External Aerodynamic analysis of NACA Airfoil 0012 using STAR-CCM+

Introduction:

 The main reason for the Aerodynamic analysis is to determine the drag coefficient of the vehicle which affects fuel consumption, predict low and high-pressure areas, separation points and downforce which affects Vehicle dynamics. Airfoils were found in Air crafts, helicopters, racecars,  propellers, fans, compressors and turbines. Sails are also airfoils, and the underwater surfaces of sailboats, such as the centreboard and keel, are similar in cross-section and operate on the same principles as airfoils.

CFD Workflow in STAR-CCM+

1) 3D CAD Modeler/ Import CAD: To model the geometry necessary for the CFD analysis

2) Surface Repair: To check for errors, get a watertight model

3) Meshing: Split the geometry into small pieces on which equations are solved

4) Physics setup: Defining the characteristics of flow

5) Run: Actual solving of the equations

6) Post-processing: Graphical and numerical results

Step 1) The NACA_0012 airfoil Parasolid file has been imported and a virtual wind tunnel has been created around the imported airfoil. 

In order to apply/define boundary conditions, it is necessary to discretize (divide) the block into multiple boundaries. The whole body is divided into 3 boundaries 1. Inlet, 2. Outlet, 3. Walls(remaining sides). Since the geometry is created in star ccm+ the process of repairing the surface can be eliminated. 

In order to assign initial conditions, it is necessary to assign regions to the geometry. The regions were created from the predefined boundaries. After creating the regions the boundary conditions were defined as follows.

Naca Inlet `to` Velocity Inlet

Naca Outlet `to` Pressure Outlet

Naca Sides `to` Symmetry plane

Naca Wing `to` Wall

The next step is to mesh the whole geometry. Automated mesh was selected and Surface Remesher was enabled. Then Automated surface repair was also enabled. In order to mesh the whole domain with hexahedral meshes Trimmed cell mesher and also in order to capture better wall surface mesh Prism layer mesher was enabled. 

The base size of the mesh was set to 0.01m

The maximum sell size of the mesh (relative to base) was set to 800% of the base size. That is 0.08m

The cell count can be restricted on the Inlet, Outlet and Wing surfaces. The mentioned surfaces were restricted from the following:

1. Target surface size

2. Minimum surface size

The size of the cells was increased to 800% and finally, the meshing process was completed.

The cross-sectional view of the Meshed surface

 Physics Modal Selection:

The flow does not change with time. So Steady-state was selected.

The working fluid has been chosen as Gas.

The flow has been set to Segregative flow and the density was set to constant.

The viscous Regime was Turbulent

The K-`epsilon` turbulence model has been chosen.

 The Inlet velocity of air has been set to 10 m/s

 The Outlet pressure was set to 0 pascals with reference to atmospheric pressure.

The angle of attack has been set to zero so drag and lift coefficients cannot be evaluated.

Simulation and Results

The Simulation was set to run for 200 iterations.