Abstracts - KTH Mechanics

Introduction of newly developed towing wind tunnel facility
S. Yoshioka a, T. Kato a, Y. Kohama a, F. Ohta a, M. Tokuyama a
We have built 7 km long testing line in Sunrise beach research facility of Tohoku
University in Hyuga city, Miyazaki, Japan in 2003. In the first 2 km out of total 7 km
we constructed a testing track of the towing wind tunnel. A schematic of this facility
is shown in Fig. 1. The first 910 m is accelerating region, the next 515 m is the
measuring region, where is covered by acoustic material, see Fig. 2, and the final 475 m
is the decelerating region. In this track an electrically driven vehicle runs. We named
this facility as HART which stands for Hyuga Aerodynamic Research facility by
Towing. We call the vehicle as HART vehicle.
As a first experiment we put a vertical flat plate, see Fig. 3, on this HART vehicle and
tried to measure the boundary layer transition on this flat plate. Fig. 4 shows the
obtained velocity signals. Signals in Fig. 4 are representative signals measured in
laminar, intermittent and turbulent boundary layers. In the signals measured in the
intermittent boundary layer, the passage of the turbulent spots is clearly observed as a
positive spike. The transitional Reynolds number where intermittency factor falls to
0.5 was Re50~4.0×106. This very high transitional Reynolds number shows very low
free stream turbulence condition.
a Institute of Fluid Science, Tohoku University, Sendai, Japan
Figure 1: Schematic of HART facility Figure 2: HART vehicle in measuring region
Figure 2: Vertical flat plate Figure 3: Velocity signals in boundary layer
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