Ballooning in Spiders using Multiple Silk Threads

TL;DR

This study uses numerical simulations to explore how electric charges on spider silk threads influence ballooning behavior, revealing the effects on velocity, thread dispersion, and the role of electric forces in three-dimensional configurations.

Contribution

It introduces a validated numerical model of spider ballooning with multiple charged silk threads, analyzing the impact of electric charge distribution on ballooning dynamics.

Findings

Terminal ballooning velocity decreases linearly with lift force.

Velocity is unaffected by thread stiffness and viscous forces.

Electric charge causes threads to disperse, forming a conical shape.

Abstract

In this paper, three-dimensional numerical simulations of ballooning in spiders using multiple silk threads are performed using the discrete elastic rods method. The ballooning of spiders is hypothesised to be caused by the presence of the negative electric charge of the spider silk threads and the positive electric potential field in the earth's atmosphere. The numerical model presented here is first validated against experimental data from the open literature. After which, two cases are examined, in the first it is assumed that the electric charge is uniformly distributed along the threads while in the second, the electric charge is located at the thread tip. It is shown that the normalized terminal ballooning velocity, i.e. the velocity at which the spiders balloon after they reach steady-state, decrease linearly with the normalized lift force, especially for the tip located charge case. For the uniform electric charge case, this velocity shows a slightly weaker dependence on the normalized lift force. Moreover, it is shown in both cases that the normalized terminal ballooning velocity has no dependence on the normalized elastic bending stiffness of the threads and on the normalized viscous forces. Finally, the multi-thread bending process shows a three-dimensional conical sheet. Here we show that this behavior is caused by the Coulomb repelling forces owing to the threads electric charge which leads to dispersing the threads apart and thus avoid entanglement.