Aerodynamic and Structural Design of a Small Nonplanar Wing UAV

TLDR: In this paper, the performance of a biplane with endplates was evaluated with respect to both structural and aerodynamic considerations for a candidate mission similar to that of the AeroVironment Raven.

Abstract: The overall air vehicle performance of a multipl e lifting surface configuration has been studied with respect to both structural and aerodynamic considerations for a candidate mission similar to that of the AeroVironment Raven . The configuration studied is a biplane joined at the tips with endplates. M ore specifically , this study aims to determine if this particular nonplanar wing concept can meet the requirements of the mission for a small Reconnaissance, Surveillance and Target Acquisition UAV. The mission capabilities of small UAVs are constantly gro wing by implementing recent developments in miniature computers and peripherals, electronic sensors, and optical sensing equipment at affordable cost. The requirements for the mission profile of a small UAV using the aforementioned equipment are defined w ith an emphasis on the potential advantages that can be offered by the nonplanar concept wing under investigation. A structural analysis using the finite element software ADINA and an aerodynamic analysis based on wind tunnel experimental data and vortex p anel code results are performed. The results, compared under varying assumptions specific to an equivalent monoplane and a biplane, suggest potential efficiency gains for the new configuration may be possible using the nonplanar wing configuration under ex plicit conditions . The results also show structural characteristics and not aerodynamics alone are critical in determining the utility of this nonplanar concept.

Figures

Fig. 72 L/D vs. angle of attack: monoplane vs. biplane: In order to make a final choice about which wing configuration should be used for the Small UAV under design, an equivalent monoplane was considered and modelled with the software AVL, and then compared to the nonplanar configuration under study. This figure shows a comparison in the L/D ratio vs. angle of attack between the two configurations.

Fig. 41: gust diagram for a Small UAV. For each of the characteristic speeds, stall, cruise and dive speed, the load factor was calculated. It can be noticed that the highest load factor is reached for the cruise speed and is 3.92.

Fig. 55 Adina: natural frequencies: ADINA can also determine the first few natural frequencies and modes for the structure under study. A list of the natural frequencies can be displayed as shown in this figure. The first mode happens at 14.9 Hz, the second at 63.6 Hz and the third at 87.11 Hz.

Fig. 60 Stress variation with gap and stagger: This figure shows a plot where the change in max

Fig. 15 Constraint diagram: This figure shows the constraint diagram obtained plotting the constraint equations. This graph is very useful because each point of the design space in grey, represents a possible aircraft design for the class of aircraft and for the profile mission in consideration, based on physics alone

Fig 12 Joined wing configuration: This figure represents a Joined wing configuration. The shape of a joined wing configuration is obtained by attaching the forward wing low on the fuselage, then sweeping backward and upward while tapering it to the tip. The aft wing is attached high on the vertical fin.

Full text

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AERODYNAMIC AND STRUCTURAL DESIGN OF A
SMALL NONPLANAR WING UAV
Thesis
Submitted to
The School of Engineering of the
UNIVERSITY OF DAYTON
In partial fulfillment of the Requirements for
The Degree of
Master of Science in Aerospace Engineering
By
Giuseppe Landolfo
Dayton, Ohio
May 2008

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ABSTRACT
AERODYNAMIC AND STRUCTURAL DESIGN OF A SMALL NONPLANAR
WING UAV
Name: Landolfo, Giuseppe
University of Dayton
Advisor: Dr. Aaron Altman
The overall air vehicle performance of a multiple lifting surface configuration has
been studied with respect to both structural and aerodynamic considerations for a
candidate mission similar to that of the AeroVironment Raven. The configuration
studied is a biplane joined at the tips with endplates. More specifically, this study aims to
determine if this particular nonplanar wing concept can meet the requirements of the
mission for a small Reconnaissance, Surveillance and Target Acquisition UAV. The
mission capabilities of small UAVs are constantly growing by implementing recent
developments in miniature computers and peripherals, electronic sensors, and optical
sensing equipment at affordable cost. The requirements for the mission profile of a small
UAV using the aforementioned equipment are defined with an emphasis on the potential
advantages that can be offered by the nonplanar concept wing under investigation. A
structural analysis using the finite element software ADINA and an aerodynamic analysis
based on wind tunnel experimental data and vortex panel code results are performed. The
results, compared under varying assumptions specific to an equivalent monoplane and a

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biplane, suggest potential efficiency gains for the new configuration may be possible
using the nonplanar wing configuration under explicit conditions. The results also show
structural characteristics and not aerodynamics alone are critical in determining the utility
of this nonplanar concept.

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Dedicated to Dalila and Pietro

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ACKNOWLEDGEMENTS
I would like to acknowledge Dr. Aaron Altman, my advisor, for bringing this
thesis to the conclusion with patience and expertise and for directing my steps towards a
better professional and human path.
I would also like to express my appreciation to Cardinal Silvestrini for giving me
the tools to complete my education and for giving me the possibility to develop my skills
in a challenging environment as Villa Nazareth.
Finally my special thanks are in order to my family and my friends, who represent
my restless fans and my source of inspiration.

Frequently asked questions

Q1. What contributions have the authors mentioned in the paper "Aerodynamic and structural design of a small nonplanar wing uav" ?

In this paper, the authors present a list of abbreviations and abbreviations for ACKNOWLEDGEMENTS and ABBREVIATIONS and ANNOTATIONS. 

Q2. What is the lift to drag ratio for a biplane?

Increasing the gap on the biplane with endplates increases the lift force and reduces the lift-induced drag, improving the lift-to-drag ratio. 

Q3. Why is the UAV designed to be able to perform several missions without failures?

Due to the expensive payload carried by the aircraft, due also to the important data stored during the mission by the aircraft and due to the same high technology product this UAV represents, it is desirable to design a reliable aircraft capable of accomplishing several missions without failures and without being caught by the enemy. 

Q4. Why was an outrunner motor chosen for the proposed aircraft?

Due to the potential advantages in performance and weight, the choice of anoutrunner brushless motor was preferred for the proposed aircraft. 

Q5. What is the lift slope of the biplane joined at the tips?

The lift slopes of the biplane joined at the tips and the monoplane are 0.072 and 0.054 respectively with a consequent gain in lift slope for the biplane joined at the tips:=∆ αddCL 24.7 

Q6. What is the smallest and lightest micro autopilot on the market?

At 16.65 grams (2” x 1.37” x .47”),Kestrel 2.2 is the smallest and lightest fully featured micro autopilot on the market – ideal for surveillance and reconnaissance applications. 

Q7. Why are nonplanar wings not increased to reduce drag?

But one of the reasons wingspans are not increased to reduce drag is that the higher structural weight and cost make such efforts counterproductive. 

Q8. What is the definition of a mission capability of a small UAV?

Grasping the recent developments in miniature-sized computers, their peripherals, electronic sensors, and optical sensing equipment at affordable cost, the mission capabilities of small UAV’s are ever increasing. 

Q9. How many percent of the vertical tail volume was increased?

Tocompensate the increase in the moment in the yaw direction created by the wing endplates, and due to the fact that the weight of the endplates represents ¼ of the weight of the wings, the vertical tail volume coefficient was increased by twenty-five69percent. 

Q10. What is the voltage required to power a battery?

The voltage required is determined by the motor being59used because the motor’s windings will be tailored to a particular voltage and power range. 

Q11. What is the angle between the wing chords of a biplane?

The acute angle between the wing chords of a biplane usually considered positive when the lower wing is at a lower incidence angle than the upper wing. 

Q12. What is the induced drag coefficient of a biplane?

The theoretical expression for determining the induced drag coefficient of abiplane compared to that of a monoplane, where 1DC and CL are the induced drag and lift coefficients of the monoplane respectively: − −= 2 2 2 2 2 2 1 2 1 1 2 12 kb S kb SCCC LDD 

Q13. What is the drag coefficient for a monoplane without endplates?

The total drag coefficient is:S SC b RSCCC FLDpD ′ ++= 22πTo obtain the gain with a given set of endplates the authors subtract from this expression, the expression for drag coefficient for a monoplane without endplates: − + = ′ ++− +=∆b hCb hb hb SC S SC b RSCC b SCCC FLFLDpLDpD 22 266.11266.1222222πππ − + =∆ b hCb hb hb SCC FLD 22 266.11266.122πFig.9 shows for a monoplane with endplates, the reduction of drag against liftcoefficient for various values of 2h/b, where 2h is the height of the end plate. 

Q14. How much can a design Cl be calculated for a small reconnaissance aircraft?

considering its proposed physical characteristics derived in chapter IV, with a weight at takeoff of 3 Kg and a reference surface area of 0.5 m2, for a cruise speed of 18 m/s, a design Cl of 0.25 can be calculated.