nascar drag coefficientsteven fogarty father
At the other end of the spectrum are the single seat racers, with some heavily-aeroed Formula 1 cars seeing values of up to 1.1. When automobile companies design a new vehicle they take into consideration the automobile drag coefficient in addition to the other performance characteristics. A common way to measure the drag of the vehicle is through the drag area. With the radiator flow open, the OEM body must have a radiator velocity ratio (VR) within +/ 0.005 of the NASCAR generic body, which also occupies the centre of a lift / drag box with tolerances in each direction. This mitigates the amount of drag by decreasing the frontal area of the blade. This downforce is the key to maintaining traction through the tight and constant turns of a short-track race. Your email address will not be published. The main results are compared to a wind tunnel experiment conducted with 1/18 replica of a Nascar. For the men and women of NASCAR R&D, Dallara, and the industry involved in making the new car a reality, the start of the regular season in Daytona will be not so much the birth of a new era, but more like a college graduation. Two cars drafting together can go 3 to 5 miles an hour faster than a solo car, and extra trailing cars add a little more speed, which is why the drivers spend so much time in single-file. document.getElementById( "ak_js_1" ).setAttribute( "value", ( new Date() ).getTime() ); This site uses Akismet to reduce spam. Two zones were opened up for OEMs to place their radiator exits, with the majority of the underlying radiator ducting common. Front fender skirts have the same effect on reducing drag as the rear wheel skirts, but must be further offset from the body in order to compensate for the tire sticking out from the body of the vehicle as turns are made.[18]. Indeed the drag coefficient follows the same trend as the downforce (Fig. Minimizing variables is always a good thing. Even casual fans are constantly exposed to the terminology of automotive aerodynamics. Body inspection at the track will still be conducted by NASCARs Optical Scanning Station, which compares a rapid photo scan of the car to the approved CAD surface of the vehicle. Since Goodyear builds each race tire by hand, the tire structure and compound have to be determined well in advance of each race. Which one falls off first? Secondly, there has to be some weight on the tire besides the weight of the tire itself. . Most hatchback and saloon car producers want you to seem like youre coursing down the motorway at 70mph without disturbing the slightest bit of air, cutting through it like a slippery salmon. In an effort to draw in higher energy air from the outside of the floor, the rear of the rocker boxes is ramped upward, and the diffuser outer tunnels feature a double hump design. After nearly nine months of private development testing, all three OEMs submitted their vehicles at the end of August 2021 for three grueling days at Aerodyn wind tunnel in Mooresville, North Carolina. Track surfaces change with temperature, humidity and the aging of the race surface. Lift is the aerodynamic force perpendicular to the direction of the body in motion. Boattails create a teardrop shape that will give the vehicle a more streamlined profile, reducing the occurrence of drag inducing flow separation. The air behaves as if the two cars are one. A rod with a hemispherical cross section will even have a drag coefficient of 2.3 (right column in the graph below). So its not like you can say that Bristol always needs x amount more friction in the upper lane. This pushed the initial outer tunnel ramp forward and outward. This is done to direct airflow around and over the vehicle rather than allowing air to travel under it. Associated Press. This meant moving the downforce balance rearward by 12-14 per cent, a significant departure from the existing Gen 6 architecture. While skirts are effective at generating downforce in a simple manner, they give the appearance of the cars being sealed to the track, along with the inevitable and undesirable wrinkling and deformation they experience. Because the Gen 6 car had a restorative yawing moment due to the rear asymmetry, teams were able to run very high front downforce percentages, often exceeding 50 per cent. Most vehicles with very low drag coefficients, such as race cars and high efficiency concept cars, apply these ideas to their design. Aside from qualitative and quantitative CAD reviews, the wind tunnel performance of the body is the most critical component. With the radiator flow open, the OEM body must have a radiator velocity ratio (VR) within +/ 0.005 of the NASCAR generic body, which also occupies the centre of a lift / drag box with tolerances in each direction. This force also depends on the. It also allows the car to correct itself when the driver oversteps the bounds of traction at the rear. Early aero development focused on matching the evenly distributed downforce number. u0001 Nevertheless, the Superbird was a success at NASCAR and beyond. Does anyone have any information on how many millimetres of rubber deposit there is on a track after heavy use? If its hotter, it may need less. Much anecdotal information pertaining to the drag reduction (drag benefit) of platoon operation exists. Stock cars are characteristically designed with rake -- meaning the car's rear is higher off the ground than the front end of the chassis. Lets say it takes you 30 lbs of force to push the file cabinet on the wood floor. Dr Eric Jacuzzi explains how those involved in the aero development of the NASCAR NextGeneration racecar see it not so much as the birth of a new era, but more like the completion of a study course. Another was at the rear of the car, where the production wheel tubs further closed off the rear of the boot (trunk) area, sealing in hot air from the transaxle cooler. The component within the equation that will have the largest effect on car design will be the frontal area, as this will shape the front profile of the car, influencing the rest of the design. However, achieving all that presented significant aesthetic challenges for manufacturers and NASCAR, since car designs not only had to be stretched at the rear, but also have different shapes on the left and right sides. During a high-speed spin, air can move rapidly enough over the roof and hood to produce a powerful lift force. Goodyear produces different tire compounds for different tracks, as well as different left- and right-side tires. . Contoured deflectors, or tire spats, are often made as part of the front bumper in order to direct airflow around the tire without having any increase to the outward flow. Lift -- colloquially called a skyward force -- is usually present to one degree or another in a moving object. With the 426 Hemi producing 425 horsepower, the zero to sixty acceleration was just 4.8 seconds, but they produced only 135 of these. Since most coefficients of friction are less than 1 (even tires wouldnt be more than 1.5), you need a scale that goes to 1.5 times the weight of the object. It was evident as well that the outer tunnels were ingesting the front tyre wakes. Nonetheless, for practical and style reasons, a kammback is more commonly seen in racing, high efficiency vehicles, and trucking.[24]. Spoilers, front air dams and wings produce this effect. This creates a low-pressure region behind the flap and increases the lift-off speed of the car when nearly backward by 10-20 per cent. {\displaystyle F={\tfrac {1}{2}}\times {\text{air density}}\times {\text{drag coefficient}}\times {\text{reference area}}\times {\text{speed}}^{2}} USA, Leslie-Pelecky, Diandra. MEW really? (Accessed 12/17/08 via Google Books) http://books.google.com/books?id=OAK3yFlHoTAC, Tierney, John. As expected, an aerodynamic body makes a big difference in lap time. But the quest to engineer racecars with high net downforce sometimes leads to additional drag. (When making spherical-cow jokes, and only when making spherical-cow jokes, you may read it as moo.). Sport utility vehicles (SUVs), with their typically boxy shapes, typically achieve a Cd=0.350.45. [14], While they do not have the biggest impact on the drag coefficient due to their small size, radio antennas commonly found protruding from the front of the vehicle can be relocated and changed in design to rid the car of this added drag. On the contrary, some drag force is very much needed to keep all four wheels firmly stuck on the tarmac in a controllable manner, and of course you want to make sure some airflow is slapping up against the radiators and other heat exchangers that your vehicle may have to maximise cooling. Dividing the weight of the tire assembly by the force needed to pull it gives them the coefficient of friction. 2 Power can only do so much when it comes to creating spectacular top speeds, with the drag coefficient being the next piece of the puzzle. PRO NOTE: This linear relationship doesnt hold for large downward forces. For short-track racing, the strategy is reversed -- because the driver spends more of the race negotiating curves, an emphasis on downforce will lead to greater overall speed as well as increased safety [source: Tierney]. air density Drafting can be a very powerful racing technique, but it has a serious liability. In all cases, the reference area is the cross section orthogonal to the flow direction. It was understood early in the process that the reduction of rear side force due to body symmetry would impact the useable aero balance, but initially it was a guessing game, although not entirely without value. This added up to extremely hot engine temperatures. The Cd of a given vehicle will vary depending on which wind tunnel it is measured in. After Daytona, the NASCAR R&D aerodynamics team embarked on a month-long extensive study of the problem, thermally modeling the entire vehicle in much more detail than it had previously. The submission process itself consists of two distinct components. Some of this was attributable to inadequate insulation and material changes in production, but a great deal was due to the ingestion of hot radiator air into the cockpit and inadequate evacuation of air from the cockpit. Sure. In 2003, Car and Driver magazine adopted this metric as a more intuitive way to compare the aerodynamic efficiency of various automobiles. A well-prepared student entering a world of possibility and excitement, with a proud group of invested parents standing behind it, wishing it every success. Studying downforce means paying attention to its opposing force, lift. The process was primarily undertaken in CFD, with over 2000 runs dedicated to underwing development for both performance and lift-off safety testing. Lift is an aerodynamic force that acts perpendicular to the airflow around the body of the vehicle. A low coefficient is conducive to high top speed and low fuel consumption, while a higher drag coefficient is generally found in cars searching for high cornering speeds influenced by downforce. Attaining more downforce by manipulating racecar bodies is an obsessive task in the stock car business. On the one hand, many drivers can remain competitive in a close race by piggybacking on the lead vehicle, taking advantage of the increased force and decreased engine strain. The following is a small part of the story of its development from an aerodynamic standpoint, as told by managing director of aerodynamics for NASCAR, Dr Eric Jacuzzi. The trailing car suffers a reduction of downforce on its front tires, resulting in a loss of stability and handling coming out of turns. NASCAR turned to PJ1 Trackbite in 2017 to selectively increase grip at tracks with one-groove racing. But there are other forces involved too such as Newton's Law of Motion and centripetal force. In a streamlined design the air flows around the vehicle rather than through; however, the grille of a vehicle redirects airflow from around the vehicle to through the vehicle, which then increases the drag. First of all, which one? (Accessed 12/15/08) http://www.nytimes.com/2008/02/12/science/12tier.html?pagewanted=all, Special Offer on Antivirus Software From HowStuffWorks and TotalAV Security. For the most part, any increase in downforce will also bring an accompanying increase in aerodynamic drag. The effects are especially beneficial on straightaways. The above dataset yielded an average drag coefficient of 10.5 and a standard deviation of 1.9. Automotive designers and NASCAR teams rely on aerodynamic principles to create improvements in the power and handling of vehicles at high speeds. Drag is a force that acts parallel to and in the same direction as the airflow. The average modern automobile achieves a drag coefficient of between 0.25 and 0.3. This equation is simply a rearrangement of the drag equation where we solve for the drag coefficient in terms of the other variables. speed On a track like Daytona, with its long straightaways and banked, sharp corners, the designs tend toward keeping drag to a minimum. These are all for normal tires, like the ones on your passenger car. The drag coefficient of a vehicle is affected by the shape of body of the vehicle. Streamlining the body requires assumptions about the surrounding airspeed and characteristic use of the vehicle. Aerodynamic force results from differences in pressure on the sides of the moving object. This video, from Harvey Mudd College, shows the experiment pulling a block, but cmon a tire would be much more interesting, wouldnt it? Automotive engineers and pit crews strive to keep the two forces in balance. You hear number for stock-car tire coefficients of friction around 1.0 to 1.5. Aero push forces drivers to make careful calculations. 2 The OEM vehicle(s) must pass the first gate with no radiator flow, which must be worse in lift and drag than the generic body. Dutton: 2008. This is a 3.48% decrease in the drag coefficient and a 0.12% decrease in the lift coefficient (or 0.12% increase in downforce).10 Jan 2018 Several safety innovations are installed on NASCAR vehicles for such emergencies, such as a recessed right-side window. Learn how your comment data is processed. This is held in place at the centre of the diffuser and, when deployed, releases downward and blocks the central tunnel of the diffuser. The introduction of more road courses and short tracks reduces the need for the cars design to focus on high-speed ovals, and more toward a shape that can do it all: ovals, road courses and short tracks. [15], The effect that windshield wipers have on a vehicle's airflow varies between vehicles; however, they are often omitted from race vehicles and high efficiency concepts in order to maintain the smallest possible coefficient of drag. This scan is located off targets on the chassis and has a tolerance of +/- 0.15in for the body, which presents challenges to the teams to build to that tolerance but also keeps the competition on a level playing field. Its 200 mile per hour speed set in March 1970 . The most common methods for increasing the downforce of a vehicle involve reducing the air pressure underneath the vehicle. "Going With the Flow." 12h ago. In most racing vehicles this is eliminated by covering the entire underside of the vehicle in what is called an under tray. on the actual NASCAR. The wide slicks used for racing are designed to maximize the coefficient of friction between the tire and the racetrack. A grille block covers up a portion of, or the entirety of, the front grille of a vehicle. [22][pageneeded], The underside of a vehicle often traps air in various places and adds turbulence around the vehicle. So how does NASCAR test for coefficient of friction? The back of the car must have its share of downforce to handle properly. air density The discovery of the mysterious powers of downforce in recent decades sent the auto racing world into a frenzy of wind-tunnel testing and subtle tweaking of stock car bodies. "ESPN Will Show the Unseen of NASCAR." Add in the fact that the ability of the rear of a car to generate downforce is hampered by the mass in front means, basically, that the front of any car has the first choice on making downforce. Some sports cars have a surprisingly high drag coefficient (such as the Ariel Atom at 0.40), but this is to compensate for the amount of lift the vehicle generates, while others use aerodynamics to their advantage to gain speed and as a result have much lower drag coefficients. Finally, Goodyear constantly improves their tires. The primary tool for tuning racing grip is the tire. fResults - Pressure fCoefficient of Pressure f Lift and Drag i The model, was connected to a dynamometer that measured force in both the x and y direction, essentially lift and drag. In the real world, road cars only really need to decrease drag force, especially in this age of fuel consumption obsession. The value of drag coefficient for a something of the general dimensions of a car lies around the 0.3-0.4 mark. Another factor in moving toward a symmetric body was the evolution of the NASCAR racing calendar. More Storage. 2), suggesting an induced drag (vortex drag) contribution (Jones [1990]). Perhaps the best place to start is at the nose of the vehicle. If you restrict the competition to solid objects, still the half sphere wins with a drag coefficient of 1.17. In fact, the. NASCAR has to do this in a slightly more advanced way: Theyre interested in the grip all the way around the track, so they map the coefficient of friction values and collect them on a computer with a GPS index. One example was the use of Kevlar composites to form the seals between the exhaust and the cockpit, which appear to have resulted in greater conduction into the steel chassis of the car since no heat is dissipated from the composite surfaces. As production parts began to arrive in early 2021, the first major test of team cars occurred at Daytona International Speedway. The sleek lines, tilted windshields and rounded corners of modern race cars -- and passenger cars for that matter -- are designed to minimize drag. Minor improvements in shapes, fit and finish yield greater results at the front of the car, where the highest energy air is found. Overall, the Next Gen car has been a once-in-a-lifetime project for most of those involved, who may never see another project quite as revolutionary to an ecosystem as this. "Passenger Car Aerodynamics." A rear spoiler usually comes standard in most sports vehicles and resembles the shape of a raised wing in the rear of the vehicle. Overall, the path of development for the underwing was aggressive but successful, thanks to the strong correlation between CFD and the wind tunnel. [9] Some cars now feature automatically adjustable rear spoilers, so at lower speed the effect on drag is reduced when the benefits of reduced lift are not required. Thats pretty much what they do: they drag an airplane tire around the track and measure how much force it takes. It was the first time in many years that the entirety of the vehicle, from nose to tail, was unique to each manufacturer (within certain parameters), harking back to the fiercely competitive manufacturer racing days of old. Thats as bad as What kind of underwear does a mermaid wear? In addition to the usual friction, hot race tires molecules interact with rubber on the track. Aerodynamic drag increases with the square of speed; therefore it becomes critically important at higher speeds. The drag coefficient is a common measure in automotive design as it pertains to aerodynamics. "BMW Side Skirts." of just 0.28, by way of comparison the Ferrari F40 has a drag coefficient of 0.34, the Lamborghini Murcielago measures in at 0.33, and the McLaren F1 sits at 0.32 - smaller numbers mean less drag. In ESPN's NASCAR coverage, a special-effects gimmick called Draft Track shows viewers how aero push works in real time, representing air currents via animated green puffs on the screen [source: Hiestand]. (Accessed 12/14/08) http://www.circletrack.com/techarticles/0304_aerodynamics_tech_definitions/index.html, Cislunar Aerospace. A coefficient of friction above one would be like trying to push your file cabinet along a really hot asphalt road if the bottom of the file cabinet is made of chewing gum. Right-side tires must deal with more force, so they are harder and dont wear as quickly. At the rear, the diffuser also underwent an evolution at the same time as the front splitter when the balance change was implemented. A Ford F-150 race truck is a "stock" truck that has some modifications for racing speed and safety. 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This effect is more pronounced in the incremental drag data in Fig. "Aero Push." 2 Do you know of any cars that have particularly low drag coefficients? Therefore, it plays a crucial role in reducing drag. Comparison of Aerodynamic Measurements on a Full-Scale NASCAR in Open and Closed Jet Test . Race drivers - particularly NASCAR drivers - make a convincing case for platooning, although drafting is the term the drivers prefer. Lets examine the coefficients of friction, , for tire rubber on various surfaces. = Ordinary drivers needn't worry about the downforce of their vehicles, but passenger cars can reduce drag by lowering the chassis, adding an air dam, wheel well and hood fairings [source: Beauchamp]. This leads to various interpretations of what is acceptable, and often lengthy lists of revisions from NASCAR in terms of qualitative styling, as compared to the production vehicle. The danger is especially present when a car is spinning, which radically alters the aerodynamic forces in play. This is why: The actual values of coefficients of friction for race tires are trade secrets and closely guarded. The drag area of a bicycle (and rider) is also in the range of 6.57.5sqft (0.600.70m2). 2023 Chelsea Magazine Company | Perhaps the greatest departure of the Next Gen (Gen 7) vehicle from the Gen 6 is the move to a coupe-like roof line, and the symmetry of the rear of the vehicle. Early in the process, the goal was to match the relative aero performance of the Gen 6 vehicle, primarily in terms of total downforce and balance. This allowed Buddy Baker to drive his Dodge Charger Daytona past the 200 mph barrier in 1970 - a world first at NASCAR. Conversely, drag is a resisting force parallel to, but coming opposite from, the moving object. Either louvred or open designs were permitted, based on the styling desires of the OEM, which is apparent when comparing the different design paths of the three vehicles. Cowl induction at the base of the windscreen has been a mainstay of NASCAR competition for decades but is not compatible with heated radiator air exiting out of the bonnet. The vehicles were so aerodynamic they achieved a drag coefficient of 0.28, which was unheard of at the time. After reviewing ride height data from early tests and determining where the drivers felt comfortable after the car was adjusted, it was easy to identify that it correlated with a downforce distribution of approximately 30 per cent front. This is why something like a Bugatti Veyron sits nice and snug on the tarmac with a small and efficient frontal profile when compared to something like a family saloon or hatchback. The term drag area derives from aerodynamics, where it is the product of some reference area (such as cross-sectional area, total surface area, or similar) and the drag coefficient. One of the first production passenger automobiles to swap out mirrors for cameras was the Honda e, and in this case the cameras are claimed by Honda to have decreased aerodynamic drag by "around 90% compared to conventional door mirrors" which contributed to an approximately 3.8% reduction in drag for the entire vehicle. That's pretty much what they do: they drag an airplane tire around the track and measure how much force it takes. The Physics Behind Auto Racing. Since drag accounts for roughly 90% total. Stories have floated around Formula 1 paddocks of trusting CFD analysis on front and rear wings only for them to completely defy aerodynamic logic during a race weekend. It keeps the pressure underneath the car down, preventing lift. Development of the underwing was done in parallel with common elements development on the body. I didnt know you could have coefficients of friction greater than one before I got into NASCAR. [3] Lowering the drag coefficient comes from streamlining the exterior body of the vehicle. Source: Brad Bruno i This data was collected using a data acquisition system as well, and processed with a u0002u0004 u0001u0004 u0001 PC. This relation also allows an estimation of the new top speed of a car with a tuned engine: Or the power required for a target top speed: Average full-size passenger cars have a drag area of roughly 8sqft (0.74m2). It was therefore decided to take the engine air from the front side of the radiator core rather than create an additional opening in the front fascia for stylistic reasons. -3.80. Using the expertise of industry professionals, we look in detail at racecar design and innovation, whilst also keeping you up to date with news and developments from all the major race series across the globe. drag coefficient Table 8.1 lists the drag coefficient for some simple shapes, (each of these objects has a Reynolds number of order 104 ). The wheel wells are another area to shape. A large share of the drag on a NASCAR race car is due to the highly separated underbody flow (see Figure 6). If youre moving file cabinets, you want a low coefficient of friction. reference area With its forward emphasis on manufacturer identity, it was a breakthrough for the sport. The obvious element in the physics of NASCAR is the aerodynamic design required by these cars in order to achieve top speeds of near 200 mph with the minimum drag coefficient. At the front of the car, one of the most substantial downforce-generating characteristics, aside from ground effect, is the outwash of the front splitter in front of the tyres. The value of drag coefficient for a something of the general dimensions of a car lies around the 0.3-0.4 mark. So there really is no replacement for either scale or full-size aerodynamic testing in a wind tunnel. The outward sweep of the splitter footplate, which is a wear limiting device for track contact, proved to be a very significant generator of downforce. Both cars can travel faster than either car can go by itself [source: Turner]. The body uses flanges and a common mounting system to attach to the chassis, with adjustment built in of up to 0.15in in each direction to accommodate manufacturing tolerances. How much of it to apply? As drag area CdA is the fundamental value that determines power required for a given cruise speed it is a critical parameter for fuel consumption at a steady speed. Goodyear tailors the frictional properties of their tires to each track. Drag coefficient Cdfor a sphere as a function of Reynolds numberRe, as obtained from laboratory experiments. Smooth wheel covers are hub caps with no holes in them for air to pass through. If another car trails immediately behind, nose to tail, it continuously enters airspace affected by the car in front. Please copy/paste the following text to properly cite this HowStuffWorks.com article: "How Stock Car Aerodynamics Work"