Where Did We Get the World Famous Maibara Wind Tunnel?

General Manager,
Administration Div.

  I think the Maibara Wind tunnel was once introduced in this review in the past, but I would like to give a brief explanation so that readers may have a general understanding of its characteristics.

  The wind tunnel is of a closed circuit type. The test section can be changed for open type or closed type. The instrument section is 5m x 3m for the closed type and 3m x 2.5m for the open type, almost the same as the dimensions of wind tunnels we see frequently in automobile manufacturers. However, it is not the size of the facility that we can be proud of. What makes this wind tunnel unique is that it is without equal in the low level of its noise. Its background noise is 75 dB (A) at wind velocity of 300km/h, so we can say that in this respect, there are no other wind tunnels comparable with this one in the world. Of course, its maximum wind velocity is also an attractive feature.

  On the other hand, a noticeable feature of this closed type is a large moving belt ground plate that is able to move at high speeds to simulate air flow near the ground surface. The plane is 6m long x 2.7 in width, and although its maximum wind velocity is very high, 60m/s, the vertical movement of the moving belt is very stable, only 1mm at the proximity of the belt center. The closed cylinder also has the following features: maximum wind velocity 300km/h and long measurement section 20m. The measurement length is made this long to facilitate the test of long railway cars, and is advantageous in simulating the natural wind with a developed boundary layer, enabling us to study the problems in the behavior of cars when exposed to cross winds.

  My first experience with this wind tunnel was nine years ago. In those days, I was the chief of the Procurement Section of Materials, responsible also for the construction works in RTRI. I was fearful that our section might have to be in charge of a project for the construction of a huge wind tunnel. Fortunately, this project did not fall to our section, but for the next five years, I switched between to various posts. I led a small group of staff members, starting from sub-director responsible for the wind tunnel project in the Planning Division, Director of the Wind Tunnel Construction Promotion Department to the director of The Wind Tunnel Technology Center. I then spent two years at Maibara, which corresponded to the initial operational period of the wind tunnel facilities.

  Reflecting on the past, we can say that the Maibara Wind Tunnel Facilities were completed with an extremely high level of performance of which we can be proud; I feel strongly that this is because our project has always had talented personnel at key positions. Of course, I must not fail to express my appreciation not only the performance of MHI (Mitsubishi Heavy Industries) in charge of this project, but also the opinions given by researchers from the standpoint of users. However, considering any wind tunnel facility from its functional soundness as a plant, it is not enough that it have a high level of performance. If it requires high maintenance cost, it should not be considered as a top facility. If it involves difficulties in preparation of tests and operational software handling, we could not proceed.

  From this point of view, it is true that a lot of researchers at RTRI [SPACE] specialize in railway aerodynamics. The experience of such researchers alone is inadequate to decide detailed specifications for a wind tunnel. The same could be said about the opinions of wind tunnel makers.

  Under these circumstances, it was fortunate that we could introduce valuable human resources from outside into our group. An excellent engineer, with mastery of actual wind tunnels, who has a wide experience in equipment maintenance of wind tunnels, preparation of test steps, operation of wind tunnels, has participated into this project. Currently, he assumes the role of a director of the Wind Tunnel Technology.

  Already, almost five years have passed since the Maibara Wind Tunnel Facilities were put in operation. Every year, it continues operating at full capacity, by responding to needs by RTRI, including those for outside clients such JRs and automobile makers. We feel this project has a positive future, because we know that new human resources (engineers) are developing, who are able to construct wind tunnels, operate them and perform maintenance on them. Even if their activity field is limited to improvements, these engineers desire to create further advanced wind tunnels. The center was awarded ISO 9002 in 2001 as an organization, and authorized as having an organizational structure able to provide clients with tools necessary for testing. We are strongly convinced that the clients may use, without anxiety, these facilities together with the technologies provided.