  The bundling of flagella is known to create a "run" phase, where the bacteria
moves in a nearly straight line rather than making changes in direction.
Historically, mechanical explanations for the bundling phenomenon intrigued
many researchers, and significant advances were made in physical models and
experimental methods. Contributing to the field of research, we present a
bacteria-inspired centimeter-scale soft robotic hardware platform and a
computational framework for a physically plausible simulation model of the
multi-flagellated robot under low Reynolds number (~0.1). The fluid-structure
interaction simulation couples the Discrete Elastic Rods algorithm with the
method of Regularized Stokeslet Segments. Contact between two flagella is
handled by a penalty-based method. We present a comparison between our
experimental and simulation results and verify that the simulation tool can
capture the essential physics of this problem. Preliminary findings on
robustness to buckling provided by the bundling phenomenon and the efficiency
of a multi-flagellated soft robot are compared with the single-flagellated
counterparts. Observations were made on the coupling between geometry and
elasticity, which manifests itself in the propulsion of the robot by nonlinear
dependency on the rotational speed of the flagella.
