GROUND TRANSPORTATION NISMO TAKES THE LEAD WITH STAR-CCM+ 5252 3939 NISMO TAKES THE LEAD WITH STAR-CCM+ GROUND TRANSPORTATION CROWNING THE SUPER GT SERIES CHAMPION FOR 2014: NISMO TAKES THE LEAD WITH STAR-CCM+ TO DESIGN DISTINCTIVE LOW DRAG CARS YOSHITAKA YAMAMOTO Nissan Motorsports International Co., Ltd. KUNINORI MASUSHIGE, YUKA TAKAHASHI & SAHAR FAZLI CD-adapco INTRODUCTION Nissan, Toyota and Honda, along with JUGGLING THE USE OF WIND Nissan Motorsports International Co., their affiliated companies TUNNEL TESTS AND CFD IN Ltd. (NISMO), located in the Tsurumi - GT300 class: Marked by a trend AERODYNAMIC DEVELOPMENT district of Yokohama, is sacred ground toward amateurs, with the majority In race car development, the traditional for Nissan GT-R enthusiasts. NISMO of participating teams comprised of approach is to run wind tunnel tests on is the development site of SUPER GT privateers scale models, with visualization realized and other premier racing cars, as well through pressure measurements at as production and development of In the actual race, vehicles from these specified points, smoke, tuft, PIV, and automobile parts. Launched in 1984 as two different categories compete other methods. However, with these the Nissan works team, NISMO has risen together on the same course. The speed methods, it is almost impossible to to the challenges of a long list of races, differences translate into even more visualize the entire domain of the compiling an illustrious track record along complex and exciting race conditions. aerodynamic flow. On the other hand, the way. After three decades of legendary Cars fight tooth and nail to outstrip each the recent advances in CFD software, performance, success and distinction over other as they roar around the circuit, hardware, and computing capabilities, its core competitors, NISMO uncovers making the race very attractive. has enabled engineers to simulate a how the unique capabilities of CFD helps complete race car in a highly detailed CFD the aerodynamic engineers improve The NISMO team develops and model from scratch, and to gain deeper their most recent aero-packages during produces vehicles for both of these insight into their designs, which would not the development process. Yoshitaka categories. In particular, the GT500 be viable through any other means. CFD Yamamoto, the chief aerodynamicist of class vehicle, on which the company substantially helps with understanding the development division of NISMO GT-R has truly staked its reputation as an the phenomena involved in fluid flows, GT cars, believes that “CFD serves as automaker, is formed based on the permitting accurate display and analysis an indispensable tool in development GT-R. In 2013, the GT regulations of the information, with a level of detail aimed at bringing visibility to the invisible became more aligned with those of the that is hard to provide experimentally. It dimension of flow.” German DTM series, which stimulated enables engineers to test the car virtually new mechanical and aerodynamic prior to any wind tunnel session, so as changes for 2014 Nissan GT-R NISMO to pre-evaluate various configurations SUPER GT SERIES GT500. Utilized in its development and “what if” scenarios, and submit to The SUPER GT, a FIA-sanctioned is STAR-CCM+® – the flagship test only the most promising solutions. international race, contains two different product of CD-adapco. In his role as This makes CFD a widely accepted tool regulations known as the “GT500” for chief aerodynamicist at the NISMO for the design and development of racing the top class racing category and the Development Division, Yoshitaka cars, complementing wind tunnel tests. “GT300” for the privateer category. Yamamoto oversees the aerodynamic Alongside this rapid growth of computing - GT500 class: Consists primarily of development for the GT500 GT-R, and resources, it can be hoped that CFD can vehicles developed and manufactured shares his knowledge and experience in hold the promise of offering itself as the by the big three Japanese automakers simulation through this article. “digital wind tunnel” that can replace 39 53 GROUND TRANSPORTATION NISMO TAKES THE LEAD WITH STAR-CCM+ FIGURE 1: Chief aerodynamicist Yoshitaka Yamamoto of the NISMO Development Division, posing alongside the 2014 NISMO GT-R. the physical testing in coming years as that is caused by turbulence and slows selecting the low drag specification was the science behind CFD improves and the car down. The harder and faster you to prepare an aero-package specifically computers become even more powerful. drive, the more low pressure air (higher designed for the Fuji speedway in 2012. Yoshitaka Yamamoto explains the speed) goes underneath the car, and the Because of its long straight course, lap contributions of CFD and the advantages more downforce will be created. time could be decreased significantly by this method offers in comparison to reducing the drag. wind tunnel testing in aerodynamic On the other hand, with increase in speed development: “When attaching small comes an increase in drag which is not Under the low drag specifications for parts to the car, for example, wind desirable. The ideal setup is normally to 2013, the front fender assumed a tunnel testing alone is not sufficient to get the maximum amount of downforce for configuration along the lines of a steep determine the impact of these parts on the smallest amount of drag generated. wall (Figure 2). That resulted in an the backside, especially where the effects However, the decision on either to create extremely distinctive front mask for the occur, and whether or not downforce an aero-package which is balanced or vehicles. Yoshitaka Yamamoto’s team has been obtained. CFD however offers leaning towards one of these two forces conducted an initial CFD simulation using valuable insight into the flow behavior. is highly dependent on the track and STAR-CCM+ to find the potential areas for GT cars are growing more complex every condition. A track with tight turns requires drag reduction, and they found out that the year. The number of intricate devices is a car with higher downforce configuration pressure on the mentioned fender section also on the rise, making it increasingly to navigate the turns. But on tracks with has lowered comparing to their previous tough to get the job done on the strength long straightway, wide and banked turns, design in 2012 (Figure 3). Yoshitaka of experience alone. This is where CFD such as speedways, less downforce is Yamamoto explains: “As a result of the becomes necessary.” required; higher speed can be negotiated, CFD analysis, we realized that the front and hence the drag reduction is of fender is an effective area regarding greater importance. When Yoshitaka drag reduction. Under the regulations, HOW CFD INSPIRES NISMO Yamamoto re-joined NISMO in 2011, he the only means of expanding that area Every aerodynamic engineer in racecar started developing an aero-package with was to widen it vertically. When we development has two major concerns; low drag specification that improves the attempted that, the results were favorable the creation of downforce to help push high speed, while prior to this year, all – as expected.” Prior to that, they had the car’s tires onto the track and keeping the improvements were carried out to attempted to eliminate the drag by it from sliding off in corners due to increase downforce while maintaining the rounding the configurations, but with the centrifugal forces; and minimizing the drag drag level. One of the initiatives behind help of CFD, the NISMO team understood 54 39 NISMO TAKES THE LEAD WITH STAR-CCM+ GROUND TRANSPORTATION FIGURE 2: Front mask engineered to FIGURE 3: CFD results using STAR-CCM+ show reduced pressure on the front fender reduce drag (photographed at the NISMO for the 2013 design (right) compared to the previous design (left) showroom) continuum, it has been used until now in a supplementary role rather than as a replacement for the work in the wind tunnel. As he explains: “One of the areas that still has room for improvement lies in evaluating portions that bear the wake of the parts in the front. As a case in point, I still regard assessments of tire wake as posing a stiff challenge. In addition to the wake, we have also failed to get 100% satisfactory 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.” APPLYING TECHNOLOGIES CULTIVATED THROUGH MOTOR SPORTS The GT500 vehicle development work involves pooling the essence of various different technologies. NISMO channels know-how cultivated through motor sports into the development of commercially marketed cars like GT-R NISMO, JUKE NISMO and other Nissan high-performance vehicles as the automaker’s self-styled “performance brand.” Yoshitaka Yamamoto explains that “with sports-oriented models that bear the name ‘NISMO,’ we instill our race car expertise into the development work. These vehicles have a key selling point featuring their high-performance. 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.” FIGURE 4: JUKE NISMO (above) and GT-R NISMO (below) that it was possible to reduce such drag their new achievement, as he continues: 2015 NISMO GT-R CURRENTLY without streamlining the shape in that “Measurements may be carried out in wind UNDER DEVELOPMENT way. They featured this so-called approach tunnels as well, but the visualization that In 2014, SUPER GT vehicle regulations as “aerodynamic harnessing modulation” becomes necessary is difficult to achieve were unified in tune with the German in their 2014 model. This refers to raising over the entire vehicle. CFD is an effective Touring Car Championship (Deutsche performance through the adept use tool to view the body as a whole.” Tourenwagen Masters, DTM), with broad of pressure differences – a step that Although CFD has led Yamamoto’s revisions carried out.