STAR CCM+ - FLOW OVER NACA WING
Aim
To plot the Angle of attack vs Lift coefficient curve for the NACA 0012 from 0 to 15 for every 2 degree intervals
Procedure
Stage 1 Modelling : Naca Wing
1) Import the file using Import CAD button from the menu bar.
Naca Wing
Block (Wind Tunnel)
1) Right click on Parts > New shape part > Block.
2) 6 balls corresponding to the vertices of the rectangle block will appear, enlarge them in such a way that the sphere is inside the block.
3) Click create and close.
4) To give initial conditions split the block by patches by right clicking on it and clicking split by patches.
5) Select the Front & rename it as inlet and the back face as outlet and the side faces as walls.
Block with Naca wing inside
Combine the Block and Naca Wing by selecting both and right clicking on any of the selected one and click combine.
Stage 2 Surface Repair
Checked for surface errors & Face Quality error was found & it can be rectified by surface remeshing.
Stage 3 Surface Wrapper
Since there were no surface errors, a surface wrap wasn't needed.
Right click on the wind tunnel and click on the Assign to regions, a dialog box will appear in that chanhe the boundary setting as Create a boundary each part surface, & click ok.
Setting up Regions
Stage 4 Surface remecher and Volume Mesher.
1) Select Operations > New > Mesh > Automated Mesh.
2) A dialog box will appear Select the following
- Surface remesher
- Automatic surface repair
- Trimmed Mesher (Core mesher)
- Prism layer Mesher
and click ok
Selected Meshers
3) Expand Default Controls, and select Base size and give the value as 1 cm(less than the lenght of the wing ).
4) Right click Custom control > New > Surface control and select inlet & outlet of the wind tunnel and increase the target & minimum surface size by 10 times the base value(1 cm) and click ok
5) Right click Custom control > New > Surface control and select the walls of the wind tunnel and increase the target & minimum surface size by 50 times the base value(1 cm) and click ok
6) Right click Custom control > New > Surface control and select cube & expand controls > Trimmer Wake refinement & check the box in the property window and give the spread angle as 20 deg & length as 6.1m.
7) Go to values & give 100 % of base and default growth rate as slow and click ok
Block (to capture near the cube)
1) Right click on Parts > New shape part > Block.
2) 6 balls corresponding to the vertices of the rectangle block will appear, enlarge them in such a way that the cube is inside the block.
3) Click create and close.
Block inside the wind tunnel
NACA wing partially inside the block
5)Right click on the Automated mesh and select Execute.
6) After the volume mesh is complete we need to generate the mesh scene to do that, go to title bar and click Create/Open scene & select Mesh scene.
Volume mesh of the wind tunnel
Volume mesh of the NACA Wing
6) To see the quality of the volume mesh a cut section of the modeled can be viewed, for that right click on derived parts > New parts > Section > Plane.
7) A new window will open and orient the plane in such a way it is perpendicular to Y axis, and click ok.
8) To view the cut section, go to Scenes and select the Mesh Scene 1, then go to Scenes/Plots window, and Expand Displayers > Mesh 1 > Parts > Wind tunnel.
9) Right click on Wind tunnel and select Hide and the plane section can be viewed
For Reynolds number(Re) = 1e7 (K-epsilon)
To calculate velocity we use the formula Re = `(rho*v*D)/mu`
`nu=mu/rho`
where
rho = density
mu = dynamic viscosity
nu = kinematic viscosity
v = velocity
L = Chord length
to find v
L = 0.4 m
mu = 1.51e-5 (Air at temp 20 C )
Re = 1e7
v = 1e6 x 1.51e-5 / 0.4 = 37.75 m/s
Velocity can be resolved into two components i.e horizontal & vertical directions to give a angle of attack
Vel horizontal = v*Cos`alpha`
Vel vertical = v*Sin`alpha`
1) Goto Continua > Physics 1 > Select Models.
2) A dialog box will appear and select > Steady > Gas > Segregated flow > Constant Density >Turbulent >K-Epsilon Turbulence & click close.
3) Go to Regions & expand it and click Regions > Boundaries.
4) Select inlet >Physics Values > Velocity Magnitude in that give the value of v
5) Select outlet and check whether the value is 0 pa.
Values input
Plots
`alpha`= 0
Velocity Contour plot
Residual Plot
Coeffecient of Drag plot
Coeffecient of Lift plot
`alpha`= 2
Velocity Contour plot
Residual Plot
Coeffecient of drag plot
Coeffecient of Lift plot
`alpha`= 4
Velocity Contour plot
Residual Plot
Coeffecient of Drag plot
Coeffecient of Lift plot
`alpha`= 6
Velocity Contour plot
Residual Plot
Coeffecient of Drag plot
Coeffecient of Lift plot
`alpha`= 8
Velocity Contour plot
Residual Plot
Coeffecient of Drag plot
Coeffecient of Lift plot
`alpha`= 10
Velocity Contour plot
Residual Plot
Coeffecient of Drag plot
Coeffecient of Lift plot
`alpha`= 12
Velocity Contour plot
Residual Plot
Coeffecient of Drag plot
Coeffecient of Lift plot
`alpha`= 14
Velocity Contour plot
Residual Plot
Coeffecient of Drag plot
Coeffecient of Lift plot
Result
Coefficent of lift & drag for different Angle of attack & corresponding velocity components
By observing the results from the table we come to know that for angle of attack of 2 degrees the coefficient of drag is less when compared to others values & the coefficient of lift is maximum for the angle of attack of 8 degrees. For angles 0 & 2 we get negative Cl which means the wing doesn't generate any lift.