COMPUTATIONAL AND EXPERIMENTAL AERODYNAMIC ANALYSIS FOR THE WING OF A MINI UNMANNED

AERIAL VEHICLE (UAV)

José Manuel Herrera FarfánNohemí Silva NuñezHernán Darío Cerón MuñozNelson Javier Pedraza Betancourth

COMPANY OVERVIEW

• The ‘Fundación Universitaria Los

Libertadores’ is an institution of higher

education and nonprofit public utility which

has the mission to make professionals and

critical citizens with broad sense of the social,

ethical, aesthetic and political; research

relevant, innovative and entrepreneurial spirit.

INGENIERIA AERONÁUTICA

• The Aeronautical Engineering program,

educate competent professionals with strong

ethics, humanistic and scientific basis;

committed to their social environment,

participants in the research and finding

appropriate means to generate new

opportunities in the aviation industry.

ESCOLA DE ENGENHARIA DE SÃO (EESC)

• The Escola de Engenharia de São Carlos (EESC) is

one of the units of instruction, research and

extension of the University of São Paulo (USP),

which through its 10 undergraduate programs,

including the Aeronautical Engineering course make

highly qualified engineers to meet the demands of

the labor market or continue their academic career.

• The EESC is a national reference in the field of

engineering and has contributed to the development

of Brazilian society, implementation and

dissemination of scientific, cultural and technological

knowledge.

• Is also attentive to new global paradigms, it has

established internationalization actions, with the

completion of agreements with abroad institutions

and implementing exchange programs.

PROBLEM DESCRIPTION

The UAV-SOLVENDUS, aircraft its lack of

aerodynamic analysis for the wing surface.

Therefore it is necessary to rigorously design

the wing of a mini-UAV where the aerodynamic

analysis is important to consider that the wing

profile is selected from the mission for which it

is designed.

METHODOLOGY

MESH GENERATION

• Unstructured mesh it does not have a specific

guidance in this cell line is much simpler but carries a

higher computational cost; this type of mesh is used

more irregular and complex geometries in which a

structured mesh is very difficult to implement.

STRUCTURED MESH• Is characterized by: all cells lines are regularly oriented in two or three

directions.

• Algebraic methods: include using the values specified on the frontiers of

the geometry to interpolate functions and generate curves within a

domain; this is accomplished by interpolation through unidirectional

Lagrange polynomials and Hermes polynomials interpolations.

CFD ANALISYS

For this analysis, ANSYS, FLUENT was used in the modeling

of airflow over the wing. The simulation was performed with

atmospheric conditions of Sao Carlos, Brazil, where the

experimental tests were performed.

The next pictures, shows the aerodynamics lines for angles of

the 4° and 10°respectively. It can be observed the presence of

fluid and separation cross the wing to 10 °.

Não é possível exibir esta imagem no momento.

• The structured mesh is performed in GAMBIT then is

exported to ANSYS-FLUENT, this mesh type offers distinct

advantages over unstructured; in their main features, the

implementation is simple and suitable for the finite difference

solution stands.

• For this analysis in ANSYS-FLUENT the Spalart Allmaras

turbulence model was used, due its more common in

aerospace-related limited by walls and model simulations at

low Reynolds numbers flow applications.

EXPERIMENTAL CONFIGURATION

The model was built in a 1:3 scale (taking into the dimensions of the

test section of the wind tunnel LAE) made in MDF (Medium Density

Fiberboard) with a thickness of 6.3x10-2

m, and PVC (Poly Vinyl

Chloride) with 5x10-3m thick and flexible plastic tubes at 25% of the

chord for the pressure taps.

• The experimental model used a semi-span of 1m, a chord of 0.13

m and a root tip of 0.05m, taper ratio of 0.375, having a constant

section of 0.60 m and a sweep section at the tip of 0.40 m . The

wind tunnel model is presented in the next picture:

LABORATORY AIRCRAFT EESC-USP

The top view of the wind tunnel circuit closed LAE, School of

Engineering of São Carlos, University of Sao Paulo, Brazil is

illustrated. The dimensions of the test section of the tunnel is 3 m

long, 1.30 m high and 1.70 m wide, with a level of 0.25% turbulence

and maximum speed of 50 m / s.

GOALS

The figures of the computationally data from ANSYS-FLUENT which

are compared with experimental data, which are analyzed for the

maximum speed of 25m / s with a variation of angle of attack of -4 °

to 18 ° are presented.

-0,2

0

0,2

0,4

0,6

0,8

1

1,2

1,4

-5 0 5 10 15 20 25

Co

efi

cie

nte

de

Su

ste

nta

ció

n

Alpha

Experimental

Fluent 25 m/s

Comparison of lift coefficient versus angle of attack.

The Figure shows, that for low angles of attack the computational and

experimental results are very close. However, from 8 ° begins to be a

divergence in the results. Since an angle of 10 ° the slope of the curve

changes and the growth rate decreases lift coefficient.

Furthermore, an excellent approximation to lower angles of attack of

experimental and computational results with regard to drag coefficient

was obtained.

0

0,05

0,1

0,15

0,2

0,25

-10 -5 0 5 10 15 20 25

Co

efi

cie

nte

de

Arr

ast

re

Alpha

Experimental

Fluent 25 m/s

Comparison of drag coefficient versus angle of attack.

At the Figure, both experimentally and computationally the moment

coefficient is negative, confirming that the wing has a tendency to have a

static stability.

y = -0,0072x + 0,0539

-0,25

-0,2

-0,15

-0,1

-0,05

0

0,05

0,1

0,15

-5 0 5 10 15 20 25

Co

efi

cie

nte

de

mo

me

nto

Alpha

Fluent 25 m/s

Experimental

Linear (Fluent 25 m/s)

Linear (Experimental)

Comparison of moment coefficient versus angle of attack.

Aerodynamic parameters Experimental ANSYS-FLUENT

CL máximo 1,11 1,18

Alpha para CLmáx 15° 15°

CD 0,126 0,110

Alpha para CD 15° 15°

δCM / δAlpha -0.0072 -0.012CL/CD máximo 22,23 24,88

Alpha para CL/CDmáx 4° 5°CL^1,5/CD máximo 19,34 22,61Alpha para CL^1,5/CD máximo 6° 7°CL^0,5/CD máximo 28,46 30,67Alpha para CL^0,5/CD máximo 4° 5°

The table shows the different results obtained are shown, for a speed of

25 m / s.

CONCLUSION

• In developing the project was presented numerical and

experimental analysis of the wing to the mini-UAV

Solvendus. Experimental results compared with

computational simulations are next in relation to the

aerodynamic coefficients.

• Aerodynamic efficiency (L / D) obtained was 4 °, so the angle

of attack is recommended for best aerodynamic efficiency in

cruise flight mini-drone.

• For three-dimensional analysis, favorable results were

obtained with the ANSYS, FLUENT software.

• With the turbulence model used, Spalart Allmaras consistent

for models at low Reynolds numbers were obtained.

• Finally, the results suggest that the wing design is within the

requirements proposed for implementation in the UAV-

Solvendus.