2040 Aircraft PrototypeFlying Arrow Team

Analysis of NACA 4421 AirfoilRRV PVT BCV CSA MB

EUROPEAN UNIVERSITY OF MADRIDENGINEERING SCHOOLBACHELORS DEGREE ON AEROSPACE ENGENEERING

FINAL REPORT

AIRFOIL PROJECTANALYSIS OF NACA 4421 AIRFOIL

Bosco Campomanes VarelaPablo Villanova TamayoRaphael Rubiano VascoCarlos Sans AjoMarcos Benedi

YEAR 2013-2014

8

ABSTRACT

Nowadays the interest in aerospace vehicles development is growing and driving the need for an improved understanding of the relevant aerodynamics. A reasonable starting point is the study of airfoil section aerodynamics.Performance of several geometry characteristics of two-dimensional airfoils are study using different fluid analysis software to know its general effects. Variations in the thickness, camber, and leading/trailing edge shape are considered. An analysis of NACA 4421 were being held the results obtained the results obtained show how pressure distribution, lift-to-drag ratio and velocity magnitude of fluid change with the Reynolds selected and the different angles of attack in our case 0, 5, 10 and 15 degrees were evaluated.

CONTENTS

ABSTRACT31INTRODUCTION51.1Project objectives52BASIC CONCEPTS52.1Lift52.2Drag63ANALYSIS NACA 442173.1Theoretical results of NACA 442173.2Experimental results with ANSYS Workbench fluid flow software.83.2.1Velocity Magnitude93.2.2Velocity Vector103.2.3Absolute Pressure123.2.4Pressure Distribution144CONCLUSIONS175REFERENCES17

INTRODUCTION

The analysis performed under this study are intended to provide theoretical predictions for comparison with experimental measurements.The first step in airfoil analysis is choosing a method that has the proper balance of fidelity and speed for the given application. These range from linear methods, concerned with solving velocity potential equation, to more complicated methods that involved solving the Euler (inviscid) or Navier-stokes (viscous) equations at various points on and around the airfoil to determine the nature of the flow.

Project objectives

The main objective of this project is to evaluate the NACA 4421 airfoil with artificial compressibility methods offering a straightforward and efficient means of preconditioning to allow for the solution of an incompressible homogenous flow field.The analyses make use of three assumptions about the flow field. The flow is incompressible by the formulation of the flow solver, the flow is fully laminar, and the flow field is steady.BASIC CONCEPTS

Lift An airfoil develops lift at positive angles of attack through lower pressures over the top of the airfoil compared to pressures under the airfoil. The lift and drag coefficients are strongly dependent on angle of attack and less dependent on Reynolds number. Reynolds number effects are particularly important in the region of maximum lift coefficient just prior to stall.The lift force can be found from the lift coefficient, CL, in the following way:

Where is the density of the fluid through which the airfoil moves, A is the area equal to the span times the mean chord of the airfoil, V is the undisturbed flow speed, CL is the lift coefficient, and L is the lift force.The lift coefficient then expresses the ratio of the lift force to the force produced by the dynamic pressure times the area. Relation between angle of attack and Cl is generally linear at moderate angles. Cl increases as angle of attack increases smoothly until a maximum value is reached (Cl max). After that maximum value is reached, the airfoil is said to be stalled.

Also, the lift to drag ratio is often of interest to the designer since it represents a kind of aerodynamic efficiency-the most economical cruising condition for an airplane is determined from the point of maximum lift to drag ratio.Delivering that lift with lower drag leads directly to: Better fuel economy. Climb performance. Glide ratio.DragThe force on an object that resists its motion through a fluid is called drag. When the fluid is a gas like air, it is called aerodynamic drag. When the fluid is a liquid like water it is called hydrodynamic drag.Fluids are characterized by their ability to flow. In somewhat technical language, a fluid is any material that can't resist a shear force for any appreciable length of time. This makes them hard to hold but easy to pour, stir, and spread.Drag depends on the density of the air, the square of the velocity, the air's viscosity and compressibility, the size and shape of the body, and the body's inclination to the flow. In general, the dependence on body shape, inclination, air viscosity, and compressibility is very complex.

The drag coefficient then expresses the ratio of the drag force to the force produced by the dynamic pressure times the area. The drag coefficient contains not only the complex dependencies of object shape and inclination, but also the effects of air viscosity and compressibility.

ANALYSIS NACA 4421

Theoretical results of NACA 4421Cl/Cd ratio on the four digit airfoil NACA 4421.

The curve represents the ratio of the lift coefficient to the drag coefficient of NACA 4421. The rapid decline of the Cl/Cd ratio for high angles of attack is clear.

Lift and drag coefficients against angle of attack for a NACA 4421 airfoil. As the angle of attack exceeds about 20 degrees, the lift drops off while the drag begins to increase, so that understanding the rapid decline but smoothly decreasing of the drag-to-lift ratio.A higher ratio is typically one of the major goals in aircraft design.Experimental results with ANSYS Workbench fluid flow software.The analysis were made for different angles of attack at a velocity of 50 m/s, assuming the three assumptions mentioned before: incompressible flow, laminar flow and steady state.Velocity Magnitude

Figure 1. Velocity Magnitude at 0In the upper image we can see that a zero degrees, since the airfoil NACA 4421 is almost symmetrical, the lift produced is very low but there still exist life as we can see the velocity distribution is higher in the upper wall.

Figure 2. Velocity Magnitude at 5

Figure 3. Velocity Magnitude at 10

Figure 4. Velocity Magnitude at 15Velocity distribution is growing faster at the leading edge while decreasing at the trailing edge, where we can see that it has been produced separation of the fluid an so that vortex are being generated.Velocity Vector With the velocity vector we can see the direction of the fluid, combining with the color of the velocity distribution magnitude for better understanding.In all below images we can see at the leading edge and their nearest the stagnation point through concentration of vectors and low velocity. Also at the trailing edge in blue we see the reduction of the fluid velocity and the change in the direction due to the layer separation.

Figure 5. Velocity Vector at 0

Figure 6. Velocity Vector at 5

Figure 7. Velocity Vector at 10

Figure 8. Velocity Vector at 15Absolute PressureThe absolute pressure is inverse to the velocity magnitude, it is due in simple words for the Bernoulli theorem it means when the velocity increases the pressure drops and when the velocity decreases the pressure increase.

Figure 9. Absolute Pressure at 0

Figure 10. Absolute Pressure at 5

Figure 11. Absolute Pressure at 10

Figure 12. Absolute Pressure at 15Pressure DistributionIn the below images we can see how the absolute pressure is being distributed along the entire airfoil length.We can see that there is always lower pressure in the upper wall of the airfoils so that generating always lift for the angles of attack study in this project.Also, as the angle of attack increases the magnitude of the pressure is being reduce until the angle where better performances are achieved in this case and according with theoretical results is at an angle of attack of 20 degrees, from this point pressure will increase in the upper face and the stall will be produce.

Figure 13. Pressure Distribution at 0

Figure 14. Pressure Distribution at 5

Figure 15. Pressure Distribution at 10

Figure 16. Pressure Distribution at 15

CONCLUSIONS

NACA 4421 airfoil tends to progressive and gradual movement of separation from trailing edge toward leading edge as the angle is increased (Trailing Edge Stall).

Trailing edge stall shows gradual bending-over of lift curve at maximum lift, soft stall.

Maximum lift coefficient, Cl max. Effective airfoil shape produces high value of Cl max. Stalling speed of aircraft (take-off, landing). Improved maneuverability (turn radius, turn rate).As more information and data on this report have been obtained by computational fluid dynamics, future efforts should focus on obtaining a complete range of experimental data that will confirm the results.

REFERENCES

References used in this report:1. Juan P. Murcia, Alvaro Pinilla. CFD Analysis of Blunt Trailing Edge Airfoils. 2009.2. Dam, K. J. Standish and C. P. Van. Experimental Research on Blunt Trailing Edge Airfoils. 2003.3. Drag and Lift coefficient. The Engineering Toolbox. [En lnea] http://www.engineeringtoolbox.com/drag-coefficient-d_627.html.4. Heffley, David. Baylor. [En lnea] January de 2007. http://www.baylor.edu/content/services/document.php/41147.pdf.