Optimal speed in rain: A numerical model of a dynamically deforming human body

The optimal speed for a person running in the rain trying to get soaked as little as possible has long been discussed in the physics and mathematics community. In practice, so far, the human body has mostly been represented as a simple geometric shape such as a parallelepiped or a cylinder. Here we introduce a far more refined model for the complex and dynamically deforming shape of a walking/running person. We introduce a numerical technique akin to ray tracing to evaluate the total amount of intercepted rain with an accuracy never reached in this field before. The main result is that under most wind conditions, running is preferable to walking, with a notable exception occurring when the following conditions a both met: (i) the advancing speed is close to the tailwind and (ii) the crosswind component is negligible.