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BoxWing: Drawing and Flow Analysis

This article is about how to design a boxwing. If you’re interesting about boxwing design you should also read 2025 YILINDAKİ UÇUŞA İLK BAKIŞ

For a reference wing, it is considered that a mid-range commercial transportation airplane’s wing characteristics. It is determined to get references from mostly Boeing 737-800 and Airbus A320 airplanes’ wings. Since it is not possible to reach all necessary specifications to use.

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Specifications of Airbus A320 (Left) and Boeing 737-800 (Right)

 

For the reference wing, general specifications are listed below. Airbus A320 and especially Boeing 737-800 characteristics are used to draw the reference wing because of making a comparison with Boxwing design.

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Some specifications for reference wing

Airfoil Selection of Reference Wing
Airfoil provides an aerodynamic lift force which is necessary to fly for air vehicle. The meaning of the word, Airfoil or Aerofoil (They are the same words, but
They are used by different accents, American English and British English), is the shape of the section profile of wing, blade, or sail.
In the reference wing, four wing profiles are used. These are listed below.

 (b737a-il) BOEING 737 ROOT AIRFOIL

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 (b737b-il) BOEING 737 MIDSPAN AIRFOIL

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 (b737c-il) BOEING 737 MIDSPAN AIRFOIL

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 (b737d-il) BOEING 737 OUTBOARD AIRFOIL

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Wing profiles were selected from Boeing 737-800’s wing. At the root of reference wing, b737a-il airfoil profile was used. At the tip of reference wing, b737d-il was used. B737b-il and b737c-il were used in the middle of the reference wing with 6 m intervals from the root.

General Information About BoxWing
In BoxWing Design, for easily comparison to reference wing, it’s wingspan was determined 17 m. The general specifications of forward wing of BoxWing are listed in the Table.

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Some specifications of BoxWing’s forward wing

As it can be seen from the Table, swept angle is 30o. To fix the wingspan length of aircraft constant and connect with the rear wing and forward wing, swept angle has increased.

In the reference wing, according the longitudional length of the aircraft, the position of the wing is 15.92, from the nose of the aircraft to leading edge of reference wing. Initially, this dimension was fixed, while dimensions of BoxWing design had been considering. To connect the rear wing and forward wing, swept angle of rear wing was found 26.35o. In this calculations, the aircrafts length is 39.47 m that is Boeing 737-800’s length.
Secondly, swept angle of the forward wing has increased to 27.25o. Therefore, rear wing’s swept angle was decreased to 26. However, the moment, which is occurred due to the rear wing lift force, considered.

Finally, the position of the forward wing according to lontitudional length of the aircraft was taken more ahead. The dimension, between the nose of the aircraft and leading edge of forward wing was determined 7.86 m by considering the moment that was mentioned above. The mentioned swept angle of rear wing is opposite direction according to forward wing.

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Some specifications of BoxWing’s rear wing

In addition to swept back angle, dihedral angle has changed to anhedral angle as it can be seen from Table.

Between the two wings, there is a connection structure. It was called Stagger in some studies. Therefore, in this project, this structure is called as Stagger. There are not any references to use for stagger’s dimensions, it was made inferences from other concept drawings. Dimensions of stagger, which was used in BoxWing drawing, are listed at the Table.

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Some specifications of BoxWing’s stagger

In the stagger, swept angle expresses the angle between the vertical axis of aircraft and the line that is from the aerodynamic center of stagger’s bottom chord to the aerodynamic center of stagger’s top chord.

Airfoil Selection of BoxWing design

In the forward wing of the BoxWing design, airfoils was used as same as
the reference wing. Only their longtiduional positions have been changed.

In the rear wing, two type of airfoil, which were used in the reference
wing have been used. These are the b737c-il and b737d-il. The reason for using these
airfoil is the requirement of BoxWing concept.

In the stagger, a symmetrical airfoil have been used because it did not
demanded to affect the flow around the wing. NACA 0008-34 profile has been used
in the stagger.

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NACA 0008-34 Airfoil profile

DRAWING

   The both wings, reference wing and BoxWing, were drafted in CATIA V5R19. Firstly, their plan were considered, then how to draw in CATIA was considered and searched. It was prepared a skecth for specific dimesion to draw. Dimensions, which are showed in skecthes, are sufficient to draw the reference wing and BoxWing.

Normal Wing Design

Firstly, point datas in x-y coordinate system for airfoils, which have been used reference wing, were obtained from Airfoil Tools website. Then, these coordinates were transferred to the Microsoft Excell. After that, they were adjusted to transfer to the CATIA according to dihedral angle, position by using the sketch. Adjusted coordinates were transferred to the CATIA by using macro excell. Then, these points were combined spline command one by one. Required twist angle was given in this stage. By combining these profiles with line, it was composed a volume.

Finally, spars and ribs were placed with reference to Boeing 737-800 and Airbus A320 aircrafts wing structure. Two spar was placed into the reference wing. The first spar is on %15 of the chord and the second spar is on the %80 on the chord. There have been used 22 ribs in the reference wing. The distance between the ribs increase as the farther from the root of wing. All of the spar and ribs were drafted with the extrude command. Therefore, they have not any thickness in CATIA.

Some picture of drawing process, in CATIA, of reference wing are showed in below figures.

Reference Wing

The schema which have been used for drawing the reference wing

Normal airfoil kesitler

The appearance of transfered airfoil to the reference wing

Tek Kanat-Surface

The appearance of the reference wing’s created surface

Tek Kanat_Spar and Ribs

The structure of ribs and spars of reference wing

Boxwing Design

In the BoxWing drawing, the process, which have been applied in the reference wing, was repeated. Differently and additionally from the reference wing, processes are mentioned in below.

  • After four airfoil profiles of forward wing were created, they have been transferred to the backward to fit the new swept back angle.
  • The two airfoils, b737c-il and b737d-il, were transferred to the rear wing’s position and scaled in accordance with BoxWing swept angle.
  • At the tip of forward and rear wings, airfoils were rotated 90o for the stagger. Then, the airfoil, rotated from the forward wing, was transferred to the backward and the airfoil, rotated from the rear wing was transferred to the forward.
  • The symmetrical airfoil NACA 0008-34 was obtained and transferred to the CATIA by applying the same process as others.
  • Ribs were placed as same as the reference wing in the forward wing and rear wing. But, the number of ribs are 24 ribs because high swept angle increases the length of the wing.
  • In the stagger, there are 2 ribs.

Some picture of drawing process, in CATIA, of reference wing are showed in below figures.

BoxWing

The schema which have been used for drawing the BoxWing

BoxWing airfoil kesitler

The appearance of transfered airfoil to the BoxWing

render

The appearance of the BoxWing’s created surface

structure

The structure of ribs and spars of BoxWing

ANALYSIS

    For the analysis, ANSYS 19 was used. It was made a flow analysis.

Firstly, reference wing was analyized. It was transferred to the ANSYS as a catpart file type. It was created a box environment of air, which the reference wing was fitted, for the flow analysis.

A commercial plane flies at about 10000 m altitude. For this simulation, pressure and density of air were chosen at this altitude.

Meshing Process

For flow analysis, the inner surface of box environment of air was used. The environment was meshed with 250 mm face sizing on the inner air surface.

Some pictures of analysis and graphs, which were obtained as consequences of analysis, are shown in below.

Reference Wing Analysis

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The static pressure distribution on reference wing.

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The velocity distribution on reference wing.

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The graph of lift coeficient with respect to iteration number.

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The graph of drag coefficient with respect to iteration number.

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The graph of lift froce on reference wing with respect to iteration number.

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The graph of drag force on reference wing with respect to iteration number.

Boxwing Wing Analysis

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The static pressure distribution on Boxwing.

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The velocity distribution on BoxWing

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The graph of lift coeficient with respect to iteration number.

The graph of drag coeficient with respect to iteration number.

The graph of drag coeficient with respect to iteration number.

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The graph of lift force on BoxWing with respect to iteration number.

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The graph of drag force on BoxWing with respect to iteration number.

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