Reversed Engineering Worksheet

Design Worksheet

The following figure is the varieties of winglet designs that are currently available in the market.

Figure 1

Method for induced drag calculation

Airbus A320 aircraft’s specifications are taken and the total drag of the aircraft is calculated using the following formula. 

Figure 2

Where;

Cf -Skin friction drag coefficient

F-Form factor

Q-Interference factor

Swet-Wetted area of the surface

Sref -Wing area

Rec = Reynolds number of the component

V = Velocity

l = component characteristics length

u = kinematic viscosity for that flight condition 

Figure 3 

e - Span efficiency or Ostwald’s efficiency factor

AR – Aspect ratio

Cl – Lift coefficient

Λ – Sweep angle

Take-off performance calculation

The take-off distance of an aircraft is the total distance covered by an aircraft to clear the obstruction of height about 35 ft.

Figure 4

The above figure represents the standard take-off velocities that should be maintained during the take-off. In this work, the motive is to find the parameters associated with the take-off performance of an aircraft. Airbus A320’s specification is taken for the calculation and the take-off field length provided for the aircraft is 1500m. There are three phases in the aircraft take-off mission such as Ground roll, Transition to climb and Climb. Normally, the ground roll, i.e. distance covered by the aircraft on the ground before climb, is calculated by resolving the forces horizontally and vertically. The approximation formula for the ground roll is given by,

Figure 5

W = 78000 kg, 

C_L,max = 2.1 (approximate)

T (during take-off) = 24494 kg

S = 123 sq.m(calculated from wing span)

g = 9.81 (acceleration due to gravity)

ρ = 1.225 kg/m³ (density ground level)

A320 is operated with two CFM56-B engines where the take-off thrust for each engine is 23,500lbs. The total drag “D” in the above formula is calculated after substituting the values obtained from specification table. The total drag reduction is calculated from the total induced drag reduction for different velocities. Further, this total drag calculated with winglets is substituted in the ground distance formula in order to obtain the new total weight (W_new). The simplified formula for the W_new is given by the following equation,

Figure 6 

The take-off weight value for the same take-off distance is calculated for different values of total drag.

CAD Modelling

CATIA V5 R18 tool is used to develop the templates of different winglets and tip devices. Each winglet has been defined by a user feature where the user could choose between the types of winglet and modify the parameters associated with respective winglet model. A detailed description of the winglet templates are discussed in the following section.

Blended Winglet Template

Blended winglet template has been modelled with two different sections namely blended base and blended vertical. Blended base is a shape design model where it forms the intersection at the main wing tip chord and continues as a smooth curve to avoid the interference drag. The leading edge of blended base is formed by the conic section which depends on sweep plane, two tangent lines and two points which lies on the same plane. Radius of the leading edge could be varied by a real parameter and also it depends on base height associated with height parameter. The other parameters controlling the blended base were base span, cant angle, sweep angle and tip chord length figure 1(c). Cant and Sweep angles are made with respect to the base span line and not from root chord of the base. 

The later section i.e. the skeleton model of blended vertical is created in dependent with the blended base.  The leading edge is made tangent with the base leading edge curve in order to obtain a smooth surface. Blended vertical is also associated with a set of parameters which are height and tip chord length figure 1(c). 

Vertical and horizontal reference area of the blended template model are calculated and given as an output parameter figure 1(c). The height parameter for both sections of blended template does not represent the vertical height but the length of respective lines. The exact vertical height for the blended template is given as an output parameter named “reference leading edge vertical” from which the reference area is calculated based on the root chord and tip chord of the respective section. Similarly, the horizontal span of entire blended section varies with the cant angle and also with base span length. The total projected span is calculated by measuring the length of projected leading edge line which shown as green dotted line in figure 1(a) and figure 1(b).   

Figure 7

Figure 8

 1. Do you think your product, building, or system would work if manufactured?

Yes, because the methods of designing were based on the literature reviews. The necessary calculations were conducted to apply the mathematical solutions into the design of the winglet. The design was drawn in the CAD software for better precision. Then, the CAD model will be simulated by using the computational fluid dynamic (CFD) software to get the required results. The CFD results will be compared to the experimental results. If all these methods were conducted carefully and accurately, the numerical results will be similar to the experimental results. The results obtained that meet the objective of the construction of winglet will definitely work in real case scenario if manufactured according to the design.

2. Do you think that you could raise funds to pay for manufacturing? How would you go about raising funds?

Yes, definitely.

·        Get sponsorships from the companies (technical or financial) that are related to the airplane industry.

·        Raise funds is to pitch the idea to the public through crowd funding website, PitchIn

.

3. Do you think that many engineers explore solutions from nature into their inventions?

Yes. In the past, Engineers had used concepts and inspirations from nature in their inventions. One of the example is the invention of Velcro that is based on nature. In this modern era, sustainability of the product is the main concern as more Engineers look into biomimicry to improve the current inventions today to adopt more sustainable traits for future generations to come.

Furthermore, biomimicry provides design techniques to optimize engineering products or systems. An example is the re-derivation of Murray’s law, this determines the ideal diameter of the blood vessels by providing equation for tube diameter.