Automotive and transportation

Nissan Motorsports International Product Manufacturer uses Simcenter STAR-CCM+ to design Simcenter distinctive low-drag cars and win 2014 Super GT Series

Business challenges Reduce reliance on expensive development process. Yoshitaka Yamamoto, and time-consuming wind Siemens Digital Industries the chief aerodynamicist of the develop- tunnel tests Software solution helps Motorsports International ment division of NISMO GT-R grand touring Develop a full understanding (GT) cars, believes that “CFD serves as an of the complete flow field achieve synergy between CFD indispensable tool in development aimed at Use motorsport technology to results and wind tunnel testing bringing visibility to the invisible dimension drive design of high-perfor- of flow.” ”An indispensable tool” mance road cars and increase brand value In spite of three decades of excellence on Super GT Series the race track, Nissan Motorsports The SUPER GT, an International Automobile International (NISMO) is always seeking Federation (FIA) sanctioned race, has regu- Keys to success ways to run faster. It has recently lations known as the GT500 for the top-class Facilitate faster turnaround employed the unique capabilities of com- racing category and the GT300 for the priva- and more insight by using putational fluid dynamics (CFD) to help the teer category (entrants with no manufac- Simcenter STAR-CCM+ to firm’s aerodynamic engineers improve turer backing). The GT500 class consists complement wind tunnel tests their aero-packages during the primarily of vehicles developed and Provide full-scale vehicle analysis that is not possible in the wind tunnel Capture pressure and flow features that might not be seen experimentally

Results Won 2014 Super GT Series Achieved low-drag specification Achieved synergy between CFD results and wind tunnel testing Enhanced performance of the rear wing

Figure 1: The front mask engineered to reduce drag (photographed at the NISMO showroom).

siemens.com/simcenter “As a result of the CFD analy- manufactured by the big three Japanese However, with these methods it is almost sis, we realized that the automakers, Nissan, and , impossible to visualize the entire domain front fender is an effective and their affiliated companies. The GT300 of the aerodynamic flow. On the other area for reducing drag. class is mainly for amateurs, with the hand, the recent advances in CFD soft- Under the regulations, the majority of participating teams comprised ware, hardware and computing capabili- only means of expanding of privateers. ties has enabled engineers to simulate a that area was to widen it complete race car in a highly detailed CFD vertically. When we In the race, vehicles from these categories model from scratch, and to gain deeper attempted that, the results compete on the same course. The speed insight into their designs, which would not were favorable as expected.” differences translate into even more com- be viable through any other means. plex and exciting race conditions. Cars Using Simcenter STAR-CCM+ substantially Yoshitaka YamamotoChief compete fiercely to outstrip each other as helps with understanding the phenomena Aerodynamicist, Development they roar around the circuit, creating a involved in fluid flows, permitting accurate Division compelling spectacle. The NISMO team display and analysis of the information NISMO GT-R GT develops and produces vehicles for both of with a level of detail that is hard to provide these categories. The GT500 class vehicle, experimentally. It enables engineers to which the company staked its reputation test the car virtually prior to any wind tun- on, is based on the GT-R. nel session, so as to pre-evaluate various configurations and what-if scenarios, and In 2013, the GT regulations became more to test only the most promising solutions. aligned with those of the German Touring This makes Simcenter STAR-CCM+ a widely Car Masters (DTM) Series, which stimu- accepted tool for the design and develop- lated new mechanical and aerodynamic ment of racing cars, complementing wind changes for the 2014 Nissan GT-R NISMO tunnel tests. Given the rapid growth of GT500. Simcenter™ STAR-CCM+™ software computing resources, it seems likely that from product lifecycle management (PLM) CFD holds the promise of offering itself as specialist Siemens PLM software was used the digital wind tunnel that can replace to develop it. the physical testing in coming years as the science behind CFD improves and comput- Juggling wind tunnel tests and CFD ers become even more powerful. In race car development, the traditional approach is to run wind tunnel tests on Yamamoto explains the contributions of scale models, and visualize them with Simcenter STAR-CCM+ and the advantages pressure measurements at specified this method offers in comparison to wind points, smoke, tuft, particle image velo- tunnel testing in aerodynamic develop- cimetry (PIV) and other methods. ment: “When attaching small parts to the “CFD serves as an indispensable tool in development aimed at bringing visibility to the invisible dimension of flow.”

Yoshitaka Yamamoto Chief Aerodynamicist, Development Division NISMO GT-R GT “However, using Simcenter STAR-CCM+ offers valuable insight into the flow behav- ior. GT cars are growing more complex every year. The number of intricate devices is also on the rise, making it increasingly tough to get the job done on the strength of experience Figure 2: CFD results using Simcenter STAR-CCM+ show reduced pressure on the front fender for the alone. This is where 2013 design (right) compared to the previous design (left). Simcenter STAR-CCM+ becomes necessary.” car, for example, wind tunnel testing alone caused by turbulence and slows the car is not sufficient to determine the impact of down. The harder and faster you drive, the Yoshitaka Yamamoto these parts on the backside, especially more low-pressure air (higher speed) goes Chief Aerodynamicist, where the effects occur, and whether or underneath the car, and the more down- Development Division not downforce has been obtained. force will be created. NISMO GT-R GT However, using Simcenter STAR-CCM+ offers valuable insight into the flow behav- On the other hand, with an increase in ior. GT cars are growing more complex speed comes an increase in drag, which is every year. The number of intricate devices not desirable. Normally, the ideal setup is is also on the rise, making it increasingly to generate the maximum amount of tough to get the job done on the strength downforce for the smallest amount of of experience alone. This is where drag. However, the decision on whether Simcenter STAR-CCM+ becomes to create an aero-package that is balanced necessary.” or leans toward one of these two forces is highly dependent on the track and condi- CFD inspires NISMO tion. A track with tight turns requires a car Every aerodynamic engineer in race car with higher downforce configuration to development has two major concerns: the navigate the turns. But on tracks with a creation of downforce to help push the long straightway and wide and banked car’s tires onto the track and keeping it turns such as speedways, less downforce from sliding off in corners due to centrifu- is required. gal forces, and minimizing the drag that is

“Any car carrying the NISMO name is supported by development on the aerodynamics side by NISMO engineers, which means that I am also personally engaged in the work.”

Yoshitaka Yamamoto Chief Aerodynamicist, Development Division NISMO GT-R GT Higher speed can be negotiated, and hence the drag reduction is of greater importance. At NISMO in 2011, Yamamoto started developing an aero-package with low-drag specifications that improved the high speed, while prior to that year, all the improvements were carried out to increase downforce while maintaining the drag level. One of the initiatives behind select- ing the low-drag specification was to pre- pare an aero-package specifically designed for the in 2012. Because of its long straight course, lap time could be decreased significantly by reducing the drag.

Under the low-drag specifications for 2013, the front fender was configured along the lines of a steep wall (figure 1). That resulted in an extremely distinctive front mask for the vehicles. Yamamoto’s team conducted an initial CFD simulation using Simcenter STAR-CCM+ to find the Figure 3: GT-R NISMO (above) and JUKE NISMO (below) potential areas for reducing drag, and they found out the pressure on the fender sec- tion was lower compared to their previous Yamamoto highlights the impact of CFD in design in 2012 (figure 2). Yamamoto their new achievement, as he continues, explains: “As a result of the CFD analysis, “Measurements may be carried out in wind we realized that the front fender is an tunnels as well, but the visualization that effective area for reducing drag. Under the becomes necessary is difficult to achieve regulations, the only means of expanding over the entire vehicle. CFD is an effective that area was to widen it vertically. When tool to view the body as a whole.” we attempted that, the results were favor- able as expected.” Although CFD has led Yamamoto’s team to a better design by offering a valuable Prior to that, they had attempted to elimi- insight on the entire design continuum, it nate the drag by rounding the configura- has been used until now in a supplemen- tions, but with the help of CFD, the NISMO tary role, rather than as a replacement for team understood that it was possible to the work in the wind tunnel. As he reduce such drag without streamlining the explains: “One of the areas that still has shape in that way. They featured this so- room for improvement lies in evaluating called approach as “aerodynamic harness- portions that bear the wake of the parts in ing modulation” in their 2014 model. This the front. As a case in point, I still regard refers to raising performance through the assessments of tire wake as posing a stiff adept use of pressure differences, which challenge. In addition to the wake, we can only be performed with CFD. have also failed to get 100 percent satis- factory results with the rear diffuser and other reverse pressure gradients. If we can achieve that, I feel confident that the time will arrive when we no longer need wind tunnels.” Figure 4: The shape and position of the rear fender turning vane.

Applying technologies cultivated regard. For example, we understand that the through motor sports know-how for the upper side of the exterior The GT500 vehicle development work is generally uniform, meaning that there involves pooling the essence of various were actually no differences linked to the technologies. NISMO channels know-how amended regulations.” cultivated through motor sports into the development of commercially marketed Rear fender turning vane makes cars like GT-R NISMO, JUKE NISMO and a brief appearance1 other Nissan high-performance vehicles as The regulation for the second Fuji race in the automaker’s self-styled performance 2012 stipulated that engineers were at lib- brand. erty to tweak the design of the rear fender. From that time onward, this has become a “With sports-oriented models that bear the standard measure for all Formula (F) 1 races. name ‘NISMO,’ we instill our race car Following the rule change, NISMO attached expertise into the development work. The turning vanes that had winged cross-sections key selling point in these vehicles is high mounted on the rear fender (figure 5). performance,” says Yamamoto. “Any car According to Yamamoto, the primary goal carrying the NISMO name is supported by was to create an eye-catching external development on the aerodynamics side by appearance that could be presented in the NISMO engineers, which means that I am Formula One (F1) Series. also personally engaged in the work.” Figure 5: Flow patterns with (top) and without In addition to its distinctive appearance, it (bottom) the rear fender turning vane. In 2014, SUPER GT vehicle regulations also contributed positively to the rear wing were aligned with the German Touring Car performance. As can be seen in figure 5 Masters, and broad revisions were carried (top), CFD results showed the air flow out. For that reason, it became necessary churned up from the wheel arch lip on the to coordinate the development work with front fender alleviated the breaking away at each of the new regulations. the rear fender and top surface of the trunk lid. As shown in figure 5 (bottom), the addi- “Because 2014 necessitated the first-ever tion of the rear fender turning vane changed use of regulations integrated with the the flow pattern and improved the flow DTM, we couldn’t tell which of the various attachment towards the trunk lid. This ulti- rules offered advantages or disadvantages mately helped reduce the drag and improve for GT cars,” says Yamamoto. “Today we’ve the efficiency of the rear wing. generally ironed out the details in that Solutions/Services But it is notable the upside-down winged tunnel testing to reach the optimum low- Simcenter STAR-CCM+ cross section profile of the turning vane drag specification. The race car developers siemens.com/simcenter generated lift in specific locations near the at NISMO continue using Simcenter front, back and center of the vehicle. STAR-CCM+ as an indispensable tool in Therefore, the turning vanes did not their development process because it pro- Customer’s primary business improve the downforce. But the aerody- vides accurate pre-evaluation, deeper Nissan Motorsports namic team approved its addition since it insight into a full-scale model and the International Co., Ltd. reduced drag, and hence improved the ability to assess as many configurations (NISMO), located in Yokohama, overall performance of the rear fender. as possible. Japan, is sacred ground for However, the ruling authorities such as the Nissan GT-R enthusiasts. Grand Touring Association (GTA) had a dif- Following the interview for this article, the NISMO is the development site ferent interpretation of the newly company announced its plans to partici- of the SUPER GT and other pre- mounted turning vanes. Although the pate in the Le Mans 24 Hours Race, further mier racing cars. Launched in rules stipulated only one wing, GTA con- fueling the need for CFD in vehicle devel- 1984 as the Nissan works sidered the rear fender turning vane a sec- opment. Hence, once again, Simcenter team, NISMO has compiled ond wing. Therefore, it was shelved after STAR-CCM+ will be used by NISMO to com- an illustrious track record. having been installed for only 10 minutes pete at the highest levels of the sport. www.nismo.co.jp/en during the open inspection, and became little more than a memory. 1. “Motor Fan Illustrated Special Edition”, Kota Sera, Motor Journalist

Customer location Competing at the highest level Yokohama NISMO was crowned series champion in Japan 2014. The aerodynamic engineers at NISMO used the synergy between Simcenter STAR-CCM+ results and wind

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