Hello,

I'm currently in the process of learning how to use Solidworks Flow Simulation and so I've started with a simple simulation measuring the lift force generated by a particular aerofoil as the angle of attack changes.

The simulation started by importing the coordinates of aerofoil into Solidworks (NACA 2415) from an online database and extruding to a length of 10m. The behaviour of this aerofoil was then tested using Solidworks' Flow Simulation package. The simulation is an external analysis using air as the fluid. Velocity was defined using aerodynamic angles option as a 40 m/s flow across the wing, i.e. 

The study was a parametric sweep that altered the angle of attack for the flow, from -0.1 radians to 0.2 radians. The goal of the study was a surface goal measuring the force in the x and y directions, i.e. the drag and lift forces respectively.

I ran this study and exported the lift forces into an Excel spreadsheet. The lift coefficient was calculated using the formula CL=(2*Lift)/(Density*Velocity*Aspect Ratio), with Density = 1.225 kg/m^3 , Velocity = 40 m/s and the Aspect Ratio being 10. 

N.B. I assume the aspect ratio is 10 since the chord length is 1m and the wingspan is 10m.

I plotted the lift coefficient against the angle of attack to get the following graph:

Theoretically speaking, the slope of the Lift Curve-Angle of attack graph should be in the range of 5.0 to 5.5, ideally 5.23 for an aspect ratio of 10. Some other simulations of the NACA 2415 aerofoil back this up.

However, my results are mixed. The section from an angle of attack of 0 radians to 0.2 radians has a gradient of 5.08. This increases further to 5.26 if I remove the result at 0.18 radians. However, the results at a negative angle of attack are at a completely different gradient to the positive results and the result at 0.18 radians is not on the same line as the rest of the positive results. 

I am confused as to why these results came out. Can anyone advise?

Thanks.