocity Cut plot :
Drag force and Lift Force:
Plots:
Case 4). Angle of Attack = 6 Degree
Results Calculation :
Velocity Cut plot :
Drag force and Lift Force:
Plots:
Case 5). Angle of Attack = 8 Degree
Results Calculation :
Velocity Cut plot :
Drag force and Lift Force:
Plots:
Case 6). Angle of Attack =10 Degree
Results Calculation :
Velocity Cut plot :
Drag force and Lift Force:
Plots:
Observations :
| Angle of Attack | Avg.Drag Force | Avg.Lift force |
| 0 | 302.0851 | 0.022754 |
| 2 | 341.853 | 785.765 |
| 4 | 419.0521 | 1488.704 |
| 6 | 550.1811 | 2285.752 |
| 8 | 754.2683 | 3223.638 |
| 10 | 992.1285 | 3991.298 |
Plots :
Conclusion :
While increasing the angle of attack :
- The number of iterations required to give the result get reduced.
- Drag force increases slowly and lift force increases rapidly.
- The velocity of air over the airfoil increased.