Simulation of a 3d Wing

Contents 1

Idea ..................................................................................................................................... 2

2

Problem ............................................................................................................................... 2

3

NACA2412 geometry characteristics ................................................................................ 3

4

Methodology....................................................................................................................... 4

5

4.1

Pre-processing ............................................................................................................. 4

4.2

Mesh generation .......................................................................................................... 5

4.3

Simulation ................................................................................................................... 6

4.4

Post processing ............................................................................................................ 7

4.5

Data analysis ............................................................................................................... 9

Conclusion ........................................................................................................................ 11

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1 Idea In this chapter, it analyzes the airflow around a 3D wing. Wing is a streamlined body, so the airflow around a wing is very different to an airflow around a common general object. The behavior around the external surfaces changes substantially. So creation of the mesh is different and these methods will help to generate meshes for any wing.

2 Problem The NACA 2412 is chosen, flying at a speed of V=340ms-1 at sea level. The operating medium is taken as air. As the medium is air the Reynolds number is, Dynamic viscosity = 1.7894x10-5 Ct = 0.56m Cr = 1m 𝑅𝑒 =

𝜌𝑉𝐶 µ

For a finite wing chord length should be taken as mean aerodynamic chord length. C=

2 1 + 𝜆 + 𝜆2 𝐶𝑟 3 1+𝜆

𝜆 = 𝑡𝑎𝑝𝑒𝑟 𝑟𝑎𝑡𝑖𝑜

Where,

𝐶𝑡

𝜆 = 𝐶𝑟 1

𝜆 = 0.56 = 1.7857 𝐶=

2 1 + 1.7857 + 1.78572 ∗ 0.56 ∗ 3 1 + 1.7857 𝐶 = 0.8007𝑚

𝑅𝑒 =

1.225∗340∗0.8007 1.7894∗10−5

2

=1.864 ∗ 107

NACA2412 airfoil is chosen because it is a basic aero foil which is been used for many aerodynamic analysis and experiments. So there were lot of experimental data available for this airfoil both wind tunnel and mathematical. As applications of this airfoil, it is been used as a rear spoiler for modern day race cars. Further it was using for lot of early aircraft main wing.

3 NACA2412 geometry characteristics

Figure 3-1NACA 2412 AIR FOIL

Details, Maximum thickness 12% at 30% chord Max camber 2% at 40% chord (Airfoil tools, 2015)

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4 Methodology 4.1 Pre-processing First we modeled the NACA 2412 airfoil from the coordinates we obtained from the uiuc coordinates database. After saving it as a txt file type, it is being imported to excel since it consist of two coordinates, we had to include Z coordinates too(0 for Z coordinates). Then again it was saved as a txt file. After that importing NACA 2412 coordinates For the creation of the tapered wing model, we used solid work software. Initially we need to take a new page in solid works. We used, Feature→ curves→curve through XYZ points and select the txt file and it will create the 2D model of the airfoil. Since it’s not enclosed. To close that first we went through close entities and we used tangent curve to close under sketch. After exiting from sketch, using reference geometry we should make a parallel plane to the front plane using reference geometry→ plane and distance set as 2.3 m. after that using convert entities we have to select the made geometry and went to scale entities and set as 0.56 of the size of the created geometry. after creating it, exit from the sketch and used the lofted feature and selected the two planes and created the tapered wing. To import it to the GAMBIT we saved it as STEP file type.

Wing designed from Solid Works Figure 4-1solid model of 3d wing

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4.2 Mesh generation

For the mesh generation we used the Gambit software. First we imported the .step file to Gambit. Then we drew a box covering the wing which is our boundary to simulate. Then we choose the boundary conditions for the simulation and we started meshing.

Figure 4-2 mesh genarated from GAMBIT Mesh generated from gambit

It took about one hour to create the mesh with 0.01 spacing. It was exported as an .msh file.

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4.3 Simulation To simulate we used the software Ansys Fluent. First we imported the .msh file to the fluent. Then we check the scale of the mesh. We selected the viscous model as Spalart– Allmaras and Spalart- Allmaras options as Strain/Vorticity based production. Then we changed the fluid material to air. We checked for the properties of the fluid and we changed it. Then we went for the boundary conditions where we gave the exact values for the inlet velocity, temperature and pressure. We selected the wing as wall. Outlet as pressure outlet and the other faces of the box we created for the boundary as symmetry. Then we set the Monitors. In Monitors there is option called Residual Monitors. In Residual Monitors we changed the Convergence Criterion as none and in option we selected both print and plot. In Monitors there is another option called Force Monitors. We have to set the Force Monitors. We have to select print, plot and write in options and set different Monitors for the Cm, Cd and Cl. Then we can see the change of each parameter with the number of iterations. It is being written in a text file in the selected folder when running the simulation Next we should change the velocity in the Reference Values. Finally, before we start the simulation we should initialize mesh. To initialize we should go to Solution Initialization in solve. In that window we should select the inlet from the drop down menu ‘Compute From’ and initialize. Finally, we started the simulation. To start the simulation, we should go to Solve and select iterate. In iterate we selected 1000 iteration and started iteration. It went about 4hrs to finish the simulation.

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4.4 Post processing These are the results that we got from the simulation.

Contours of static pressure

Velocity vector colored by velocity magnitude

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Figure 4-3velocityVelocity vector colored vector by static pressure

Turbulent velocity

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4.5 Data analysis When the simulation is finalized we can see that the every graph Cl, Cd, Cm vs.

Drag convergence

iterations the value has come to constant value (values get converged). Figure 4-4drag convergence

Lift convergence

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Moment convergence

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5 Conclusion As we know CFD is used to observe the flow patterns over a body. This can be used in the areas of aeronautical, mechanical, civil, marine, astronautic and bio-medical engineering purposes. There are many software which can be used to simulations. In this project we are using FLUENT as the simulating software. We use GAMBIT as the meshing software. After completing the simulations I compared results with the NACA airfoil data sheets. But it didn’t coincided with the results. That is because the meshing process was not accurate. Solid model shape was changed after the simulation. Flow separation was not seen with the increase of the angle of attack

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