2. Basic Technology Development
      In fiscal 2001, research and development was focused on clarification of superconducting magnet vibration and analysis of aerodynamic characteristics in tunnels.

(1) Measures against Vertical Bending Vibration of a Superconducting Magnets at High Speed
      One possible measure to reduce the costs of Superconducting Magnetically Levitated Transportation System is to reduce the number of ground coils.
Reducing the current number of levitation coils by half leads to the problem of vertical flexural resonance modes arising in the superconducting magnets currently in use, resulting in an increased heat load. It has been verified that, among these resonance modes, the primary flexural resonance mode is strongly affected by outer vessel rigidity, while the secondary flexural resonance mode is strongly affected by rigidity of the vertical load support material.
As a measure against the vertical secondary flexural resonance mode at high speed contributing substantially to increase of heat load, performance tests were carried out this fiscal year on vibration characteristics and heat penetration amounts. These tests used a mechanical vibration-testing device in which vertical load-supporting material with enhanced rigidity was attached to the superconducting magnet for testing (Fig. 9).
The prospect was thus opened up of raising resonance frequencies above a running speed range with no substantial effect on the steady-state amount of heat penetration.

(2) 500km/h-compliant Simulation of Pressure Variations in a Tunnel
      A train running through a tunnel causes pressure variations within that tunnel. Since these variations increase roughly in proportion to the square of the train speed, it is necessary to understand the pressure variations received by a car body running at high speed.
Extensive simulations have been performed for Shinkansen trains, and it is well known that their results closely correspond to running test results. However, calculation results of pressure variations according to conventional methods for vehicles on the Yamanashi Test Line did not closely correspond to these results. This may be because the calculation method used was a simplified one applicable for trains with speeds significantly lower than that of sound, creating relatively large errors when applied to a vehicle running at about 0.4 times the speed of sound.
A simulation method was therefore developed that can be used to accurately forecast pressure variations in a tunnel for a vehicle running at 500 km/h. Calculation results at about 400 km/h corresponded closely to model experiment values (Fig. 10).
The error ratio of the new simulation method decreases as compared to the measured values on the Yamanashi Test Line. The speed dependency also becomes smaller, while the error ratio calculated according to the conventional method increases with speed (Fig. 11). In addition, the error of the new simulation method shows lower speed dependence.

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