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Aerodynamics in motorsports

December 2019
Proceedings of the Institution of Mechanical Engineers Part P Journal of Sports Engineering and Technology 235(4):175433711989322

DOI:10.1177/1754337119893226

Authors:

San Diego State University

Motor racing, like other popular forms of competitive sports, requires physical fitness, concentration, and vigorous preparation and training. Although progress in technology may dominate the race, governing bodies are continuously updating the rulebooks to keep the human factor dominant in winning races. On the other hand, vehicle performance depends on elements such as the engine, tires, suspension, road, and aerodynamics. In recent years, however, vehicle aerodynamics has gained increased attention, mainly due to the utilization of the negative lift (downforce) principle, yielding several significant performance improvements. The importance of drag reduction and improved fuel efficiency are easily understood by the novice observer and are still at the center of racing vehicle design. Interestingly, however, generating downforce by the vehicle usually increases its drag but improves average speed in closed circuits. Consequently, various methods to generate downforce such as inverted wings, diffusers, and vortex generators will be discussed. Also, generic trends connecting a vehicle’s shape to its aerodynamics are presented, followed by more specific race-car examples. Due to the complex geometry of these vehicles, the aerodynamic interaction between the various body components is significant, resulting in vortex flows and wing shapes which may be different than those used on airplanes.

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Effect of ground clearance on the lift and drag coefficients of two generic ellipsoids having the same width/height ratio (1.25) and length/height ratio (3.6). Also maximum thickness is located at 1/3 rd length. After Ref. 4. 4. Vortices and flow separation The discussion about generic automotive shapes cannot be complete without observing typical vortex flows resulting from slanting the upper or lower surfaces. In case of the upper surface (Ref. 7) it was demonstrated that two major vortices are observed in the back, as shown in Fig. 5a. One interesting aspect of this flow is that the lift and drag will increase up to a slant angle of about 30 deg, at which point the trend is reversed (due to vortex breakdown, see Ref 7). Naturally a similar slant at the lower section will create downforce, and this region is frequently called lower or rear diffuser (Fig. 5b). The effect can be increased significantly by adding fences on both sides (as in Fig 5c), a principle widely used in many forms of motor racing. Ground proximity, in this last case, will have a strong effect on downforce, which was demonstrated experimentally, and is shown in Fig 5d (Refs 8 -10). The flow in diffusers like the one depicted in Fig. 5c fascinated researchers for many years and some more recent results were reported in Refs. 11 - 13. A closer observation of the numerical values in this figure indicate that downforce increases even for very small ground clearance values and the trend is reversed only when the body is almost touching the ground.

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Lift and drag variation versus ground clearance for the generic shape with a diffuser. Fig 5d is after Ref 10. On most automotive shapes the flow cannot follow exactly the vehicle's surface shape, resulting in flow separation. At this point it is worth mentioning the effect of Reynolds number (Re = ) * , particularly when smaller scale models are used to evaluate

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Effect of rear wing height on vehicle drag and downforce (after Ref 4). The above examples demonstrate the complex nature of racecar aerodynamics. In practice, however, engineers explore other options such as blowing or using wing flexibility to gain performance advantages. Blowing into separated flow areas, for example, can reattach the airflow to reduce drag and increase downforce. In some years the exhaust momentum was used, or 'passive blowing' by redirecting higher momentum free-flow into lower speed areas (Ref 35). Also, changing vehicle attitude (rake) by raising the rear and lowering the front, usually results in increased downforce (Ref. 36 page 331) and is best if used with a smooth flat underbody.

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Figures - uploaded by Joseph Katz

Content may be subject to copyright.

Content uploaded by Joseph Katz

Content may be subject to copyright.

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1.-Introduction-

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C.</0GD0<4E$B%4.%#EE.K%/D/10</>.<%49#A0E% #4% 2>=2% /100HB%420%/D/10</>.<%FD/4%I0%A09$%/4>77B%

K2>:2%<.4%.<E$%F#J0/%420%A02>:E0%D<:.F7.94#IE0B%ID4%#E/.%9#>/0/%/.F0%20#E42%:.<:09</(

2.-Generic-trends-(Aerodynamic-vs-Vehicle-shape)-

O20% >F1.94#<:0%.7%E.K09% H9#=% #<H% 1092#1/% /.F0% H.K<7.9:0% 7.9% 9#:><=% A02>:E0/% K#/%

H>/:D//0H% ><% 420% 190A>.D/% /0:4>.<(%O.% H0F.</49#40% 420% 0P10:40H% 9#<=0% .7%E>74% #<H% H9#=%

:.077>:>0<4/% !#/% H07><0H% I$% ;G(% ',% E04% D/% 190/0<4% /.F0% =0<09>:% 0P#F1E0/(% 8% /0:.<H#9$%

.Ic0:4>A0%.7%42>/% /2.94%H>/:D//>.<%>/%4.% 19.A>H0%#% />F1E0%A>/D#E%:.<<0:4>.<% I04K00<%A02>:E0%

/2#10/%#<H%420%0P10:40H%#09.H$<#F>:%1097.9F#<:0(%

% % %

Figure-3.%O$1>:#E%H9#=%#<H%E>74%:.077>:>0<4/%7.9%/0A09#E%=0<09>:%#D4.F.4>A0%/2#10/%

8/%420%E.K0/4%E>F>4%7.9%420%0P10:40H%H9#=B%#%/490#FE><0H%/2#10%:#<%I0%:.</>H090HB%K2090%420%

7E.K% >/% 7.EE.K><=% 420% I.H$ % /2#10% !<.% 7E.K% /01#9#4>.<,% #<H% F./4% .7% 420% H 9#=% >/% HD0% 4.% 420%

79>:4>.<% I04K00<% 420% #>9% #<H% 420% I.H$% !:#EE0H% A>/:.D/% /20#9,(% [0:#D/0% 420% /2#10% >/%

/$FF049>:B%<.%E>74%>/%0P10:40H%#<H%420%H9#=%:.077>:>0<4%:#<%I0%0P10:40H%4.%I0%#/%E.K%#/%*(*a(%

[$% I9><=><=% #% />F>E#9% =0<09>:% I.H$% :E./0% 4.% 420% 9.#HB% %>4/% D1109% /D97#:0% >/% :#FI090HB%

90/DE4><=% ><% 7#/409% 7E.K% .A09% 420% 4.1% !#<H% E.K09% 190//D90B% #/% [09<.DEE>% 190H>:40H,(%

C.</0GD0<4E$B%E>74%#<H%#HH>4>.<#E%H9#=%>/%=0<09#40H%#<H%:.FI><0H%K>42%420%#HH0H%K200E/%420%

H9#=% ><:90#/0/% <0#9E$%a% 4>F0/%!/00% :#/0% h)% ><% T>=(% &,(% O2>/% :.<7>=D9#4>.<%90190/0<4% #<%

>H0#E>50H% /490#FE><0H% /2 #10B% K2>:2% >/% /4>EE% I04409% 42#<% #% =0<09>:% #D4.F .I>E0% /2#10B% K2090%

I.42% H9#=% #<H% E>74% ><:90#/0% />=<>7>:#<4E$%!#/% ><% T>=(% &B% /2#10% h&,(% V.KB% /.F0% .7% 420% F./4%

1.1DE#9% 9#:><=% /09>0/% #90% I#/0H% .<% .9H><#9$% /0H#</B% /.% #7409% F.H>7>:#4>.</%!0(=(B% #HH><=% #%

90#9% K><=% #<H% #% 79.<4% /1E>4409% 1E#40,% 420 % E>74%4D 9</% ><4.% F.H09#40% H.K<7.9:0% #<H% 420% H9#=%

><:90#/0/% .<E$% /E>=24E$%!ha% ><% T>=(% &,(% O20% /F#EE09% 42#<% 0P10:40H% H9#=% 10<#E4$% :#<% I0%

:.<49>ID40H% 4.% 420% #HH>4>.<#E% /490#FE><><=% .7% 420% 9#:><=% /0H#<%A09/>.<(% T><#EE$B% #% 2>=2%

H.K<7.9:0%19.4.4$10%9#:09%>/%/2.K<%4.%H0F.</49#40%420%D1109%E>F>4/%.7%H.K<7.9:0(%U>=209%

A#ED0/% K>EE% 90GD>90% 0P490F0E$% /4>77% /D/10</>.<% !HD0% 4.% 420% E#9=0% H.K<7.9:0% #4% 420% 2>=209%

/100H/,B%K2>:2%K>EE%F#J0%420%:#9%A09$%D<1E0#/#<4%4.%H9>A0(%V.K#H#$/B%90=DE#4.9/%#440F14%4.%

:2#<=0%420%9DE0/%/.%42#4%H.K<7.9:0%E0A0E%K>EE%<.4%0P:00H%#119.P>F#40E$%Ce%i%N)(Y(%

3.-Ground-effect--

O20%7>9/4%4K.%0P#F1E0/%><%T>=(%&% /D==0/4%42#4%=9.D<H% 19.P>F>4$%2#/%#% />=<>7>:#<4%0770:4%.<%#%

A02>:E0Q/% #09.H$<#F>:/(% %O2>/% 0770:4% K#/%7D94209% ><A0/4>=#40H% I$% :.F1#9><=% 420% =9.D<H%

19.P>F>4$%0770:4%.7%4K.%=0<09>:%0EE>1/.>H/B%#/%/2.K<%><%T>=(%a(%[.42%0EE>1/.>H/%2#A0%420%/#F0%

79.<4#E% #90#% #<H% A.EDF0B% #<H% 90190/0<4% 4$1>:#E% /4$E><=% 490<H/% /00<% ><% #D4.F.I>E0% !#<H%

9#:0:#9,% H0/>=<(% O20% 7DEE% 0EE>14>:% /2#10% #EE.K/% 7900% 7E.K% D<H09% 420% A02>:E0B% K2 >E0%42 0% /0F>%

0EE>1/.>H% /2#10% #110#9/% 4.% IE.:J% 420% 7E.K% D<H09% 420% :#9(% [.42% /4$E><=% #119.#:20/%:#<%

0A0<4D#EE$%90/DE4%><%E.K%H9#=%:.<7>=D9#4>.</(%U.K0A09B%K20<%#EE.K><=%F.90%7E.K%D<H09%420%

A02>:E0B%E#9=09% H.K<7.9:0% E0A0E/% :#<% I0% =0<09#40H(% _>42% 420/0% />F1E0% =0.F049>0/B% 420%

/$FF049>:% 0EE>1/.>H% #EE.K/% 7#/409% 7E.K% D<H09% >4B% 90/DE4><=% ><% ><:90#/0H% H.K<7.9:0% !K>42%

90HD:0H% =9.D<H% :E0#9#<:0,(%M<% :#/0% .7%420% /0F>N0EE>1/.>H% 420% 7E.K% D<H09% 420% I.H$% >/% F.90%

90/49>:40H%!#/%#%90/DE4%.7%420%/2#91%0H=0/%/D99.D<H><=%420%E.K09%/D97#:0,B%#<H%K>42%90HD:0H%

=9.D<H%:E0#9#<:0B%I.42%E>74%#<H%H9#=%K>EE%><:90#/0(%%?.F0%9#:0:#9/%2.K0A09%90E$%.<%420%/0F>N

0EE>1/.>H%19><:>1E0%#<H%49$%4.%/0#E%420%7E.K%D<H09%420%:#9%!0(=(B%D/><=%E#9=0%/1.>E09%><%79.<4,(%M7%

/D::0//7DEE$%D/0HB% 420%E.K%190//D90%79.F%420%90#9%.7%420% A02>:E0%190A#>E/%D<H09%420%:#9B%#<H%

42>/% K#$B% />=<>7>:#<4% H.K<7.9:0% :#<% I0% =0<09#40H(% 8<.4209% E.=>:#E% #119.#:2% 4.% =0<09#40%

H.K<7.9:0%K.DEH%I0%4.%/0#E%420% /D99.D<H><=%0H=0/%.7% 420% 7E#4%E.K09%/D97#:0%#<H% =0<09#40%

E.K%190//D90%42090%K>42%/.F0%#DP>E>#9$%7#<%!E>J0%><%#%A#:DDF%:E0#<09,(%O2>/%>H0#%K#/%40/40H%

/D::0//7DEE$B%ID4%I#<<0H%I$%F./4%/#<:4>.<><=%.9=#<>5#4>.</%!#<H%K>EE%I0%H>/:D//0H%E#409,(%

%%%%

% % %

Figure-4-;770:4%.7%=9.D<H%:E0#9#<:0%.<%420%E>74%#<H%H9#=%:.077>:>0<4/%.7%4K.%=0<09>:%0EE>1/.>H/%

2#A><=% 420% /#F0% K>H42b20>=24% 9#4>.% !'()Y,% #<H% E0<=42b20>=24% 9#4>.% !&(Z,(% 8E/.% F#P>FDF%

42>:J<0//%>/%E.:#40H%#4%'b&9H%E0<=42(%87409%\07(%a(%

4.-Vortices-and-flow-separation-

O20% H>/:D//>.<% #I.D4% =0<09>:% #D4.F.4>A0% /2#10/% :#<<.4% I0% :.F1E040% K>42.D4% .I/09A><=%

4$1>:#E%A.940P%7E.K/%90/DE4><=%79.F%/E#<4><=%420%D1109%.9%E.K09%/D97#:0/(%M<%:#/0%.7%420%D1109%

/D97#:0%%!\07(%],% >4% K#/% H0F.</49#40H% 42#4% 4K.% F#c.9% A.94>:0/% #90% .I/09A0H% ><%420%I#:JB%#/%

/2.K<%><%T>=(%Y#(%L<0%><4090/4><=%#/10:4%.7%42>/%7E.K%>/%42#4%420%E>74%#<H%H9#=%K>EE%><:90#/0%D1%

4.% #% /E#<4% #<=E0% .7% #I.D4% &*% H0=B% #4% K2>:2% 1.><4% 420% 490<H% >/% 90A09/0H% !HD0% 4.% A.940P%

I90#JH.K<B%%/00%\07%],(%V#4D9#EE$%#%/>F>E#9%/E#<4%#4%420%E.K09%/0:4>.<%K>EE%:90#40%H.K<7.9:0B%

#<H% 42>/% 90=>.<% >/% 790GD0<4E$% :#EE0H% E.K09% .9% 90#9% H>77D/09% !T>=(% YI,(% O20% 0770:4%:#<% I0%

><:90#/0H%/>=<>7>:#<4E$%I$%#HH><=%70<:0/%.<%I.42%/>H0/%!#/%><%T>=%Y:,B%#%19><:>1E0%K>H0E$%D/0H%

><%F#<$%7.9F/%.7%F.4.9%9#:><=(%^9.D<H%19.P>F>4$B%><%42>/%E#/4%:#/0B%K>EE%2#A0%#%/49.<=%0770:4%

.<% H.K<7.9:0B% K2>:2% K#/%H0F.</49#40H% 0P109>F0<4#EE$B% #<H% >/%/2.K<% ><% T>=%YH% !\07/%+% N%

'*,(%O20% 7E.K% ><%H>77D/09/% E>J0% 420% .<0%H01>:40H%><%T>=(% Y:% 7#/:><#40H% 90/0#9:209/% 7.9% F#<$%

$0#9/%#<H%/.F0%F.90%90:0<4%90/DE4/%K090%901.940H%><%\07/(%''%j%'&(%8%:E./09%.I/09A#4>.<%.7%

420% <DF09>:#E% A#ED0/% ><% 42>/% 7>=D90%><H>:#40 % 42#4%H.K <7.9:0% ><:90#/0/% 0A0<% 7.9%A09$% /F#EE%

=9.D<H%:E0#9#<:0%A#ED0/%#<H%420%490<H% >/% 90A09/0H% .<E$% K20<%420%I.H$%>/% #EF./4% 4.D:2><=%

420%=9.D<H(%

%%%%%%%%%

% %

Figure- 5- - e>74% #<H% H9#=% A#9>#4>.<% A09/D/% =9.D<H% :E0#9#<:0% 7.9% 420% =0<09>:% /2#10% K>42% #%

H>77D/09(%T>=%YH%>/%#7409%\07%'*(%

L<% F./4% #D4.F.4>A0% /2#10/% 420% 7E.K% :#<<.4% 7.EE.K% 0P#:4E$% 420% A02>:E0Q/% /D97#:0% /2#10B%

90/DE4><=% ><% 7E.K% /01#9#4>.<(% 84% 42>/% 1.><4% >4% >/% K.942%F0<4>.<><=% 420% 0770:4% .7% \0$<.EH/%

<DFI09% !\0% f% ,*B% 1#94>:DE#9E$% K20<% /F#EE09% /:#E0% F.H0E/% #90% D/0H% 4.% 0A#ED#40%

#D4.F.I>E0%/2#10/(%"./4%7ED>H%H$<#F>:%I..J/%K>EE%19.A>H0%420%0770:4%.7%\0$<.EH/%<DFI09%.<%

420% H9#=% .7% #% :$E><H09%!#<H% 7E.K% /01#9#4>.<,B% ID4%><% :#/0% .7% A02>:E0% #09.H$<#F>:/B% 42>/%

<.<H>F0</>.<#E% <DFI09B% F./4E$% 90190/0<4/% 420% /:#E><=% 0770:4/% !#<H% 420% 9#<=0% >/% D/D#EE$%

#I.A0%\0% i%'*Y,(%8E/.B%.<0%FD/4%90F0FI09%42#4%><%420%S#D4.F.4>A0%#09.H$<#F>:/%9#<=0Q%.7%

420%\0$<.EH/%<DFI09B%E#F><#9%I.D<H#9$%E#$09% :#<% I0%F#><4#><0H%!K>42%7#A.9#IE0%190//D90%

=9#H>0<4/,%4.% 90HD:0% /J><% 79>:4>.<% H9#=(% L<% 420% .4209% 2#<HB% 42090% #90% :.<H>4>.</% K20<%

49#</>4>.<%4.%4D9IDE0<4%7E.K%:#<%90HD:0% 7E.K% /01#9#4>.<% #<H% 42090I$% 90HD:0% H9#=B%4..(%O2>/%

F0#</% 42#4% 420% 0770:4% .7% #% A02>:E0% /2#10% .<% >4/% #09.H$<#F>:% >/% <.4% 0#/>E$% H0409F><0H(%

8<.4209%>F1.94#<4% GD0/4>.<B% K20<% /F#EE09% /:#E0% F.H0E%40/4><=%>/%D/0H%>/R%how will a lower

Reynolds number test compare with actual full-scale performance? A generic answer suggests

that if the flow is attached in the lower Reynolds number case, then it will be attached in the

higher Reynolds number case, too. Therefore the expected effects on automobile aerodynamics

will be fairly small and limited to boundary layer friction effects. However, if the flow is

separated from curved surfaces (such as wheels, wings, etc.) in the lower Reynolds number case,

then, due to reattachments, large differences are possible when comparing this to the larger

Reynolds number case. To demonstrate this sensitivity to the Reynolds number let us use two

simple examples. For the first case, consider the lift coefficient of the symmetric airfoil in Fig. 6

(After Ref. 14, p. 496). Note that the lift slope is not affected and initially, the lift increases in a

linear manner with increasing angle of attack, until a point called “stall” where the flow separates,

resulting in a reduction in the lift of the airfoil. The interesting observation is that with an increase

in the Reynolds number the flow separation (stall) is delayed, and considerably larger lift

coefficients can be generated. The significance of this information can be interpreted as follows:

suppose that a race car wing is developed at a Re number of 0.3 x 106 (using the wing chord for

the length - L in the Reynolds number definition). The maximum lift coefficient is obtained just

before the wing stalls, and the corresponding value in Fig. 6 is about 0.8. However, at a higher

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

*%@/D#EE$B%r%>/%#>9%H0</>4$B%e%>/%#%E0<=42%/:#E0B%@%>/%420%A0E.:>4$%#<H%µ%>/%A>/:./>4$(%

(a) Slanted upper surface

(b) Tapered lower surface

(d)

0.9

0.8

0.7

0.6

0.5

0.4

0.3

0.2

00.05 0.1 0.15 0.2 0.25 0.3

-CL

h/L

10o

speed and scale (e.g., at Re = 3.0 x 106) the maximum value of the lift coefficient can be as high

as 1.5! This, of course, is not reflected by the low Reynolds number tests and the vehicle based on

these experiments may end up generating only half of the potential downforce of its wing.%

% % % %

Figure 6 Effect of the Reynolds number on the lift coefficient of a NACA 0012 airfoil. After Ref.

14.

The second example, in Fig. 7, shows an isolated stationary wheel placed on the wind tunnel

floor, tested through the critical range (for flow over cylinders) of Re = 0.1 x 106 to 0.3 x 106.

This interesting variation in both the lift and drag coefficients can be related to the changes in the

size of the separated flow region behind the wheel, due to the flow turning fully turbulent. It is

quite remarkable that such a small Reynolds-number increment can change the lift and drag by

more than 50%. So when testing a 1/4-scale model in a wind tunnel at 150 km/hr, and making

decisions about a race car traveling at 300 km/hr, then those two points (based on the wing’s

chord) are exactly at the opposite edges of this Reynolds number range. Consequently, the 1/4-

scale based wing design will be too conservative.

% %

Figure 7. Trends in the variation of drag and lift for a stationary wheel versus Reynolds number.

Coefficients are based on wheel frontal area (after Ref. 15).

5.-Methods-to-Generate-Downforce-

O20%F#<$%7.9F/% .7% F.4.9%9#:><=%><A.EA0%/49#>=24NE><0%H9#=% /49>1/B%I#<J0H%.A#E/%49#:J/% #<H%

9.#H% :.D9/0/% K>42% FDE4>1E0% 4D9</(% M<% #EF./4% #EE% 420/0% A0<D0/B% /.F0% E0A0E% .7% H.K<7.9:0% >/%

<00H0H%4.%>F19.A0% 4>90%!#<H%A02>:E0,%1097.9F#<:0(% U.K0A09B%420%7.90b#74%#PE0%H>/49>ID4>.<%

.7% 420% H.K<7.9:0% >/% 0A0<% F.90% >F1.94#<4% I0:#D/0% >4% #770:4/% A02>:E0% /4#I>E>4$% !\07/%)B% 'Z,(%%

d#=0']B% ><% 2>/% H0/:9>14>.<% .7% #<% .10<NK200E% M<H$% 4$10% 9#:><=% :#9/% E>/4/%420% 7.EE.K><=%

H0/>9#IE0% H.K<7.9:0% E0A0E/%!#4% )**% "12,% #<H% 420% 109:0<4% .7% 420% 79.<4% #PE0% #09.H$<#F>:%

H.K<7.9:0B%7.9%A#9>.D/%9#:049#:J/R%

Downforce(lb@200Mph)- - %F-

\.#H%:.D9/0%%%Y***%%%aY%

?2.94%LA#E%%%%&Y**%%%&Y%

e.<=%LA#E%%%)Y**%%%&Y%

?D109%/100HK#$% % 'Y**%%%&&%

Table-1:%O$1>:#E%4.4#E% H.K<7.9:0%#<H%109:0<4%.7%79.<4% H.K<7.9:0% 90GD>90F0<4%7.9%A#9>.D/%

9#:0%49#:J%:.<H>4>.</(%

V.KB%420%<DFI09/%><%O#IE0%'%#90%GD>40%E#9=0B%ID4%#4%E.K09%/100H/B%E>J0%'**"12B%H.K<7.9:0%

E0A0E/%K>EE%I0%90HD:0H%I$% a% !90:#EE%42#4%#09.%7.9:0/%><:90#/0%K>42%420%/GD#90% .7% /100H,(%O20%

I#E#<:0%<DFI09/%/2.K<%2090%><%409F/%.7%7.9K#9H%H.K<7.9:0%109:0<4%#90% GD>40%4$1>:#EB%ID4%

#4%E.K09%/100H/%#<H%1#94>:DE#9E$%.<%D<1#A0H%:>9:D>4/B%>4%:#<%90#:2%Y*k(%%\04D9<><=%4.%T>=(%&B%

K2>:2% /2.K/% 42#4% 4$1>:#E% #D4.F.I>E0% /2#10/% 2#A0% 1./>4>A0% E>74B% .<0% :#<% #/J% 420% GD0/4>.<R%

2.K% :#<% E>74% I0% 90HD:0H% .9% 0A0<% 4D9<0H% ><4.% />=<>7>:#<4% E0A0E/% .7% H.K<7.9:0l% O20% F./4%

:.FF.<%F042.H/%D/0H%><%420%9#:><=%><HD/49$%#90R%

0.50 3 5 1•1053

51•106

0.60

0.55

0.8

Separation

Point

Width

Diameter

0.6

= 0.28

0.2

0.4

CDCD

'( 8HH>4>.<%.7%><A0940H%K><=/%j%42>/%>/% 420%F./4%E.=>:#E%#119.#:2%#<H%K#/%D/0H% .<%420%

7>9/4%9#:0%:#9%42#4%:90#40H%H.K<7.9:0%!O20% 'WZZ%C2#1#99#E%%);%%N%/00%\07(%&B% C2#1409%

Y(,%

)( @/><=% =9.D<H% 0770:4% #<H% D<H09I.H$% H>77D/09/B% #/% /2.K<% ><% T>=(% YH(% V.40% 42#4% 42>/%

K.9J/%I04409%K>42%#%/F..42%D<H0949#$g%

&( C90#4><=%/D:4>.<%D<H09%420%:#9%I$%/0#E><=%420%=#1%I04K00<%420%A02>:E0%I.H$%#<H%420%

9.#H%!#EE%#9.D<H,(%"#<$%/0H#<%I#/0H%9#:0:#9/%!F./4E$%K>42.D4%#%/F..42%D<H0949#$,%

D/0%42>/%19><:>1E0B%#<H%420%E.K%190//D90%>/%.I4#><0H%I$%E0#A><=%420%#74%#90#%.10<%!.7%

:.D9/0% 42>/% #E/.% ><:90#/0/% 420% H9#=,(% 8<% 0E0=#<4% /.ED4>.<% 7.9% 42>/% F042.H% >/% 4.% D/0%

/D:4>.<%7#</% 4.%:90#40%E.K%190//D90%D<H09%420%:#9B%ID4%#/%<.40HB% %>4%>/%<.4%#EE.K0H%><%

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fans blew air backward thereby reducing the vehicle’s drag. Needless to say that the idea worked

immediately and the car appeared to be significantly faster that the competition. Ironically, the 2J

didn’t win any races (due to mechanical gremlins) and was banned, after only four entries, on

ground of ‘using movable aerodynamic devices’. A few years later the Brabham BT46B suction

car using the same principles (but fans were driven by the engine) entered the 1978 Swedish GP

to win directly out of the box. The story repeats itself and the suction car was banned from racing

in F1 immediately.%

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CL CD

Upper bodywork 0.26 0.09

Undertray+diffusor -1.63 0.14

Front wing -0.89 0.18

Rear wing -0.78 0.26

Front wheels + suspension 0.01 0.10

Rear wheels + suspension -0.06 0.17

Total -3.09 0.94

Table- 2- O$1>:#E% I90#JH.K<% .7% 420% #09.H$<#F>:%:.<49>ID4>.<% .7% A#9>.D /% :.F1.<0<4/% .7% #%

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As expected the upper bodywork produces a small amount of lift and drag, while wheels drag is

also moderate (indicating a well developed design). In case of the front wing, the numerous

deflector surfaces mounted on the wing and on its side plates probably reduce the separated flow

area behind the front wheel. Similar deflector vanes and plates also reduce the drag on the larger

rear wheels. The undertray downforce, however has the same order of magnitude as the combined

downforce contribution of the front and rear wings. This high level of the undertray downforce is

achieved simply because this is the largest aerodynamic surface and by careful tailoring the

underbody vortex flow, ground clearance and rake. In Ref. 30, Toet also shows a force

breakdown for the rear wing components, which consists of a two element upper and a single

element lower surfaces. Quite interestingly, the forward, upper wing element is generating 71%

of the assembly downforce and its flap is responsible for 44% of the assembly drag (only 10% of

downforce). The data also indicates that the lower (rear) wing is producing only 14% of the

assembly’s downforce, but in fact it has a positive effect on the diffuser flow. This is again an

interesting observation, because without the low pressure induced by this lower wing the flow

under the car would be reduced and the undertray/diffuser contribution to downforce will be

reduced, as well.

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References-

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15. Cogotti, A., “Aerodynamic Characteristics of Car Wheels,” Int. J. of Vehicle Design,

Technological Advances in Vehicle Design Series, SP3, Impact of Aerodynamics on Vehicle

Design, pp. 173–196, 1983.

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Formula 1 Race Car Aerodynamics: Understanding Floor Flow Structures and Why It Is a Key Component in Modern Racing

Conference Paper

Apr 2024

div class="section abstract"> This paper delves into the intricate realm of Formula 1 race car aerodynamics, focusing on the pivotal role played by floor flow structures in contemporary racing. The aerodynamic design of the floor of a Formula 1 car is a fundamental component that connects the flow structures from the front wing to the rear end of the car through the diffuser, thus significantly influencing the generation of lift and drag. In this work, CFD was used to predict the structure of the vortices and flow pattern underneath a Formula 1 car using a CAD model that mimicked the modern Red Bull Racing Team’s car in recent years. Through comprehensive analysis and simulation, a detailed understanding of the complex flow patterns and aerodynamic phenomena occurring beneath the floor of the car and its vicinity is presented. This entails a close examination of how air interacts with the floor of the car and how the flow around the car can be manipulated to alter the flow rate and the quality of air going into the diffuser, generating crucial insights into the underlying principles at play. Finally, special attention was focused on the tire squish area and the resulting structures affecting the diffuser. Vortex structures were illustrated utilizing volume renders of vorticity and velocity in the domain, alongside Velocity-based Line Integral Convolution (LIC) total pressure contours at the diffuser. The assessment was carried out for three different speeds of 30 m/s , 50 m/s , and 90 m/s with two different ride heights for each speed. This research aims to shed light and understand the critical factors that engineers and designers consider when optimizing Formula 1 race car aerodynamics, how different geometric elements interact, and why it is considered a difference maker in modern racing. </div

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Article

Feb 2024
INT J AUTO TECH-KOR

Aerodynamic forces acting on a racing car will impact its handling, stability, and steering characteristics. Oversteering typically occurs in racing cars with a significant front-end downforce. In the process of racing, the car’s attitude will change, causing a shift in the distribution of front and rear downforce. This, in turn, will impact the car’s handling performance. Therefore, in this study, a set of aerodynamic devices with attitude-adaptive function linked to the suspension is designed to reduce aerodynamic attitude sensitivity. The range of the car’s attitude changes, the adjustment ability of the front and rear flaps, and the reasonable matching relationship between different operating conditions and the attack angle of the front and rear flaps are confirmed. In this work, the matching relationship is achieved through the use of multiple groups of linkage mechanisms. The aerodynamic characteristics of the entire car are analyzed and simulated in the lap speed simulation. Results showed that the installation of the device reduces the center of pressure (CoP) movement during braking by 52%, the aerodynamic resistance of the entire racing car during acceleration by 19.5%, and the single lap time by 1.5%, while also inhibiting the generation of aerodynamic torque during roll.

Aerodynamic Study of MotoGP Motorcycle Flow Redirectors

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Full-text available

Jun 2023

In recent years, the introduction of aerodynamic appendages and the study of their aerodynamic performance in MotoGP motorcycles has increased exponentially. It was in 2016, with the introduction of the single electronic control unit, that the search began for alternative methods to generate downforce that were not solely reliant on the motorcycle’s electronics. Since then, all types of spoilers, fins and wings have been observed on the fairings of MotoGP motorcycles. The latest breakthrough has been Ducati’s implementation of flow redirectors at the front and bottom of the fairing. The aim of the present study was to test two hypotheses regarding the performance of the flow redirector by responding to the corresponding research questions on its aerodynamic function and advantage, both in the straight and leaning position. In a preanalytical cognitive act, a visual study of MotoGP motorcycles was conducted and, accordingly, a 3D-CAD model was designed ad hoc in compliance with the FIM 2022 regulations for both the motorcycle and flow redirector. Numerical simulations using OpenFOAM software were then carried out for the aerodynamic analysis. Finally, the Taguchi methodology was applied as an effective simulation-based strategy to narrow down the combinations of geometric parameters, reduce the solution space, optimize the number of simulations, and statistically analyse the results. The aerodynamic performance of the flow redirector is highly dependent on the inlet flow when the motorcycle is in a straight position. The results indicate that all models with leaned motorcycle bearing the flow redirector, regardless of geometry, have an aerodynamic advantage, as the appendage generates downforce with a minimal increment of the drag coefficient. In a cornering situation, the flow separator in the flow redirector reduces the disadvantageous influence of wheel rotation on the “diffuser effect” by drawing the flow towards the outside of the curve, creating extra downforce.

Effects of Location and Height of Vortex Generators on Aerodynamic Performance of NACA 4412 Airfoil

Article

Apr 2025

This study focuses on the aerodynamic effect of vortex generators (VGs) placed on the wing surface, with a focus on the height and chordwise position of the VGs. NACA 4412 airfoil was used for the investigation, which is a frequently used and well-researched airfoil in the aerospace industry, with a chord length (c) of 200 mm. Six different configurations have been analyzed with Computational Fluid Dynamics (CFD), with three chordwise positions (x) and two trailing edge heights (h). The results showed that VGs placed furthest from the leading edge (x/c = 20%) were able to increase lift and reduce drag to the greatest extent. In terms of height, the shorter (h/c = 0.5%) VGs produced the most lift. These results provide valuable insights as to how vortex generator design can be optimized for aerodynamic performance across various operating conditions.

Numerical Evaluation of the Effectiveness of the Use of Endplates in Front Wings in Formula One Cars under Multiple Track Operating Conditions

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Full-text available

Oct 2024

The last change in the technical regulations of Formula One that came into force in 2022 brought with it significant changes in the aerodynamics of the vehicle; among these, those made to the front wing stand out since the wing was changed to a more straightforward shape with fewer parts but with no less efficiency. The reduction in its components suggests that if one part were to suffer damage or break down, the efficiency of the entire front wing would be affected; however, from 2022 to date, there have been occasions in which the cars have continued running on the track despite losing some of the endplates. This research seeks to understand the endplates’ impact on the front wing through a series of CFD simulations using the k-ω SST turbulence model. To determine efficiency, the aerodynamic forces generated on the vehicle’s front wing, suspension, and front wheels were compared in two different operating situations using a model with the front wing in good condition and another in which the endplates were removed. The first case study simulated a straight line at a maximum speed where the Downforce is reduced by 2.716% while the Drag and Yaw increase by 7.092% and 96.332%, respectively, when the model does not have endplates. On the other hand, the second case study was the passage through a curve with a decrease of 17.707% in Downforce, 6.532% in Drag, and 22.200% in Yaw.

Numerical Iterative Analysis of Drag Reduction System for a Racing Car Rear Wing

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Full-text available

Nov 2023

In Formula Student competitions, the active adaptation of the aerodynamic components to the current race track conditions can significantly enhance the overall dynamic performance of the car. Due to the abundant low-speed corners, angles of attack of fixed aerodynamic components are usually exaggerated, preventing the car from achieving higher acceleration capabilities due to induced drag. This issue can be tackled by introducing an active drag reduction system (DRS). In this work, a strategy for performing iterative numerical simulations is proposed, with the goal of obtaining a range of different configurations suitable for certain track conditions. Specifically, the case of lowest drag is exploited. Different macros were developed to couple the utilization of computational fluid dynamics tools for aerodynamic analysis with an extensive iterative process with minimal user interference. An initial mesh refinement study was conducted. Afterward, angles of attack and centers of rotation of the two most rear flaps are iterated. The lowest-drag configuration was found to be at α_flap_1 = 0° and α_flap_2 = −6 ° , the latter mostly due to its aerodynamic interaction with the rest of the system. Results show that the angle of attack of flap 2 had the most influence on the overall forces, while varying the centers of rotation had a weaker impact. Nevertheless, combining the investigation of the angles of the attack with the center of rotation yields optimal DRS configuration with the minimum drag. Within one loop of the proposed strategy, a reduction of up to 94 . 5% in rear-wing drag was found. The strategy proposed can be looped until a configuration is obtained for specific optimization targets, such as drag reduction.

Agreement between Different Methods to Measure the Active Drag Coefficient in Front-Crawl Swimming

Article

Full-text available

Jan 2023
J HUM KINET

The aim of this study was to analyze the agreement of the active drag coefficient measured through drag and propulsion methods. The sample was composed of 18 swimmers (nine boys: 15.9 ± 0.9 years; nine girls: 15.3 ± 1.2 years) recruited from a national swimming team. The velocity perturbation method was used as the drag measurement system and the Aquanex system as the propulsion system. For both sexes combined, the frontal surface area was 0.1128 ± 0.016 m², swim velocity 1.54 ± 0.13 m.s⁻¹, active drag 62.81 ± 11.37 N, propulsion 68.81 ± 12.41 N. The level of the active drag coefficient agreement was calculated based on the mean values comparison, simple linear regression, and Bland Altman plots. The mean data comparison revealed non-significant differences (p > 0.05) between methods to measure the active drag coefficient. Both the linear regression (R² = 0.82, p < 0.001) and Bland Altman plots revealed a very high agreement. The active drag coefficient should be the main outcome used in the interpretation of the swimmers’ hydrodynamic profile, because it is less sensitive to swimming velocity. Coaches and researchers should be aware that the active drag coefficient can also be calculated based on propulsion methods and not just based on drag methods. Thus, the swimming community can now use different equipment to measure the hydrodynamics of their swimmers.

On the Co-Design of Components and Racing Strategies in Formula 1

Conference Paper

Jun 2024

Computational fluid dynamics analysis for an active rear-wing design to improve cornering speed for a high-performance car

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Dec 2022

Vehicle Cornering Stability Analysis of Aerodynamic Kit Based on Active Tilting Rear Wing

Conference Paper

Oct 2022

Automatic Wind Tunnel-Based Optimisation of an Automotive Underbody Diffuser

Conference Paper

Full-text available

Jan 2018

A wind tunnel-based morphing system was devised and utilised for aerodynamic data collection and real-time optimisation of an Ahmed body equipped with a diffuser. Three degrees of freedom were controlled, i.e. ride height, rake angle of the underfloor, and angle of the diffuser plane. Their impact on performance was investigated with a fixed ground. Real-time optimisation was carried out with the aim of determining the most suitable optimisation method for this problem. Tests were carried out using simulated annealing, particle swarm optimisation, pattern search and two genetic algorithms. The results showed that the algorithms demonstrated significantly different performance. However, they were all able to converge on a solution in spite of the hysteresis, which is a characteristic of diffuser flows, and the noise inherent in the system. Pattern search provided the most efficient convergence to the global maximum, despite several discrete aerodynamic changes within the search space, such as sudden flow separation or vortex breakdown. However, it was found to be sensitive to the initial position and noise in the data. The genetic algorithms were found to provide the most reliable convergence, although they were hindered by their inability to make small adjustments in the final stage of convergence. Population sorting was demonstrated as a way to improve the performance of population-based algorithms. Several new trends in diffuser performance were also observed, most notably that rake, even at small angles, not only generates downforce, but also significantly decreases the critical ride height and energises the diffuser, allowing it to work at higher angles. Up to 1000 different configurations per hour could be tested, making the system attractive for multi-dimensional aerodynamic optimisation, which would be very costly using computational fluid dynamics or conventional wind tunnel testing.

Lateral Aerodynamics of a Generic Sprint Car Configuration

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Full-text available

Dec 2002

Effect of Wing/Body Interaction on the Aerodynamics of Two Generic Racing Cars

Conference Paper

Full-text available

Feb 1992

Flow patterns, pressures, and forces on the underside of idealized ground effect vehicles.

Article

Full-text available

Jan 1983

Studies the flow underneath two types of 'ground effect' vehicles, plenum and venturi, noting application to racing car design. Discusses the differences between plenum and venturi flow noting the longitudinal vortex pair characteristics of the latter. A low speed wind tunnel was used to test the plenum and venturi models, and for some tests a moving belt ground plane was used. Presents results of pressure profile for the plenum model, noting importance of the inside pressure as a determinant of lift and drag. Shows how plenum pressure (nearly uniform) depends on relative gap sizes in high or low external pressure regions. Discusses static pressure distribution, flow visualization and lift/drag coefficient results for the venturi model. Examines how the lift and pressure distribution changed with modifications to the venturi model. (C.J.U.)

NASCAR Race Vehicle Wake Modification via Passive Blown Ducts and its Effect on Trailing Vehicle Drag

Conference Paper

Jan 2018

Viscous-Flow Simulation of an Open-Wheel Race Car

Conference Paper

Nov 1998

Wind Tunnel and Tract Testing an ARCA Race Car

Conference Paper

Sep 1990

Louis T. Duncan

The Effect of Gurney Flaps on Three-Dimensional Wings with and without Taper

Conference Paper

Oct 1996

The Origins of Drag and Lift Reductions on Automobiles with Front and Rear Spoilers

Conference Paper

Feb 1977

Franz K. Schenkel

Aerodynamics and aerodynamic research in Formula 1

Article

Jan 2013

W. Toet

This paper will address the engineering performance differentiators for an F1 car and highlight the difference aerodynamics can make to that performance. It will also consider some basic aerodynamic challenges and the main tools used for aerodynamic exploration by teams.

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