2019 年 14 巻 1 号 p. 18-00321
A numerical simulation model for the evaluation of the effectiveness of lifejackets against drowning in tsunamis considering both unsteady water currents and human movement was developed. The Constrained Interpolation Profile-Combined Unified Procedure scheme was combined with the link segment model to simulate interactions between the fluid and subjects in the developed model. The developed model was experimentally validated using a large flume. A manikin laid on blocks was swept down by a tsunami-like water current and caught by a vortex behind the blocks. The developed model accurately reproduced both water currents and the movement of the manikin and was thus considered adequate to analyze the movement of human bodies in tsunamis. The model was then used to analyze the movement of a human body in the same currents but with higher buoyancy, assumed to represent a lifejacket. Consequently, buoyancy greater than a human’s body weight was required to keep the subject afloat; a buoyancy corresponding to the body weight caused the total submergence of the entire subject. Through comparison of forces applied to the body with its movement, it is revealed that a human body receives strong downward force while and immediately after passing over the vortex. These forces are caused due to the attractive pressure at the center of the vortex and downward currents in the downstream side of the vortex. These forces are considered to be remarkable in the evaluation of lifejackets in actual tsunamis.