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Tokai University
Students Take the Lead in Simulating Solar Car Aerodynamics

 







Tokai Challenger

The Solar Car Team at the Tokai University Student Project Center (Kanagawa, Japan) has to be considered one of the premier student-led solar car design teams in the world after winning back to back World Solar Challenge races (2009 and 2011) in Australia. A critical aspect of successful vehicle design is minimizing aerodynamical drag since one major goal is to achieve high speeds while using minimal energy. The Tokai student-led team used Computational Fluid Dynamics (CFD) simulations to optimize the vehicle geometry. In particular they used Software Cradle SC/Tetra CFD Software for the simulations. Following are highlights from an interview with the Tokai team that discussed the educational advantages and usability of SC/Tetra in this challenging environment.

 

Dr. Hideki Kimura
Professor
Department of Electrical and Electronic Engineering,
School of Engineering,
Tokai University 
Assistant Executive Director
Tokai University Student Project Center

About the Tokai University Student Project Center

 The Solar Car Team belongs to the Light Power Project at the Tokai University Student Project Center. The Center is an educational organization that provides a nucleus for student-led activities following various themes. These themes range from local revitalization to environmental issues and social actions. Activities include participation in competitions, joint projects with industry, and hosting workshops. Using these activities, the Center helps students learn fundamental skills that will help them in their professional careers and in life. These include communication, leadership, problem-solving, and inventiveness. In addition to the Solar Car Team, other teams include the Electric Vehicle Team, and the Human-Powered Aircraft (HPA) Team. These three teams are a part of the Light Power Project, which is focused on designing environmentally friendly means of transportation.

 The first Solar Car Team was assembled in 1991. The Tokai University Student Project Center was established in 1996. The team works within the Prof. Hideki Kimura Laboratory under the Department of Electrical and Electronic Engineering. Dr. Kimura is the Assistant Executive Director of the Student Project Center. Students from various schools within the University are Solar Car team members. These include participants in Engineering but also students from the Department of Arts.

Tokai University Student Project Center

About the Tokai Challenger

 Solar cars are the ultimate environmentally friendly vehicles. They run solely on solar energy and batteries. Once on the road, they do not require any refueling. The Tokai Challenger, the solar car created by Tokai University, uses the most advanced technologies in the industry. It uses optimized Panasonic silicon series HIT Solar Cells, which have a 22% conversion efficiency with 5KWh lithium-ion batteries. The vehicle's frame is constructed from CFRP (carbon fiber reinforced plastic) manufactured by DOME Carbon Magic Co., Ltd., and carbon fibers are supplied by Toray Industries, Inc. The high efficiency motor is produced by Mitsuba Corporation. The car is 4.98 m (16.3 ft) long, 1.59 m (5.2 ft.) wide, and .88 m (2.9 ft) high. It cruises at 90 km/h (56 mph) using solar power and has a theoretical maximum speed of 160 km/h (99 mph).

 The Tokai Challenger won the Australian World Solar Challenge in 2009 and again in 2011. These are back to back wins since the race takes place every other year. In addition, the team won three straight "Solar Challenge South Africa" races in the Republic of South Africa from 2010 to 2012.

Dr. Kota Fukuda

Department of Aeronautics and Astronautics, School of Engineering, Tokai University

Using SC/Tetra for Solar Vehicle Design

 The design of the solar car begins with a three dimensional body design, in accordance with competition regulations, using SolidWorks CAD software. The 3D geometry data is input into SC/Tetra CFD software, which is used to run aerodynamic simulations to optimize the vehicle geometry. SC/Tetra has been used for the aerodynamic simulations at Tokai University since 2009. At that time the simulations were performed with the help of Atsuya Ikegami and Kiyoshi Shimada, experts in body design and aerodynamics at Yamaha Motor Co., Ltd. During those early days, determining the vehicle geometry was largely a trial and error process. They first began by simulating the designs of their competitors. From there they sought to incrementally reduce air resistance by minimizing CDA (the product of aerodynamic drag and projected area).

 

 Students are a central part of the design and simulation process and lead the detailed engineering and analysis work. They work under the guidance of Dr. Kota Fukuda, the aerodynamics expert and lecturer at the Department of Aeronautics and Astronautics. Dr. Fukuda began guiding the simulation work when he came to the University. Currently three students are skilled at performing the vehicle aerodynamics simulations.

Students performing simulations on their own

Simulating a Variety of Geometries

 Unlike the early days, when the team started their designs by analyzing competitors' designs, the mindset today, as described by Dr. Kimura, is, "We don't show any specific examples. We let the students design freely". This enables the students to be unconstrained by the past and to think out of the box. This approach can lead to unanticipated and novel designs.

 

 When designing a solar car, the first physical limitation is the large surface area needed for mounting the solar cells. Aerodynamic efficiency is a critical performance criterion. In addition, the cockpit size and overall vehicle dimensions must be within the competition regulations. 3D CAD data is passed to SC/Tetra by converting IGES format into STL. In the early days, this data conversion was difficult. Because of moving parts, such as the axles, the wrapping function could not capture all the geometry modifications. Over time, the expertise to perform the data conversion has been developed, reducing the time needed to perform this task. In addition, as the vehicle matures, fewer vehicle geometry modifications are required. Today, a single CFD simulation can be performed in approximately eight hours using a vehicle half model.


 Because of the constant change of students at the University, the Solar Car Team realized the importance of training. Not only do students attend lectures given by Yamaha Motor and Software Cradle staff, they also teach each other and instruct their junior colleagues.

*All product and service names mentioned are registered trademarks or trademarks of their respective companies.
*Contents and specifications of products are as of December 1, 2012 and subject to change without notice. We shall not be held liable for any errors in figures and pictures, or any typographical errors.

Institute Details

Tokai University Solar Car Team

Tokai University - Solar Car Team

History
1991 Solar Car Project launched at Tokai University
1996 Hideki Kimura Laboratory begins design of a high performance solar car as a member of the solar car team
2006 Program restructured to become the Light Power Project's Solar Car Team at the Tokai University Student Project Center
Manager/Advisor
Professor Dr. Hideki Kimura (Top left in picture) Department of Electrical and Electronic Engineering, School of Engineering
Advisor
Lecturer Kota Fukuda, Dr. Eng. (Top right in picture) Department of Aeronautics and Astronautics, School of Engineering
Staffs
Ryuji Otsuka (Bottom left in picture) Sophomore in Department of Prime Mover Engineering, School of Engineering

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