自転車競技用ヘルメットの非定常流体力に及ぼす頭部姿勢の影響

抄録

The aim of this investigation is to estimate drag force acting on a bicycle helmet and power required for wind speed of bicycle race. It is known that a helmet of bicycle race has not only role to protect the head but also reduce aerodynamic drag force. Since the required power of caused by aerodynamic force acting on the helmet and head is about 18% of the total power of cycling, development of the low drag force helmet is required. To evaluate and understand the unsteady aerodynamic force and its generation mechanism, LES analysis was performed. As a result, the streamlined shape helmet placed in straight against the flow has low drag, but the drag force rapidly increases in the posture during goal sprinting. Therefore, the power required for top speed of bicycle race is more than three times that in steady state. Since, the flow around the helmet is unsteady, the maximum fluid force reaches 3.5 times that of the average. For this reason, it is required to develop robust shape helmet against changes in posture with small fluctuating drag force.