Aerodynamic Analysis of NACA Airfoils

The goal of this project is to apply theoretical analysis to different NACA airfoils of 4 and 5 digits. The study was performed through various softwares like MATLAB and Xfoil applying a panel method with the objective of understanding the influence of different parameters such as lift and momentum coefficients and polar curve when different variables were modified like angle of attack, curve, thickness and others.

NACA Airfoils

NACA airfoils are a series of aerodynamic profiles designed and created by NACA (National Advisory Commitee for Aeronautics). These airfoils are described using analytic equations and certain parameters. In this project 4 and 5 digit airfoils were studied.

4 and 5 digit Airfoils

4-digit Airfoil: First digit describes the maximum curvature, second the maximum distance of curvature from and the last two the thickness with respect to chord percentage.

5-digit Airfoil: First one relates to lift coefficient, next two gives distance of maximum curvature, the last two represent the maximum curvature.

Software

There are many softwares available to study aerodynamic properties of airfoils. Each software has its own properties and characteristics that can make it more or less complex depending on the problem. The different softwares analyzed were:

Xfoil
JavaFoil
FoilSim
PABLO

In this project Xfoil is the one used, it does apply panel method which gives some issues when working with samll thickness profiles but it has a simple use and has many different airfoils.

Software Comparison

Although Xfoil is the one used, Javafoil is also a good software for airfoil analysis, it has good apperance and it's not very complex to use. The figures show the software appearance.

The figures below show the result comparison for lift coefficient when angle of attack was modified for both Javafoil and Xfoil as well as drag coefficient and polar curve.

NACA 3212

The graphs show the performance of the airfoil NACA 3212 when Reynolds number was fixed to Re = 3.5e6. The analysis was made for ideal and viscous fluid.

NACA 25012

The graphs show the performance of the airfoil NACA 25012 when Reynolds number was fixed to Re = 3.5e6. The analysis was made for ideal and viscous fluid.

Airfoil Comparison

An analysis of the two airfoils was performed to study possible differences in performance or characteristics when varying main parameters. Both ideal and viscous cases were studied.

Result Comparison along Lineal Potential Theory

In order to compare the results offered by the software, the lineal potential theory was applied to validate the results for both airfoils. Lif and momentum coefficients were calculated to compare these results with the ones from the graphs.

To solve the problem, the Glauert's Method was applied.

NACA 3212

NACA 25012

Xfoil Analysis: NACA 3212

The influence in the lineal potential theory is a key aspect when computing the pressure coefficient. The more thicnkess of the airfoil, the more perturbation on the exhaust region and the pressure drop will be larger. This will make the lift coefficient increase small values, these variations are not considered in the theory uncoupling the lift problem.

Below are the results for the ideal and viscous cases for lifting curve CL and mass center variation.

Ideal Case

Viscous Case

Maximum Curvature

The analysis of the maximum curvature of the airfoil was studied. The next graphs show how the different parameters behave when varying the curvature for both ideal and viscous cases.

Conclusions

After conducting the same analysis for the 5-digit NACA airfoil and the different variations of the parameters it can be seen the influence of the parameters and how each one of them can affect the airfoil performance and what types can be applied for different cases.

Aerodynamic performance is a very complex problem and has many different parameters involved and connected om between, when one of them is varied, the rest will vary too. It was also considered both the ideal and viscous case for the two airfoils to also understand the difference when a specific theory is applied and how neglecting specific parameters can lead to different results.

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