Flow over an airfoil

AIM:To perform simulation of air over NACA0017 aerofoil for different angle of attacks in Solidworks Flow Simulation.

INTRODUCTION:

• This challenge deals with variation in lift and drag force for different angle of attacks(0,2,4,6,8,10).Angles are measured in degrees.
• Pressure distribution is analysed for each angle of attack of NACA0017 Aerofoil.
• Cut plots are performed on XY plane of computational domain of aerofoil.

THEORY:

About NACA aerofoil specifications and organisation.

• The NACA airfoils are airfoil shapes for aircraft wings developed by the National Advisory Committee for Aeronautics (NACA). The shape of the NACA airfoils is described using a series of digits following the word "NACA".
• This NACA airfoil series is controlled by 4 digits e.g. NACA 0017, which designate the camber, position of the maximum camber and thickness.
• NACA MPXX is designation of aerofils.If MPXX=0017,i.e.

1. M is the maximum camber divided by 100. In the example M=0 so the camber is 0.0 or 0% of the chord
2. P is the position of the maximum camber divided by 10. In the example P=0 so the maximum camber is at 0 or 0% of the chord.
3. XX is the thickness divided by 100. In the example XX=17 so the thiickness is 0.17 or 17% of the chord.

What is angle of attack,lift and drag force?

• The angle between the line of the chord of an aerofoil and the relative airflow is called angle of attack.
• Lift is the force that acts at a right angle to the direction of motion through the air.
• Drag is the force that acts opposite to the direction of motion. Drag is caused by friction and differences in air pressure.
• The chord length is the distance between the trailing edge and the point where the chord intersects the leading edge.

INPUT PARAMETERS:

Medium selected: Air

At room temperature(101325 Pascal and 293.2 Kelvin),

length of aerofoil in z direction=0.2m

chord length=1m

input air speed=500m/sec

curve selected=NACA0017 aerofoil from http://airfoiltools.com/airfoil/

PROCEDURE:

CURVE INSERTION AND ROTATE CURVE BY DIFFERENT ANGLE OF ATTACKS.

1. Download Curve coordinates(data) from above site.Here,NACA0017 coordinates are taken and arranged properly in excel which solidworks software agrees.Save in notepad(.txt) file.
2. Insert Curve in Solidworks Part window,then do convert entities and close loop by joining straight vertical line at trailing point.
3. Use rotate entities command to give angle of attacks for different values(0,2,4,6,8,10) degrees by selecting origin as rotating point.
4. Extrude sketch in Z direction to 0.2 m.

FLOW SIMULATION BY MAKING COMPUTATIONAL DOMAIN

1. On flow simulation command,click on wizard option ,give appropriate project name and set simulation as external and time dependent.
2. Creation of Computational domain : In flow direction(x direction),the total length of domain in this direction should be total 15-20 times of chord length.i.e. 5 times of chord length in left of leading edge and 15 times of chord length in right of trailing edge.
3. For our case,total analysis time=0.015 sec and output time interval=0.015/5=0.003sec(i.e.total length of domain=3.75m and speed of air=500m/sec,so [(3.75/500)*2]=0.015 sec=total analysis time).
4. Then,by edit definition of computational domain,y direction is enlarged for clear simulation.

SET GLOBAL AND SURFACE GOALS.

1. Select FORCE(X&Y direction) and FRICTION FORCE(X&Y direction) as Global Goals.
2. Select FORCE(X&Y direction) and surface in Surface Goals.

MESHING

1. Show basic mesh.(cartesian mesh).
2. Insert Local Mesh,by refining cells to 5.

RUN SIMULATION

1. Insert preview,select Contours and Pressure variation develops in window.
2. Insert Goal ,select SG Force(Y) .

Iterations are completed and results are loaded.

CUT PLOTS,GOAL PLOTS

1. On cut plots options of Result,plot velocity distribution contours in XY plane.
2. On goal plot options of Result,select SG force(X&Y);both lift and drag force are obtained.Then,export values to excel.

RESULTS:

A)ANGLE OF ATTACK=10 DEGREE

pressure preview:

velocity cut plot:

lift and drag force:

B)ANGLE OF ATTACK=8 DEGREE

pressure preview:

velocity cut plot:

lift and drag force:

C)ANGLE OF ATTACK=6 DEGREE

pressure preview:

velocity cut plot:

lift and drag force:

D)ANGLE OF ATTACK=4 DEGREE

pressure preview:

velocity cut plot:

lift and drag force:

E)ANGLE OF ATTACK=2 DEGREE

pressure preview:

velocity cut plot:

lift and drag force:

F)ANGLE OF ATTACK=0 DEGREE

pressure preview:

velocity cut plot:

lift and drag force:

GRAPHS:

CONCLUSION:

From above challenge,lift force is linearly dependent to angle of attack.Drag force is somehow stable with increase in angle of attack.As angle of attack increases,lift and drag forces also increases.