Modelling the undulation patterns of flying snakes

Some species of snakes are good gliders and can travel as far as 330 feet from a height of 15m through air at speeds of around 9-12m/s. They possess a unique and complex aerial locomotion compared to other species of gliders. During glide, the snake morphs its transverse body section into an airfoil-like shape. In addition, it undulates its body in a characteristic fashion. Understanding the change in shape of flying snake due to this undulation is vital for gliding and maneuvering during glide. Previous studies have explained the effects of 2-D shape. Earlier computational studies on a fixed 3-D wing inspired by the snakes have revealed favorable aerodynamic characteristics. In the current work undulation patterns of a representative snake geometry is modelled mathematically and numerically. The generated shape exhibits lot of similarity to experimentally observed ones. By adding the cross-section of the snake to this shape, the 3-D snake geometry at different instances of time during undulation can be generated. Three dimensional CFD study using ANSYS is performed on these shapes assuming quasi-steady flow. The computed average glide angle agrees well with experimental data. This shows promise for the undulatory model proposed. The current work throws a better understanding of the undulatory motion and may lead to advances in the development of unconventional Micro-Air Vehicles and Snake-Bots apart from biomimetics.

I. Introduction

Earlier studies on flying snakes reveal that their gliding abilities are surprisingly good which can be beneficial in the development of Micro-Air Vehicles (MAVs) and Snake-like robots (known as Snake-bots) which are of immense interest in defense and homeland security SAR (search and rescue) missions. This is also an interesting research area in the field of biomimetic due to their superior flight abilities. These snakes are gliders, which use free fall to gain velocity and undulation of their bodies to glide through the air [1]. Though they do not have any control surfaces, they exhibit good glide performance. During the glide they undulate from one side to the other which helps them to maintain a stable flight trajectory. This gliding mechanism makes them unique compared to other flyers like flapping bats and gliding ants [2]. Understanding the undulation pattern is key to understanding the maneuvering capabilities of the snake [1].