3. LIST OF FIGURES
FIGURE 1. The hydrogen bubbles flow visualization experimental setup and the battery source
that provides the voltageβ¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦...9
FIGURE 2. Ink dye testing on symmetrical airfoil at zero angle of attackβ¦β¦β¦β¦β¦β¦β¦β¦.....10
FIGURE 3.Ink dye testing on symmetrical airfoil at an increased angle of attack, a)β¦β¦β¦β¦....10
FIGURE 4. Ink dye testing on symmetrical airfoil with an increased angle of attack, b)β¦β¦..β¦.11
FIGURE 5. Ink dye testing on symmetrical airfoil with an increased angle of attack, c)β¦β¦..β¦.11
FIGURE 6. Eppler 420 obtained from the NACA Databaseβ¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦..12
FIGURE 7. Eppler 423 obtained from the NACA Databaseβ¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦..13
FIGURE 8. Concept 1 β single element wingβ¦β¦β¦β¦β¦β¦β¦β¦β¦β¦........................................14
FIGURE 9. Concept 2 β multiple element wing (based on a previously designed wing a few years
prior)β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦.. 14
FIGURE 10. Concept 3 β dual element wingβ¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦.15
FIGURE 11. Concept 4 β multiple element wing (main element and 2 flaps)β¦β¦β¦β¦β¦β¦β¦....15
FIGURE 12. Concept 1 β 3 Views and Isometric drawing (dimensions in millimeters)β¦β¦β¦...16
FIGURE 13. Concept 3 β 3 Views and Isometric drawing (dimensions in millimeters)β¦β¦β¦β¦16
FIGURE 14. An approximate relationship between lift and velocity for Concept 1β¦β¦β¦β¦β¦..18
FIGURE 15. An approximate relationship between lift and velocity for Concept 3β¦β¦β¦β¦β¦..19
FIGURE 16. The data for Eppler 423 at alpha of 0 degrees using XFOILβ¦β¦β¦β¦β¦β¦β¦β¦β¦.25
FIGURE 17. The data for an alpha of 0 degrees and Reynolds No. of 3e6β¦β¦β¦β¦β¦β¦β¦β¦β¦.26
FIGURE 18. The pressure distribution of Eppler 423 at alpha 0 degrees and 3e6 Reynolds No....26
FIGURE 19. The data for an alpha of 18 degrees and Reynolds No. of 3e6β¦β¦β¦β¦β¦β¦β¦β¦...27
FIGURE 20. The data for Eppler 420 at alpha of 0 degrees using XFOILβ¦β¦β¦β¦β¦β¦β¦β¦β¦.27
FIGURE 21. The pressure distribution of Eppler 420 at alpha 0 degrees, and 2e6 Reynolds No...28
FIGURE 22. The data for an alpha of 0 degrees and Reynolds No. of 2e6.....................................28
FIGURE 23. The pressure distribution of Eppler 420 at alpha 0 degrees, viscous flow and 2e6
Reynolds Noβ¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦...29
FIGURE 24. The mounting setup for Concept 4 wingβ¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦...30
4. FIGURE 25. The mounting setup for Concept 1 wingβ¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦...30
FIGURE 26. The strain gauge mounting setup underneath the floor of the wind tunnelβ¦β¦β¦β¦31
FIGURE 27. The single element wingβs (printed model) downforce
resultsβ¦β¦β¦β¦β¦β¦β¦β¦..32
FIGURE 28. The multiple element wing's (printed model) downforce resultsβ¦β¦β¦β¦β¦β¦β¦.32
FIGURE 29. The multiple element wingβs (printed model) downforce results β
extrapolatedβ¦...33
FIGURE 30. The streamlines of the airflow over the wing produced by the use of a smoke
machineβ¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦..34
FIGURE 31. The velocity contour for a multiple element wing design using Eppler 420 profile
shape and flaps at 40 and 60 degrees deflectionsβ¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦34
FIGURE 32. The pressure contour for a multiple element wing design using Eppler 420 profile
shape and flaps at 40 and 60 degree deflectionsβ¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦..35
FIGURE 33. The airflow over the wing represented by streamlines and its velocity contourβ¦β¦35
FIGURE 34. The airflow over the wing from the front viewβ¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦.36
FIGURE 35. The airflow over the wing from the back viewβ¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦..36
FIGURE 36. The vortices formed by the endplates of the wing shown by the streamlinesβ¦β¦β¦36
FIGURE 37. The velocity contour on the front wing design β upper surfaceβ¦β¦β¦β¦β¦β¦β¦β¦.37
FIGURE 38. The velocity contour on the front wing design β bottom surfaceβ¦β¦β¦β¦β¦β¦β¦...37
FIGURE 39. The pressure contour on the front wing design β upper surfaceβ¦β¦β¦β¦β¦β¦β¦β¦37
FIGURE 40. The pressure contour on the front wing design β bottom surfaceβ¦β¦β¦β¦β¦β¦β¦..38
FIGURE 41. The force contour on the front wing design β upper surfaceβ¦β¦β¦β¦β¦β¦β¦β¦β¦..38
FIGURE 42. The force contour on the front wing design β bottom surfaceβ¦β¦β¦β¦β¦β¦β¦β¦...38
FIGURE 43. Three different types of endplate designs, created to redirect airflow and produce
more downforceβ¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦.39
FIGURE 44. The single element wingβs (printed model) downforce results β raw
dataβ¦β¦β¦β¦.41
FIGURE 45. The single element wingβs (printed model) downforce results β raw data
smoothenedβ¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦41
FIGURE 46. The multiple element wingβs (printed model) downforce results β raw data.............42
5. FIGURE 47. The multiple element wingβs (printed model) downforce results β raw data
smoothenedβ¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦42
LIST OF TABLES
TABLE 1. Airfoil characteristics for Eppler 420 obtained from the NACA Databaseβ¦β¦β¦.......13
TABLE 2. Airfoil characteristics for Eppler 423 obtained from the NACA Databaseβ¦β¦β¦.......13
TABLE 3. Values calculated and determined for Concept 1β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦..17
TABLE 4. Values calculated and determined for Concept 3β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦..18
7. 1.0 INTRODUCTION
Aerodynamics, the study of flow around an object, is important and relevant to race cars
because it can improve the carβs performance on the track. Altering the body shape of the car to
be more streamline and having a smooth external surface, the drag effects on the car can be reduced
which ultimately can have potential improvements in the fuel economy. With the addition of
aerodynamic components like front and rear wings, aerodynamic downforce can be created.
Aerodynamic downforce is created through the use of inverted wings, in other words, negative lift.
This is beneficial as increasing carβs weight negatively affects straight line racing, as the goal is to
reduce the overall weight of the car. However, more weight is required for the car to maintain
speed in a skid-pad to avoid sliding. Therefore, downforce increases tiresβ cornering ability by
increasing loads on the tires without actually increasing the carβs weight. Aerodynamics is also
known to improve the vehicle stability and high speed braking. The effects of aerodynamics are
significant when the speeds at which the car is travelling at is high. Hence, the purpose of A1 β
Aerodynamics this year, is to prove the benefits of front and rear wings for the low speeds at which
Carletonβs Formula Student car travels at.
To determine the effectiveness of wings for low speeds, a design process must be followed.
First step is to understand the theory of flow around an airfoil then with that understanding, create
conceptual designs of wings, following, calculate theoretical lift and drag values for those designs.
Then a hypothesis will be made before obtaining experimental and computational fluid dynamic
data of whether wings are beneficial. The initial focus will be on front wings; unlike the rear, front
wings not only provides downforce, but since it precedes the entire car, it is responsible for
directing the airflow back towards the rest of the car. In addition, it can be used to manipulate the
air above the front tires to decrease wheel drag. The front wings are known to produce
approximately 25-40% of the carβs downforce [2]. The report has been divided into sections:
theory, design process, future work and conclusion. Theory section will include information of
wings, design process section has been broken down to subsections that will discuss the process
in detail, and future work section will state the work that needs to be completed.
2.0 THEORY
This section outlines some of the basic theory needed before starting the design process.
As mentioned before, downforce is negative lift due to the airfoils in wings being inverted for cars.
Therefore, in this report when wings are discussed, the term, lift, will be used in certain cases but
with the understanding that lift is similar to downforce. For example, if it states lift is higher, that
directly suggests the downforce is higher when the airfoils are inverted.
The effect of downforce increases with ground proximity. The effect becomes noticeable
when the ground clearance is less than one chord length of an airfoil. Chord length is the distance
from the leading edge of the airfoil (the rounded edge) to the trailing edge (the streamlined
portion). Therefore, the closer the wings are to the ground, the more downforce the wing will
produce. When incorporating wings to the design of the car, an important factor is the front/rear
lift ratio. The ratio needs to be close to one, or more precisely, it needs to be close to the front and
rear weight distribution in order to keep the balance of the car with its increasing speed. Thus, lift
can be analyzed by further dividing it into front axle lift, Clf and Clr [1].
8. Another important part of the front wing design is the endplate design. Endplates are
significant because it redirects the flow around the front tires, as tires are one of the biggest
sources of drag on the car. By redirecting the flow, it minimized the amount of drag resistance
produced and allows the airflow to continue back towards the rest of the car. The endplates are
responsible for also providing additional downforce. To also help redirect the flow around the
front tires, the front wing designs can have multiple elements. Having, for example, a main
wing and a flap, can help reduce the drag by directing the flow above the front tires. The
elements are separated by slot gaps, and the gaps allow the airflow under the wing where the
air pressure is lower, therefore resulting in higher downforce and reducing the chances of wing
βstallingβ. Stalling is when there is a loss of lift and a dramatic increase in drag produced. The
main wing and the flaps are not connected directly to the endplates at either end of the front
wings. Instead, the elements form their own endplates in the form of a turning vane. This allows
improved airflow redirection and also improves the efficiency of the overall endplate design.
When designing the wing flaps for either side of the nose cone of the car, they are to be
asymmetrical. It being asymmetrical suggests that the flaps reduce in height nearer to the nose
cone as this would allow air to flow into the radiators if they were to be mounted in the side-
pods. However, this is not required as the radiator for the RR15 is not being placed in the side-
pods, therefore the wing flaps can have their height maintained right to the nose cone [3].
Effects that need to be considered created by the front wings and the front wheels include
the tip vortex on the front wing and the front wheel wake. The objective is to avoid the creation
of vortexes and the front wheel wake to places of the car that could possibly get damaged. To
comply with the rules of SAE for aerodynamics, front wings ends overlap the front wheels
when viewed from the front. This can cause unnecessary turbulence in front of the wheels,
contributing to reduced aerodynamic efficiency and increased drag. To overcome this design
problem, the inside edges of the endplates must be curved in order to direct the air away from
the chassis and around the wheels. In addition to the previously mentioned functions of
endplates, they are part of wing designs to eliminate induced drag which is created by the
development of high-pressure air on top of the wing rolling over to the low pressure air beneath
at the end of the wing. The aim through the design of incorporating endplates is to ultimately
discourage βdirtyβ, meaning clean, undisturbed flow created by the front tire going into the
floor of the car [2].
3.0 DESIGN STEPS
3.1 BASELINE TESTING
A baseline test was performed with the RR14 car to collect data, so that final
outcome of the project can be effectively be compared to the start situation. Initially, pitot
tubes and flow visualization methods were to be used at the test, but was unable to collect
any data.
The flow visualization method consisted of using a paraffin-based light solution to
be sprayed on the car to determine the airflow over the bodywork of the car. This is the
solution F1 cars use, even transparent oil based paint of non-gelling characteristic and with
a specific viscosity chosen in a way that the solution will not flow downwards when the
9. car is stationary, could be used. Through this method, details like direction and
attached/non-attached flow can be observed. The disadvantage of this flow visualization is
only the surface airflow can be determined, and therefore would be more beneficial if it
were to be used to confirming wind tunnel and computational fluid dynamic findings [4].
3.2 HYRDOGEN BUBBLES FLOW VISUALIZATION
To understand how the flow behaves around an airfoil, a method called hydrogen
bubbles flow visualization was looked into. This flow visualization occurs in a water
channel and will show areas of smooth flow, areas of flow separation and flow structures
that form around the airfoil. The water channel to be used is a re-circulating type, with the
water continuously being pumped and filtered in a circuit. Wind tunnel and water channel
studies are directly comparable. Water being approximately 1000 times denser than air
which means the flow speed can be lowered to achieve the same conditions. Using this
method, it would provide a clear picture of the dynamics of how the flow structure is
occurring around the geometry [5].
The process used in hydrogen bubbles flow visualization is called electrolysis.
Placing two electrodes in the water channel and applying a DC current through them splits
the hydrogen and oxygen gas that breaks up the water molecules into separate gases. The
creation of hydrogen gas bubbles is on a very small diameter wire, and with the flow of the
water in the channel, the visualization of the bubbles moving can be seen [5].
The method was tested in a small scale, using a battery source and two coins, which
represented the two electrodes, and the method proved to work. However, when the
experimental setup was created, shown in the Figure below, and tested in the water channel,
the hydrogen bubbles did not appear on the thin diameter steel wire. Therefore, for the flow
visualization, the ink-dye method was performed in the water channel with the same airfoil.
FIGURE 1. The hydrogen bubbles flow visualization experimental setup and the battery
source that provides the voltage.
10. 3.3 INK DYE TESTING
Since, the hydrogen bubble flow technique did not work, the ink dye was used to
visualize how the flow behaves around a symmetrical airfoil, which are illustrated below
in the following figures.
FIGURE 2. Ink dye testing on symmetrical airfoil at zero angle of attack.
FIGURE 3. Ink dye testing on symmetrical airfoil at an increased
angle of attack, a).
11. 3.4 SYMMETRICAL AIRFOILS VS. CAMBERED AIRFOILS
Airfoils are a two dimensional cross sections of three dimensional wings that have
a finite span length. Airfoils are designed to have an overall effect on the surrounding fluid
to result in faster flow on the upper surface and slower flow on the lower surface (reversed
when the wings are inverted). The velocity differences is caused by the pressure variation
between the two surfaces, creating suction on the higher velocity surface. This suction
causes the resultant force to act upward, thus creating lift (downforce when wings are
inverted). Therefore, the pressure distribution is directly related to the velocity distribution
FIGURE 4. Ink dye testing on symmetrical airfoil with an increased
angle of attack, b).
FIGURE 5. Ink dye testing on symmetrical airfoil with an increased
angle of attack, c).
12. of the airfoil. This shape of the pressure distribution can be altered by changing the angle
of attack of the airfoil and the camberline shape. Camberline shape determines the
curvature difference between the two surfaces. Hence, airfoils could be either symmetrical
or cambered.
Symmetrical airfoils produce zero lift at a zero angle of attack unlike cambered
airfoils. This is because cambered airfoils for the same angles of attack compared to the
symmetrical will produce larger lift. The trailing edge of the camberline has the largest
effect on the airfoilβs ability to produce lift, compared to the rest of the camberline. Higher
lift can be achieved also by just changing the camberline geometry without increasing the
angle of attack; for example, adding flaps. To observe the improvement in lift, the change
has to occur at the trailing edge region, however, this is only valid for attached flows.
3.5 ANGLE OF ATTACK
Lift increases with angle of attack, but it only increases to a certain point after which
the wing stalls and no additional lift is produced. This point is when the flow is no longer
attached and a flow separation is developed. At large angles of attack, flow streamlines do
not follow the surface shape and eventually separates causing the lift to drop. Every airfoil
type has a certain angle of attack that once passed, the magnitude of the suction on the
upper surface is reduced. This flow separation alters the pressure distribution which results
in loss of lift and a large increase in drag.
3.6 SELECTION OF AIRFOIL
As discussion above, the airfoil required for the conceptual designs were to be
cambered airfoils. Since, data of other SAE teamsβ wing airfoil shapes are not readily
available, the airfoil had to be approximated. Several sources suggested mainly two
airfoils: Eppler 420 and Eppler 423. These airfoils were popular among wing design
suggestions because they are highly cambered airfoils that have a good coefficient of lift
to coefficient of drag ratio, which was found from the UICC Database. In addition, these
airfoils are known to provide high lift for low speeds, which is what the goal is to achieve.
FIGURE 6. Eppler 420 obtained from the NACA Database [6].
13. When the airfoil characteristic values, like the coefficient of lift and coefficient of
drag were compared between the two types, Eppler 420 had better values. Even though
from that observation, theoretical calculations were performed for both airfoil types and as
expected, Eppler 420 produced more lift, and less drag. Therefore, for the following
sections, only Eppler 420 airfoil is considered and presented. Listed below are the
characteristic values for both the airfoils for the certain Reynolds number, as the lift and
drag are dependent on the speed of the flow, which is directly comparable to the Reynolds
number. The coefficient of lift and coefficient of drag is also given for an alpha attack of
approximately 10 degrees, as well as the Cl/Cd ratio and its corresponding angle of attack.
TABLE 5. Airfoil characteristics for Eppler 420 obtained from the NACA Database [6].
Reynold's No. = 100,000 and Ncrit = 5 Reynold's No. = 500,000 and Ncrit = 5
alpha = 0deg
alpha = approx.
10deg alpha = 0deg
alpha = approx.
10deg
Cl 1.0597 1.2467 Cl 1.0941 1.9758
Cd 0.02564 0.11197 Cd 0.01285 0.02251
Max. Cl/Cd = 47.77 at alpha = 4.75 deg Max. Cl/Cd = 106.07 at alpha = 6.25 deg
Reynold's No. = 200,000 and Ncrit = 5
alpha = 0deg
alpha = approx.
10deg
Cl 1.0958 1.9037
Cd 0.01793 0.03254
Max. Cl/Cd = 75.62 at alpha = 5.5 deg
TABLE 6. Airfoil characteristics for Eppler 423 obtained from the NACA Database [7].
Reynold's No. = 50,000 and Ncrit = 5 Reynold's No. = 200,000 and Ncrit = 5
alpha = 0deg
alpha = approx.
10deg alpha = 0deg
alpha = approx.
10deg
Cl 0.6769 0.05431 Cl 1.0723 1.8457
Cd 1.1712 0.11739 Cd 0.01644 0.0279
Max. Cl/Cd = 13.9 at alpha = 2.25 deg Max. Cl/Cd = 84.29 at alpha = 4.5 deg
FIGURE 7. Eppler 423 obtained from the NACA Database [7].
14. Reynold's No. = 100,000 and Ncrit = 5 Reynold's No. = 500,000 and Ncrit = 5
alpha = 0deg
alpha = approx.
10deg alpha = 0deg
alpha = approx.
10deg
Cl 1.0177 1.5567 Cl 1.074 1.8885
Cd 0.02408 0.05731 Cd 0.01158 0.02153
Max. Cl/Cd = 51.9 at alpha = 4.25 deg Max. Cl/Cd = 120.55 at alpha = 5.5 deg
3.7 CONCEPT DESIGNS
Based on the theory stated above, four concept designs were created for front wings.
Each concept has a certain aspect that is different but keeping the airfoil chosen to be
consistent in all designs. Concept 1 is a single element wing that is at zero angle of attack,
Concept 2, is a multiple element wing based on a previously made design a few years prior,
Concept 3 is a dual element wing with the main element to be at zero angle of attack while
the second element acts like a flap and has a deflection angle. Finally, the Concept 4 is also
a multiple element wing that has the main element at zero angle of attack while the other
two act like flaps with increasing deflection angles. All four concepts are shown below,
and they are initial sketches that have been altered and finalized further down the report.
FIGURE 8. Concept 1 β single element wing.
FIGURE 9. Concept 2 β multiple element wing (based on a previously designed wing a
few years prior).
15. The reason why the concepts have a variation of number of elements is because
having a multiple element wing is proven to be more effective than single element wings.
Theoretically, they generate more downforce because of the suction thatβs created due to
the slot gaps between the elements which also leads to a more attached flow. Like
previously mentioned, without increasing the angle of attack, higher lift can be achieved
by altering the trailing edge flow behaviour through the addition of flaps. Therefore, the
concepts include a single and multiple elements design in order to prove this theory through
theoretical calculations and experimental testing. Another reason why single element wing
is less efficient is because of the single large vortex that would be produced by the wing.
This large vortex is considered powerful and is pointed outwards to a smaller area
downstream on the car. Having multiple element wing, the vortex can be split into separate
sections creating several smaller vortices. These smaller vortices are lower in energy and
will be spread over a wider area. Vortices are extremely high energy structures that can
negatively affect the performance of the wing, unless vortex generators are positioned
correctly for it to have a positive effect. If positioned correctly, the vortices created can
keep the high pressure air around the car from entering the low pressure underbody region
which leads to maintaining the downforce created by the wings. These theories have to be
proven experimentally once a model of the wings are tested in the wind tunnel [2].
3.8 SIZING
Among the four concepts presented in the previous section, only two concepts were
chosen to move forward to sizing and 3-D modelling for performing theoretical
calculations. The concepts that were chosen were Concept 1 and Concept 3 and the design
has been altered to be a bit different, as illustrated in the figures below. The concepts have
FIGURE 10. Concept 3 β dual element wing.
FIGURE 11. Concept 4 β multiple element wing (main element and 2 flaps).
16. been sized, complying with the SAE rules of the sizing of aerodynamic devices, and from
observing other SAE team designs of front wings.
In Concept 3, the second element, as previously mentioned, is considered to be a
flap. In terms of sizing, the flap chord length has to be approximately 26% of the main
wing chord length and the slot gap between the two main wing and the flap is to be
approximately 3.5% of the main wing chord length. Also the flap is designed to be at a 40
degree deflection, which is one of the standard deflection angles for flaps. The endplates,
however, are not designed to meet any specific requirements as of yet, and will be altered
and improved on given the results from wind tunnel testing.
FIGURE 12. Concept 1 β 3 Views and Isometric drawing (dimensions in millimeters).
FIGURE 13. Concept 3 β 3 Views and Isometric drawing (dimensions in millimeters).
17. 3.9 THEORETICAL LIFT CALCULATIONS
Using the sizing of the concepts and the coefficient of lift values presented above,
theoretical lift values were obtained. The equation used is listed below:
ππ’ππ =
π
π
Γ π ππ’π« Γ π π
Γ ππ₯ Γ π
The variables used in lift equation are: density of air equal to 1.225 kg/m3
, the
coefficient of lift value obtained from the NACA Database for the Eppler 420 airfoil at
specific Reynolds number, S denoted for planform area of the wing in m2
which was
calculated from the selected concepts and finally the velocity, representing the speed at
which the car travels at in m/s. Lift values were found for velocities ranging from 10 km/hr
to 80 km/hr at increments of 5 km/hr, however, for these speeds the coefficient of lift was
interpolated. Only for specific Reynolds number, as stated in Section: Selection of Airfoil,
does the NACA Database provide coefficient of lift and coefficient of drag values. The
corresponding velocity of those Reynolds numbers were calculated, using the equation
listed below, and the lift values for those Reynolds number are the most accurate data
points.
ππ =
ππ―π
π
=
π―π₯
π
The significance of Reynolds number is that, in the field of race car aerodynamics,
this non-dimensional value quantifies the product of speed times size. In other words, test
results can be easily compared from different model scales by using the Reynolds number
to size the testing model from the original size of the product. The basic definition of
Reynolds number is that it represents the ratio between inertial and viscous forces created
in air, and using the magnitude of the number, the flow can be determined to be either
laminar or turbulent [1].
For both concepts, 1 and 3, the accurate data points are illustrated as black points
in the graphs below, which show the approximate relationship of how lift increases with
velocity. Those points have also been presented in a tabular form below.
TABLE 7. Values calculated and determined for Concept 1.
18. TABLE 8. Values calculated and determined for Concept 3.
0
20
40
60
80
100
120
140
160
180
0 10 20 30 40 50 60 70 80 90
LIFT[N]
VELOCITY [km/hr]
LIFT VS. VELOCITY (Concept 1 β Eppler 420)
FIGURE 14. An approximate relationship between lift and velocity for Concept 1.
19. The exact same calculation method was performed for Concept 3, but the graph for
Concept 3 does not illustrate the total lift produced for the dual element wing because the
flaps were not included in the calculation. This was because the coefficient of lift for Eppler
420 at a flap deflection of 40 degrees, was not provided in the NACA Database, especially
because the velocities that are being considered is varied, therefore the Reynolds numbers
are varied. In order to determine the coefficient of lift, with the flaps included,
computational fluid analysis must be performed which is currently under progress.
Therefore, the data presented above is for the lift produced only by the main wing.
Furthermore, the data calculated seems to suggest that Concept 3 is producing less lift,
which is going against the theory stated earlier on in the report. The data is not proving the
theory wrong because the increased coefficient of lift due to the flaps have yet to be
determined, but once that has been updated, the lift values for Concept 3 will be larger than
those of Concept 1.
3.10 HYPOTHESIS
Based on the calculations performed, an extra calculation was done in order to make
a hypothesis on whether the wings will be beneficial for low speeds in a skid pad run. The
calculation involved the following equations:
π πͺ =
ππ π
π
π πͺ = ππ΅ π΅ = ππ + π«ππππππππ
0
20
40
60
80
100
120
140
160
0 10 20 30 40 50 60 70 80 90
LIFT[N]
VELOCITY [km/hr]
LIFT VS. VELOCITY (Concept 3 β Eppler 420)
FIGURE 15. An approximate relationship between lift and velocity for Concept 3.
20. The variables stated above represent: Fc is the centrifugal force present on the car
when it turns in a skid pad track, m is the mass of the car, r is the radius of the skid pad, π
is the friction coefficient and N represents the normal force active on the car. The normal
force for a car without wings is just the weight of the car, but with the addition of wings,
the normal force then equals the weight of the car plus the downforce generated by the
wings. In order effectively do this calculation, there are couple of assumptions that had to
be made. When performing the calculation, it is being assumed that the wing is placed at
an optimal position on the car. Optimal position suggests that the wing gets maximum
undisturbed and clean airflow (an example of a position would be placing the wing near
the roll hoop of the car). Which this placement of the wing, it is also assumed that the
downforce produced will be equally distributed between the front and rear axle.
Given those assumptions and considering the car as point in a free body diagram,
the calculation is performed. So, for an arbitrary downforce of 84.67 N, which is
approximately 8 kg in mass, the car would have to be traveling at a speed of 56.82 km/hr
(values corresponding to 500 000 Reynolds for Concept 1). To maintain this speed around
a skid pad, without sliding and understeer, provided that the mass of the car is 435 lbs and
the coefficient of friction is equal to one, the radius of curvature of the skid pad needs to
be 25.38 m. Analyzing this exact scenario but with the Concept 1 wing and the assumptions
stated earlier, the calculation yields a speed value of only 58.03 km/hr around the skid pad.
This shows that the change in speed around a skid pad when a wing is included is not very
significant. Also, this increase in speed is the highest theoretical speed that can be achieved,
but in a real life situation there are several factors that would not allow this increase and
could potentially even eliminate this improvement. Although, the 2 km/hr increase in speed
might look significant, for the competition the skid pad radius is only 8 m. This would
mean the speed at which the car travels into the skid pad would be much slower, leading
to lower downforce created, finally resulting in a difference in velocity to be far less.
Therefore, at this stage of the design process and with the data in hand, the hypothesis
being made of the usefulness of wings at low speeds is negligible, when compared to the
drag and weight consequences the wing will have on the car.
3.11 COAST DOWN TESTING
The purpose of conducting a coast down testing using the RR14, is to determine
the drag effects that are currently on the car. The test is performed by driving the vehicle
to max. speed at which the traction force will be removed and the vehicle will be let to
coast freely until the velocity reduces to a zero or a specific defined value. During the test,
the velocity over time is recorded and through those values, the drag characteristics can be
found. The drag is related to the time rate of change of linear momentum. The test must be
performed several times under the same conditions in order to achieve an adequate level of
statistical confidence on the results. Instead of measuring the velocity over time, the
acceleration over time could be recorded or even the displacement of the car over time can
be used. The advantage of using acceleration is that it simplifies the analysis procedure as
acceleration can be easily applied to the following differential equation [8]:
21. FT = FD(v) + ME
dv
dt
+ MGs i ΞΈH
The disadvantage of this method is it introduces errors that can significantly affect
the data due to the low levels of accelerated obtained. The displacement of car over time,
is the run distance of the test and this method is not recommended because of the noisy
integration procedure that must be performed twice. Finally, the velocity approach
introduces the need to differentiate the experimental curve obtained from the test, to find
the acceleration over time and this differentiation step is prone to errors. However, the
velocity method is the recommended approach because the experimental values obtained
from the several tests can be fitted to an analytical function which then can be differentiated
to obtain acceleration over time. The following equations shows the major steps [8]:
FD(v) = β ME
dv
dt
π πΈ = π +
πΌ4π€
π 2 π
+
πΌ πΊπ΅ πΊ πΉπ·
π π2
FD(v) = FM + FA
FD(v) = AO + A1 π£ + A2 π£2
The final equation derived, stated directly above, represents the drag force is equal
to the mechanical drag (AO + A1 π£) with the addition of the aerodynamic drag, A2 π£2
.
Mechanical drag consists of all the forces opposing the movement of the car except for the
aerodynamic drag. Therefore, it includes tire-rolling, drive-train resistance as well as minor
losses like the bearing friction and the energy dissipated in the suspension. Tire rolling
accounts for approximately 75% of the mechanical losses. The tire rolling resistance can
usually be calculated by dividing the resistant torque of a free-rolling tire by the rolling
radius. To go more in depth, when the tire acts in traction, there is slip occurring between
the tire and road. The energy dissipated from the tire can be through three mechanisms.
First being the hysteresis losses due to the cyclic tire deformation, secondly, the occurrence
of slip and lastly from the windage aerodynamic losses [8].
The rolling resistance includes three regions: a constant, linear and quadratic in the
curve. The quadratic zone is usually neglected, therefore assuming only the linear portion
of the curve to be accounted in the rolling resistance equation [8]:
FR = MG( AO + A1 π£)
Considering the initial start time of the test to be zero, the differential equations are
integrated as follows:
t = β«
ME
AO + A1v + A2v2
v1
v2
dv = β«
1
Ξ²[(v)] + Ξ³2 + Ξ±2
v1
v2
dv
22. Where the secondary variables are as follows:
Ξ±2
=
AO
A2
β
A1
2
4A2
2 Ξ² =
A2
π πΈ
, Ξ³ =
A1
2A2
π§ = π£ + πΎ
Using the following equation for time:
t = β«
dz
z2 + Ξ±2
z1
z2
This then can be integrated for Ξ±2
> 0 and will result an equation for V2 as a
function of elapsed time:
π2 = πΌ [
[
π1 + πΎ
πΌ
] β tan(πΌ)π½π‘
1 + [
π1 + πΎ
πΌ
] π‘ (πΌπ½π‘)
] β πΎ
With the above equation, a curve fitting the experimental data obtained from the
test can be generated, therefore solving for the mechanical and aerodynamic resistance
coefficients [8]. The process of calculating has yet to be refined and perfected before the
data obtained from the RR14βs coast down test is used to get any values.
4.0 CONCLUSION
This report has stated all the preliminary work completed in the fall semester. It outlines
the aerodynamics theory required, and the steps taken in the design process like understanding the
flow around an airfoil, selecting the appropriate airfoil and finalizing on some designs of front
wings. With those designs, theoretical lift values and hypothesis calculations were performed.
Given the data presented in the report, the hypothesis is that the wings will not be beneficial for
low speeds that the competition car will be travelling in. However, this hypothesis has to be proven
by conducting computational fluid dynamic analysis as well as wind tunnel testing with model of
the concepts shown above.
23. 5.0 REFERENCES
[1] J. Katz, in Race Car Aerodynamics, Cambridge, Bentley Publishers, 2004.
[2] "Formula1 Dictionary," 2012. [Online]. Available: http://www.formula1-
dictionary.net/f_w_endplate.html. [Accessed 28 September 2014].
[3] C. Kirk, "Badger GP," 30 March 2012. [Online]. Available:
http://badgergp.com/2012/03/badger-gp-gives-you-front-wings/. [Accessed 28
September 2014].
[4] "Formula1 Dictionary," 2012. [Online]. Available: http://www.formula1-
dictionary.net/flow_viz_paint.html. [Accessed 28 Septmeber 2014].
[5] Gray, "Automotive Aerodynamics," Youtube, 30 September 2014. [Online]. Available:
https://www.youtube.com/watch?v=quDLzxmJl5I. [Accessed 19 October 2014].
[6] "Airfoil Tools," 2014. [Online]. Available:
http://airfoiltools.com/airfoil/details?airfoil=e420-il. [Accessed November 2014].
[7] "Airfoil Tools," 2014. [Online]. Available:
http://airfoiltools.com/airfoil/details?airfoil=e423-il. [Accessed November 2014].
[8] Z. T. Cai, J. J. Worm and D. D. Brennan, "Experimental Studies in Ground Vehicle
Coast-Down Testing," American Society for Engineering Education, 2012.
25. 1.0 INTRODUCTION
What was accomplished in the fall semester, as previously stated in the report, was the
theory behind the flow around an airfoil depending on its profile shape, 3D rendering of front wing
designs and theoretical lift calculations for those designs. This semester some of the values used
for the theoretical calculations are supported by performing computational analysis using XFOIL
and conducting wind tunnel testing to obtain experimental data. Two concepts of front wings were
3D printed for the wind tunnel testing to determine if the wing produced any downforce. The
models that were printed was a single element front wing and a multiple element front wing that
includes two flaps. In addition, computational analysis was conducted using Workbench ANYSYS
to determine velocity, pressure and force contours for the multiple element wing design, as well
as the airflow simulation over the wing. Finally, a few concept sketches were created to start the
design process for a more complex and beneficial endplate, rather than a simple piece that used
for testing purposes. Therefore, Part 2 of this report will mainly focus on presenting results
obtained.
2.0 XFOIL
XFOIL is a program that is written in FORTRAN and is used to analyse subsonic isolated
airfoils given the coordinates detailing the shape of the airfoil profile, the Reynolds and Mach
numbers [1]. The program then calculates the pressure distribution that is occurring under those
conditions which then leads to finding the airfoilβs lift and drag characteristics [1].
2.1 EPPLER 423
The airfoil profiles that were considered in Sec. 3.6 were Eppler 423 and Eppler
420, and from the selection process and the theoretical data that was calculated, Eppler 420
proved to produce more downforce. To support that conclusion, the coordinates of both
Eppler 423 and Eppler 420 were inputted into XFOIL. Fig. 16 illustrates the Eppler 423
airfoil along with its coefficient of pressure corresponding to the airfoilβs chord length at a
zero angle of attack and a Reynolds number of 300 000. It also states the resulting
coefficient of lift and drag.
FIGURE 16. The data for Eppler 423 at alpha of 0
degrees using XFOIL.
26. The pressure distribution at zero angle of attack and a Reynolds number of
approximately 300 000 for an Eppler 423 airfoil is shown below in Fig. 17 with the use of
vectors. The conditions were then changed to include viscous flow and the results are
shown in Fig. 18. The dotted line in the figure represents the previous graph shown in Fig.
16 and the yellow and blue is the new curves of coefficient of pressure along the chord
length, due to the viscous effects. The blue line represents the bottom surface of the airfoil
while the yellow represents the upper curved surface of the airfoil. Those colored lines are
also on the airfoil to represent the attached airflow. The image also states the new
coefficient of lift and drag, as well as the coefficient of moment and the lift to drag ratio.
FIGURE 17. The data for an alpha of 0 degrees and
Reynolds No. of 3e6.
FIGURE 18. The pressure distribution of Eppler 423
at alpha 0 degrees and 3e6 Reynolds No.
27. Keeping all the previous conditions the same except for the angle of attack, it can
be observed how this affects the airflow over the airfoil. Choosing an arbitrary angle of
attack of 18 degrees, the coefficient of pressure vs. chord length changed significantly and
it can be observed that increasing the angle of attack has introduced a flow separation on
the airfoil. This change in one parameter has also affected the coefficient of lift, drag and
moment and lift to drag ratio values.
2.2 EPPLER 420
The same analysis was performed for Eppler 420 airfoil in XFOIL. Just like how
previously Eppler 420 proved to be the better airfoil through theoretical calculations,
XFOIL outputted the same results. Fig. 20 shows the airfoil, the coefficient of pressure vs.
chord length and the resulting coefficient of lift and drag at a zero angle of attack and
Reynolds No. of 200 000.
FIGURE 19. The data for an alpha of 18 degrees and
Reynolds No. of 3e6.
FIGURE 20. The data for Eppler 420 at alpha of 0
degrees using XFOIL.
28. The following Fig. 21 illustrates the pressure distribution along the airfoil under the
conditions of zero angle of attack and Reynolds number of 200 000. Then viscous effects
were introduced under the same conditions and the results are illustrated in Fig.22. As
shown in the image, the new coefficient of lift is 1.1606, which very close to the value used
for the theoretical calculations for lift in Sec. 3.9. This confirms that the calculated data
was based on relatively accurate values. For comparison purposes, the pressure distribution
over the airfoil when viscous effects are in play are illustrated in Fig. 23.
FIGURE 21. The pressure distribution of Eppler 420 at
alpha 0 degrees, and 2e6 Reynolds No.
FIGURE 22. The data for an alpha of 0 degrees and
Reynolds No. of 2e6.
29. 3.0 WIND TUNNEL TESTING
In Sec. 3.7, four concept sketches were created, of which two were chosen to perform
theoretical calculations on: Concept 1 β the single element wing and Concept 3 β the multiple
element wing with one flap. For wind tunnel testing, the Concept 1 was scaled down and 3D
printed. To scale down the model to be able to test, Reynolds number matching was done.
Reynolds number matching is done to determine the size of the model in the wind tunnel that
accurately represents a life size wing. To achieve speeds of approximately 25 km/hr for an Eppler
420 airfoil, the targeted Reynolds number was 200 000. Using the Reynolds number equation,
shown in Sec. 3.9, the variables that remained constant between a life size model and a printed one
were density and viscosity. Therefore, the remaining variables were just the chord length of the
main airfoil and the velocity. To achieve a speed of 25 km/hr with a size of the printed model to
fit in the wind tunnel without any boundary wall blockage occurring, the wind tunnel should be
able to operate at a speed of approximately 80 km/hr. This was not possible as the wind tunnel that
was to be used had a maximum speed of around 45 km/hr. In addition, to those limiting factors,
the price of the model being printed restricted the size. Therefore, the model was scaled to a ratio
of 1: 3.55, meaning the life size model would be 3.55 times larger than the printed version. Initially,
when the model was tested, it didnβt show to produce any quantifiable downforce. So, when a
second concept was chosen to be printed, Concept 4 was chosen rather than Concept 3 because
having more flaps, theoretically, is said to produce more downforce. In order to obtain quantifiable
data, the concept that had more flaps was chosen. To increase the chance of recording downforce,
another factor that was changed is the scale of the model. With the approval of budget, the Concept
4 was made larger and was in two sections, so that it could it be 3D printed. Therefore, the scale
for the second printed model was 1:2.64.
The following sections will outline the experimental setup and the results obtained for each
model.
FIGURE 23. The pressure distribution of Eppler 420 at
alpha 0 degrees, viscous flow and 2e6 Reynolds No.
30. 3.1 EXPERIMENTAL SETUP
3.1.1 MOUNTING SETUP
To have the wing fixed in place within the tunnel, the printed wings were rigidly
mounted to two brackets, which were also rigidly mounted to a metal plate. The brackets
were used to elevate the wing so that there was clearance between the plate and the bottom
of the wing for airflow. The height of the wings were arbitrarily chosen and does not
accurately represent the ground clearance for a life size wing. This was not a significant
factor that affected the results to be inaccurate because even if the height was too large and
the wing produced downforce, then decreasing the height would only increase the
downforce produced. This is so, because ground proximity helps create more downforce.
If both the models showed no signs of producing downforce, then the height of the brackets
would have to be altered to see if that could change the results. The flat metal plate had a
hole in the center, so that a bolt could pass through the plate and the hole that was present
in the middle of the tunnel floor. The purpose of this was so that the entire deflection the
wing would create would pass right through the bolt in the center of the plate. The metal
plate was also not flush against the floor of the tunnel, instead it was elevated by four pieces
of tape. The tape ensured that the deflection the wing was causing does not dissipate
through the contact between the plate and the tunnel floor, as well as keeping the plate
parallel to the floor. Therefore, when the wind tunnel was turned on, the plate remains fixed
to the floor but in such a way that the majority of the deflection the wing causes is travelled
to the bolt in the middle of the metal plate. This was very important because, that bolt was
connected to a strain gauge, the measurement device used to record the downforce
generated. The mounting setup for the Concept 1 wing and Concept 4 wing can be seen in
Fig. 24 and 25, respectively.
3.1.2 STRAIN GAUGE
A strain gauge that measures in micro-strain was the method used to calculate the
generated downforce. The recorded strain values were then converted to force using the
force and strain equations, given that the material was 1020 Steel, has a Youngβs Modulus
of 29 700 ksi and the strain gage within has an area of 60 mm2
. As mentioned before, the
bolt at the center of the metal plate is directly connected to the strain gauge which is firmly
FIGURE 24. The mounting setup for
Concept 1 wing.
FIGURE 25. The mounting setup for
Concept 4 wing.
31. attached to the bottom side of the wind tunnel floor. The mounting of the strain gauge can
be seen in Fig. 26. There are two notches on the strain gauge and through its deflection is
how the strain is measured via a strain indicator. The wire seen in Fig. 26 is the wire that
connects to the strain indicator. The connection for the strain indicator was a full bridge,
with a gauge factor of 6.018 and an amp zero of 3. Before the testing was conducted, the
effect of the wing mounting setup on the strain gauge was calibrated to be zero.
3.2 TESTING RESULTS
3.2.1 CONCEPT 1 β SINGLE ELEMENT WING
Initially, when this printed model was tested, barely any strain was recorded which
indicated that there was no downforce being produced. First thought was that maybe the
size of the model was too small for it be producing any downforce at the speed the wind
tunnel was operating at. Second factor might have been a human error during the setup of
the strain gauge, or another factor could have been that the model did not have a smooth
finish. Therefore, before running the tests again, the model was sanded down to have a
smooth surface finish. It mostly might have been due to the smooth surface that when the
tests were run again, there was considerable amount of strain being recorded. This does not
mean the human error of the setup can be fully neglected.
Five test runs were conducted to obtain an average of results, and Fig. 27 displays
the converted strain to downforce corresponding to the speed of the wind tunnel. The
results presented are the refined version, the raw data obtained can be seen in Appendix A.
The relationship between the downforce and this range of speed that the wind tunnel was
operating at seems to be linear. At a maximum speed of approximately 45 km/hr, the model
is generating about 11 lbs of downforce. When using the scale of which the model was
sized down, converting the 45 km/hr of the wind tunnel to real speed, it is approximately
13 km/hr. At that speed, the 11 lbs of downforce also converts to around 3 lbs of downforce
generated by a life size wing.
FIGURE 26. The strain gauge mounting setup
underneath the floor of the wind tunnel.
32. 3.2.2 CONCEPT 4 β MULTIPLE ELEMENT WING WITH 2 FLAPS
As mentioned before, this model was larger and was printed as two pieces that could
snap together and remain flush against each other. Since, having a smoother finish appeared
to have benefited in producing better results, this model was sanded down as well before
the testing was conducted. For this model as well, five test runs were done and the results
obtained are shown below in Fig. 28 (refer to Appendix A for raw data).
FIGURE 27. The single element wingβs (printed model) downforce results.
0
5
10
15
20
25
30
35
40
45
50
55
0 5 10 15 20 25 30 35 40 45 50
DOWNFORCE[LBS]
SPEED [KM/HR]
DOWNFORCE VS. SPEED
Test Run 1 Test Run 2 Test Run 3 Test Run 4 Test Run 5
0
5
10
15
20
25
30
35
40
45
50
55
0 5 10 15 20 25 30 35 40 45 50
DOWNFORCE[LBS]
SPEED [KM/HR]
DOWNFORCE VS. SPEED
Test Run 1 Test Run 2 Test Run 3 Test Run 4 Test Run 5
FIGURE 28. The multiple element wing's (printed model) downforce results.
33. The relationship between the downforce produced and the speed for this model
appeared to be exponential. Meaning that as the speed increased, the rate at which the
downforce was being produced increased as well. At a maximum speed of approximately
45 km/hr, this model produced around 50 lbs of downforce. When scaled back to a life size
model, that is equivalent to 20 lbs at a speed of 17 km/hr. Since these speeds do not
accurately depict the speeds at which perhaps the car travels at during autocross or skid-
pad tests, the results were extrapolated. Refer to Fig. 29, to see the extrapolated data.
In the Fig. 29, at a speed of approximately 60 km/hr which is equivalent to a scaled
speed of 23 km/hr, this wing design in a life size will be producing approximately 37 lbs
of downforce. Although, this value of downforce seems to be quite large, this accounts for
all the flaws that may be present within the testing setup. However, it still provides an
understanding and an approximation of how much downforce a front wing may produce.
Comparing both the printed models, evidently the multiple element wing proved to
be more beneficial. The single element had results similar to that of the theoretical data that
was calculated in Sec. 3.9 and including flaps into the wing design aided in generating
more downforce, as it was stated theoretically.
3.3 FLOW VISUALIZATION β SMOKE MACHINE
Just for flow visualization purposes, using a smoke machine, the behaviour of the
airflow over Concept 4 was captured. From the images below, it can be seen how the flow
remains attached throughout the wing and only separates at the trailing edge of the second
flap. The suction that occurs within the gaps between the elements is what keeps the flow
attached throughout, hence resulting in a higher downforce.
FIGURE 29. The multiple element wingβs (printed model) downforce results
β extrapolated.
0
5
10
15
20
25
30
35
40
45
50
55
60
65
70
75
80
85
90
95
100
0 5 10 15 20 25 30 35 40 45 50 55 60
DOWNFORCE[LBS]
SPEED [KM/HR]
DOWNFORCE VS. SPEED
Test Run 1 Test Run 2 Test Run 3
Test Run 4 Test Run 5 Poly. (Test Run 5)
34. .
4.0 WORKBENCH ANSYS
In addition to the wind tunnel testing, further computational analysis was performed to
determine velocity, pressure and force contours for Concept 4 design. The 3D rendered modelβs
geometry was exported into Workbench and a mesh, believed to be refined, was created. To
simulate the conditions of a wind tunnel surrounding, the model was the same size as the one
printed and the speed that was inputted was 80 km/hr. The speed inputted was higher to see results
that were not able to obtain experimentally.
FIGURE 30. The streamlines of the airflow over the wing
produced by the use of a smoke machine.
FIGURE 31. The velocity contour for a multiple element wing design
using Eppler 420 profile shape and flaps at 40 and 60 degrees deflections.
35. The velocity contour appears to be relatively accurate as it does illustrate that the flow is
faster on the curved bottom surface than the upper surface of the wing. This also relates to the
pressure contour as the curved bottom surface has lower pressure than the upper surface of the
wing. The pressure contour, in fact, looks similar to the pressure distribution that the XFOIL
program had outputted.
The following figures illustrate the velocity, pressure and force contours on the wing, as
well as the airflow simulation.
FIGURE 32. The pressure contour for a multiple element wing design
using Eppler 420 profile shape and flaps at 40 and 60 degree deflections.
FIGURE 33. The airflow over the wing represented by streamlines and its
velocity contour.
36. FIGURE 35. The airflow over the wing from the back view.
FIGURE 34. The airflow over the wing from the front view.
FIGURE 36. The vortices formed at the endplates shown by the streamlines.
37. FIGURE 37. The velocity contour on the front wing design β upper surface.
FIGURE 38. The velocity contour on the front wing design β bottom surface.
FIGURE 39. The pressure contour on the front wing design β upper surface.
38. FIGURE 40. The pressure contour on the front wing design β bottom surface.
FIGURE 41. The force contour on the front wing design β upper surface.
FIGURE 42. The force contour on the front wing design β bottom surface.
39. 5.0 ENDPLATE DESIGNS
In order to make front wings more efficient, the endplate designs can be designed to be
more complex. Endplates are critical parts of a wing design, it could be created in a way where it
can aide in producing more downforce as well as redirecting the airflow up and around the front
tires. Changing the airflow away from the front tires can significantly reduce the drag of the car as
the front tires are one of the main sources of drag. A few concept sketches were made of possible
endplate designs, seen below.
FIGURE 42. Three different types of endplate designs, created to
redirect airflow and produce more downforce.
40. 6.0 CONCLUSION
According to the results obtained from the wind tunnel testing, the Concept 4 wing
produced significantly higher downforce than Concept 1, proving that multiple elements are more
beneficial. The values that the Concept 4 wing produced results in a conclusion that front wings
do have a performance advantage, though it may not be as high as the values obtained from the
testing. One entire engineering product cycle has been completed this year, so for the future
aerodynamics role, it is recommended to build a life size scale front wing. With a life size wing,
the weight and drag effects to the amount of downforce the wing is producing, can be compared
and then firmly concluded if a front wing should be a part of the future FSAE cars
7.0 REFERENCES
[1] Wikipedia, "XFOIL," 1 March 2015. [Online]. Available: http://en.wikipedia.org/wiki/XFOIL
41. APPENDIX A
-4.5
-4
-3.5
-3
-2.5
-2
-1.5
-1
-0.5
0
0 5 10 15 20 25 30 35 40 45 50
MICROSTRAIN
SPEED [KM/HR]
MICROSTRAIN VS. SPEED
Test Run 2 Test Run 1 Test Run 3 Test Run 4 Test Run 5
FIGURE 44. The single element wingβs (printed model) downforce results β raw data.
FIGURE 45. The single element wingβs (printed model) downforce results β raw data
smoothened.
-4.5
-4
-3.5
-3
-2.5
-2
-1.5
-1
-0.5
0
0 5 10 15 20 25 30 35 40 45 50
MICROSTRAIN
SPEED [KM/HR]
MICROSTRAIN VS. SPEED
Test Run 1 Test Run 2 Test Run 3 Test Run 4 Test Run 5
42. -22
-20
-18
-16
-14
-12
-10
-8
-6
-4
-2
0
0 5 10 15 20 25 30 35 40 45 50
MICROSTRAIN
SPEED [KM/H]
MICROSTRAIN VS. SPEED
Test Run 1 Test Run 2 Test Run 3 Test Run 4 Test Run 5
-20
-18
-16
-14
-12
-10
-8
-6
-4
-2
0
0 5 10 15 20 25 30 35 40 45 50
MICROSTRAIN
SPEED [KM/H]
MICROSTRAIN VS. SPEED
Test Run 1 Test Run 2 Test Run 3 Test Run 4 Test Run 5
FIGURE 46. The multiple element wingβs (printed model) downforce results β raw data.
FIGURE 47. The multiple element wingβs (printed model) downforce results β raw data
smoothened.
